To see the other types of publications on this topic, follow the link: Rock Fracture.
Dissertations / Theses on the topic 'Rock Fracture'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Rock Fracture.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Lock, Yick-bun. "An examination of failure criteria for some common rocks in Hong Kong /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17665164.
Full text
2
Felton, David Scott. "Theoretical dissolution coefficient for rock fractures." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21505.
Full text
3
Sharpe, Colin James 1962. "Experimental effectiveness of rock fracture grouting." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291736.
Full textAbstract:
The objective of this investigation is to experimentally determine the effectiveness of fracture sealing in welded tuff using ordinary portland cement and microfine cement grouts. Fracture grouting will most likely be used to seal fractures intersecting high level nuclear waste repositories. Fractures are potential pathways for the migration of radionuclides. Laboratory experiments have been performed on seventeen tuff cylinders. (1) tension induced cracks, (2) natural and, (3) sawcut surfaces serve as fractures. Prior to grouting, the hydraulic conductivity of the intact rock and that of the fractures themselves are measured under a range of normal stresses. Grouts are injected through axial boreholes at pressures of 0.3 to 4.1 MPa while holding fractures under a constant normal stress. Five grout formulations have been selected. Minor amounts of bentonite (0 to 5 percent by weight) have been added to these grouts to increase stability. Water to cement ratios range from 0.45 to 1.0. Permeameter testing of grouted fractures is used to evaluate the effectiveness of fracture grouting.
4
Yu, Xiaomeng. "Stochastic modeling of rock fracture geometry." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12176.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993.Includes bibliographical references (second sequence, leaves 1-3).
by Xiaomeng Yu.
M.S.
5
Akram, Muhammad. "The effect of zero point charge environment on rock fracture behavior." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040230/.
Full text
6
Ran, Chongwei 1956. "Effectiveness of rock fracture sealing with bentonite grouting." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278016.
Full textAbstract:
A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.
7
Ivanova, Violeta Mintcheva. "Three-dimensional stochastic modeling of rock fracture systems." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11810.
Full textAbstract:
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.Includes bibliographical references (leaves 143-146).
by Violeta Mintcheva Ivanova.
M.S.
8
Xu, Chaoshui. "Fracture mechanics and its application in rock excavation." Thesis, University of Leeds, 1993. http://etheses.whiterose.ac.uk/754/.
Full textAbstract:
The two chevron notched specimen geometries for rock Mode I fracture toughness measurement, CB and SR, recommended by the ISRM have several disadvantages, such as very low loads required to initiate failure, complicated loading fixtures, difficult to be developed for rock mixed mode fracture testing, relatively large amounts of intact rock core needed for the test and complex specimen preparation for the SR geometry. The cracked chevron notched Brazilian disc (CCNBD) and the cracked straight through Brazilian disc (CSTBD) specimen geometries overcome these problems and they are believed to be ideal geometries for rock fracture investigations. The general case for the cracked Brazilian disc fracture problem is when the specimen is loaded diametrically with the crack inclined at an angle to the loading direction. Different combinations of Mode I and Mode II fracture intensities can be obtained simply by changing this angle and the loading fixture still remains as simple as for a normal Brazilian test. A special superimposition technique is developed to theoretically solve the stress intensity factor (SW) values for the CSTBD fracture problem with the help of dislocation and complex stress function methods. This evaluation can generate accurate SIF results for the problem with any crack length a(a/R) = 0.05-0.95, while the mixed mode SIF solution for a>0.60 has not been reached by previous researchers. The relative theoretical SW solution for the corresponding CCNBD fracture problem (single or mixed fracture modes) is obtained by using Bluhm's slice model proposed for general crack problems. Numerical calibrations for Mode I fracture problems of the CSTBD and the CCNBD specimens have been conducted by using 194 different specimen geometries and the results prove the correctness of the theoretical evaluations. The valid CCNBD geometrical range for a valid rock Mode I fracture toughness test is numerically investigated and then experimentally validated based on 40 different CCNBD geometries by using 42 different rocks. Experimental studies on the minimum specimen size requirement for a valid CCNBD rock Mode I fracture toughness test are also carried out and the approximate critical criteria is given. The great advantages of using the CCNBD specimens for rock fracture toughness measurement have been investigated and the documentation for recommending the CCNBD specimen geometry to the ISRM as the third suggested method for rock Mode I fracture toughness test is presented. The rock Mode I fracture toughness values are then related to rock conventional properties for the purpose of prediction. Rock cutting mechanics is analyzed by probabilistic fracture mechanics and Weibull's distribution model is found to better express the characteristics of rock cutting performance parameters. Some initial predictions for these parameters based on this mode are then presented.
9
SAVELY, JAMES PALMER. "PROBABILISTIC ANALYSIS OF FRACTURED ROCK MASSES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184249.
Full textAbstract:
Stability analysis of rock masses composed of small, discrete rock blocks that are in-place and interlocked should consider four components of failure: (1) Sliding between blocks. (2) Shearing through rock blocks. (3) Rolling blocks in a shear zone. (4) Crushing of rock blocks. Statistical rock mass description is used to define the characteristics of the rock blocks and the block assemblage. Clastic mechanics is one method of predicting stresses produced by the arrangement of rock blocks and the loading conditions. Failure begins at a point of maximum stress behind the slope. Progression of the failure is assumed if the first block fails because adjacent blocks will become overstressed. The location of the point of maximum stress is determined from the shape and arrangement of the constituent rock blocks. Because strength is mobilized block-by-block rather than instantaneously along a continuous shear surface, sliding between blocks shows less stability than a soil rotational shear analysis or a rigid block sliding analysis. Shearing through rock blocks occurs when maximum shear stress exceeds rock shear strength. Crushing of rock blocks is predicted if the normal stress exceeds the compressive strength of the rock block. A size-strength relationship is combined with the rock block size distribution curve to estimate crushing strength. Rotating blocks in a shear zone have been observed in model studies and as a mechanism in landslides. Stability analysis assumes that the rock mass is sufficiently loosened by blasting and excavation to allow blocks to rotate. The shear strength of rolling blocks is dynamic shear strength that is less than static sliding shear strength. This rolling mechanism can explain release of slope failures where there are no other obvious structural controls. Stability of each component of rock mass failure is calculated separately using capacity-demand reliability. These results are combined as a series-connected system to give the overall stability of the rock mass. This probability of failure for the rock mass system explicitly accounts for the four components of rock mass failure. Criteria for recognizing rock mass failure potential and examples applying the proposed method are presented.
10
Zhang, Wenbing. "A method and program for quantitative description of fracture data and fracture data extrapolation from scanline or wellbore data /." May be available electronically:, 2001. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
11
Eberhardt, Erik Brian. "Brittle rock fracture and progressive damage in uniaxial compression." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0008/NQ27403.pdf.
Full text
12
Crook, A. J. L. "Numerical modelling of rock fracture in deep level mining." Thesis, Swansea University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378830.
Full text
13
Lopez, Philippe. "Comportement mécanique d'une fracture en cisaillement : analyse par plan d'expériences des données mécaniques et morphologiques connues sur une fracture /." Thèse, Chicoutimi : [Talence, France] : Université du Québec à Chicoutimi, Université Bordeaux 1, 2000. http://theses.uqac.ca.
Full textAbstract:
Thèse (Ph.D.)--Université du Québec à Chicoutimi, 2000."...pour obtenir le grade de docteur de l'Université Bordeaux I - France et comme exigence partielle au philosophiae doctor de l'Université du Québec à Chicoutimi - Canada. Spécialité: mécanique" La thèse avec ses annexes sont accessibles via le curriculum vitae, section "COMMUNICATIONS". CaQCU CaQCU Document électronique également accessible en format PDF. CaQCU
14
Decker, Jeramy Bruyn. "Building, Updating and Verifying Fracture Models in Real Time for Hard Rock Tunneling." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27220.
Full textAbstract:
Fractures and fracture networks govern the mechanical and fluid flow behavior of rock masses. Tunneling and other rock mechanics applications therefore require the characterization of rock fractures based on geological data. Field investigations produce only a limited amount of data from boreholes, outcrops, cut slopes, and geophysical surveys. In tunneling, the process of excavation creates a priceless opportunity to gather more data during construction. Typically, however, these data are not utilized due to the impedance of sampling and analysis on the flow of construction, and safety concerns with sampling within unlined tunnel sections. However, the use of this additional data would increase the overall safety, quality, and cost savings of tunneling.
This study deals with several aspects of the above, with the goal of creating methods and tools to allow engineers and geologists to gather and analysis fracture data in tunnels without interrupting the excavation and without compromising safety. Distribution-independent trace density and mean trace length estimators are developed using principles of stereology. An optimization technique is developed utilizing Differential Evolution to infer fracture size and shape from trace data obtained on two or more nonparallel sampling planes. A method of producing nearly bias free empirical trace length CDF's is also introduced. These new methods and tools were validated using Monte Carlo simulations. A field study was conducted in an existing tunnel allowing the above methods and tools to be further validated and tested. A relational database was developed to aid in storage, retrieval, and analysis of field data. Fracture models were built and updated using fracture data from within the tunnel. Utilization of state of the art imaging techniques allowed for remote sampling and analysis, which were enhanced by the use of 3d visualization techniques.Ph. D.
15
Schaffer, Andrew 1952. "PERMEABILITY TESTING AND GROUTING OF FRACTURED ROCK." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275420.
Full text
16
Li, Song. "Modeling fracture and deformation of brittle rock under compressive loading." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0014/NQ41619.pdf.
Full text
17
Bobet, Antonio 1960. "Fracture coalescence in rock materials : experimental observations and numerical predictions." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10391.
Full textAbstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.Vita.
Includes bibliographical references (v. 2, p. 817-821).
by Antonio Bobet.
Sc.D.
18
Liu, Hongyuan. "Numerical modelling of the rock fracture process under mechanical loading." Licentiate thesis, Luleå tekniska universitet, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17758.
Full textAbstract:
The fracture of rock has been the subject of the extensive research in the mechanical fragmentation. With the rapid development of computing power, interactive computer graphics and topological data structure, numerical tool has become a good tool to gain some insights into the problem of rock fracture. However, most of the commercial programs are not so robust that they can model the fracture progressive process with rock fabric characteristics (heterogeneity) considered. Based on this background, a novel numerical code, rock and tool interaction code (R-T2D) has been developed to understand the fracture progressive process of heterogeneous rock. The research, development (R & D) and calibration of R-T2D code (Paper A and B) mainly consists of (1) characterization of rock heterogeneity, (2) mesoscopic constitutive law, nonlinear behaviour and associated seismicity, (3) Mohr-coulomb and double elliptic strength criterion, and (4) calibration of R-T2D code by simulating basic rock mechanics experiments. In the second part of the thesis (Paper C and D), preliminary industrial applications of R-T2D code in mechanical fragmentation are conducted. In rock cutting, the peculiarities in cutting heterogeneous brittle materials are investigated. Besides, the fracture processes induced by cutters with different back rake angles are examined and compared with each other. In indentation, indentation-induced fractures are researched by R-T2D code. The influences of confining pressure on the formation of side cracks are discussed. In the simultaneous loading by multiple indenters, the propagation, interaction and coalescence of side cracks induced by neighbour indenters are simulated to check how the side cracks propagate, interact and coalesce to form large rock chips. At last, the indexing-effect in the simultaneous loading is discussed. The major results for the two parts can be summarized as the following: On the basis of Weibull distribution, a heterogeneous material model is proposed to characterize the heterogeneity in rock, where rock is specified by a few characteristic parameters: the homogeneous index and the elemental seed parameters. Corresponding to the specific rock, the homogeneous index can be determined based on the defects distribution of microstructure and the elemental parameters can be gotten from the laboratory tests. Rock heterogeneity has an important influence on the crack initiation location and subsequent propagation path. Compared with the traditional Mohr-coulomb and Hoek-Brown strength criterion, the double elliptic strength criterion is more useful to model the fracture in mechanical fragmentation, which can represent the transition from brittle failure to ductile cataclastic failure with increasing confining pressure. A series of numerical experiments including both the intact rock and the notched rock are conducted by R-T2D code to obtain the physical-mechanical properties and fracture toughness, and to simulate the crack initiation, propagation and the whole fracture progressive process. The developed R-T2D code seems to have built a bridge between the physical-mechanical parameters and fracture toughness. The detailed visually shown stress distribution and redistribution; crack nucleation, initiation, stable and unstable propagation, interaction and coalescence; and corresponding load-displacement curves can be proposed as benchmarks for numerical programs for crack propagation. In mechanical fragmentation, a crushed zone is always available near the tool. The crushed zone has an important influence on the chipping process and energy utilization. The crushed zone is in fact the zone with a high density of microcracks and some of the rocks in this zone behave in a ductile manner with stress satisfying the ductile failure surface of the double elliptic strength criterion. A simple description and qualitative model of the rock fragmentation process induced by truncated indenters are summarized as follows: Little damage to the rock was observed at the linear elastic deformation stage. Then conical Hertzian cracks were initiated adjacent to both corners of the truncated indenter and propagated in the well-known conical Hertzian manner. As the loading displacement increased, some of the elements in the high confining pressure zone immediately under the indenter failed in the ductile cataclastic mode with the stress satisfying the ductile failure surface of the double elliptic strength criterion. With the cataclastic failures and tensile conical cracks releasing the confining pressure, the elements in the confining pressure zone were compressed into failure and the crushed zone came into being. In the crushed zone, microcracking was pervasive. The intensity of the microcracking within the zone increased and a re-compaction behaviour occurred with increasing loading displacement. Associated with this microcracked region there was a volumetric expansion and a tensile stress field, which drove side cracks to propagate in a curvilinear path. It is thought that the curvilinear path was caused by the heterogeneity of the rock. With an increased loading displacement, the side cracks rapidly propagated and intersected with the free rock surface to form rock chips. The confining pressure has an important influence on the failure mode in indentation test. As the confining pressure increases, a small but noticeable increase in the indentation strength was measured. With decreasing confining pressure, of particular interest is a change in the rock failure mode when the confining stress is reduced below a critical value. Instead of the usual formation of rock chips adjacent to the punch, vertical cracks are propagated beneath the punch, causing the specimen to be split in half when the confining pressure on the sample is less than a critical value. This result is of practical interest. In boring hard rock at low confining stresses, the creation of such tensile fractures beneath an indenter may serve to fragment the rock sufficiently to facilitate its removal. The simultaneous loading of the rock surface by multiple indenters seems to provide a possibility of forming larger rock chips, controlling the direction of subsurface cracks and consuming a minimum total specific energy. The simulated results by R-T2D code reproduce the progressive process of rock fragmentation under mechanical loading: the build-up of the stress field, the formation of the crushed zone, surface chipping, and the formation of the crater and subsurface cracks. Therefore, R-T2D code is indeed a valuable numerical tool to research rock fracture, which can be utilized to improve our understanding of rock-tool interaction and the rock failure mechanisms under the action of mechanical tools, which, in turn, will be useful in assisting the design of fragmentation equipment and fragmentation operations. Based on the above researches, a number of interesting problems are discussed and the future studies are suggested in the last part of the thesis.Godkänd; 2003; 20070218 (ysko)
19
Roach, Daniel Edward. "Fractal analyses and geometrical models of fracture surfaces in rock." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7844.
Full textAbstract:
Fracture propagation in rock often produces complex patterns, such as the branching patterns of fracture networks, or the irregular radiating patterns on fracture surfaces. These patterns often appear complex because they are unpredictable in detail, yet predictable in the sense that smaller pieces of the pattern, when suitably enlarged, are statistically similar to larger pieces of the pattern. This property of statistical self-similarity can be quantified using fractal geometry. The fractal nature of rock fracture patterns is related to lithological properties and to the dynamics of the fracturing processes. Joint surfaces in homogeneous rocks display rough radiating ridges. A "plumose joint" surface was analyzed using the slit island method and found to have a fractal dimension (D$\sb{\rm f}$) of 2.24 $\pm$.14 (95%). Surfaces with similar fractal dimensions (2.2-2.5) are produced by a three-dimensional computer simulation of jointing. In the simulation, randomly-distributed defects cause local mis-orientations of the stress field and local deflection of the propagating fracture front. After passing through the defect the joint surface is re-oriented relative to remote stresses, and a planar radial fracture segment (i.e. inclusion hackle) is formed. Collectively, the numerous inclusion hackle form the plumose surface pattern. For the simulation results, D$\sb{\rm f}$ increases (i.e. the surface gets rougher) in proportion to the log of the defect density. The simulation also demonstrates a complex relationship between D$\sb{\rm f}$ of the propagating fracture front and D$\sb{\rm f}$ of the fracture surface. Shatter cones are conical fracture surfaces produced during high energy events such as meteorite impact and nuclear explosion. These fractures also display radiating surface features. Using a modified version of the slit island method, the fractal dimension of a shatter cone surface in limestone is estimated to be 2.24 $\pm$ 0.09. The observation of shingled convex fracture surfaces within the conical envelope surrounding the shatter cone surface is demonstrated to support the genetic model of Johnson and Talbot (1964). Striations on these fracture surfaces are reinterpreted as micro-fracture intersections. The measured fractal dimensions of the joint and shatter cone surfaces (i.e 2.24) are within the range reported for most fracture surfaces in metals (i.e. 2.1 $\sim$ 2.3).
20
Moore, Brian Hector Mathias. "A comparison between solute transport in a discrete fracture and in a fracture network using a novel method for tracer detection." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1367.
Full text
21
Hazzard, James F. "Numerical modelling of acoustic emissions and dynamic rock behaviour." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265036.
Full text
22
Pathan, A. G. "A study of fracture toughness in relation to mine design." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376643.
Full text
23
Meyer, Thomas 1970. "Geologic stochastic modeling of rock fracture systems related to crustal faults." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9317.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (p. 223-225).
In this study, the capabilities of the MIT three-dimensional geologic stochastic fracture model were extended so that fracture systems related to crustal faulting can be simulated. As presented here, the model comprises four stochastic processes: 1) a homogeneous, anisotropic Poisson process to model the orientation of the potential fracture planes according to an orientation distribution; 2) a homogeneous Poisson line process that tessellates the fracture planes and associates the polygons with fractured and intact rock; 3) a zone marking process that retains or discards the polygons according to their location in the modeling volume; 4) a process that translates and rotates the polygons from their original position in order to accommodate local geologic features. This research enhanced the capabilities of the model by introducing various ways of defining the zones in the zone marking process, and by developing new procedures to analyze the connectivity of the fracture systems. Two case studies of fracture systems generation were addressed. The first one discussed the formation of fault zones in igneous rock. It demonstrated that fracture sets with different properties can be generated in different, sharply defined zones of the same modeling volume. The second case analyzed the fracture systems in the bedrock underlying the Aberjona Valley. It showed that a correct treatment of field data could lead to reliable input parameters for the model, and therefore to reliable properties of the simulated fracture systems, in terms of fracture intensity, fracture size, fracture spacing along boreholes and fracture trace length on outcrops. Connectivity assessment of the simulated fracture systems in the bedrock underlying the Aberjona Valley was performed through analysis of the isolated clusters of interconnected fractures (fracture sub-networks). The horizontal extent of the largest sub-networks appeared to be limited to 9 meters in direction East-West and 11 meters in direction North-South, regardless of the size of the modeling volume. The extent in the vertical direction was not limited. The geometry of the sub-networks seems therefore to limit horizontal fracture flow over long distances, while providing significant storage capacity. Simulations of the fracture flow run with a finite element model developed at ETHZ confirmed the geometry of the phreatic surface as observed in field pumping tests. They also pointed out the role of large discontinuities in fracture flow and the need to model large volumes of rock to account for it.
by Thomas Meyer.
S.M.
24
Wang, Xiaohai. "Stereological Interpretation of Rock Fracture Traces on Borehole Walls and Other Cylindrical Surfaces." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29105.
Full textAbstract:
Fracture systems or networks always control the stability, deformability, fluid and gas storage capacity and permeability, and other mechanical and hydraulic behavior of rock masses. The characterization of fracture systems is of great significance for understanding and analyzing the impact of fractures to rock mass behavior. Fracture trace data have long been used by engineers and geologists to character fracture system. For subsurface fractures, however, boreholes, wells, tunnels and other cylindrical samplings of fractures often provide high quality fracture trace data and have not been sufficiently utilized. The research work presented herein is intended to interpret fracture traces on borehole walls and other cylindrical surfaces by using stereology. The relationships between the three-dimension fracture intensity measure, P32, and the lower dimension fracture intensity measures are studied. The analytical results show that the conversion factor between the three-dimension fracture intensity measure and the two-dimension intensity measure on borehole surface is not dependent on fracture size, shape or circular cylinder radius, but is related to the orientation of the cylinder and the orientation distribution of fractures weight by area. The conversion factor between the two intensity measures is determined to be in the range of [1.0, π/2]. The conversion factors are also discussed when sampling in constant sized or unbounded fractures with orientation of Fisher distribution. At last, the author proposed estimators for mean fracture size (length and width) with borehole/shaft samplings in sedimentary rocks based on a probabilistic model. The estimators and the intensity conversion factors are tested and have got satisfactory results by Monte Carlo simulations.Ph. D.
25
Hao, Bin. "Use of fracture mechanics parameters to characterize comminution." Master's thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-02162010-020306/.
Full text
26
Jackson, Richard Robert. "Geometries and mechanics of veins and dykes." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385102.
Full text
27
Astakhov, Dmitriy Konstantinovich. "Permeability evolution as a result of fluid-rock interaction." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21693.
Full text
28
Mouritz, Adrian Paul. "The abrasive wear of rock drill bit materials." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315846.
Full text
29
Yeo, In-Wook. "Anisotropic hydraulic properties of a rock fracture under normal and shear loading." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286893.
Full text
30
Styles, Thomas Daniel. "Numerical modelling and analysis of slope stability within fracture dominated rock masses." Thesis, University of Exeter, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496103.
Full textAbstract:
Numerical modelling of rock slopes can involve a number and variety of techniques, the selection and requirement of which depends on the factors deemed to control the potential for Instability. This thesis presents a number of case studies involving slopes in fractured rock, encompassing a range of scales. The case study slopes have provided a means to question the way in which particular slope instabilities should be analysed. Currently there are few methods available for analysing the complex behaviour within slopes of fractured rock. A review of available techniques is given within this thesis, with the use of limit equilibrium, finite element and hybrid methods, to highlight their specific advantages and limitations for the chosen case study slopes. By modelling slope Instability within fractured rock, the understanding of both discrete and mass behaviour increases considerably. Numerical modelling can therefore be used as a tool to help improve both the safety and efficiency of open pit mining and the management of natural rock slopes.
31
Salvati, Peter. "The Examination of Fracture Behavior in Anisotropic Rock with Digital Image Correlation." Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10287221.
Full textAbstract:
Modern hydraulic fracturing designs assume that drilled formations are both isotropic and homogeneous, and fractures are linear and symmetrical. However, unconventional resources are often obtained from formations that are both anisotropic and heterogeneous, resulting in complex fracture behavior. The objective of this study is to evaluate fracture behavior based on the influence of anisotropy and water saturation. Isotropic and homogeneous Austin Chalk, Berea Sister Gray Sandstone, and Silurian Dolomite, laminated anisotropic and heterogeneous Parker Sandstone, Nugget Sandstone, and Winterset Limestone Carbonate, and fully anisotropic and heterogeneous Edwards Brown Carbonate cores were ordered for testing. Brazilian discs were cut according the ISRM and ASTM standards, and prepared as dry, brine saturated, and fresh water saturated samples. All samples were fractured by the Brazilian test, and laminated anisotropic samples were tested at various loading angles (0?, 15?, 30?, 45?, 90?). Tensile strengths were calculated using the peak load of the primary fracture of each sample, and the fractures were observed for geometrical trends. Additionally, the strain development of each fracture was analyzed through the application of Digital Image Correlation (DIC) software. The results determined that anisotropy and saturation can decrease the tensile strength of a formation. The fracture geometries were influenced by planes of anisotropic lamination, and fully anisotropic rocks produced winding, erratic fractures. DIC allowed for closer 101 examination of fracture development, and identified that saturation can cause failure along lamination planes subjected to less than the maximum, load induced stress. This research can be utilized to improve the hydraulic fracturing design models to optimize formation fractures, and increase revenue for the oil and gas industry.
32
Rizzo, Roberto Emanuele. "Quantifying fracture patterns : implications for mechanical and transport properties." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=233636.
Full text
33
Bäckström, Ann. "Rock damage caused by underground excavation and meteorite impacts." Doctoral thesis, KTH, Teknisk geologi och geofysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4824.
Full textAbstract:
The intent of this thesis is to contribute to the understanding of the origin of fractures in rock. The man-made fracturing from engineering activities in crystalline rock as well as the fracturing induced by the natural process of meteorite impacts is studied by means of various characterization methods. In contrast to engineering induced rock fracturing, where the goal usually is to minimize rock damage, meteorite impacts cause abundant fracturing in the surrounding bedrock. In a rock mass the interactions of fractures on the microscopic scale (mm-cm scale) influence fractures on the mesoscopic scale (dm-m scale) as well as the interaction of the mesocopic fractures influencing fractures on the macroscopic scale (m-km scale). Thus, among several methods used on different scales, two characterization tools have been developed further. This investigation ranges from the investigation of micro-fracturing in ultra-brittle rock on laboratory scale to the remote sensing of fractures in large scale structures, such as meteorite impacts. On the microscopic scale, the role of fractures pre-existing to the laboratory testing is observed to affect the development of new fractures. On the mesoscopic scale, the evaluation of the geometric information from 3D-laser scanning has been further developed for the characterisation of fractures from tunnelling and to evaluate the efficiency of the tunnel blasting technique in crystalline rock. By combining information on: i) the overbreak and underbreak; ii) the orientation and visibility of blasting drillholes and; iii) the natural and blasting fractures in three dimensions; a analysis of the rock mass can be made. This analysis of the rock mass is much deeper than usually obtained in rock engineering for site characterization in relation to the blasting technique can be obtained based on the new data acquisition. Finally, the estimation of fracturing in and around two meteorite impact structures has been used to reach a deeper understanding of the relation between fracture, their water content and the electric properties of the rock mass. A correlation between electric resistivity and fracture frequency in highly fractured crystalline rock has been developed and applied to potential impact crater structures. The results presented in this thesis enables more accurate modelling of rock fractures, both supporting rock engineering design and interpretation of meteorite impact phenomena.QC 20100709
34
Ryttberg, Mattias. "Significance of Fracture Patterns in a Rock Mass during Excavation by Blasting in Bandhagen, Sweden." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-260885.
Full textAbstract:
When excavating a rock wall by blasting, pre-existing structures in the rock has a strong impact on the stability of the wall. For excavation in Bandhagen in Stockholm, the nature and orientation of the pre-existing geological features, namely fractures, were not taken into consideration before excavation begun. Geological field studies were carried out in order to investigate the possibility of a more favorable outcome than in the Bandhagen case. Mapping conducted in March 2015 was focused on fracture distribution and the results showed two sets of open shear fractures with fresh surfaces. The first set of the fractures cross-cuts the wall with a strike of NNW-SSE and dips between 70°±30°. The second set of fractures strikes WSW-ENE and are almost parallel to the wall (which strikes roughly 65° E) with a dip towards it, ranging between 55°±35°. The two set of fractures intersect with an acute angle of around 80° and due to their orientation, and that one of the sets dip towards the free face of the wall, they create an unfavorable fracture pattern that makes the wall, at parts, very instable in regard to rockfall and rockslide. Fractures within the respective sets dip towards opposite cardinal points and making an acute angle of 50° for set 2 and 70° for set 1 fractures within the own set are interpreted to conjugate. In addition, there is a well-developed folded foliation that change in strike from parallel to perpendicular to the excavated wall. The foliation is aligned to the strike of both of the fracture sets. This has enabled fractures to open parallel to the mica-rich layers in the gneiss which further adds to the unfavorable pattern of fractures that creates rhombohedral unstable blocks in the rock mass. Due to the fracture pattern, sliding and rockfall have been frequent and safety measures such as rock bolts and a wire mesh have been installed to increase the security factor for the wall. During mapping, a general fracture pattern was possible to deduce from mapping of solely an unexcavated, vegetated part of the area. It became clearer though together with the excavated surface of the wall. Several pre-blast measures could have been preformed to limit rockfall and sliding of rock after excavation. Line-drilling could have been used when blasting near the contour of the wall to decrease the blast-induced fractures by the more effective venting of the excess explosion gas. This could have decreased the closely spaced blast-induced fractures that have been mapped on both the crest and the body of the wall. Another measure would have been to install pre-blast reinforcements on the crest of the wall, which could have prevented at least two large rockfalls that have occurred. If the fracture pattern were known before excavation begun and the aforementioned measures would have been considered, the stability of the wall and the first excavation would undoubtedly have been more successful. A proposal for future open face excavations is to thoroughly assess the geological features to, in a preliminary stage of the planning, eliminate the risk for this outcome to occur in the future.Vid uttag av berg genom sprängning för att skapa en bergvägg har strukturerna i berget en stor betydelse för stabiliteten av väggen. Exempel på strukturer i berggrunden som kan orsaka problem vid uttag av berg är sprickor och då speciellt sprickor som stupar mot väggens teoretiska kontur. Dessa sprickor kan orsaka att hela skivor av berg kan glida från väggen. Om dessa sprickor också korsas av andra sprickor kan de tillsammans bilda kilar som stupar ut mot den fria ytan där utschaktning av berg skett. Kilar som dessa som förekommer på krönet av bergväggen faller ofta ut från väggen och kan vara både farliga för de som utför arbetet samtidigt som de kan göra block runtomkring dem mer instabila. För en utschaktning av berg i Bandhagen, Stockholm togs inte sprickmönstret in i planeringen inför hur sprängning skulle utföras. Detta ledde till att sprängningen som utfördes orsakade mycket glidningar av block och utfall från krönet. Det har lett till att projektet blivit försenat och budgeten överskridits för att korrigera de misstag som gjorts. Korrigeringarna har varit nödvändiga för att väggen i slutändan ska nå en säkerhetsfaktor som inte kan orsaka några person- eller materialskador i framtiden. Kartering med fokus på sprickfördelning utfördes i Mars 2015 för att undersöka om sprängningen hade kunnat utföras på ett annorlunda och bättre sätt om sprickmönstret varit känt innan sprängning inleddes. Karteringen visade två korsande spricksystem där ett av spricksystemen stryker parallellt med väggen och även stupar mot den. De två systemen av sprickor bildar block med plan som lutar ut från väggen vilket resulterar i att många utfall av block skett. Med vetskapen om dessa spricksystem, samt övriga sprickor som förekommer i området, hade de utfall av berg som skett kunnat förutsägas och därigenom hade förslag av sprängmetodik kunnat ges för att minska utfall och för att generellt fått en säkrare vägg redan ifrån början. Både sprängning med tätsöm nära den teoretiska konturen av väggen och förförstärkning av krönet av den teoretiska väggen innan första sprängningen hade kunnat leda till en mycket stabilare vägg. Det hade kunnat leda till att projektet inte blivit försenat och att budgeten för projektet tagit hänsyn till de problem som skulle kunna uppstå. Ett förslag för uttag av berg för bergsslänter är att de geologiska förhållandena ska undersökas mer noggrant, för att i ett tidigt skede upptäcka liknande strukturer i berget och utifrån dessa eliminera risken för att liknande problem uppstår i framtiden.
35
Bennett, Richard Antony. "Impact fragmentation of boulders confined in soil." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323184.
Full text
36
Mehrapour, Mohammad Hadi, and Mohammad Hadi Mehrapour. "Development of a Failure Criterion for Rock Masses Having Non-Orthogonal Fracture Systems." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625679.
Full textAbstract:
Two new three-dimensional rock mass strength criteria are developed in this dissertation by extending an existing rock mass strength criterion. These criteria incorporate the effects of the intermediate principal stress, minimum principal stress and the anisotropy resulting from these stresses acting on the fracture system. In addition, these criteria have the capability of capturing the anisotropic and scale dependent behavior of the jointed rock mass strength by incorporating the effect of fracture geometry through the fracture tensor components. Another significant feature of the new rock mass strength criterion which has the exponential functions (equation 6.7) is having only four empirical coefficients compared to the existing strength criterion which has five empirical coefficients; if the joint sets have the same isotropic mechanical behavior, the number of the empirical coefficients reduces to two in this new strength criterion (equation 6.10).
The new criteria were proposed after analyzing 452 numerical modeling results of the triaxial, polyaxial and biaxial compression tests conducted on the jointed rock blocks having one or two joint sets by the PFC3D software version 5. In this research to have several samples with the same properties a synthetic rock material that is made out of a mixture of gypsum, sand and water was used. In total, 20 joint systems were chosen and joint sets have different dip angles varying from 15 to 60 at an interval of 15 with dip directions of 30 and 75 for the two joint sets. Each joint set also has 3 persistent joints with the joint spacing of 42 mm in a cubic sample of size 160 mm and the joints have the same isotropic mechanical behavior. The confining stress combination values were chosen based on the uniaxial compressive strength (UCS) value of the modeled intact synthetic rock. The minimum principal stress values were chosen as 0, 20, 40 and 60 percent of the UCS. For each minimum principal stress value, the intermediate principal stress value varies starting at the minimum principal stress value and increasing at an interval of 20 percent of the UCS until it is lower than the strength of the sample under the biaxial loading condition with the same minimum principal stress value.
The new rock mass failure criteria were developed from the PFC3D modeling data. However, since the joint sets having the dip angle of 60 intersect the top and bottom boundaries of the sample simultaneously, the joint systems with at least one of the joint sets having the dip angle of 60 were removed from the database. Thus, 284 data points from 12 joint systems were used to find the best values of the empirical coefficients for the new rock mass strength criteria. λ, p and q were found to be 0.675, 3.16 and 0.6, respectively, through a conducted grid analysis with a high R2 (coefficient of determination) value of 0.94 for the new criterion given by equation 6.9 and a and b were found to be 0.404 and 0.972, respectively, through a conducted grid analysis with a high R2 value of 0.92 for the new criterion given by equation 6.10.
The research results clearly illustrate how increase of the minimum and intermediate principal stresses and decrease of the joint dip angle, increase the jointed rock block strength. This dissertation also illustrates how different confining stress combinations and joint set dip angles result in different jointed rock mass failure modes such as sliding on the joints, failure through the intact rock and a combination of the intact rock and joint failures.
To express the new rock mass strength failure criteria, it was necessary to determine the intact rock strengths under the same confining stress combinations mentioned earlier. Therefore, the intact rock was also modeled for all three compression tests and the intact rock strengths were found for 33 different confining stress combinations. Suitability of six major intact rock failure criteria: Mohr-Coulomb, Hoek-Brown, Modified Lade, Modified Wiebols and Cook, Mogi and Drucker-Prager in representing the intact rock strength was examined through fitting them using the aforementioned 33 PFC3D data points. Among these criteria, Modified Lade, Modified Mogi with power function and Modified Wiebols and Cook were found to be the best failure criteria producing lower Root Mean Square Error (RMSE) values of 0.272, 0.301 and 0.307, respectively. Thus, these three failure criteria are recommended for the prediction of the intact rock strength under the polyaxial stress condition.
In PFC unlike the other methods, macro mechanical parameters are not directly used in the model and micro mechanical parameter values applicable between the particles should be calibrated using the macro mechanical properties. Accurate calibration is a difficult or challenging task. This dissertation emphasized the importance of studying the effects of all micro parameter values on the macro mechanical properties before one goes through calibration of the micro parameters in PFC modeling. Important effects of two micro parameters, which have received very little attention, the particle size distribution and the cov of the normal and shear strengths, on the macro properties are clearly illustrated before conducting the said calibration. The intact rock macro mechanical parameter values for the Young’s modulus, uniaxial compression strength (UCS), internal friction angle, cohesion and Poisson's ratio were found by performing 3 uniaxial tests, 3 triaxial tests and 5 Brazilian tests on a synthetic material made out of a mixture of gypsum, sand and water and the joint macro mechanical parameter values were found by conducting 4 uniaxial compression tests and 4 direct shear tests on jointed synthetic rocks with a horizontal joint. Then the micro mechanical properties of the Linear Parallel Bond Model (LPMB) and Modified Smooth Joint Contact Model (MSJCM) were calibrated to represent the intact rock and joints respectively, through the specific procedures explained in this research. The similar results obtained between the 2 polyaxial experiments tests of the intact rock and 11 polyaxial experimental tests of the jointed rock blocks having one joint set and the numerical modeling verified the calibrated micro mechanical properties and further modification of these properties was not necessary.
This dissertation also proposes a modification to the Smooth Joint Contact Model (SJCM) to overcome the shortcoming of the SJCM to capture the non-linear behavior of the joint closure varying with the joint normal stress. Modified Smooth Joint Contact Model (MSJCM) uses a linear relation between the joint normal stiffness and the normal contact stress to model the non-linear relation between the joint normal deformation and the joint normal stress observed in the compression joint normal stiffness test. A good agreement obtained between the results from the experimental tests and the numerical modeling of the compression joint normal test shows the accuracy of this new model. Moreover, another shortcoming associated with the SJCM application known as the interlocking problem was solved through this research by proposing a new joint contact implementation algorithm called joint sides checking (JSC) approach. The interlocking problem occurs due to a shortcoming of the updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem increases the joint strength and dilation angle and creates unwanted fractures around the intended joint plane.
37
Lanaro, Flavio. "Geometry, Mechanics and Transmissivity of Rock Fractures." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3168.
Full text
38
Price, Jeffrey Richard. "Coupled analysis of two-phase flow in rough rock fractures." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050819.153247/index.html.
Full text
39
Zhao, Xuan Liang. "A fracture mechanics study of unassisted and water jet assisted rock disc cutting." Thesis, University of Newcastle Upon Tyne, 1989. http://hdl.handle.net/10443/823.
Full textAbstract:
The work presented in the thesis introduces the use of the principles of fracture mechanics on the mechanism of rock breakage by disc cutters with and without water jet assistance. The work may be divided into five major parts: 1. Rock fracture tests; The values of fracture toughness are measured from three different directions of the rock blocks by three different testing methods: radially cracked ring specimens, three point bend specimens and short bar specimens. The effect of moisture on the fracture toughness was also investigated. 2. Indentation tests; A primary study of the use of a disc cutter as a type of indenter has been carried out. These tests provided a parameter, contact pressure, for predicting the disc cutting forces and understanding the fragmentation of the rock during cutting. 3. Water jet assisted disc cutting tests; The factors influenced the performance of water jet assisted disc cutting were investigated, including: a) The pressure of the water jet; b) The position of the water jet nozzle; c) The cutting speed; and d) The spacing distance and penetration depths. 4. Theoretical analysis of disc forces; Based on a widely accepted assumption, a simple mathematical model was developed for the relationships between the cutting forces. The indentation fracture theories were used to predict the performance of disc cutting. A further use of the predictor equations in the water jet assisted cutting was also investigated. 5. The analysis of stress distribution beneath the disc cutter; Boundary element method was used in the investigation of the stress distribution beneath the disc cutter. The effects of geometries of the disc cutters, spacing distance, penetration depth were also considered.
40
Melendez, Castillo Maria Georgina. "The effects of acid contact time and rock surfaces on acid fracture conductivity." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1956.
Full text
41
Al-Yaarubi, Azzan H. B. "Numerical and experimental study of fluid flow in a rough-walled rock fracture." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/61130.
Full textAbstract:
Understanding the hydraulic properties of rock fractures is an issue of great importance in fields such as petroleum engineering, groundwater hydrology, and underground waste isolation. Traditionally, models of fluid flow through rock fractures have been based on the cubic law, which asserts that the local value of the fracture transmissivity is equal to /i^/12, where h is the fracture aperture. The local cubic law is mathematically equivalent to assuming that flow in the fracture is governed by the Reynolds lubrication equation. However, this equation is only applicable if the aperture does not change too abruptly, and flow-rates are suitably low. Recent previous investigations showed that the Reynolds equation may over-predict the transmissivity of a fracture by as much as 100%. Other analyses, both theoretical and computational, have estimated that the cubic law will also break down if the Reynolds numbers reach some critical value, variously estimated to be between 1-10. The implication of these results has been that the full three-dimensional, nonlinear Navier-Stokes equations are actually needed to accurately simulate fluid flow in a rock fracture. This conjecture, however, has never been verified, and its verification is the main objective of this research. A surface profilometer was used to measure fracture profiles every 20 nm over the surface of a replica of a fracture in a red Permian sandstone of size 4 cm^. These surface data were used as input to two finite element codes that solve the Navier-Stokes equations and the Reynolds equation, respectively. Numerical simulations of flow through these measured aperture fields were then carried out at different values of the mean aperture, which corresponds to different values of the relative roughness (which is defined as the ratio of the roughness to the mean aperture). At low Reynolds numbers, the Navier-Stokes simulations yielded transmissivities that were 10-100% lower (depending on the relative roughness) than those predicted by the Reynolds simulations, in close agreement with the range of discrepancy between the Reynolds equation and experimental flow measurements reported by previous investigators. At Reynolds numbers << 1, the computed transmissivity is constant. Appreciable deviations from Darcy's law began to be observed when the Reynolds number (defined using the mean aperture as the length scale) exceeded unity. In the regime Re > 20, the computed transmissivities could be fit very well to a Forchheimer-type equation, in which the additional pressure drop varies quadratically with the Reynolds number. The initial deviations from linearity, for Reynolds number around 1, are consistent with the "weak inertia" model of Mei and Auriault (1991). Experimental flow measurements were conducted, on the same fracture replica for which the surface measurements were taken and on which the simulations were conducted. The experiments showed that the measured transmissivities were in close agreement to the values predicted by the Navier-Stokes equations, whereas the Reynolds equation over-estimated fracture transmissivity by as much as 30%. Appreciable deviations from Darcy's law began to be observed when the Reynolds number exceeded unity. When the Reynolds number exceeds about 15, measured transmissivities could be described by the Forchheimer equation, which is consistent with the numerical solutions of the Navier-Stokes equations.
42
Gong, Yiwen. "Toward Better Understandings of Unconventional Reservoirs - Rock Mechanical Properties and Hydraulic Fracture Perspectives." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1605633687308252.
Full text
43
Kostakis, Ekaterini. "Investigations on the movement of gas bubbles in a water-filled rock fracture." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/7217.
Full text
44
Backers, Tobias. "Fracture toughness determination and micromechanics of rock under Mode I and Mode II loading." Phd thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/229/.
Full textAbstract:
This thesis work describes a new experimental method for the determination of Mode II (shear) fracture toughness, KIIC of rock and compares the outcome to results from Mode I (tensile) fracture toughness, KIC, testing using the International Society of Rock Mechanics Chevron-Bend method.Critical Mode I fracture growth at ambient conditions was studied by carrying out a series of experiments on a sandstone at different loading rates. The mechanical and microstructural data show that time- and loading rate dependent crack growth occurs in the test material at constant energy requirement.
The newly developed set-up for determination of the Mode II fracture toughness is called the Punch-Through Shear test. Notches were drilled to the end surfaces of core samples. An axial load punches down the central cylinder introducing a shear load in the remaining rock bridge. To the mantle of the cores a confining pressure may be applied. The application of confining pressure favours the growth of Mode II fractures as large pressures suppress the growth of tensile cracks.
Variation of geometrical parameters leads to an optimisation of the PTS- geometry. Increase of normal load on the shear zone increases KIIC bi-linear. High slope is observed at low confining pressures; at pressures above 30 MPa low slope increase is evident. The maximum confining pressure applied is 70 MPa. The evolution of fracturing and its change with confining pressure is described.
The existence of Mode II fracture in rock is a matter of debate in the literature. Comparison of the results from Mode I and Mode II testing, mainly regarding the resulting fracture pattern, and correlation analysis of KIC and KIIC to physico-mechanical parameters emphasised the differences between the response of rock to Mode I and Mode II loading. On the microscale, neither the fractures resulting from Mode I the Mode II loading are pure mode fractures. On macroscopic scale, Mode I and Mode II do exist.
Diese Arbeit beschreibt eine neue experimentelle Methode zur Bestimmung der Modus II (Schub) Bruchzähigkeit, KIIC, von Gestein und vergleicht die Ergebnisse mit Resultaten aus Versuchen zur Bestimmung der Modus I (Zug) Bruchzähigkeit, KIC.
An einer Serie von Versuchen mit verschiedenen Belastungsraten wurde das kritische Modus I Rißwachstum eines Sandsteines untersucht. Die mechanischen Daten zeigen, daß zeit- und belastungsratenabhängiges Rißwachstum in dem Material bei konstantem Energieverbrauch stattfindet.
Der neu entwickelte Versuchsaufbau zur Ermittlung der Modus II Bruchzähigkeit wurde Punch- Through Shear Test genannt. Die Proben werden aus Bohrkernen hergestellt in deren Endflächen Nuten eingebracht werden. Eine Last auf den Innenzylinder induziert eine Schubspannung. Auf die Mantelfläche der Proben kann ein Umlagerungsdruck aufgebracht werden. Da durch Normalspannungen das Modus I Rißwachstum unterdrückt wird, wird das Modus II Rißwachstum gefördert.
Die PTS- Probengeometrie wurde bezüglich Nutentiefe, -durchmessers, -breite und des Probendurchmessers optimiert. KIIC steigt bi-linear mit Zunahme des Umlagerungsdruckes an. Ein starker Anstieg ist bis zu Umlagerungsdrücken von etwa 30 MPa zu beobachten, oberhalb ist die Steigung geringer. Bisher wurden Umlagerungsdrücke bis maximal 70 MPa aufgebracht. Die Entwicklung der entstehenden Risse und deren Variation mit Umlagerungsdruck wird beschrieben.
Ob die Entstehung eines Modus II Risses in Gestein möglich ist, wurde vielfach in der Literatur diskutiert. Der Vergleich der Ergebnisse der Modus I und II Experimente, insbesondere bezüglich der Rißmuster und der Korrelationsanalysen von KIC und KIIC zu physiko-mechanischen Parametern, zeigt die Unterschiede der Reaktion auf Modus I und Modus II Belastung auf. Mikroskopisch gesehen wachsen die Risse weder unter Modus I noch unter Modus II Belastung in einem reinen Modus. Allerdings existieren Modus I und Modus II Risse auf der makroskopischen Betrachtungsebene.
45
Ryan, Thomas Michael 1963. "A laboratory assessment of flow characteristics and permeability of fractures in rock." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276629.
Full textAbstract:
Intact and fractured rock samples were studied in the laboratory in order to understand more fully the mechanism of closure of fractures subjected to high confining stresses and the resultant effect on specimen permeability. Confining stresses applied to the specimens ranged from 3.0 to 20.0 MPa, and the closure of fractures was observed by monitoring the change in the hydraulic conductivity of the specimens. Test results suggest that some resealing may occur due to crushing and realignment of mineral grains along a fracture surface. The closure of fractures is dependent upon the strength of the rock mass, the physical nature of the fracture, and the fluid pressure present in the fracture. Fracture closure is highly time dependent, and a number of nonlinear pressure flow relationships have been identified. These deviations are thought to represent two fundamentally different processes, the most important of which are turbulence in the flow and fracture expansion.
46
Ding, Xiaobin. "Development of a Rock Expert System (RES) for Evaluating Rock Property Values and Utilization of Three Dimensional Particle Flow Code (PFC3D) to Investigate Rock Behavior." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293428.
Full textAbstract:
This research consists of two main parts: development of a rock expert system (RES) as an easy-to-use and effective tool for evaluating rock properties, and modification and utilization of the three-dimensional Particle Flow Code (PFC3D) to analyze rock behavior. Because of different reasons, it is often difficult to obtain the rock property values directly. As an alternative, typical values and empirical correlations are often used to evaluate the rock property values. However, the typical values and empirical correlations come in various forms and are scattered in different sources. It is often difficult, time-consuming or even impossible for an engineer to find appropriate information to estimate the required rock properties. So in the first part of the research, the RES was developed as an easy-to-use and effective tool for evaluating rock properties by conducting detailed review and evaluation of well determined values and empirical correlations of rock properties in the published literature, and developing a central database and data application tools. The study of RES demonstrates the storage of rock property values and correlations is strongly applicable and the web based data application tool is effective to use and easy expandable. Considering its granular nature, the discrete element method (DEM) has been widely adopted to analyze the mechanical behavior of rock. The Particle Flow Code (PFC) is one of the most popular DEM softwares. The basic idea of PFC is to treat rock as an assembly of bonded particles that follow the law of motion and consider the model behavior dominated by the formation and interaction of micro cracks developed within the particle-particle cement (bond). Unlike the continuum methods, PFC can deal with the natural process from micro cracking to macro failure, without predefining a failure criterion for the rock. However, there are still issues related to the application of PFC to analyze different rock problems. For example, so far, most of the studies use PFC2D although many of the problems are three dimensional and should be better simulated with PFC3D. It is also found that the simulations using the default PFC parallel bond model extremely underestimate the ratio of unconfined compressive strength to tensile strength (UCS/T). So in the second part of the research, the important aspects related to the application of PFC3D, including model scale, particle size distribution and contact model, were studied, a new contact model was developed for addressing the limitation of the default PFC3D on obtaining unrealistically low UCS/T ratios, and finally the new contact model was used to investigate rock fracture initiation and propagation.
47
Donovan, James George. "Fracture Toughness Based Models for the Prediction of Power Consumption, Product Size, and Capacity of Jaw Crushers." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28544.
Full textAbstract:
There is little process control employed at aggregate crushing plants and essentially no optimization at the primary or jaw crushing stage. Jaw crusher selection is very dependent on the subjective judgment/experience of individuals, the characterization of rock material using inadequate and unrepresentative tests, and the desire to limit secondary breakage, resulting in the conservative selection and operation of jaw crushers. A method for predicting the power consumption, product size, and volumetric capacity of jaw crushers based on fracture toughness has been proposed in this study. A new fracture toughness test, the Edge Notched Disk Wedge Splitting test, has been developed and verified in order to rapidly assess the fracture toughness of six quarry rocks. A High Energy Crushing Test system has been used to simulate the operational settings of a jaw crusher so that comparison of fracture toughness, specific comminution energy, and breakage distribution could be performed. The results indicate that the specific comminution energy required to reduce a rock particle to a given size increases with fracture toughness. The breakage distribution has also been shown to be dependent upon fracture toughness as long as the elastic modulus is taken into account. Laboratory jaw crushing experiments show that the capacity of a jaw crusher is dependent upon fracture toughness and the elastic modulus. Models for the prediction of power consumption, breakage function/product size, and volumetric capacity have been developed based on these results. At the experimental level, the models were able to predict the specific comminution energy to within 1% and t10 (characteristic crushing parameter) to within 10%. Prediction of the product size distribution produced by a lab-scale jaw crusher, for four different rocks, was within ± 5% (in terms of percent passing). The models allow for the selection of a jaw crusher based on the nature of the rock being broken and the average amount of size reduction done on the feed material. The models can also be used to optimize feed and operational settings, as well to determine the product size produced for a given rock and reduction ratio.Ph. D.
48
Feng, Quanhong. "Novel methods for 3-D semi-automatic mapping of fracture geometry at exposed rock faces." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3181.
Full text
49
Sevindi, Gokhan. "Joint Analysis In The Rock Settlements Of Cappadocia." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1054840/index.pdf.
Full textAbstract:
This thesis attempts to seek a relationship between the joints developed in the ignimbrites and the rock settlements carved in the same units. Orientation of rooms, directions of walls and joints (both in the rooms and in the field) are input data used in the study. Two sites in Cappadocia (Eskigümü
Sler and Ç
anlikilise) are selected to investigate the relationship. Both sites are carved within the same ignimbrite (Kizilkaya) and are located on the south-southeastern slopes of the ignimbrite scarp. Measurements taken from 61 rooms of the former and 27 rooms of the latter are analyzed for the room and joint directions, joint locations in the room and joint densities both in the rooms and in the field. Conclusions derived from the analyses are: 1) The rooms are oriented oblique to joint strike to get the maximum sunlight, 2) Joint directions in the rooms strike in one single direction and greatly differ from the field joint directions, 3) Density of the room joints is less than the field joints indicating that joint spacing is an important factor in the selection of sites, 4) Joints in the Eskigü
mü
Sler sites are concentrated towards the margins of the room while an opposite observation is made for the Ç
anlikilise site, 5) Total length of joints in the largest rooms are relatively shorter.
50
Marchiori, Daniela Gírio. "A mecânica da fratura elástica linear e o modelo coesivo na previsão do fraturamento de rochas." Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-14112012-105517/.
Full textAbstract:
O presente trabalho foi desenvolvido com o intuito de verificar a influência do efeito escala na variação da forma da curva tensão-deformação e na resistência de duas rochas brasileiras: o arenito silicificado da Formação Botucatu e o basalto da Formação Serra Geral. Para tanto, foram executados ensaios de flexão a três pontos, com controle do processo de fraturamento, em amostras de ambas as rochas. Os ensaios foram conduzidos sobre quatro tamanhos diferentes de corpos de prova. Experimentalmente, não foi observada variação na forma da curva força-deslocamento com o tamanho das amostras. Observou-se também que a variação da resistência em função dos tamanhos das amostras aproxima-se do previsto pela Mecânica da Fratura Elástica Linear. As curvas força-deslocamento obtidas experimentalmente foram comparadas com duas outras curvas obtidas numericamente, uma através de simulações baseadas na Mecânica da Fratura Elástica Linear, e outra com base na teoria do Modelo Coesivo de propagação de fraturas em análise não linear. Os dados obtidos mostram que entre as duas simulações numéricas a que apresenta melhor aproximação à simulação experimental é a do Modelo Coesivo e que ambas subestimam os deslocamentos no trecho pós-ruptura dos ensaios.This present work has been developed aiming to verify the scale effect influence on the stress-strain curve form as well on the strength of two Brazilian rocks: Botucatu sandstone and basalt from Serra Geral Formation. Using samples of those rocks three point beam bending experiments have been made in with the crack displacement opening mouth was controlled. The experiments have been conducted using four different samples size. In the experiments no variation in the form of the force-displacement curve has been observed considering those chosen samples sizes. The rock strength variation for those samples is approximately the one predicted by the Linear Elastic Fracture Mechanics Theory. The force-displacement curves experimentally achieved were compared with two other curves obtained numerically, one using the Linear Elastic Fracture Mechanics Theory with FEM and other assuming the fictitious Cohesive Crack Model with BEM. It has been verified that among the two numerical procedures the Cohesive Crack Model gives better results and both give smaller displacements after the rupture.