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Gamboa, Erwin. "Stress corrosion cracking of rock bolts /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18302.pdf.
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Thomas-Lepine, Capucine. "Rock bolts - Improved design and possibilities." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for vann- og miljøteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18691.
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SummaryRock Bolts, improved design and possibilitiesMaster thesis NTNU 2012Student : Capucine Thomas-LepineSupervisor : Leif LiaKey words : rock foundation, small concrete dam, rock mass classification, rock joints, shear strength of rock discontinuities, fully grouted passive rock bolts designMasters Thesis : “Rock bolts, improved design and possibilities” is a continuation from the Masters Thesis NTNU 2011 “Rock bolts in dams, expected capacity” by Lars Kristian Neby. Internationally, dam engineering focuses mainly on pre-stressed anchors in rehabilitation and improvement of stability of large dams, which is undergoing constant research in North America. Passive rock bolts are used in small concrete dam foundations to ensure sufficient stability against overturning moment from ice loads. This concerns the majority of dams in Norway, over 98% of whose electricity comes from hydropower developed over the last 100 years and still developing. Design is ruled by regulation from NVE (Norwegian water resources and energy directorate) published first in the 1980s, and regularly revised until the retroactive “Retningslinjer for betongdammer” in 2005. This design method for passive rock bolts is conservative with regards to rock capacity, as it is worldwide. The model, developed in the early age of rock bolt development in 1977 by Littlejohn and Bruce, considers the rock resistance as equivalent to the weight of the cone of rock around the bolt. Rock engineering has improved since, often with regards to underground engineering, which is not necessarily transposable to dam engineering. The inherent uncertainty in rock mass characterization slowed development of new design method for passive rock bolts. This is however of great interest in the Norwegian hydropower industry, and for applications to other civil engineering structural foundations. This thesis is meant to develop knowledge of qualitative and quantitative rock mechanisms in passive rock bolts in order to improve their design.The work is composed of three parts, as follows :A study on rock mass capacity and mechanisms in dam foundations, comes first. An empirical and quantitative estimation of rock mass strength with regards to recognized classification Q, RMR or GSI is proposed, based on Wyllie (1992) and results from Lars K. Neby. Full scale tests are then performed to the assess validity of empirical relationships developed in the first part between rock mass quality and rock bolt capacity (maximal tension load in pull out tests). 50 steel bolts with diameter 25mm and mortar grouted length 0.4m were pulled out with logging of strength and deformation in a rock quarry presenting various degrees of rock quality (RMR 40 to 80), representative of expected conditions for dam foundations. Rock quality was assessed for each bolt by laboratory testing (intact material properties) and rock mass characterization on site supplemented by core drilling or video inside hammer drilled holes. This program of tests was an improvement on the protocol developed and performed by Lars K. Neby on 18 bolts, whose results give the first relevant clues on parameters such as limit range of quality of rock (RMR>40), length of bolt (0.4m), maximal capacity (more than 20 tons, when conservative calculations assessed 0.2 tons). The results of testing confirm the relationships developed in a more statistical approach.Conclusions from these two parts lead to a proposition for a new design model, with a higher resistance contribution from the rock. The three modes of failure (rock, steel, grouting) are considered for ensuring resistance of a maximal stress of 180MPa (to avoid important deformations in the structure). Factors of safety and the range of validity in the rock mass condition for the proposed design are also considered. The thesis concludes with propositions for further works in order to :- Further extend the domain of validity of the proposed design.- Review methods of control of installed passive rock bolts.- Document and improve knowledge of load transfer mechanisms in passive rock bolts in dams.
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Berzell, Carl. "Load capacity of grouted rock bolts in concrete dams." Thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147180.
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The purpose of this thesis is to evaluate the contribution of grouted rock bolts on the stability of concrete dams. The load capacity of the grouted rock bolts are assessed considering eventual deteriorating processes. An additional objective was to compare the resulting load capacity with the prevailing regulations in RIDAS (the power companies’ guidelines on dam safety) and possibly suggest new guideline values. The literature study consists of two parts; concrete dams and grouted rock bolts. In the first part concrete dams are discussed and especially the inherent forces and aspects when controlling their stability. The second part treats grouted rock bolts and the theoretical focus is on their function and possible failure modes as well as on the degrading processes (primarily corrosion) that are affecting the rock bolts. Subsequently, the theory was applied on the Swedish concrete buttress dam Storfinnforsen, which is the largest concrete dam in Sweden. The dam was selected for this study mainly because its shape is archetypical for buttress dams. In addition, a digitalized model of the dam was obtainable from previous research projects. A numerical analysis with the finite element analysis software ABAQUS was performed in order to evaluate the stability of the dam and to support the analytical analysis. The load capacity of the grouted rock bolts was analytically evaluated with consideration to eventual degradation. Assuming a corrosion rate of 60 μm/year, the grouted rock bolts in Storfinnforsen could after 100 years be trusted with a load capacity of approximately 180 MPa. That load capacity is due to shear failure, which constitutes the most plausible failure mode for rock bolts in buttress dams. The value 180 MPa is to be seen in contrast to the current limitation of 140 MPa that is defined in RIDAS (2011). The conclusion of this thesis is accordingly, that the maximum allowed load capacity that can be assigned the grouted rock bolts in the stability calculations of concrete dams can be increased from todays 140 MPa. This conclusion is substantiated by the analytical analyses with the numerical calculations as support.
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Kristjánsson, Gunnar. "Rock bolting and pull out test on rebar bolts." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for geologi og bergteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25429.
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Pull out tests were carried out in the laboratory of rock mechanics at Norwegian University of Science and Technology (NTNU) for the purpose of determining the critical embedment length of fully grouted rebar bolts. The 20-mm rebar bolts and the grouting material, “the Rescon Zinc bolt cement” used in the testing are widely used in underground projects in Norway. Different embedment lengths, ranging from 10 cm to 40 cm, were employed in the tests under different water-cement ratios for the grouting mortar. The critical embedment length for a given water-cement ratio is determined on the diagram of the pull - out load versus the embedment length. A chart of the critical embedment bolt length versus the water-cement ratio as well as the uniaxial compressive strength of the cement mortar is established based on the testing results. In the theoretical part of the thesis, the main focus is on rock bolting. Bolting principals are introduced along with different types of rock bolts, design of bolting systems and stability problems caused by rock stresses. In the final part of the theoretical part the procedure of pull out testing is described and the load bearing capacity of rock bolts are categorized into the groups in accordance with load deformation performance. Finally, previous pull out test research is presented.
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Manoharan, Ravindran. "Estimation of free and total anchor lengths for integrity assessment of rock bolts." Thesis, University of Aberdeen, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=214186.
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This thesis describes the investigation of a non-destructive test method for integrity assessment of rock bolts using the resonance spectroscopy method. Although other methods exists these all present certain limitations. Initial experimental investigations included the assessment of a number of excitation mechanisms, namely, hammer tests, chirp tests and swept sine tests.
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Kostecki, Todd. "DESIGN METHODS FOR ROCK BOLTS USING IN-SITU MEASUREMENT FROM UNDERGROUND COAL MINES." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1695.
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The research in this dissertation was undertaken because of a need for a more accurate, reliable and relatively simple method for determining the combined loading (i.e., axial, flexure and shear) along rock bolts. This combined load determination and understanding also resulted in a relatively simple and reliable new rock bolt design methodology. The new design method was based on a clearer understanding of the actual loading along a grouted rock bolt. To accomplish these research goals, double shear tests were conducted in the lab with reinforced concrete specimens, and field trials were conducted in room and pillar coal mines, with the aim to measure in-situ rock shear. Strain measurements were obtained using rock bolts instrumented with optical fibers that possessed high spatial resolution (≈ 1.25 – 2.5 mm). Corroboration with a past database of rock bolt measurements in shale aided in the deduction of the final support design method. The scientific contributions from this research include the conceptualization of a ground reaction curve that considers time effects such as rock relaxation, long term weakening effects, and lateral rock movement. A new explanation as to why rock bolts creep in practice (i.e., dislocation creep) is described based upon field measurements, which also indicated that the process of in-situ rock shear involves slow episodic movements. Specifically, there are localized compression (i.e., rock pinch) and tensile zones (i.e., dilatation) prior to the occurrence of plastic relief (i.e., rock slip). Finally, the design method is developed using simple factors (i.e., strain and shape factors) and loading conditions (e.g., installed load, rock slip) that occurred throughout the rock bolt’s design life. This approach results in a methodology that considers effects on reinforcement with time and combined loadings. The method is then extended by producing survival and hazard functions for rock bolts to ultimately reduce risk associated with design.
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Randolph, Michael David. "Load transfer mechanisms and performance of prestressed rock anchors for dams." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19917.
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Xu, Haixue. "The dynamic and static behaviour of resin bonded rock bolts in tunnelling." Thesis, University of Bradford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601346.
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The literature on the design, construction, testing and performance of resin bonded rock bolts has been surveyed, and particularly focused on vibration prediction and the behaviour of rock bolts when subjected to dynamic loading. The dynamic load transfer mechanism, the dynamic and static service behaviour of two-speed resin bonded rock bolts in microdiorite, and the dynamic behaviour of rock anchorages in mudstone when subjected to tunnel blasting have been investigated through two extensive full-scale field and laboratory tests. The investigation on two-speed resin bonded rock bolts has been performed with twenty four rock bolts installed within 1.1 to 5.7 m from the blasting face. All rock bolts were instrumented using load cells and accelerometers fixed on the anchor heads to monitor the instantaneous dynamic load and residual static load, and axial dynamic vibration of the bolts. Eight of the bolts were also instrumented with five inserted load cells along their length to monitor the dynamic load transfer mechanism and static load distribution. The dynamic load transfer mechanism, the dynamic response of rock bolts with scaled distance, and safe distance for the installation of permanent resin bonded rock bolts have been established. The effects of prestress load (from 0 to 100 kN) and distance to blast source have been assessed. For the investigation on mudstone anchorages, nine anchorages were instrumented with accelerometers at the anchor heads and in the vicinity of the fixed anchor zone to monitor vibration levels when subjected to nearby tunnel blasting. Residual loads were checked by lift-off test A relationship of vibration between the anchor head and fixed anchor has been established, and a safe peak particle velocity of 48 mm / s has been established. A physical model, which simulates the dynamic and static behaviour of resin bonded bolts subjected to blast loading, has been developed. Three instrumented bolts were tested, and different prestress and confining pressure levels were applied to the instrumented bolts.
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Mothersille, Devon Kenningtham Vernon. "The influence of close proximity blasting on the performance of resin bonded bolts." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329297.
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Full scale field trials, carried out during the construction of the Penmaenbach Tunnel in North Wales, have shown that two-speed resin bonded rock bolts are resilient to close proximity blasting. Fully grouted 6m long rock bolts, installed within 0.7m of the tunnel face, have shown no significant signs of distress or failure. Instantaneous loads of up to 40% of the characteristic strength of the bolt were observed together with average residual load losses of 5% of the working load, which compares favourably with the acceptable tolerance of 10% working load stipulated by current practice. Analysis has also shown that rock bolts with low prestress sustain greater vibrations and proportionately higher dynamic load changes during blasting. However, bolts with relatively high prestress loads sustain greater induced loads. Empirical relations have been established to describe rock bolt behaviour in terms of induced vibration and scaled distance. In particular, a predictive equation relating dynamic load changes in the experimental rock bolts to scaled distance, is presented. Calculations based on approximate bolting costs have indicated that cost savings of up to 38% of the total bolting cost could have been effected if the results of this work had been implemented at the design stage. Physical modelling work has confirmed that the distribution of loads in the fixed anchor of a resin bonded bolt are non-linear when both static and impulsive loads are applied to the bolt head. Corroboration of the field results has also been established with respect to the significant influence of initial prestress load on dynamic load change. Complementary finite element modelling work has successfully predicted fixed anchor load distributions under static and dynamic loading conditions. Attempts to establish a detailed relation between distance from blast, magnitude of charge and change in residual load, for low to medium capacity rock anchorages on the West Portal of the tunnel, were thwarted by the poor performance of instrumentation with respect to temperature sensitivity. However, a simplistic approach to analysis has enabled the establishment of a tentative predictive relationship.
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Bylapudi, Gopi. "CORROSION OF ROCK ANCHORS IN US COAL MINES." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/287.
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The mining industry is a major consumer of rock bolts in the United States. Due to the high humidity in the underground mining environment, the rock bolts corrode and loose their load bearing capacity which in turn reduces the life expectancy of the ground support and, thus, creates operational difficulties and number of safety concerns [1]. Research on rock anchor corrosion has not been adequately extensive in the past and the effects of several factors in the mine atmosphere and waters are not clearly understood. One of the probable reasons for this lack of research may be attributed to the time required for gathering meaningful data that makes the study of corrosion quite challenging. In this particular work underground water samples from different mines in the Illinois coal basin were collected and the major chemical content was analyzed and used for the laboratory testing. The corrosion performance of the different commercial rock anchors was investigated by techniques such as laboratory immersion tests in five different corrosion chambers, and potentiodynamic polarization tests in simulated ground waters based on the Illinois coal basin. The experiments were conducted with simulate underground mining conditions (corrosive). The tensile strengths were measured for the selected rock anchors taken every 3 months from the salt spray corrosion chambers maintained at different pH values and temperatures. The corrosion potential (Ecorr), corrosion current (Icorr) and the corresponding corrosion rates (CR) of the selected commercial rock bolts: #5, #6, #6 epoxy coated and #7 forged head rebar steels, #6 and #7 threaded head rebar steels were measured at the solution pH values of 5 and 8 at room temperature. The open circuit potential (OCP) values of the different rock anchors were recorded in 3 selected underground coal mines (A, B & C) in the Illinois coal basin and the data compared with the laboratory electrochemical tests for analyzing the life of the rock anchors installed in the mines with respect to corrosion potential and corrosion current measured. The results of this research were statistically validated. This research will have direct consequence to the rock related safety. The results of this research indicate that certain corrosive conditions are commonly found in mines but uniform corrosion (around 0.01-0.03mm loss per year across the diameter) is generally not considered a serious issue. From this study, longer term research for long-term excavation support is recommended that could quantify the problem depending on the rock anchor used and specific strata conditions.
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Buys, B. J. "Rock bolt condition monitoring using ultrasonic guided waves." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06222009-135318/.
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Rahman, Md Sazzadur. "Electrochemical behavior of alloy 22 and friction type rock bolt." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239881.
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Mahony, Luke T. School of Mining UNSW. "Development of a laboratory facility for testing shear performance of installed rock reinforcement elements." Awarded by:University of New South Wales. School of Mining, 2006. http://handle.unsw.edu.au/1959.4/25700.
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Rock reinforcing elements provide a significant proportion of their ground control capability through offering resistance to shear movement of adjacent rock masses or blocks. This potential shear movement may take the form of sliding on horizontal bedding planes leading to strata bending; or block displacement along other geological structures such as joints or similar discontinuities. Much has been reported about this type of behaviour of rock bolts and other tendons, in theoretical concepts. However, there is a shortage of quality data available on the exact nature of this mechanism for shear resistance, and the role played by parameters such as pre-tensioning. A clearer understanding of the nature and significance of this type of behaviour has major implications for rock reinforcing materials and installation design. This thesis, which was supported by the Australian Coal Research Program (ACARP) describes the design, construction and commissioning of a laboratory testing facility at the School of Mining Engineering, University of New South Wales (UNSW), Australia and a subsequent testing program. The single failure plane design adopted in the test rig has been successful in allowing shear loading to be directly applied to fully installed rockbolts. Rockbolts were installed into an offset concrete rockmass, which consisted of two separate concrete samples that created a smooth shear plane surface. The reinforced samples were subjected to an applied shear load and critical parameters such as load and shear displacement were recorded. Influencing parameters such as concrete strength and applied pre-tension were altered and recorded to determine their effects on the overall shear performance of the sample. The failure mode of the rockbolts was also examined. The results indicate that a relative stronger rockmass material caused the rockbolt to fail within a lower shear displacement compared to a relatively weaker material. Also, a pre-tensioned rockbolt tended to resist shear displacement at least initially, until high shear loads developed. This phenomena is beneficial to ground support as less movement would tend to maintain integral strength of the rockmass. The use of strain-gauged rockbolts indicated as would be expected that the shear loading arrangement induced a compressive axial loading that tended to dissipate with distance from the shear surface.
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Sinha, Sankhaneel. "ANALYSES FOR DESIGN AND SUPPORT OF COAL MINE INTERSECTIONS." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2059.
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Rock bolts have been extensively used as a support element in coal mines in the US for about 40 years. Longwall development and partial extraction room-and-pillar mining systems now rely heavily on fully-grouted roof bolts as the primary support with as needed inclined bolts, trusses, and cable bolts as secondary support. These two coal mining systems develop 3- and 4-way intersections during extraction processes. A study of Illinois (2004-2008) and US coal mines found that over 70% of roof falls occurred at intersections. It is therefore necessary to perform additional research in stress and displacement distributions around intersections and then design support systems to improve stability of intersections. This thesis research, in cooperation with a bolt supplier and NIOSH, analyses the stress and strain redistribution in and around intersections in typical lithologies in the Illinois Basin coal mines with the goal to develop a better understanding of failure initiation and propagation mechanisms with and without roof supports. Analyses were corroborated with field observations wherever possible. Non-linear continuum analyses using the Generalized Hoek-Brown failure criterion with rock mass properties is the foundation for these analyses. The first task (Task 1) toward these goals was to develop rock mass properties from available laboratory data using estimates of Geological Strength Index (GSI) for different lithologies. An important subtask was to perform an error analysis in estimates of rock mass properties assuming an amount of error in GSI estimates. Analyses and field observations were done for typical 4-way intersections at two mines in southern Illinois operating at depths of 150 m and 80 m, respectively in the No. 6 coal seam, which averages 1.8 m in thickness. Pre-mining horizontal stresses of 7.58 MPa and 4.13 MPa were applied in the E-W and N-S directions. These coal companies provided geologic logs and rock mechanics data for roof and floor strata. Rock mass engineering properties for different roof and floor lithologies were developed using estimated values of Geological Strength Index (GSI), and Hoek-Brown (H-B) rock mass failure parameters. A recent laboratory study provided normal and shear stiffness properties of the immediate roof interfaces within the bolting range of 1.8 m. MSHA-approved roof support plans were used for initial modeling. Short Encapsulation Pull Test (SEPT) data provided by bolt suppliers in the region were used to assign bolting system stiffness and strength parameters. Task 2 analyzed normal and shearing stresses and strains in and around mine intersections for typical pre-mining stress fields and then identified critical areas of failure initiation and progressive failure propagation. Failure initiation was hypothesized to occur for critical values of compressive (1 mm/m), tensile (0.5 mm/m), and shearing (0.5 mm/m) strains based on a review of laboratory stress-strain properties. This approach allows quantifying areas in and around an intersection where failures are likely to initiate with and without artificial supports. It computes three reinforcement factors with and without supports: reinforcement against tensile (RFT), compressive (RFC) and shearing (RFSS) strains. Task 3 assessed the performance of currently practiced roof support plans and identified where inadequacies exist and how they could be improved through spatial distribution of supports and their characteristics. Analyses were completed for two mines with one orientation of pre-mining horizontal stress field. The next logical step (Task 4) was to extend analyses in Task 3 to assess the effect of maximum compressive stress orientation in relation to entry direction (0o, 30o, 60o & 90o) and different cut sequences and their effect on changes in failure initiation and failure propagation mechanisms. Numerical analyses have shown that stress and strain distributions are significantly different when the cut sequence is included in models. For a horizontal stress ratio of two (2), the 60o orientation provided maximum stability. Separate models with all cuts excavated simultaneously corresponded well with the well-established NIOSH software AHSM and previous research. The effect of cut sequence combined with the directional effect of pre-mining stresses becomes evident from the dissimilar results. A separate statistical study was conducted on 211 SEPT test data provided by a roof support manufacturer and marketing company in the region. Goals were to analyze the database for grip factor (GF) and anchorage stiffness (AS) characteristics using histograms and frequency distributions and, perform regression analyses to relate GF and AS values on the basis of height above coal seam and bolt diameter. Results were used for one stochastic run with variable GF and AS values assigned to different bolts in a roof control plan. Results indicated Gamma distribution best fitted AS and GF data. It was thought that the reinforcement factor for such a bolting layout would be more realistic than assigning a single value of GF and AS to bolts in the model.
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Ljungberg, Jakob. "Pullout test of rock bolts at the Lima Hydropower station : -Assessment of the test method." Thesis, KTH, Betongbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192448.
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During construction of dams, rock bolts are in general installed in the interface between concrete and rock as an extra safety measure against overturning failure. These bolts are however not allowed to be taken into consideration for the stability calculations of large dams. New standards and new design criterias have increased the requirements of the safety of the old dams, leading to a need for expensive rehabilitation and strengthening. It is possible that consideration of these bolts in stability calculations may lead to money being saved. In order to do so more information about the long term strength of these bolts is needed. One way of getting this information has been the destructive testing of old dugout bolts found during reconstruction works. At the Lima hydropower station in Sweden, this kind of testing was made. The test rig used had a design where a piston pressed down on the rock around the bolt in order to pull it out. The question was raised if this could affect the failure load of the bolt. In this thesis, an attempt was made to answer this question using finite element methods. Models of a rock bolt was made in Abaqus, where one model included the piston and one where it was not. The connection between the bolt and the rock was modelled with nonlinear springs and friction, and the results were then compared between the cases and with experimental data. The results showed that the resulting force-deformation curves may be affected by the piston in cases where the dominant failure mode was adhesive failure, which would influence failure loads and deformations. Since so little was known about the properties of the rock and grout at Lima however, it is difficult to say to which extent the test rig has affected these results.
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Holland, David Charles. "The behaviour of resin bonded rock bolts and other anchorages subjected to close proximity blasting." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU603184.
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The provision of a safe and economic rock support system is of primary importance for any excavation programme. If the excavation is to be developed by explosives, then the effect of blast forces on the performance of the rock support system must be considered. A review of current literature has highlighted a general lack of information regarding rock anchorage performance under blast loading. With this in mind, a full scale field test programme was undertaken to study the effect of close proximity blasting on resin bonded rock bolts, during the construction of the Pen y Clip Tunnel in North Wales together with a re-analysis of data from a previous study at the nearby Penmaenbach Tunnel. In both cases, accelerometers were used to monitor vibration and hydraulic load cells recorded the changes in rock bolt load during production face blasting. For the Pen y Clip trials, an additional monitoring system was developed which incorporated load cells positioned along the length of specially made experimental rock bolts. Further trials were conducted at an Edinburgh City Centre site to assess the likelihood of damage to temporary, cement grouted rock anchorages whose fixed anchors were positioned as close as 5m from nearby tunnel blasting. These trials involved the measurement of vibrations, both on the anchor head and down specially constructed boreholes, together with lift off load testing. Analysis consisted of the time and frequency domain examination of the signals, recorded on FM magnetic tape, from the three sets of field trials. Resin bonded rock bolts installed in microdiorite and rhyolite were found to be highly resilient to blasting, even those positioned down to lm from full face tunnel blasting. Temporary anchorages in mudstone were more susceptible to blasting but damage could be limited by monitoring of vibrations and careful control of blast parameters. The frequency response of the anchor head was found to be dependent on the characteristics of the anchorage and the nature of the environment in which it was installed. This raises the possibility that the analysis of spectral responses could form the basis of a technique for the non destructive testing of rock anchorages.
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Rangsaz, Osgoui Reza. "Development Of An Elasto-plastic Analytical Model For Design Of Grouted Rock Bolts In Tunnels With Particular Reference To Poor Rock Masses." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608228/index.pdf.
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The analysis presented in this thesis provides a methodology for grouted bolts design, based on empirical and analytical methods. Hence, the main objectives of this thesis are to offer practical means for better characterisation of poor to very poor rock masses, to better predict support pressure, and to develop an elasto-plastic analytical model for design of grouted bolts in tunnels excavated in such rock masses.
To improve the applicability of the GSI (Geological Strength Index) in poor to very poor rock masses, using Broken Domain Structure (BSTR), Structure Rating (SR), and Intact Core Recovery (ICR), some modifications have been offered, resulting in the Modified-GSI. Applying rock-load height concept and Modified-GSI, an approach to estimate support pressure has been developed. The main advantage of this approach is its applicability in squeezing ground and anisotropic stress conditions. Numerical modelling was carried out in order to adjust the proposed support pressure equation.
Considering convergence reduction approach, an elasto-plastic model based on the latest version of Hoek- Brown failure criterion has been developed for a more effective and practical grouted bolt design. The link between empirical approach and elasto-plastic solution makes it possible to reach more realistic and appropriate bolting pattern design. In this way, the need for the redesign procedure in the convergence reduction approach is eliminated. The results of the proposed elastic-plastic solution have been compared with a numerical model using FLAC2D, and a reasonable agreement was observed. The practical application of the developed methodology is depicted by an analysis of a case study in Turkey.
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Pieslinger, Simon, and Beatrice Lundquist. "Bergbultsmodell - optimalt och minimalt utförande." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-409988.
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Har du någonsin åkt genom en tunnel och undrat hur det kommer sig att det tunga berget över dig inte kollapsar in i detta hålrum? Har du lagt märke till underliga metallpinnar som sticker ut ur väggar och tak? Dessa metallpinnar är bultar, och de är en del av säkerhetsåtgärderna som ser till att tunnlar över hela Sverige är säkra att färdas i. När en tunnel byggs är det viktigt att ta reda på vilka egenskaper som berget har för att kunna avgöra hur stora säkerhetsåtgärder som bör implementeras. Dessa egenskaper kan vara sådant som sprickors utbredning och orientering, hur mycket vatten som finns i sprickorna, vad berget består av och krafter som påverkar berget. Säkerhetsarbetet kring tunnlar kan göra skillnaden mellan liv och död, men hur ska man forska kring detta? I ett labb kan man med hjälp av en modell undersöka vad som fungerar bäst, men även det minsta möjliga för att förhindra kollaps. I detta arbete har en modell som representerar ett tunneltak använts. Den används till undervisning för förståelse av bultar. Modellen var en upphöjd stålram med avtagbar botten, stålramen var kvadratisk med 82 cm sidolängd. I denna ram placerades skruvar och järnvägsmakadam för att simulera ett tunneltak med bultar i mindre skala. Järnvägsmakadam är krossat berg med en kornstorlek på ca 32 till 64 mm. Skruvarna trycker ihop makadamen med hjälp av brickor för att tryck ska uppstå och trycket mäts med tryckgivare som är placerade i modellen. Arbetet som har utförts med hjälp av modellen syftar till att utveckla metoder för hur sådana försök bör utföras i framtiden. Tidigare försök har gjorts och då har det observerats att denna modell har varit stabil när skruvarna spänts till 7 Nm (Newtonmeter) vridmoment och att den kollapsade av minimal påverkan när skruvarna spändes till 5 Nm. Därför gick vi in i detta arbete med hypotesen att modellens lägre gräns för stabilitet fanns strax under 5 Nm. Vid de tidigare försöken mättes inte trycket i modellen och vi hade därför ingen hypotes om detta. Försöken utfördes på olika vis. Skruvarna spändes i olika mönster och med olika vridmoment, makadamen placerades också på olika sätt när modellen byggdes upp. Som resultat ställdes vridmoment och tryck upp i tabeller och diagram. Det skulle visa sig att hypotesen om att den lägre gränsen var nära 5 Nm vridmoment inte stämde. Modellen hölls uppe även när skruvarna endast spändes till 2 Nm. Både när modellens bottenlager var fördelaktigt och ofördelaktigt uppbyggt ur ett stabilitetsperspektiv så höll modellen vid 2 Nm. Lägre vridmoment än 2 Nm kunde inte testas i brist på känsligare verktyg.<br>Have you ever traveled through a tunnel and wondered why the heavy rock above you doesn’t collapse on top of you? Have you noticed the odd metal rods that sticks out from the walls and ceiling? These metal rods are bolts, a part of the security measures that make sure that tunnels all over Sweden are safe to travel through. When a tunnel is built, it is important to know the properties of the rock to be able to assess what type of security measures that need to be applied. These properties can be fractures and their orientation, the composition of the rock and the forces that are present. The security work regarding tunnels can be the difference between life and death, but how can research in this field be carried out? Model experiments in a laboratory can be of great use to investigate the most efficient way to stabilize the rock, but also the minimal effort required to prevent collapse. For this report a model that represents the roof of a tunnel has been used. The model is used for learning about rock bolts and consisted of an elevated 82 cm square steel frame with a detachable floor. Bolts and crushed rock were placed within the frame to simulate a tunnel roof in a smaller scale. The crushed rock had a grain size of 32 to 64 mm. The bolts in combination with small metal discs compress the rock to produce pressure, and the induced pressure is measured with pressure indicators placed within the model. The experiments conducted with this model aims to develop potential new methods for future uses and experiments. Previous experiments with this type of model have shown that the model is stable when the bolts have been tightened to 7 Nm (Newton Meters) torque, and subsequently collapsed with minimal influence when the bolts were tightened to 5 Nm. Therefore, the hypothesis of this report was based on previous experiments, where the lower limit of the model seemed to be close to 5 Nm. The previous experiments didn’t measure the pressure throughout the strained rock mass, and therefore there is no hypothesis regarding this. The experiments were conducted in different ways. The bolts were tightened both in different patterns and with different torques, and the crushed rock were placed differently throughout the experiments as the model was being built. The following result of torque and pressure were presented in tables and graphs. The result showed that the hypothesis regarding the lower boundary being close to 5 Nm was not correct. The model stayed in place even when the bolts were tightened as low as 2 Nm. The model was stable at 2 Nm both with a favorable and unfavorable bottom layer of rock. Therefore, it is required to tension the bolt with torque lower than 2 Nm to determine the lower limit of stability, but that could not be tested due to the lack of proper tools.
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Toscano-Alor, Carlos, Antoni Castillo-Rodil, Humberto Pehovaz-Alvarez, Carlos Raymundo, Nestor Mamani-Macedo, and Javier M. Moguerza. "Hydrabolt and Split Set Rock Bolt Selection Method Under the Bieniawski Rock Mass Rating for Improving Horizontal Access Support in Peruvian Mid-Scale Mining Activities." Springer, 2020. http://hdl.handle.net/10757/656167.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.<br>This paper illustrates how the Bieniawski rock mass rating geomechanics classification, within the support system used by medium-scale mining companies, allows for the development of a new anchor rock bolt selection method aimed at improving horizontal access stability in underground mines. However, this case study only seeks to select the most efficient anchor rock bolt for any given horizontal access. A proper support selection method is very important for mining companies because this decision will safeguard both miners and mining infrastructure. This selection process will ultimately prevent fatal accidents, which is critical for mining companies today, especially considering the constant operation standstills reported in Peru.
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Weckert, Steven Mining Engineering Faculty of Engineering UNSW. "Anchorage and encapsulation failure mechanisms of rockbolts ??? stage 2." Awarded by:University of New South Wales. School of Mining Engineering, 2003. http://handle.unsw.edu.au/1959.4/19219.
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The Fully Encapsulated Resin Bolt (FERB) is widely utilised for strata control and ground support in civil and mining applications worldwide, with approximately 6 million installed per annum by the Australian coal mining industry. Independent studies have concluded that 30-35% of these rockbolts, which represents an annual expenditure of $40 million, are ineffective. The anchorage and failure mechanisms of FERB are yet to be quantified, and support systems are designed primarily from empirical rather than scientific methods. There are no standardised methods of assessing FERB components, installation techniques and support behaviour. The majority of research into FERB support systems remains commercial intellectual property, with little information released into the public domain. This thesis investigated several variables of FERB support systems, and also examined differences between field and laboratory pull-out test load distributions. This research was conducted in two phases, with Phase 1 seeking standardised methodology and repeatability in results, while Phase 2 further refined Phase 1 methods and extended the range of tests. The results in both phases were encouraging, with reasonable repeatability attained in all testing series. The findings included: ??? Annulus Thickness: There was little change in load capacity with small annulus thickness, however the maximum peak load (MPL) significantly reduced once annulus thickness exceeded 4mm ??? Resin Installation Spin Time: Underspinning of cartridge resin was found to have an insignificant effect on rockbolt load/deformation characteristics. Overspinning, however, led to a dramatic reduction in anchorage performance with a lessening in both MPL and stiffness ??? Rockbolt Load Transfer: The magnitude of an applied load reduced to zero along the length of the rockbolt, being greatest nearest the rock free surface (the point of load application). An exponential reduction was found when tested in the manner of laboratory tests, with the loading jack reacting against the free surface. This reduction was linear when the load was applied as in the field, with no load placed on the free surface This basic investigation into FERB support systems has validated many empirical understandings of rockbolts, while highlighting the need for further testing into several key areas.
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Kostecki, Todd. "The Instrumentation of Primary Roof Bolts in a Room-and-Pillar Mine and the Modeling of their Performance." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1120.
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This thesis is directed towards the comparison of active and passive bolts systems to reveal which system shows the most favorable behavior for improved performance, safety and cost. This was achieved through the incorporation of new technologies, field data, numerical modeling and established theories in ground control analysis. All in all, a better understanding of the quasi-static behavior of underground coal mine roofs has been attained. Over the summer of 2010, the Department of Mining and Mineral Resource Engineering at Southern Illinois University Carbondale, in conjunction with Andy Hyett of YieldPoint Inc., Peabody and the National Institute of Occupational Safety and Health (NIOSH), installed over one hundred and seventy instrumented extensometers, closure meters, shear-meters, passive rebar roof bolts, tension rebar roof bolts, and double lock rebar roof bolts at three coal mines. Two of the three coal mines were room-and-pillar mines and the other a longwall mine. Data was routinely collected over a nine-month period to analyze shearing, dilation, and axial bolt loading occurring within the rock mass, and entry closure occurring between the excavation hanging-wall and foot-wall. Based on bolt loadings, shear, axial behavior and statistical analysis, initial results indicate that active roof bolts do not show superior performance for the added cost. Active bolts seem to show no difference from passive bolts in the initial loading phase either, indicating that tension bleed-off is a concern soon after installation; however, this observation was not captured, as the data loggers were not intrinsically safe. Considering the modeling results, the trends in axial loading seem to be calibrated but the magnitudes are not. Computer modeling also shows the potential to accurately model in situ bolt performance; however, challenges remain in obtaining a good match between numerical modeling and field observations.
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Divi, Suresh Chandra. "Electrochemical corrosion study of structural materials in complex multi-ionic solutions." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3307140.
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Nutakor, David. "Design and evaluation of a virtual reality training system for new underground rockbolters." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Nutakor_09007dcc80672480.pdf.
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Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.<br>Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 1, 2009) Includes bibliographical references (p. 229-234).
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Azevedo, Maurício Birkan. "Ancoragem em rocha : avaliação da adesão entre nata de cimento e rochas sedimentares em ensaios de laboratório." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/179464.
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A presente dissertação versa sobre a determinação do parâmetro de adesão entre nata de cimento e rocha. Este parâmetro é de fundamental importância no dimensionamento de grampos e tirantes ancorados, sistemas de contenção frequentemente executados que utilizam da técnica de ancoragem. Ensaios de arrancamento in loco são comumente realizados para avaliar essa tensão de aderência, no entanto, muitas vezes, apenas se tornam viáveis financeiramente durante a etapa de execução das obras. A metodologia Composite Cylinder Bond Test (CCBT) permite a determinação da adesão de maneira mais simples e com menor custo, por meio de ensaios de laboratório utilizando corpos de prova mistos de rocha e nata de cimento, sendo, por isto, uma interessante alternativa para a etapa de definição paramétrica de projetos. Neste contexto, foram estudadas três litologias sedimentares do município de Caçapava do Sul/RS – aqui chamadas de conglomerado, arenito muito fino e arenito médio – pertencentes à Formação Varzinha. A caracterização dessas litologias foi realizada por meio de lâminas delgadas e outros ensaios de caracterização de laboratório A classificação textural do conglomerado é de conglomerado arenoso, o arenito muito fino é classificado como arenito lamoso e o arenito médio é classificado como arenito. Do ponto de vista composicional, o arenito muito fino é classificado como arcóseo, enquanto o arenito médio é classificado como arcóseo lítico. Noventa ensaios CCBT, além de ensaios de resistência à compressão simples das rochas e da nata de cimento foram realizados. As tensões de adesão médias obtidas dos ensaios de laboratório foram de 2,52 MPa para o conglomerado, 1,84 MPa para o arenito muito fino e 1,43 MPa para o arenito médio. Foi realizada uma avaliação de intervalos de confiança de valores de tensão de adesão, conforme a distribuição t-student. Concluiu-se que não apenas a resistência das rochas influencia nessa capacidade de adesão, mas também a capacidade de absorção d’água e a porosidade. Maiores valores dessas duas propriedades na rocha favorecem a adesão entre os dois materiais. Os valores encontrados em laboratório são compatíveis com dados de literatura de campo em rochas similares.<br>This dissertation evaluates the determination of the adhesion parameter between cement grout and rock. This parameter is of great importance on design of two systems frequently executed that use the technique of anchoring: rock anchors and bolts. Pull out field tests are commonly carried out to evaluate this bond strength, however, they are normally only economically feasible during the construction stage. The Composite Cylinder Bond Test (CCBT) methodology allows the adhesion determination in a simpler and cheaper way, by laboratory tests using mixed samples of rock and cement grout. Therefore, the CCBT is an interesting alternative to project definition of adhesion values. In this context, three different sedimentary lithologies from Caçapava do Sul/RS, Southern Brazil, were studied. The lithologies – called here as conglomerate, fine sandstone and medium sandstone – belong to Varzinha Formation. The characterization of these lithologies were made by thin sections and characterization laboratory tests The textural classification of the conglomerate was sandy conglomerate, the fine sandstone was classified as muddy sandstone, and the medium sandstone was classified as sandstone. In the view of their composition, the fine sandstone was classified as arkose, while the medium sandstone was classified as lithic arkose. Ninety CCBT tests, besides unconfined compression tests on rock and cement grout specimens were carried out. The average adhesion values obtained from laboratory tests were 2,52 MPa for the conglomerate, 1,84 MPa for the fine sandstone and 1,43 MPa for the medium sandstone. An evaluation of confidence intervals of adhesion was also carried out, according to t-student distribution. It was concluded that the adhesion strength was influenced not only by the unconfined compressive strength of the rocks, but also by their water absorption and porosity. Larger values of these two properties increased the adhesion between the two materials. The values obtained from laboratory tests are compatible with literature field data in similar rocks.
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Fouhy, David, and Bayona Francisco Ríos. "Reliability-Based Analysis of Concrete Dams." Thesis, KTH, Jord- och bergmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176867.
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Dams are designed and assessed based on traditional factor of safety methodology. Several drawbacks of this approach exist; for example varying failure probability for structures where the factor of safety is the same. This traditional factor of safety methodology imposes conservative assumptions in terms of both design and analysis. A probability-based analysis has been suggested to account for the omission of uncertainties and provide a less conservative analysis (Westberg & Johansson, 2014). Through the stability analyses of three existing dam structures, a minimum level of reliability or maximum failure probability may be calculated with the ultimate goal of defining a target safety index (β-target) for buttress and gravity dams. These analyses shall in turn contribute to the formulation of a probability-based guideline for the design and assessment of Swedish concrete dams. This probability-based guideline shall be known as the ‘Probabilistic Model Code for Concrete Dams.’ The calculations carried out in this study adhere to the methodologies and specifications set out in the preliminary draft of the Probabilistic Model Code for Concrete Dams. These methodologies encompass analyses within two dominating failure modes for concrete dams; sliding stability and overturning stability. Various load combinations have been modelled for each dam structure to account for the probabilistic failure of each dam under commonly occurring circumstances. A parametric study has been carried out in order to provide insight into the contribution that existing rock bolts provide to the stability of each dam. Furthermore, a study has been carried out into the existence of a persistent rock joint or failure plane in the rock foundation and the effects its presence would have on the sliding stability of a dam. Finally a discussion had been carried out in order to provide suggestions into the formulation of a target safety index through the data envisaged by our analyses for the design and assessment of Swedish concrete dams.
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Pinazzi, da Silva Ribeiro Pammela Caroline. "Analysis of Rock Bolt Behaviour under Shear and Combined Load and an Improved Rock Bolt Design Methodology." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78727.
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Rockbolts are subjected to different tensile and shear loads along their length that change with mining. Common rockbolt design methodologies, however, assume that they are loaded in tension only (the most common design assumption) or pure shear. Laboratory tests were conducted with rockbolts under different loading conditions including both tensile and shear together. From the results, a new methodology is proposed where the tensile capacity is reduced by 50% as this accounts for most loading scenarios.
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Tully, David Michael. "Rock bolt reinforcement systems for coal mine roadways." Thesis, University of Newcastle Upon Tyne, 1987. http://hdl.handle.net/10443/307.
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The utilisation of rock bolting for the support of British coal mine roadways can improve roadway strata conditions and, by permitting a reduction in the density, cross-section or total elimination of steel standing support, can produce considerable savings in roadway support costs. This study reviews worldwide experiences in the use of rock bolt reinforcement techniques to enhance the stability of coal mine roadways. Details of methods of geotechnical design data acquisition and assessment are given as well as a critical study of various empirical, analytical and observational methods of tunnel support design. The use of scale model studies is shown to be particularly effective for the design of rock bolt support systems for coal mine roadways. With reference to numerous case studies, descriptions are given of rock bolt systems available and their suitability to specific mine roadway conditions is discussed. Installation procedures and equipment are also reviewed. It is the author's intention that this study should be used as the basis for further detailed investigation of specific aspects of rock bolt support systems. A number of recommendations are made as to the fields in which further research should be undertaken.
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De, Zoysa Agampodi Ushan. "Dynamic Testing of Mesh and Rock Bolt Support Systems." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/1763.
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Combination of reinforcement and support systems are used to stabilize underground excavations. Results for laboratory testing under dynamic loading conditions are provided. Ground support schemes consisting of threaded bar and support elements such as weld and chain link mesh were studied. The results were compared using force- displacement and energy dissipated versus deformation. The combined systems were subjected to input velocities ranging from 5.4m/s to 7.3m/s with resulting input energy ranging from 27kJ to 57.5KJ.
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Luo, JunLu. "A New Rock Bolt Design Criterion and Knowlwdge-based Expert System for Stratified Roof." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28512.
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Since its development in the 1920s, bolting has become the most dominant support method in underground construction. However, because of the geological environment, the design process for roof bolt systems is an art rather than a science. To quantify the selection of bolting systems a MSBT (minimum solid beam thickness) approach was developed. The ultimate goal of this bolt design paradigm was achieved by optimizing bolt length, bolt density, and bolt pretension during installation. The impact of the number of strata layers within bolting range and pretension applied to bolts upon the stability of an opening was investigated using FLAC model. Four statistical models for predicting optimum bolt supports using a minimum solid beam thickness were established, and based on these results, a design criterion was proposed.
To meet support needs in various geological and geotechnical settings, a variety of bolt types have been developed. The installation of such bolt-based support systems is often complex and specialized, and thus imposes a challenge for engineers to identify the specific cause and to take appropriate remedial measures once problems arise. To solve these problems, a knowledge-based expert system (KBES) has been developed. The knowledge base includes the data accumulated from years of laboratory and field investigations conducted by the Mine Safety and Health Administration of the US Department of Labor. A user-friendly Windows-based program was implemented using KAPPA environment. After identifying the problem, the KBES searches its knowledge base and reasons out the most likely, secondary, and other potential causes, then provides solutions according to users' input.
The results of this research are validated and demonstrated using case studies.<br>Ph. D.
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Carlsson, Martin. "Förstärkning av betongdammar med slaka bergbultar : en studie av bultars samverkan med bergsprickor." Thesis, KTH, Jord- och bergmekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168638.
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Internationellt sett är merparten av de dammbrott som ägt rum kopplat till grundläggningen. Det är oftast kopplat till att det finns osäkerhet i de rådande grundförhållandena. Som extra säkerhet, installerades bergförankringar som en åtgärd att behandla osäkerheterna i de rådande grundförhållandena. I Sverige är merparten av kraftverksdammarna uppförda mellan 1940-och1960 talet. Det var inte ovanligt att cementingjutna slakarmerade kamstål sattes under dammarna som en extra säkerhet. När dessa bergbultar installerades var kunskapen om dess verkningssätt begränsat, då teorier om bergbultens verkningssätt började utvecklas under 70- och 80-talet. Vid dimensionering av bergförankring till dammbyggnader i nutid tillämpas RIDAS, Kraftföretagens riktlinjer för dammsäkerhet, som är upprättade av de Svenska dammägarna. I RIDAS framgår att när det endast föreligger en risk för glidning får rostfri slak armering användas som bergförstärkning och dimensioneras enligt BBK, Boverkets handbok för betongkonstruktioner, kap 3.11 "kraftöverföring genom fog". Examensarbetets inledande del är en litteraturstudie som är inriktad på den forskning som har bedrivits rörande bergbultens principiella beteende när den går till brott. Vidare i litteraturstudien har en beräkningsteori som utvecklats av Holmberg (1991) vilken beskriver en bergbults bidrag till bärförmågan för en bergspricka studerats i detalj. Teorin har även jämförts mot experimentellt utförda skjuvförsök av bergbultar. Med hjälp av den teori som presenterades i litteraturstudien genomfördes en stabilitetsanalys av en betongmonolit i utskovsdammen på en typisk Svensk vattenkraftstation. Målet var att undersöka möjligheten för bergbultarna, som är installerade i berggrunden att samverka, med ett antaget horisontell sprickplan under dammbyggnaden. Det bidrag till bärförmågan som bergbultarna och bergsprickan utgör till totalstabiliteten jämförs med de krav som ställs i RIDAS. I slutet av arbetet förs en diskussion om de presenterade teoriernas förmåga att beskriva bultens bärförmåga under olika förhållanden samt hur en bergförankring bör utformas för att säkerställa dragbrott i bulten. Efter det ges förslag på forskning rörande bergbultning som kan utföras, för att bättre förstå bergbultens principiella beteende.<br>Internationally, the majority of dam failures that have occurred are related to the foundation. It is usually linked to the large uncertainty in the actual propertys of the foundation. A common measure was to install rock bolts as an extra precaution in the subgrade to handle the uncertainties of the subgrade. In Sweden, most of the hydroelectric dams were constructed between 1940 and 1960. It was not uncommon that cemented reinforced rock bolts were installed in the subsoil as an extra precaution. When these rock bolts were installed, understanding of their stress handling was limited, considering the fact that the theory of the rock bolts behavior was first studied between 1970 and 1980. The first part of this thesis is a thorough review of the literature which focuses on the research that has been conducted on the fundamental behavior of the rock bolt when it fails. In this study, a computational theory describing a rock bolts load contribution to a rock joint is presented, verified against experimental shear tests performed on rock bolts. In the design of rock anchoring to the construction of reservoirs in the present application RIDAS, Power Companies' guidelines for dam safety, the guidelines is formed by the Swedish dam owners. Accordingly to RIDAS where there is only a risk for a slide in a rock joint stainless untensioned rock bolts are allowed to be used fore support and dimension according to BBK, Boverkets handbok för betongkonstruktioner, kap 3.11 "kraftöverföring genom fog". Using the theory presented in the literature review, a stability analysis of a monolith on Långbjörn PowerStation was carried out. The goal was to explore the possibility of rock bolts installed in the subgrade to interoperate with a rock joints under the dam building. The load contribution of rock bolts and the rock joints has to overall stability is compared with the requirements of the Swedish power company’s guidelines for dam safety, RIDAS. At the end of the thesis, the presented theories’ applicability under different conditions and how a rock anchor should be designed to be as efficient as possible is discussed. In conclusion, suggestions for research that can be performed on bolting, to gain better understanding of the fundamental behavior of the rock bolt are presented.
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Singh, Prasoon. "Integration of Instrumentation and Computer Modelling to Understand and therefore Better Design and Represent the Rock bolt Support Behaviour." Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/88908.
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A safe and efficient ground control system is one of the most vital components of an underground mine’s operations. Current rockbolt ground reinforcement design methods do not consider the actual in-situ behaviour of the rockbolt. Instrumented rock bolts can be used to understand the actual rockbolt response under different loading conditions. Work done in this thesis aims to integrate the actual in-situ response of rockbolt with improved numerical modelling procedures for designing better ground support.
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Falck, Anna-Maria. "Seglets introduktion i Skandinavien : En undersökning kring indikationer för seglets uppkomst under bronsåldern." Thesis, Uppsala universitet, Arkeologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-323844.
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The first image depicted of sail are in Egypt and dated to the late fourth millennium BC. Around the third millennium BC the introduction of sail began in the eastern Mediterranean.Some researchers do not believe that sail have existed in Scandinavia until about 8th century AD. The reason for this is because of the lack of archaeological evidence. The question that may be asked is whether it is reasonable that it took about 3000-3500 years for the sail to getto Scandinavia from the eastern Mediterranean? The purpose of this essay is to examine and describe which indications that are available to support the occurrence of the sail in Scandinavia during the Bronze Age. Indications will be studied in trade contacts, rock art boats, and boat constructions.The study is relevant to gain a greater understanding of the Scandinavia´s movements on the open water, trade contacts and boat construction during the Bronze Age.The result reveals that Scandinavia probably had an indirect contact with areas that used sails. Indications for contact with areas in Europe are shown by imports and exports of amber,metals, artefacts and similarities between rock carvings depicting ships. Some of Scandinavia´s rock art boats seem to show attributes such as mast and sails, but it is difficult to get an understanding by looking at the pictures only. One idea is that a change is required in the keel of the boats for sailing. The result reveals that an alternative to keel may have been double steering oars. From an experimental archaeological survey of Bengtsson & Bengtsson (2011), it seems that Scandinavian Bronze Age boats have managed to get sailed.<br>Den första avbilden av segel finns i Egypten och dateras till ca år 4000 f.Kr. Runt ca år 3000f.Kr. uppkommer segel i östra Medelhavsområdet, Persiska viken och möjligen Indien. I Skandinavien anser en del forskare att segel inte har existerat förrän ca 700 år e.Kr., då inga arkeologiska bevis för mast eller segel förekommer. Frågan som kan ställas är om det är rimligt att seglet har tagit omkring 3000-3500 år att nå Skandinavien från östra Medelhavsområdet? Syftet med studien är att undersöka och redogöra för vilka indikationer som finns för att seglet kan ha förekommit i Skandinavien under bronsåldern. Frågeställningarna har varit: Var Skandinavien i kontakt med områden som nyttjade segel eller hade kunskap om dem under bronsåldern? Vilka belägg finns för att kontakter med områden i Europa harförekommit? Kan hällbilderna från bronsåldern i Skandinavien tolkas ha mast och segel? Vad krävs i en båtkonstruktion för att den skall kunna segla? Har skandinaviska bronsåldersbåtar haft en båtkonstruktion som klarat av segling? Teorin som antagits i föreliggande uppsats har varit Bengtsson & Bengtssons (2011) som antar att segel kan ha uppkommit tidigare i Skandinavien, möjligtvis redan under bronsåldern. Studien utfördes genom en litteraturöversikt och metoden var empirisk och komperativ då forskares åsikter, antaganden och resultat från deras undersökningar jämfördes och presenterades utifrån frågeställningarnai analysen. En avgränsning har funnits genom att undersökningen främst berört områden därmast och segel kan tolkas ha förekommit samt på platser där tidigare forskning behandlat Skandinaviens hällristningar. Ytterligare avgränsning har funnits genom att en ingåendebeskrivning av hur båtkonstruktionen hos bronsåldersbåtarna såg ut, ej har angivits i detalj, utan i stället har de funktioner som ansetts viktiga för en möjlig introduktion av segel i Skandinavien främst undersökts. Resultatet visar utifrån analysen och diskussionen kring frågeställningarna att indikationerframkommer för att möjligheten finns för att segel förekom i Skandinavien under bronsåldern.
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Bengtsson, Boel. "Sailing rock art boats : a reassessment of seafaring abilities in Bronze Age Scandinavia and the introduction of the sail in the North." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386800/.
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This thesis examines the basis for the current belief that the introduction of the sail in the North occurred between the 7th or 8th and the 10th centuries AD, almost a thousand years later than on the British Islands and almost 3000 years later than in the Mediterranean. The foundations for this reassessment of the potential timing and development in the use of the sail derives mainly from an examination of the Bronze Age rock art (1800–500 BC) in southern Scandinavia containing imagery of boats with attributes that can be interpreted as masts and sails. In combination with experimental sail trials in Bronze Age type boats and by comparing this material to available research on the transition from paddling to sailing in ancient Egypt and Oceania, the author argues that the use of sail as a complement to paddling would have formed an integral part of the formation of centres of power in Scandinavia in the early Bronze Age. This in turn would have permitted more frequent communication, helping to expand, maintain and control power. The transitions from downwind sailing abilities to abilities to sail within a wider range might have occurred relatively swiftly between c. 1550–1300 BC, and might be directly linked to the expansion of Scandinavian centres of power during the same period, allowing for increased flexibility, both in terms of manpower, range and choice of routes with the use of a wider range of weather conditions. The emergence of the sail would primarily have been driven by increased needs for the movement of people and goods across short medium- and long distances – a process where competition by rivalling chiefs might also have played part. Furthermore, it is here suggested that the developments in sail and boat technology in the North were the result of incremental and gradual changes that eventually resulted in the boats and sails as used in the Viking Era.
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Kobielusz, Petr. "Městský okruh Blanka, tunel Královská obora - ražená část, stavebně technologická příprava stavby." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226100.
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My thesis is focused on process preparation and building construction technology of primary lining road tunnel, implemented in city part of Troja in the capital city Prague. Specifically it is a part of tunnel complex Blanka. The name of this part is Kralovská obora. If the all tunnel parts are built this tunnel complex Blanka can be complemented to already opened tunnels Zlíchovský, Mrázovka and Strahovský which are the part of city traffic circle. This technology preparation includes schedules and financial plans of the building, technological prescription for the primary tunnel lining, safety plan, control and trial/test plans, environmental plan, project of construction site, design of the main working machines, items budget of the north tunnel tube, coordination situation plan with wider relationships transport routes and technical report of building technological project.
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Larsson, Minna, and Klara Skoog. "Modellförsök avseende bergspänningars betydelse för spännvidd av valv." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411059.
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Tunnels and anthropogenic underground cavities are a very natural part of our everyday modern life. Especially in larger cities such as Stockholm where the infrastructure reaches far above ground level as well as deep below the surface. Metro, commuter train, cars along with many other ways of transportation have been moved below the surface the last century. Before then there were neither the technology nor the knowledge of how tunnels and underground cavities should be constructed so that the safety is not neglected. Several different forces are present in the bedrock below us, such as the weight of the overlying rock/strata and stresses due to tectonic, thermal, or hydrostatic forces among other. Knowledge of these forces and stresses are essential so that you will not get a piece of rock falling on your head on your way home from work with the metro. In most of the cases the roof of tunnels or underground cavities are shaped like an arch, and the stability of these arches depends on several aspects. At excavation of rock, there are natural arches in the bedrock. However, the stability of these arches depends on stresses, amount of overlying rock and the presence of rock joints and fractures (amount, directions and the characteristics of rock joints and fractures are important). These among other aspects determine the stability and the size of the arch. The natural arch in a manmade underground cavity or tunnel is seldom sufficient for it to be safe enough for humans to be in. There is a need for reinforcement of different kinds, where rock bolting is one of the most common. This bachelor’s thesis used a model to simulate arches in tunnels and cavities. The model which simulated an arch was an uplifted box (820x820x250 mm) with railroad macadam, pressure gauges and systematically placed bolts (threaded rods with nuts and washers at each end). The bottom part of the uplifted box could be removed. With a torque wrench the macadam was subjected to different torques, and the bolts were then removed according to a pattern to see at which torques and stresses the model held. The purpose of the thesis was to develop a refined method for bolt model so that controlled experiments could be done. The purpose was as well to determine how important the stresses in the rock is for the span of the arch. The thesis should also function as an instruction for future experiments at the university. According to the results of the experiments, both lower stresses and higher stresses gave rise to a large arch span. In many cases, an even stress distribution in the model resulted in a greater arch span, but in some cases not. More experiments would have to be done to reach a reliable result. Therefore, there is great potential for other students to continue these experiments.<br>Tunnlar och bergrum är i modern tid så vanliga att många knappt märker att en befinner sig i ett bergrum i sin vardag. Inte minst i större städer såsom Stockholm där infrastrukturen sträcker sig högt över markytan såväl som långt ner i berggrunden. Tunnelbana, biltrafik, tågtrafik är några transportsätt som ofta har förflyttats under jord det senaste århundradet. Innan dess fanns varken tekniken eller kunskapen om hur tunnlar och bergrum ska konstrueras för att säkerheten ska vara tillräckligt hög. I berget under oss finns det flera krafter som verkar, däribland vikten från ovanliggande berg, spänningar av tektoniska, termala eller hydrostatiska ursprung. Kunskap om dessa spänningar är väsentliga för att du inte ska få ett bergblock i huvudet när åker hem från jobbet med tunnelbanan. I de allra flesta fall har bergrummet eller tunneln ett tak format som ett valv, och stabiliteten av dessa valv beror på flera aspekter. När berguttag sker finns det en naturlig valvverkan som existerar i berget. Höga spänningar, mängden överliggande berg och förekomsten av sprickor (mängd, riktningar och egenskaper hos sprickorna) är några faktorer som påverkar stabiliteten av valvet och hur stort valvet kan vara. Den naturliga valvverkan i en antropogen tunnel är sällan tillräcklig för att valvet ska hålla och vara säkert för människor ska vistas i. Det krävs bergförstärkning av olika typer, där bultförstärkning är vanligt förekommande. Arbetet gick ut på att simulera valv i berg med hjälp av en modell. Modellen efterliknar ett tunneltak och består av en upphöjd låda (820x820x250mm) med järnvägsmakadam, systematiskt placerade bultar (stänger med bricka och mutter i varje ände) och tryckmätare. Lådan har en avtagbar botten. Experimentet gick ut på att spänna upp makadammet med olika vridmoment, och se vid vilka moment det håller när bultarna succesivt tas bort i en viss ordning. Syftet med arbetet var att ta fram en förfinad metodik för bultmodell så att kontrollerade försök kan genomföras samt fastställa spänningars betydelse för spännvidd av valv. Uppsatsen ska även kunna användas som instruktion för framtida försök vid universitetet. Resultatet visade att en stor spännvidd uppstod vid både höga och låga spänningar. En jämnare spänningsfördelning gav i flera fall en större spännvidd, men i andra fall inte. Fler försök hade behövt göras för att säkerställa ett pålitligt resultat och det finns därmed stor potential att bygga vidare på experimenten som gjorts.
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Arleij, Axel, and Mattias Åhlander. "Bultförstärkning av berg vid konventionell tunneldrivning : En jämförelse av kamstålsbult och PC-bult." Thesis, KTH, Byggteknik och design, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231013.
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Vid tunneldrivning inom infrastrukturprojekt i Sverige är den mest förekommande bergbulten för permanenta förstärkningar den konventionella kamstålsbulten. En ingjuten bult utan förspänning. Montaget sker genom att med handkraft pressa in bulten i ett cementfyllt borrhål. Detta ger upphov till spill av cement och stor fysisk ansträngning, när tusentals bultar monteras i varje projekt. Den permanenta bergssäkringen uppnås först när den omslutande cementen har härdat. Detta medför ett moment i bergförstärkningsskedet där entreprenören måste säkra tunneln med temporära driftbultar. För att undvika temporärbultning kan en förspänd ingjuten bult användas som permanent bult. Exemplet på en sådan bult är PC-bulten. Vid montage ger den en omedelbar driftsäkring och en permanent förstärkning genom injektering via det inre röret. Bulten blir då helt ingjuten av cement. Syftet med studien är att jämföra PC-bulten med kamstålsbulten. Studien undersöker den förmodade nyttan i belastningsergonomi och ekonomi av att använda PC-bulten som permanent förstärkningsbult. Genom att utföra en styrd observation på ett studiebesök där tunneldrivning med bergförstärkning skedde har de båda bultarnas montagearbete jämförts ur belastningsergonomisk synpunkt. För att utreda skillnader i arbetsvolym och tidsåtgång utfördes beräkningar på ett sammanställt bultprotokoll. Beräkningarna visar vilken förstärkningsbult som medför den lägsta kostnaden för bultförstärkning. Av resultatet i studien framgår det att det finns en stor potential i ett framtida användande av PC-bulten som permanent bult vid tunnelförstärkning. Potentialen ligger i en klart förbättrad arbetsmiljö i avseendet belastningsergonomi och i den tidsvinst framtida projekt kan nyttja.<br>The conventional rebar bolt, a grouted bolt with no pre-stress, is the most commonly used rock reinforcement bolt for tunneling in Swedish infrastructural projects. The assembly takes place by manually pushing the bolt into a borehole filled with grout. This gives rise to spillage and great physical exertion when thousands of bolts are mounted in each project. Permanent safety is only achieved when the surrounding cement has cured. This entails a moment in the rock reinforcement stage where the contractor must secure the tunnel with temporary operating bolts. To avoid temporary bolting, a pre-stressed bolt can be used as a permanent bolt. An example of such a bolt is the PC-bolt. When assembled, it provides immediate operational safety and permanent reinforcement by injection through the inner pipe. The bolt is then completely sealed with grout. The purpose of the study is to compare the PC-bolt with the rebar bolt. The study explores the supposed benefit of economics and load ergonomics of using the PC-bolt as a permanent reinforcement bolt. By conducting a controlled observation on a field study to a site where tunneling with rock reinforcement occurred. The assembly of the two bolts has been compared out of a load ergonomic view point. In order to investigate differences in work volume and time, calculations were made on a compiled bolt protocol. The calculations show which reinforcement bolt results in the lowest cost of the assembly. The result of the study shows that there is a great potential in the future use of the PC-bolt as a permanent bolt for tunneling. The potential lies in a clearly improved work environment regarding ergonomic loads and more time efficient installation that can be utilized in future projects.
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Вівчаренко, Олександр Васильович, Александр Васильевич Вивчаренко та O. V. Vivcharenko. "Обґрунтування параметрів підвищення стійкості виїмкових виробок із застосуванням податливої рамно-анкерної системи". Thesis, Видавництво НГУ, 2012. http://ir.nmu.org.ua/handle/123456789/169.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.15.02 – Підземна розробка родовищ корисних копалин. Держа-вний вищий навчальний заклад «Національний гірничий університет», Дніпропе-тровськ, 2012.<br>Диссертация на соискание ученой степени кандидата технических наук по специальности 05.15.02 – Подземная разработка месторождений полезных иско-паемых. Государственное высшее учебное заведение «Национальный горный университет», Днепропетровск, 2012.<br>Candidate of technical sciences’ dissertation on specialty 05.15.02 – Underground mining of mineral deposits. State higher educational establishment “National Mining University”, Dnipropetrovs’k, 2012.<br>У дисертаційній роботі надано нове рішення актуальної науково-технічної задачі ресурсозберігаючого управління проявами гірського тиску в підготовчих виробках шахт Західного Донбасу за рахунок саморегулювання станом системи «масив-рама-анкер» забезпеченням адаптивних режимів опору рамно-анкерного кріплення, яке має просторово-піддатливе міжелементне з’єднання.
Захищаються встановлені закономірності інтенсивного навантаження слаб-ких шаруватих порід боків виробки з боку двох утворень підвищеної жорстокості – зміцненої анкерами армопородної вантажонесучої плити в покрівлі й цілісного ви-сокоміцного вугільного пласта, у результаті чого активно проявляється так званий «ефект штампа», коли знеміцнені від концентрацій напружень слабкі породи в бо-ках виробки видавлюються в її порожнину, деформуючи стояки рамного кріплен-ня; із цієї причини виявлене стабільне утворення в стояках рами великих областей пластичного стану їх матеріалу (у районі опор стояків довжиною до 0,5-0,6 м і в районі п'яти склепіння довжиною 0,8-0,9 м) незалежно від структури прилеглих порід, площі перерізу виробки й застосовуваного номера спецпрофілю СВП рам-ного кріплення. Виявлено основну причину – роздільну роботу анкерів і рам по опору проявам гірського тиску. Доведено, що завдяки просторово-піддатливим зв'язкам анкерів і рам у єдиній вантажонесучій системі підтримується процес са-морегулювання навантаження на основні несучі елементи (зміцнені породи, раму й анкери), у результаті якого вантажонесуча система в цілому наближається до ре-сурсозберігаючого стану рівноміцності елементів, адаптуючись у просторі до збу-рювань гірського тиску.
Розробленим методом розрахунку параметрів рамно-анкерного кріплення, аналітичними й експериментальними дослідженнями доведена можливість зни-ження металоємності рамного кріплення до 30% за рахунок створення просторо-во-піддатливих зв’язків з анкерами.
Розроблена методика розрахунку, яка поєднує прогноз проявів гірського тиску (з вибором рамного кріплення) з розрахунком самих механічних зв’язків і вузлів їх кріплення на анкерах і рамах. Дослідно-промислові випробування удо-сконаленої конструкції рамно-анкерного кріплення проведені на шахтах ПАТ «Павлоградвугілля».<br>Защищаются установленные закономерности интенсивного нагружения слабых слоистых пород боков выработки со стороны двух образований повы-шенной жесткости – упрочненной анкерами армопородной грузонесущей плиты в кровле и целостного высокопрочного угольного пласта, в результате чего активно проявляется так называемый «эффект штампа», когда разупрочненные от концен-траций напряжений слабые породы в боках выработки выдавливаются в ее по-лость, деформируя стойки рамной крепи; по этой причине выявлено стабильное образование в стойках рамы обширных областей пластического состояния их ма-териала (в районе опор стоек длиной до 0,5-0,6 м и в районе пяты свода длиной 0,8...0,9 м) независимо от структуры близлежащих пород, площади сечения выра-ботки и применяемого номера спецпрофиля СВП рамной крепи. Выявлена основ-ная причина – раздельная работа анкеров и рам по сопротивлению проявлениям горного давления. Доказано, что благодаря пространственно-податливым связям боковых анкеров и стоек рам в единой грузонесущей системе поддерживается процесс саморегулирования нагрузки на основные несущие элементы (упрочнен-ные породы, раму и анкера), в результате которого грузонесущая система в целом приближается к ресурсосберегающему состоянию равнопрочности элементов, адаптируясь в пространстве к возмущениям горного давления.
Впервые разработана модель системы «массив-рама-анкер» с учетом пол-ных диаграмм деформирования каждой литологической разности, а также конеч-но-элементного построения реальных геометрических параметров рамной крепи (включая имитаторы замков податливости), сталеполимерных анкеров, механи-ческих связей и условий их силового взаимодействия. Комплексом вариантов расчета НДС усовершенствованной рамно-анкерной крепи доказано не только полное исключение областей пластического состояния материала в стойках рамы, но и формирование достаточно равномерного поля напряжений по ее контуру с обеспечением более, чем двукратного запаса прочности даже при использовании облегченного спецпрофиля СВП-19. Опытно-промышленными испытаниями усо-вершенствованной рамно-анкерной крепи установлено снижение перемещений боков выработки в 4,0 раза на уровне пяты свода и в 4,97 раза в районе опор сто-ек рам. Разработанным методом расчета параметров рамно-анкерной крепи, вы-числительными и шахтными исследованиями доказана возможность снижения металлоемкости рамной крепи до 30% за счет объединения стоек с боковыми ан-керами пространственно-податливыми связями.
Разработана методика расчета, которая соединяет прогноз проявлений гор-ного давления (с выбором рамного крепления) с расчетом самих механических связей и узлов их крепления на анкерах и рамах. Опытно-промышленные испы-тания усовершенствованной конструкции рамно-анкерного крепления проведены на шахтах ПАО «Павлоградуголь».<br>New determination of current scientific-technical task of resource-saving management of rock pressure manifestation in the development workings of Western Donbas mines is presented due to “massif-frame-bolt” condition self-adjustment and provision of adaptive modes of frame-bolt support resistance that has spatial yieldable interelement connection.
Established laws weak layered rock’s of a mine workings walls intensive load are defended from the side of two increased – reinforced by bolts of fibercrete load-bearing plate in roof and solid high-strength coal seam resulting in so-called “stamp effect”, when loosened from strain concentrations weak rocks in walls are squeezed out into its cavity and thus deforming frame support’s props; for this reason, stable formation of wide areas with plastic state in the frame’s props material (in the area of props with length up to 0.5-0.6 m and in area of the canopy’s lower part with length of 0.8-0.9 m) regardless near located rocks, cross-cut section of the working and applied special profile of support – SVP. Major reason is revealed – seperate work the bolts and frames of resistance to rock pressure manifistations. It is proved that due to spatial-yieldable connections of bolts and frames in single load-bearing system, a process of load self-control on the bearing elements is sustained (reinforced rocks, frame and bolt), consequently load-bearing system, in general, approaches resource-saving state of the elements equal strength, adapting in space to rock pressure manifistations. Possibility of frame support metal consumption to 30% due to creation of spatial yieldable connections with the bolts is proved by analytical and experimental parameters and developed frame-bolt support calculation method.
Calculation methodology lop that connects forecast of rock pressure manifestations (with frame support selection) with calculation of mechanical links and joints of their fixing on bolts and frames is developed. Experimental-industrial tests of improved bolt-frame support construction are conducted at mines of PJSC “Pavlogradugol”.
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WU, Yuh-Ren, and 吳裕仁. "Study of Holding Capacity of Reamed Rock Bolts." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/44818693297891603967.
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"Optimising the design of polyurethane and steel combination rock bolts." Thesis, 2015. http://hdl.handle.net/10210/14565.
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M.Tech.<br>The field of study is of a multidisciplinary nature and involves aspects of Mechanical Engineering Design, Materials Technology and Rock Mechanics. When rock bursts occur the rock mass moves at high velocities and the resulting impulsive load often leads to brittle fracture of fully grouted steel bars. It was therefore decided to develop a new product that would combine the strength of steel and the yielding ability of polyurethane. Such a product is envisaged to play an important role in the correct design of tunnel support. In optimizing the design of a polyurethane and steel combination, three important parameters have to be optimized simultaneously...
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Zhang, Zhi Yuan, and 張致遠. "Experimental Study on Pull-out Resistance of Disk-ended Rock Bolts." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/24909169320949478800.
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碩士<br>國立臺灣大學<br>土木工程學研究所<br>83<br>In current tunneling practice, rock bolts installed in weak
rock may not provide sufficient pull-out resistance due to
insufficient strength of weak rock itself. Therefore, it is
intended to develop a new type of rock bolt, with its end
largely enlarged, the so called disk-ended rock bolt, to
mobilize the strength of rock to greater extend.
Experimental studies were formed to evaluate the failure of
disk-ended rock bolts as well as their pullout resistance
including coaxial loading and remote loading. The experimental
results show that the pullout resistance increases with the
increase of embedded depth and the diameter of the disk end.
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Huang, Tai Lin, and 黃泰霖. "A Numerical Analysis on Mechanical Behavior of Disk-ended Rock Bolts." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/60896220884745678624.
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Ye, Jhih-Wei, and 葉至瑋. "Evaluating the Length of Rock Bolts and Grouting Quality Using the Impact-Echo Method." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/51798914601848918445.
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碩士<br>國立中興大學<br>土木工程學系所<br>94<br>The purpose of this thesis is to investigate the application of the impact-echo method to evaluation of the embedded length of rock bolts. Rock bolts have been popularly applied to keeping steep slope stable. When the embedded length is insufficient, the function of rock bolts is questionable and this may cause the failure of the system. In this thesis, both numerical analyses and experimental studies were performed to understand the behavior of stress wave propagation in a rod with/without surrounding mortar. Signals caused by the arrivals of stress waves were analyzed in both the time and frequency domains. The results obtained from numerical analyses show that the spectral analysis is much easier than the time-domain waveform analysis especially in the case of steel rods surrounded by mortar. The apparent wave speed of the rock bolts is largely affected by the thickness and the wave speed of the surrounding mortar. The experimental results verify the numerical results. It has been proved that evaluating the embedded length of rock bolts using the impact-echo method is really feasible.
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Weckert, Steven. "Anchorage and encapsulation failure mechanisms of rockbolts - stage 2 /." 2003. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040317.085411/index.html.
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Thesis (M. E.)--University of New South Wales, 2003.<br>"The precursor to this thesis was an industry-sponsored project, completed in 2000 by C. Offner at the School of Mining Engineering, UNSW ; this project is referred to as the Stage 1 project"--summary. Also available online.
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Cui, Yan. "NUMERICAL AND EXPERIMENTAL STUDY OF GROUTED ROCK BOLTS AND THEIR DEFECTS USING ULTRASONIC GUIDED WAVES." 2013. http://hdl.handle.net/10222/22018.
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A rock bolt installed in field has only one short exposed end on the rock surface. This condition has posed challenges in field instrumentation and made it difficult to use the ultrasonic guided wave method for rock bolt monitoring. In rock bolt laboratory tests using ultrasonic guided waves, the input and receiving transducers are typically installed at the two exposed ends of a bolt. This is suitable to laboratory conditions but not practical in the field because one of the ends of a rock bolt is embedded in the rock mass. A method needs to be found to install the receiving transducer at a suitable location in the field for receiving valid wave data.
In this thesis, a practical approach is proposed for conducting field tests with the installation of the receiving transducer on the grout surface near the exposed end of the bolt. The effects of the installation location of the receiving transducer are studied with numerical modeling. Experiments are conducted to verify the numerical modeling results. The results indicate that the data obtained from the receiving transducer installed on the grout surface at a proper location are representative and can be analyzed through the established correlations to determine the required parameters.
Previous researches have mostly focused on the feasibility of the ultrasonic guided wave method for rock bolt tests and on the behavior of ultrasonic guided waves of fully grouted rock bolts in laboratory conditions. No further study has been performed to identify the grout defects in grouted rock bolts. Adequate understanding of the behaviour of ultrasonic guided waves in rock bolts with defects is therefore prerequisite for this method to be applied in practice. This thesis investigates the effects of some typical defects (e.g., an insufficient rebar length, a missing grout at the ground end, and a void in grout) in grouted rock bolts using the developed field measurement method and numerical modeling. The results are verified by laboratory tests using the equipment set-up established in this research. The results indicate that it is practically possible to identify those grout defects using ultrasonic guided waves.
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Saadat, Mahdi. "The Performance of Fully Grouted Rock Bolts Subjected to Combined Pull and Shear Loads Under Constant Normal Stiffness Condition." Thesis, 2019. http://hdl.handle.net/2440/121914.
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The natural discontinuities in rock masses, which form unstable rock blocks, have a profound impact on the stability and safety of mining structures. The most commonly used means of rock block reinforcement in the field is fully grouted rock bolt because of its high tension capacity and its efficient anchoring. Rock bolting system forms a self-supporting structure in rock mass through reinforcing loosened rock blocks, improving shear strength of rock joints. According to field observations the failure of rock bolts occurs due to a combination of both pull-out and shear forces. Thus, understanding the failure mechanism of bolted rock joint under such a mixing loading condition is essential for rock support system design. The surface roughness characteristics, Constant Normal Load (CNL) and Constant Normal Stiffness (CNS) conditions, and the presence of infill material within rock joint can significantly influence its shear strength. Moreover, the mechanical and failure behaviour of rock as a heterogeneous material is controlled by various microstructural parameters, such as grain shape and size, type of minerals, and the existence of pre-existing flaws. Any damage due to the mine roof fall (e.g. rock block collapse in roadways and tunnels) or the failure of rock in open pit slopes can hinder mining activities, and results in penalties being imposed on mining companies. Therefore, an appropriate evaluation of rock block instability and response of rock bolting system is critical when designing both surface and underground mining structures. Recent developments in computational mechanics and distinct element numerical method (DEM) enable more efficient and faster design of mining structures. However, a promising DEM framework requires a robust and rigorous contact constitutive model, which is capable of mimicking the failure and mechanical response of material at microscopic scale. The key aspect of DEM contact model is its contact force-displacement law, which is responsible for capturing the essential macroscopic features of material failure and deformation. For rock joints reinforced with fully grouted rock bolts, these macroscopic features include brittle or softening behaviour of rock and grout, the cohesive or non-cohesive behaviour of infill material during shearing, and the failure of bolt-grout interface due to tension load. In the case of polycrystalline rock (e.g. granite), the inter- and intra-granular micro-cracking behaviour should also be taken into considerations. The focus of this study is on development of a DEM-based cohesive contact model for simulating the failure behaviour of rock, cohesive infill material (e.g. clay), grout, and bolt-grout interface. The proposed DEM-based cohesive model couples damage mechanics and plasticity theory in both modes I and II, and features an exponential decay damage function that considers the influence of both normal and shear stresses in reproducing a gradual, post-peak softening response in DEM contacts. Unlike conventional contact models such as Parallel Bond Model (PBM), flat-joint model (FJM), and smooth joint model (SJM), which feature no gradual degradation of contact strength after yield point, the cohesive softening behaviour incorporated in the new contact model inhibits the abrupt contact failure that enhances the macroscopic softening response of the DEM model. The proposed contact model is implemented in DEM code (PFC2D) to develop a cohesive DEM framework. A Stepwise Pull-Shear Test (SPST) scheme is developed to investigate the influence of pretension load, rib angle, and CNS boundary condition on the ultimate shear resistance of rock joints. The SPST approach allows simulation of bolted rock joints subjected to a combined pull-shear load, which is more realistic compared to previous shear testings that neglect the impact of simultaneous pull-out and shear loads. The proposed cohesive contact model is also incorporated into a Grain Based Model (GBM) to develop a cohesive GBM framework for simulating the micro-cracking behaviour of polycrystalline rocks. The numerical validations against a range of laboratory tests demonstrate that the proposed cohesive DEM and GBM frameworks are effective in reproducing the mechanical and failure behaviour of rock and grout materials as well as bolt-grout interface, the cohesive macroscopic response of clay-infilled rock joints, and micro-cracking behaviour of granitic rocks. The proposed modelling method, in conjunction with the SPST scheme, provided an efficient and inexpensive numerical framework that can be used by designers and geotechnical engineers for carrying out realistic experiments (i.e., combined pull–shear loads). Doing so will give them new insights into the mechanical performance of fully grouted rock bolts and failure behaviour of rock mass.<br>Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental & Mining Engineering, 2019
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Van, Wyk Riaan. "Non-destructive impact-testing as a method for roof bolt integrity analysis." Thesis, 2015. http://hdl.handle.net/10210/13825.
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M.Ing.(Electrical and Electronic Engineering)<br>The study investigated whether non-destructive impact testing, aided by supervised machine learning methods, could be used to identify improper roof bolt installations, related to insufficient grout coverage. The testing method involved the installation of four roof bolts, with varying installation properties, into a 1511 × 940 × 1350mm rock test block. Three fully grouted bolts served as examples of proper installations, with the fourth bolt grouted only up to half the length of the borehole serving as an improper roof bolt installation. The testing procedure involved placing sensors directly onto the bolts and mechanically impacting a chosen bolt while measuring the response on all the bolts. The focus was on gaining understanding of the working principle of the testing technique and how the measured response was influenced by the presence of signal-modifying factors of the physical test block geometry, such as changes in material properties, boundary changes, cracks or empty boreholes. It was shown that the roof bolt integrity testing method aided by supervised machine learning methods could identify and classify both properly and improperly grouted roof bolts on the small sample of test bolts, in a series of tests conducted at the CSIR Centre for Mining Innovation premises. The method was also shown to be robust enough to do so even in the presence of the signal-modifying factors of the physical test block geometry.
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Buys, Barend Jakobus. "Rock bolt condition monitoring using ultrasonic guided waves." Diss., 2009. http://hdl.handle.net/2263/25740.
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The resin anchored rock bolt is used extensively in the mining industry to stabilize the roof and prevent it from collapsing. However, there are different defects associated with a resin anchored rock bolt. Examples are partially encapsulated bolts, over-spinned bolts and corroded bolts. These defects reduce the integrity of the roof, and thereby have an effect on the safety and productivity of the mines. The integrity of the rock bolts is a critical issue for the mining industry because of its influence on the safety of mining operations. Different research groups around the world have addressed the problem of determining rock bolt integrity. The most promising technique found in the literature study was based on guided ultrasonic waves (Beard and Lowe, 2003). This study extended the previous work by Beard and Lowe (2003) using guided ultrasonic waves, to investigate damage in more realistic embedded bolts which deviate from pure cylinders. The fundamental L(0,1) mode in its lower frequency range, as suggested by Beard and Lowe was utilized. This was done through the use of finite element model simulations of various defect scenarios, which were compared to experimental measurements on bolts. Defects like loss of resin encapsulation, voids and local corrosion cracks were addressed. The time traces of the different finite element defect scenarios could be directly compared to experimental time traces which distinguish this study from the analytical approach. Some finite element modelling issues were investigated and it was found that the time step is critical if an implicit solver is used, whereas for an explicit solver the element size is critical if accurate answers are needed. Furthermore it was also apparent that the boundary of the mortar has an influence on the results. The method used in the study was to move the boundaries far enough to prevent interference. This however increases the model size and thereby the computer resources required. Axisymmetric defects were modelled using axisymmetric finite elements to reduce the problem size. These models gave results comparable to the measured bolts. Three-dimensional finite element models seemed to be promising for simulating non-axisymmetric defects. It was found that it is not possible to solve large three-dimensional models without energy absorbing boundaries. Axisymmetrical and three dimensional finite element models of a partially encapsulated bolt and a bolt with a local corrosion crack were built. It was possible to detect simulated local corrosion cracks with the finite element models. Clear reflections for the crack in the bolt could be seen. If the bolt, resin and rock are cracked, different reflections will be detected. These different reflections complicated the interpretation of the results. Once the integrity of models such as these has been established, the models could in principle be used to train neural networks for use in commercial equipment. The present study was limited to lower frequencies because of computer resource limitations. Basic principles and modelling issues could however be addressed and it may be expected that these principles could soon be extended to higher frequencies with a new generation of computers.<br>Dissertation (MEng)--University of Pretoria, 2009.<br>Mechanical and Aeronautical Engineering<br>unrestricted
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Lin, Yu-Cheng, and 林煜晟. "A study of rock bolt model using distinct element method." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/zxczsz.
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碩士<br>國立臺灣大學<br>土木工程學研究所<br>106<br>Rockbolt is one of the major support system for tunnel excavation. It is widely used to resist sliding of joint and stabilize suspension rock blocks. For the analysis of the mechanical behavior of rock mass, the conventional continuum mechanics was difficult to consider the separation and sliding of blocks. Therefore, discrete element method (DEM) provides an effective tool to investigate the rock mechanical behavior. However, in the DEM software PFC, the rock bolt behavior is less taken into account and the supporting element is lack. Hence, this study develop a rock bolt supporting model for the engineering practice.
In this study, the proposed model was firstly verified with laboratory tensile and shear tests. Then a series of tunnel case simulations are conducted to compare the influence on the displacement of the tunnel under different conditions, such as with or without rockbolts, different rock bolt lengths, different overburden, and different rock bolt number. The simulation results of this study are summarized as follows: (1) The rock bolt model of this study can effectively present the mechanical behavior of the rock bolt; (2) Under the same conditions, the rock bolts can effectively reduce the inward displacement of the tunnel; (3) The simulation results are generally consistent with the actual cases.
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江華洲. "Analyze the progressive excavations around tunnels and rock bolt installation by DDA method." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/60510984378770099776.
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碩士<br>國立臺北科技大學<br>土木與防災技術研究所<br>88<br>Discontinuous Deformation Analysis (DDA) is the numerical modeling technology which is developed by Dr. Shi Gen-hua)in 1980 A.D.Now,Dr Chihsen T.Lin extended the capability of simulating the progressive excavations around tunnels and bolt installation in rocks along the progressive excavation process. DDA can provide the engineering design of tunnelings or well excavation and analyze the joint of mechanics.
This research adopts the single bore tunnel to proceed the analysis. The tunneling cross section adopt the Tripl - circular — arcs which wide is 9.8 meter and height is 7.3 meter. This research simulates the situation of the tunnelings excavation in five types of dip angle. According to the total strain and distribution of principal stress , we can study the stability after tunnelings excavation.Then we can simulate the bolts installation in rocks along the progressive excavation process and discuss efficiency of bolt installation . And it aims to the rock bolts which were installed with right directions and numbers proceed to study.
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Zając, Anna. "Symbolika scen z przedstawieniami łodzi w sztuce naskalnej okresu pre- i wczesnodynastycznego w Egipcie." Praca doktorska, 2011. https://ruj.uj.edu.pl/xmlui/handle/item/50899.
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