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1
Maghsoudloo, Arash. "Nonlinearity Of The Residual Shear Strength Envelope In Stiff Clays." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615551/index.pdf.
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During shearing of stiff clays, plate-shaped clay particles are parallel-oriented in the direction of shear reaching the minimum resistance of &ldquoresidual shear strength&rdquo
. The residual shear strength envelopes of stiff clays are curved, but for practical purposes represented by linear envelopes. This study investigates the nonlinearity of the residual shear strength envelope using experimental evidence (i) from laboratory reversal direct shear tests on two stiff clays (Ankara clay and kaolinite) at 25 to 900 kPa effective normal stresses and (ii) from laboratory data collected from literature. To evaluate the importance of nonlinearity of the envelope for geotechnical engineering practice, by limit equilibrium method, (a) case histories of reactivated landslides are analyzed and (b) a parametric study is carried out. Conclusions of this study are: (1) The residual shear strength envelopes of both Ankara clay and kaolinite are nonlinear, and can be represented by a power function (cohesion is zero). (2) At least 3 reversals or cumulative 20 mm shear displacement of direct shear box is recommended to reach residual condition. (3) Empirical relations between plasticity index and residual friction angle can accurately estimate the residual strength of stiff clays. (4) Nonlinearity is especially important for landslides where average effective normal stress on the shear plane is less than 50 kPa, both for translational and rotational failures. For such slopes using a linear strength envelope overestimates the factor of safety (more significantly for the case of high pore pressures). (5) As the plasticity index increases, the power &ldquo
b&rdquo
of the nonlinear shear strength envelope decreases, indicating more significant nonlinearity. For less plastic materials, using linear and nonlinear shear strength envelopes does not affect the factor of safety.
2
Xu, Yingyi. "Residual Strength of Franciscan-Derived Clay." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2128.
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In February of 2017 after a period of heavy rainfall, a slope destabilized behind Fremont Hall on the campus of Cal Poly San Luis Obispo. The geology of this slope stability failure is the Franciscan Complex. The Franciscan Complex, when weathered in place, results in clay soil that makes up the typical soil mantle on the hills throughout the region. Peak strength is the typical parameter tested to assess the strength of the soil. For the Franciscan-derived clay, the residual strength is the focus of this study to understand slope failure since the clay is the weakest portion of the matrix in the Franciscan Complex. Both intact and remolded specimens were processed from the samples obtained from the slide for laboratory testing. The tested material is considered representative of the soil found in the Franciscan Complex along the California coast and other similar regions worldwide where the presence of this mélange results in slope instabilities.
Three different shearing tests were performed to study the residual strength: direct shear reversal, ring shear, and large-scale direct shear reversal. Sampling soil from the slide took place twice: once in 2017 and once in 2019. A block of soil sampled in 2017 was taken after the toe of the slope was cut for reconstruction which resulted in an exposed slide plane. In 2019, additional samples were retrieved near the toe of the slope after subsequent failure of the slope. Although the material was assumed to be from the slide plane, there is a possibility it may have originated from the surrounding matrix. Intact and remolded specimens were tested in direct shear reversal tests, and remolded specimens were tested in ring shear tests. The 2019 source was tested in the large-scale direct shear reversal tests because the material obtained during 2017 was not enough to replicate the large specimen. Remolded specimens were prepared by passing through sieve No. 40. A secondary set of tests were performed on specimens prepared by passing through sieve No. 200.
When comparing remolded against intact specimens, the clasts within the intact material exhibited an influence on the residual strength by an approximate difference of 20%. The results also indicated the liquid limit (LL) had an impact on the residual strength; higher value LL exhibited lower residual strength, and lower value LL exhibited higher residual strength. When comparing the laboratory results against in situ CPT tests, the values from the CPT fell within the range of the laboratory residual strength corresponding to the slide’s depth of movement.
The results from testing these specimens showed the soil obtained directly from the slide failure exhibited a residual strength represented as friction angle of 14° ± 2° for intact soil specimens, 11° ± 3° for remolded specimens of the 2017 failure plane passing through No. 40 sieve, and 22° ± 2° for remolded specimens of the 2019 sample location passing though No. 40 sieve. The remolded specimens passing through sieve No. 200 produced even lower results. However, since all clasts were removed by the No. 200 sieve, those results are not considered representative of field conditions. Based on the test results, and the infinite slope limit equilibrium slope stability analysis, a median range of residual strength for this slide is approximately 12.5 to 14.0°.
3
Melin, Hanna. "Controlling parameters for normal and shear behaviour of rock fractures-a study of direct shear test data from SKB." Thesis, KTH, Jord- och bergmekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93976.
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The deep mining and civil engineering industry need to perform rock stability analyses during excavation projects. The stability is mainly controlled by the shear strength of the rock fractures, which are the weakest point of the rock mass. In turn, the shear strength is governed by the mechanical properties of the fractures. It is both time and cost demanding to determine the properties of the rock fractures in laboratory. Also, the interpretation of the results requires a deep understanding of the normal and shear behaviour of rock fractures. This study aims to investigate if it is possible to determine the peak shear strength of rock fractures by merely estimating fracture parameters during field mapping and core logging. SKB supplied test results on drilled bore cores from site investigations in Forsmark and Laxemar for deep nuclear waste deposits. SKB generated data of high quality and in large quantity, which made it very valuable for the purpose of the study. The study begins with a literature review and an interaction matrix, clarifying the relationships between mechanical properties and affecting parameters of rock fractures. The predicted relationships of the parameters are then tested in an analysis based on the compiled data from SKB. The results show that the peak friction angle, the residual friction angle and the dilation angle are possible to approximate for open granite fractures in deep mining projects. Further on, the study proposes that the joint matching coefficient is included in the field mapping and core logging since it has a strong influence on the mechanical behaviour of the fracture, notably the normal and shear stiffness. Finally, the study questions estimations of JRC on small samples.
4
McGillivray, Alexander Vamie. "Enhanced Integration of Shear Wave Velocity Profiling in Direct-Push Site Characterization Systems." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19714.
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Enhanced Integration of Shear Wave Velocity Profiling in Direct-Push Site Characterization Systems
Alexander V. McGillivray
370 Pages
Directed by Dr. Paul W. Mayne
Shear wave velocity (VS) is a fundamental property of soils directly related to the shear stiffness at small-strains. Therefore, VS should be a routine measurement made during everyday site characterization. There are several lab and field methods for measuring VS, but the seismic piezocone penetration test (SCPTu) and the seismic dilatometer test (SDMT) are the most efficient means for profiling the small-strain stiffness in addition to evaluating large-strain strength, as well as providing evaluations of the geostratigraphy, stress state, and permeability, all within a single sounding.
Although the CPT and DMT have been in use for over three decades in the USA, they are only recently becoming commonplace on small-, medium-, and large-size projects as more organizations begin to realize their benefits. Regrettably, the SCPTu and the SDMT are lagging slightly behind their non-seismic counterparts in popularity, in part because the geophysics component of the tests has not been updated during the 25 years since the tests were envisioned. The VS measurement component is inefficient and not cost effective for routine use. The purpose of this research is to remove the barriers to seismic testing during direct-push site characterization with SCPTu and SDMT.
A continuous-push seismic system has been developed to improve the integration of VS measurements with SCPTu and SDMT, allowing VS to be measured during penetration without stopping the progress of the probe. A new type of portable automated seismic source, given the name RotoSeis, was created to generate repeated hammer strikes at regularly spaced time intervals. A true-interval biaxial seismic probe and an automated data acquisition system were also developed to capture the shear waves. By not limiting VS measurement to pauses in penetration during rod breaks, it is possible to make overlapping VS interval measurements. This new method, termed frequent-interval, increases the depth resolution of the VS profile to be more compatible with the depth intervals of the near-continuous non-seismic measurements of the SCPTu and the SDMT.
5
Campanini, Davide. "Comparison between Direct Tensile and Single Lap Shear for FRCM/SRG composites." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17203/.
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Negli ultimi decenni sono state sviluppati nuovi materiali e tecnologie per il rinforzo e la riabilitazione delle strutture esistenti. I sistemi più recenti per il rinforzo esterno ed il recupero strutturale sono materiali compositi costituiti da fibre raggruppate in forma di tessuto ed impregnate ed immerse in una matrice inorganica. Quando il tessuto è composto da fibre di aramide, vetro, basalto, PBO o carbonio, questi compositi sono comunemente definiti Fabric Reinforced Cementitious Matrix (FRCM), mentre, quando il tessuto è fatto da micro-trefoli di acciaio, sono definiti Steel Reinforced Grout (SRG).
In accordo con le rispettive normative, negli Stati Uniti le proprietà meccaniche dei compositi FRCM/SRG si misurano tramite una prova di tensione diretta su provini caricati utilizzando ancoraggi a forcella (clevis grip). In Europa, invece, si ricorre ad una prova di aderenza o single-lap shear su compositi applicati su un substrato cementizio o in muratura.
L’obiettivo di questa tesi è confrontare i risultati ottenuti mediante i due metodi di caratterizzazione sviluppando una campagna sperimentale su due diversi tipi di compositi: un FRCM con fibra di carbonio (CFRCM) e un composito SRG. L’effetto di tre diverse lunghezze di ancoraggio è stato studiato per il sistema CFRCM. L’influenza del numero di strati di tessuto è stata analizzata sia per il sistema CFRCM che SRG considerando uno o due strati.
I risultati mostrano che le differenti condizioni al contorno influenzano in modo significativo la caratterizzazione dei compositi. Per ottenere una misura rappresentativa delle proprietà meccaniche dei compositi FRCM/SRG, è richiesta una lunghezza di ancoraggio sufficiente. Questo studio contribuisce a sviluppare un database sperimentale che consenta la definizione di affidabili protocolli di caratterizzazione. Inoltre, fornisce informazioni rilevanti ai fini progettuali riguardo la lunghezza di ancoraggio adeguate e all’efficacia di applicazioni multistrato.
6
Echegaray, Oviedo Javier Andrés. "Upgrading the push-off test to analyze the contribution of steel fiber on shear transfer mechanisms." Doctoral thesis, Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/43723.
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The shear behavior of a specimen made of reinforced concrete is complex. The resisting mechanisms are affected by different factors such as section form, slimness of the specimen, longitudinal and transversal reinforcement arrangement, adhesion between concrete and steel, among others. Addition of steel fibers to the concrete improves the ductility as well as the tensile behavior; providing good control during the cracking process. Fibers also enhance the shear behavior of structural elements, increasing ultimate resistance and ductility.
Push-off tests had been used to study the mechanisms of concrete shear transfer. Shear strength of the specimen depends on the contribution of both concrete and reinforcement. Aggregate interlock has a significant contribution to the concrete shear capacity. In the last decades new kinds of concrete have been developed for industrial use, such as high strength concrete (HSC), self-compacting concrete (SCC) or fiber reinforced concrete (FRC), among others. In these new materials aggregate interlock phenomenon may be different when compared to conventional concrete (CC). There is a lack of information in literature about the mechanisms of shear transfer in fiber reinforced concrete elements.Echegaray Oviedo, JA. (2014). Upgrading the push-off test to analyze the contribution of steel fiber on shear transfer mechanisms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43723
TESIS
7
Hassan, Zehtab Kaveh. "An Assessment Of The Dynamic Properties Of Adapazari Soils By Cyclic Direct Simple Shear Tests." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612228/index.pdf.
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Among the hard-hit cities during 17 August 1999 Kocaeli Earthquake (Mw 7.4), Adapazari is known for the prominent role of site conditions in damage distribution. Since the strong ground motion during the event was recorded only on a rock site, it is necessary to estimate the response of alluvium basin before any study on the relationship between the damage and the parameters of ground motion. Therefore, a series of site and laboratory tests were done on Adapazari soils in order to decrease the uncertainty in estimation of their dynamic properties. In downtown Adapazari, a 118 m deep borehole was opened in the vicinity of heavily damaged buildings for sample recovery and in-situ testing. The stiffness of the soils in-situ is first investigated by standard penetration tests (SPT) and by velocity measurements with P-S suspension logging technique. Disturbed samples were recovered by core-barrel and split-barrel samplers. 18 Thin-Walled tubes were successively used for recovering undisturbed samples. A series of monotonic and cyclic direct simple shear tests were done on specimens recovered from the Thin-Walled tubes. It is concluded that the secant shear modulus and damping ratio of soils exposed to severe shaking during the 1999 event are significantly smaller than those estimated by using the empirical relationships in literature. It is also observed that the reversed-S shaped hysteresis loops are typical for cyclic response of the samples.
8
Hajdarwish, Ala' M. "Geologic Controls of Shear Strength Behavior of Mudrocks." Kent State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=kent1162259344.
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9
Iscimen, Mehmet. "Shearing Behavior Of Curved Interfaces." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7256.
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The frictional behavior of soil-construction material interfaces is of significant importance in geotechnical engineering applications such as retaining structures, pile foundations, geosynthetic liners, and trenchless technologies. Since most failures initiate and develop on the interfaces, special attention is required to predict the capacity of these weak planes in the particular application.
Pipe-jacking and microtunneling technologies are being more widely used over the past decade and there is significant interest to predict the jacking forces and jacking distances achievable in order to achieve more efficient design and construction. This study focuses on the evaluation of the frictional characteristics and factors affecting the shear strength of pipe-soil interfaces. Eight different pipes made from fiber reinforced polymer (FRP), polycrete, steel, concrete, and vitrified clay were tested in the experimental program.
For this purpose, a new apparatus was designed to conduct conventional interface direct shear testing on pipes of different curvature. This device allows coupons cut from actual conduits and pipes to be tested in the laboratory under controlled conditions. The apparatus includes a double-wall shear box, the inner wall of which is interchangeable to allow for testing against surfaces of different curvatures. By considering a narrow width section, the circular interface of pipes was approximated with a surface along the axial direction and the boundary is defined by the inner box.
Roughness tests were performed using a stylus profilometer to quantify the surface characteristics of the individual pipes and relate these to the interface shear behavior. The surface topography showed different degrees of variability for the different pipes. To extend the range of roughness values tested and force the failure to occur in the particulate media adjacent to the interface, two artificial pipe surfaces were created using rough sandpapers.
Interface shear tests were performed using the new apparatus with air-pluviated dense specimens of Ottawa 20/30 sand. Additional tests were performed using Atlanta blasting sand to evaluate the effect of particle angularity. The effect of normal stress and relative density were also examined. The interface strength was shown to increase with surface roughness and finally reach a constant value above a certain critical roughness value, which corresponded to the internal strength of the soil itself. This represented the failure location moving from the interface into the soil adjacent to the interface. Both the strength and the shearing mechanism were thus affected by the surface topography. It was also shown that the interface shear strength was affected by particle angularity, relative density and normal stress.
10
Persson, Erik. "Empirical correlation between undrained shear strength and preconsolidation pressure in Swedish soft clays." Thesis, KTH, Jord- och bergmekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213848.
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The undrained shear strength and preconsolidation pressure are key parameters in describing the characteristics of soft clays. The two parameters both reflect the clay’s structure and state of stress, and hence empirical correlations for undrained shear strength normalized with respect to preconsolidation pressure are widely used to assess soil behavior. The empirical correlations given in the literature are typically dependent on liquid limit, or plasticity index, but some studies have questioned the dependency and proposed correlations constant for consistency limits. Data from geotechnical projects often display a considerable scatter and deviate from established empirical correlations. In this thesis, statistical analyses are performed and evaluated qualitatively on direct simple shear, constant rate of strain and fall cone test data from 146 sampling points with a total of 596 soil samples from Stockholm, Gothenburg and Uppsala. The aim is to investigate the correlation between shear strength and the preconsolidation pressure. The thesis evaluates the normalized shear strength’s dependency on liquid limit, how the data corresponds to Hansbo’s (1957) and Swedish Geotechnical Institute’s (2007) linear empirical correlations, and the correction factor applied to shear strength measured by the fall cone test. The results of the study show that the correction factor typically reduces the shear strength from fall cone tests too much with respect to shear strength from direct simple shear tests. The normalized shear strength’s dependency on liquid limit may be rejected for the fall cone test data. The results for direct simple shear test data however, indicates a correlation with liquid limit. The data scatter is considerable, especially for fall cone test data, and the relevance of describing the normalized shear strength from fall cone test with a linear empirical correlation to liquid limit may conclusively be questioned.Skjuvhållfasthet och förkonsolideringstryck är två viktiga jordparametrar för lösa leror. Båda parametrar reflekterar lerans struktur och spänningstillstånd, och empiriska korrelationer för odränerad skjuvhållfasthet, normaliserad mot förkonsolideringstrycket, används därför ofta för att bedöma en leras egenskaper. De empiriska korrelationerna är vanligen kopplade till flytgräns eller plasticitetsindex. Dessa korrelationer har däremot ifrågasatts av studier som i vissa fall istället föreslagit ett konstant förhållande mellan normaliserad odränerad skjuvhållfasthet och plasticitetsgränser. Mätvärden från geotekniska projekt i Sverige visar allmänt stor spridning avseende dessa parametrar och data avviker ofta från etablerade empiriska korrelationer. I examensarbetet har data från direkta skjuvförsök, ödometerförsök och fallkonförsök utvärderats statistiskt och kvalitativt. Totalt omfattar studien 596 jordprover från 146 provtagningspunkter från Stockholm, Göteborg och Uppsala. Syftet med studien är att undersöka korrelationen mellan odränerad skjuvhållfasthet och förkonsolideringstryck. Studien behandlar den normaliserade skjuvhållfashetens flytgränsberoende, Hansbos (1957) och Statens Geotekniska Instituts (2007) empiriska korrelationer, samt den korrektionsfaktor som ska tillämpas på skjuvhållfastheter från fallkonförsök. Resultatet visar att korrektionsfaktorn reducerar skjuvhållfastheten för mycket och att korrigerade skjuvhållfastheter är i sämre samstämmighet med skjuvhållfastheter från direkta skjuvförsök än okorrigerade. Data från fallkonförsök uppvisar inget tydligt flytgränsberoende, medan resultaten från direkta skjuvförsök indikerar ett beroende. Spridningen i data är dock påfallande, särskilt för fallkonförsöket. Relevansen i att tillämpa en linjär empirisk korrelation för odränerad normaliserad från fallkonförsök mot förkonsolideringstryck beroende av flytgräns bör ifrågasättas.
11
Song, Yongxiang. "Réalisation du système triaxial assisté par ordinateur et étude du cisaillement direct 3D pour joints rocheux." Grenoble 1, 1992. http://www.theses.fr/1992GRE10209.
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On presente dans cette these un systeme triaxial assiste par ordinateur et un appareillage de cisaillement direct pour joints rocheux. Ce systeme triaxial de revolution est constitue par une presse electromecanique commerciale et deux controleurs pression-volume, ainsi qu'un micro-ordinateur avec une carte d'acquisition (a/n, n/a et e/s). Ce systeme pilote par l'ordinateur peut realiser tous les essais triaxiaux asservis en deformation ou en contrainte, ainsi que des essais cycliques. Un nouvel essai en escalier, draine ou non draine, est presente. Ce type de chemin trouve son interet dans des simulations de comportement pour connaitre des deformations resultant d'increments de contraintes apportes par des ouvrages. Ce systeme developpe recemment est analyse par les resultats des essais et par une comparaison entre deux modes d'asservissement. Quelques criteres sont presentes pour garantir la qualite d'asservissement ainsi que la reussite des essais. La precision du systeme et les facteurs resultant des erreurs sont aussi discutes. Le cisaillement direct pour joints rocheux est en cours de developpement dans la version 2d et sera transforme ulterieurement dans la version 3d. Il est possible de realiser les essais de cisaillement direct en trois modes de sollicitation (axisymetrique, homogeneite cinematique et homogeneite statique). Le principe du projet et le mode d'asservissement sont presentes avec leur calcul
12
Nam, Soonkie. "Effects of Reservoir Releases on Slope Stability and Bank Erosion." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77114.
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Reservoir release patterns are determined by a number of purposes, the most fundamental of which is to manage water resources for human use. Managing our water resources means not only controlling the water in reservoirs but also determining the optimum release rate taking into account factors such as reservoir stability, power generation, water supply for domestic, industrial, and agricultural uses, and the river ecosystem. However, riverbank stability has generally not been considered as a factor, even though release rates may have a significant effect on downstream riverbank stability. Riverbank retreat not only impacts land properties but also damages structures along the river such as roads, bridges and even buildings. Thus, reservoir releases need to also take into account the downstream riverbank stability and erosion issues.
The study presented here investigates the riverbank stability and erosion at five study sites representing straight as well as inside and outside channel meander bends located on the lower Roanoke River near Scotland Neck, North Carolina. Extensive laboratory and field experiments were performed to define the hydraulic and geotechnical properties of the riverbank soils at each site. Specifically, soil water characteristic curves were determined using six different techniques and the results compared to existing mathematical models. Hydraulic conductivity was estimated using both laboratory and in situ tests. Due to the wide range of experimentally obtained values, the values determined by each of the methods was used for transient seepage modeling and the modeling results compared to the actual ground water table measured in the field. The results indicate that although the hydraulic conductivities determined by in situ tests were much larger than those typically reported for the soils by lab tests, numerical predictions of the ground water table using the in situ values provided a good fit for the measured ground water table elevation. Shear strengths of unsaturated soils were determined using multistage suction controlled direct shear tests. The test method was validated, and saturated and unsaturated shear strength parameters determined. These parameters, which were determined on the basis of results from both laboratory and field measurements, and the associated boundary conditions, which took into account representative flow rates and patterns including peaking, drawdown and step-down scenarios, were then utilized for transient seepage analyses and slope stability analyses performed using SLIDE, a software package developed by Rocscience. The analyses confirmed that the riverbanks are stable for all flow conditions, although the presence of lower permeability soils in some areas may create excess pore water pressures, especially during drawdown and step-down events, that result in the slope becoming unstable in those locations. These findings indicate that overall, the current reservoir release patterns do not cause adverse impacts on the downstream riverbanks, although a gradual drawdown after a prolonged high flow event during the wet season would reduce unfavorable conditions that threaten riverbank stability.Ph. D.
13
Toufigh, Vahid. "Testing and Evaluation of Confined Polymer Concrete Pile with Carbon Fiber Sleeve." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293492.
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The goal of this research is to investigate the behavior of polymer concrete confined with a carbon fiber sleeve used as a pile foundation. To evaluate the behavior of a confined polymer concrete pile in this research, four steps was considered. The first step of this investigation considered the mix design of polymer concrete, polymer concrete is a new material which is a combination of epoxy resin and aggregate. Instead of using a traditional mix of cement and water to make concrete, epoxy resin is used. Three dissimilar varieties of aggregate are mixed with different ratios in order to reach the maximum bulk density to obtain the maximum strength. After discovering the optimum ratio which gives the maximum bulk density, several samples of the aggregate are mixed with different ratios of epoxy resin. Next, the samples are investigated in a compression test to observe which ratios have the maximum strength and this ratio is used for a polymer concrete mix design to create a pile foundation. The pile is a built using a cast in place method and confined with a sleeve of carbon fiber. The second part of this investigation determined the structural mechanical properties of confined polymer concrete pile material. The unconfined and confined polymer concrete was tested in compression to determine compressive strength and stress-strain behavior. Similar tests were conducted on unconfined and confined cement concrete for comparison between these materials. Additional tension tests were conducted on unconfined polymer concrete. Then, a carbon fiber sleeve was tested in compression test to determine tensile strength and tension stress-strain behavior. After these tests, the confined polymer concrete is modeled in the computer program MATTCAD which is used to calculate the theoretical bending moment capacity and load-displacement curve. Finally, the confined polymer concrete is tested with the MTS 311 Load Frame in three point load flexure test to determine the experimentally bending moment capacity, load-displacement curve and compare with theoretical results. Confined polymer concrete was tested in one and two way cyclic loading to observe the ductility behavior of this material as laterally loaded piles and compared with cement concrete results in cyclic loading. The third part of this investigation determined the geotechnical mechanical properties of confined polymer concrete pile material. Cyclic Multi Degree of Freedom (CYMDOF) device was used to determine interface reaction and friction angle between confined polymer concrete and soil with interface shear test theory method. Furthermore, the same device was used to determine the friction angle of soil with direct shear test theory, and compare the friction angle results together. The last part of this investigation considered the behavior of different sized confined polymer concrete pile in different types of soil. A confined polymer concrete pile was modeled into PLAXIS and OPENSEES PL computer software to analysis pile in axial load and lateral load respectively. Furthermore, a cement concrete pile was modeled with similar software and conditions to compare these two materials.
14
Peri, Elena. "An investigation on the behaviour of a shallow foundation resting on a layered soil near a slope." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Find full textAbstract:
In questo progetto, portato avanti alla University of Western Australia, viene analizzato il comportamento di una fondazione superficiale su un pendio in sabbia sopra un deposito di argilla.
Dopo avere ricavato sperimentalmente i parametri di resistenza di sabbia e argilla, si è proceduto al calcolo con Plaxis 2D della capacità portante della fondazione a striscia sopra questa stratigrafia. I parametri che sono stati considerati in questi modelli sono sia geometrici che di resistenza.
Dopo l'analisi numerica si è elaborata un'equazione che lega capacità portante e tutti i parametri.
Oltre alla parte 2D si è studiata un'applicazione pratica 3D. Con Plaxis 3D si sono calcolati modelli rappresentanti un bulldozer su un pendio in sabbia sopra un deposito di terreno a grana fine.
Anche per questa applicazione si è elaborata un'equazione per ricavare la capacità portante.
15
Errico, Carmine. "Determination of the influence of SRG anchors on the bond behavior of SRG/FRCM strips bonded to a quasi-brittle substrate." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The use of FRCM composites (Fiber Reinforced Cementitious Matrix) is becoming more and more widespread. The inorganic matrix guarantees many advantages, especially when dealing with masonry substrates, including a good compatibility from both a physical and a chemical point of view and the lower sensitivity to debonding phenomena at the interface.
Compared to FRP composites, which presents many data in the literature, FRCM composites must be studied in detail and research in this field has only begun in recent years. This work deals with an important problem: the realization of an anchorage system to improve the strength of composites and allow their use even in the absence of adequate development length.
In this study, the effectiveness of the anchorage system and the interaction with an externally bonded FRCM were studied on masonry columns. The columns were tested until failure condition in the Laboratory of Structural and Geotechnical Engineering (DICAM – LISG) of the University of Bologna, via del Lazzaretto 15/5, Bologna.
Test results demonstrate that the introduction of additional anchorages improves the effectiveness of the FRCM composites in terms of resistance and loading capacity.
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Stewart, Scott William. "Rock mass strength and deformability of unweathered closely jointed New Zealand greywacke." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1224.
Full textAbstract:
Closely jointed greywacke rock masses are widespread throughout both the North and South Islands of New Zealand and much of New Zealand's infrastructure is constructed upon greywacke rock masses. This thesis deals with determining the rock mass strength of unweathered closely jointed New Zealand greywacke rock masses. Currently, the estimation of rock mass strength and deformability is reasonably well predicted through the use of such empirical failure criteria as the Hoek-Brown failure criterion and empirical expressions to predict deformability. However, previous studies upon predicting the strength and deformability of unweathered closely jointed New Zealand greywacke rock masses has shown that existing empirical methods of determining strength and deformability are unsatisfactory. The problem with predicting rock mass strength and deformability moduli of New Zealand greywacke and the lack of adequate data to calibrate a failure criterion was the starting point for this work. The objective of this thesis was to increase the knowledge of intact and defect properties of closely jointed greywacke, develop reliable rock mass data with which to calibrate a failure criterion and improve the ability to estimate the rock mass strength of greywacke rock masses. A review of existing failure criteria for rock masses was conducted and of these criteria, the Hoek-Brown rock mass failure criteria was selected to calibrate to both the intact rock and rock mass failure data, because of its broad acceptance in the rock mechanics community. A database of greywacke properties was developed based on previous studies upon unweathered greywacke around New Zealand and is attached to the thesis as an Appendix. The database included descriptions of greywacke defect properties and mechanical properties of the intact rock and joints. From this database, inputs could be justified for numerical modelling and later analyses of failure criteria. Records from the construction archives of the Benmore and Aviemore hydroelectric power projects in the South Island of New Zealand were reviewed to obtain information and results from a series of shear tests carried out on unweathered closely jointed greywacke in the 1960s. Data on rock mass strength at failure and rock mass deformability were extracted from these records to assess the predictability of the failure criterion and deformability expressions. Problems experienced during the shear tests at the Aviemore dam site created doubt as to the actual rock mass strengths achieved at failure. The behaviour of these tests was studied using the finite difference code FLAC. The work was aimed at investigating the potential for transfer of shear force between the two concrete blocks sheared in each test and the impact shear force transfer had upon the likely normal stresses beneath each block at failure. The numerical modelling results indicated that a combination of preferential failure occurring in one direction, and doubt in the actual normal load applied to the concrete blocks during testing lead to premature failure in the blocks sheared upstream. The blocks sheared in the opposite direction failed at normal stresses that are reflective of the strength of an unweathered greywacke rock mass, but these results could be explained by failure occurring along defects therefore not satisfying the assumptions of homogeneity typically required of a rock mass failure criterion. The Hoek-Brown failure criterion for intact rock was investigated by fitting it to the largest intact greywacke datasets. For a full set of test data (i.e. including tensile data), the Mostyn & Douglas (2000) variant of the Hoek-Brown failure criterion gave the best fit for a full set of rock mass data. A multiple regression method was developed which improved the fitted curve to intact data in the tensile region and gave the best estimate of tensile strength if no existing lab results for tensile strength were available. These results suggest that the Hoek-Brown failure criterion is significantly limited in its applicability to intact NZ greywacke rock. Hoek-Brown input parameters different to those suggested by Hoek et al (2002) are recommended for using the Hoek-Brown failure criterion for intact NZ greywacke. For closely jointed NZ greywacke rock masses, the results from the shear tests at Aviemore and Benmore were separated into different GSI classes and Hoek-Brown envelopes fitted to the datasets by multiple regression. Revised expressions were proposed for each Hoek-Brown input parameter (mb, s, ab) as a function of the GSI. The resulting revised Hoek-Brown failure envelopes for NZ greywacke offer a significant improvement on the existing criterion used to predict the strength of NZ greywacke intact rock and rock masses. The differences in the behaviour of the reaction blocks that failed before the test blocks and the reduction in rock strength due to sliding along defects from that predicted could be reasoned from recorded observations and the behaviour of the concrete blocks during the shear tests. This study has clearly illustrated the need for continued research in this area. This includes (1) a means of assessing the role of defects upon the shear strength of closely jointed greywacke rock mass into a failure criterion, (2) further modelling of the in-situ shear tests by a discrete element procedure to expressly determine the role of the defect on failure, (3) more testing on rock masses to obtain more data to calibrate a rock mass failure criterion, and (4) more studies on predicting the strength of extremely disturbed rock masses.
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Arrelucé, Montenegro Sebastian, and Larrauri Grecia Luciana Solís. "Incorporación de fibras de polipropileno como método de reforzamiento de suelos arcillosos en Palian - Huancayo." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/656164.
Full textAbstract:
Esta tesis tiene como objetivo evaluar un método de reforzamiento propuesto en base a la incorporación de fibras de polipropileno con la finalidad de incrementar la resistencia y mejorar las características mecánicas del suelo arcilloso de Palian – Huancayo.
La arcilla es un suelo cohesivo constituido por partículas finas, estas características determinan la capacidad de deformación y compresión, además poseen baja resistencia al corte y a cargas. Debido a ello se busca reforzar y mejorar el comportamiento mecánico de la arcilla mediante métodos físicos y químicos.
Esta investigación propone la adición fibras de polipropileno como método de reforzamiento para lo cual se analizó el suelo remoldeado con diferentes porcentajes de fibras adicionadas 0.1, 0.2, 0.3, 0.4 y una longitud de fibra de 10 milímetros. Se realizaron ensayos de caracterización física para identificar el suelo natural remoldeado: granulometría por sedimentación, límites de consistencia y gravedad específica de los sólidos. Se sometió el suelo natural remoldeado y las mezclas con diferentes porcentajes de fibras a los siguientes ensayos de caracterización mecánica para determinar las variaciones en el comportamiento: ensayo de compactación estándar, ensayo de corte directo y ensayo de compresión simple.
Los valores obtenidos mediante los ensayos realizados demostraron la mejora de las características mecánicas del suelo siendo la mezcla de 0.4% de fibras de polipropileno la que brinda un mejor resultado en comparación con las mezclas de menor proporción.This thesis aims to evaluate a reinforcement method based on the incorporation of polypropylene fibers to increase the strength and improve the mechanical characteristics of Palian- Huancayo’s clay soil. Clay is a cohesive soil consisting of fine particles, these characteristics determine the capacity of deformation and compression, as well as low resistance to cutting and loads. Therefore, it seeks to strengthen and improve the mechanical behavior of clay through physical and chemical methods. This research proposes the addition of polypropylene fibers as reinforcement method for which the soil under study was analyzed with different percentages of fibers added 0.1, 0.2, 0.3, 0.4 and a fiber length of 10 millimeters. Physical characterization tests were carried out to identify the natural soil: granulometry by sedimentation, limits of consistency and specific gravity of the solids. The natural soil and the mixtures with different percentages of fibers were subjected to the following mechanical characterization tests to determine the variations in behavior: Standard compaction test, unconfined compression test, and shear direct test. The values obtained through the tests demonstrated the improvement of the mechanical characteristics of the soil being the mixture of 0.4% of polypropylene fibers the one that provides a better result compared to the mixtures of a lower proportion.
Tesis
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Nouailletas, Olivier. "Comportement d'une discontinuité dans un géomatériau sous sollicitations chemo-mécanique - expérimentations et modélisations." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3038/document.
Full textAbstract:
Ces travaux de thèse s'intéressent à l'étude du comportement d'une discontinuité dans un géomatériau sous sollicitations chemo-mécaniques à l'échelle du laboratoire. Des essais de traction-compression cyclique étudient la refermeture d'une fissure. Ils indiquent que les déformations inélastiques seraient gouvernées en partie par les frottements générés lors du ré-emboîtement des lèvres de la discontinuité, non correspondantes du fait des contraintes internes. Des joints rocheux altérés chimiquement sous sollicitation tangentielle sont étudiés au travers d'essais de cisaillement direct : le comportement des joints dégradés est profondément modifié du fait de la diminution des propriétés mécaniques du matériau de part et d'autre de la discontinuité et de l'accentuation de la non-correspondance des profils rugueux. Le comportement d'une discontinuité est modélisée par le couplage d'un modèle élasto-plastique endommageable continu avec une résolution discrète du problème de contact/frottement (code calcul aux éléments finis Cast3M). Les résultats numériques confirment les phénomènes constatés expérimentalementThis PhD dissertation presents a study aiming at a better understanding of cracks behavior in a geomaterial. The study focuses on the behavior of discontinuities under chemo-mechanical solicitations at the laboratory scale. The mechanical behavior under normal stress is assessed with cyclic tension-compression tests. Experimental data indicate that the inelastic deformations could be partially governed by the friction generated during the closing of the discontinuity lips, and the asperities mismatch is related to the internal stresses. The shear behavior of a rock joint chemically degraded was studied through direct shear tests. Results pointed out significant modifications for altered joints induced by: 1) the mismatch enhancement of the rough profiles of the discontinuity and, 2) the degradation of the mechanical properties of the material on both sides of the discontinuity due to the chemical attack. These experimental results have been used as input data to model the behavior of a discontinuity by the coupling of a continuous elastic-plastic damaged model with a discrete solving of the contact/friction problem. The simulations performed under Cast3M correctly represent the phenomena observed during the experimental testing program
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Nouailletas, Olivier. "Comportement d'une discontinuité dans un géomatériau sous sollicitation chemo-mécanique : expérimentations et modélisations." Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/110.
Full textAbstract:
Résumé : Ces travaux de thèse s'intéressent à l'étude du comportement d'une discontinuité dans un géomatériau sous sollicitations chemo-mécaniques à l'échelle du laboratoire. Des essais de traction-compression cyclique étudient la refermeture d'une fissure. Ils indiquent que les déformations inélastiques seraient gouvernées en partie par les frottements générés lors du ré-emboîtement des lèvres de la discontinuité, non correspondantes du fait des contraintes internes. Des joints rocheux altérés chimiquement sous sollicitation tangentielle sont étudiés au travers d'essais de cisaillement direct : le comportement des joints dégradés est profondément modifié du fait de la diminution des propriétés mécaniques du matériau de part et d'autre de la discontinuité et de l'accentuation de la non-correspondance des profils rugueux. Le comportement d'une discontinuité est modélisée par le couplage d'un modèle élasto-plastique endommageable continu avec une résolution discrète du problème de contact/frottement (code calcul aux éléments finis Cast3M). Les résultats numériques confirment les phénomènes constatés expérimentalement.//Abstract: To probate the technology of CO[indice inférieur 2] geological storage, the integrity of the site must be assure over time. This industruial problematic involves the study of the mechanical properties alteration of geomaterials in the presence of CO[indice inférieur 2]. The scenario at the origin of this thesis illustrates the possibility of a CO[indice inférieur 2] leakage on a fault located in the caprock. This geological problem is complicated by the many parameters to consider: in situ temperature and pressure, scale effect, heterogeneities of the geomaterial, geofluide composition, chemical reactions ... These works focus on the behavior of a discontinuity in a geomaterial solicited chemomechanically at the laboratory scale. They were realised in cotutelle between SIAME laboratory at the University of Pau and Pays de l'Adour (France) and the laboratory of rock mechanics and engineering geology from the University of Sherbrooke (Quebec, Canada). The first part of the experimental program was defined to characterize the reclosing of a crack under cyclic uniaxial stress. The second experimental campaign has studied the shear behavior of a rock joint chemically degraded. The data obtained were used to model the behavior of a discontinuity by the finite element method. The mechanical behavior of a crack under normal stress is assessed with cyclic tension-compression tests. Stress curve showed hysteresis during opening and closing cycles of a discontinuity in concrete, it indicated inelastic deformations The analysis of displacement field by image correlation indicated that theses deformations were partially governed by the friction generated during the closing of the discontinuity lips. Frictional phenomena are due to asperities mismatching induced by the internal stresses in the concrete. The shear behavior of a rock joint chemically damaged was studied through direct shear tests. Rough surfaces were immersed in acid solution during 6 hours at constant pH. Digitalization of these surfaces befor and after immesion, with a lase profilometer, indicates little modifications of the geometry induced by dissolution of material. Results of tests pointed out significant modifications for altered joints illustred by a of the peak shear strength and an increased of contractancy. They are induced by: 1) the mismatch enhancement of the rough profiles of the discontinuity and, 2) the degradation of the mechanical properties of the material on both sides of the discontinuity due to the chemical attack. Numerical contribution of the thesis lies in modeling the behavior of a discontinuity by the coupling of an continuous elastic-plastic damaged model with a discrete resolution of the contact/friction problem. The model is developed with the finite element code Cast3M. Geometries lips discontinuities are modeled directly from the roughness profiles from experimental scans. The numerical results correctly represent the friction phenomena observed experimentally. Finally, a model of the shear test altered joints is performed by coupling the mechanical model with chemical damage model.
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Reis, Jeselay Hemetério Cordeiro dos. "Modelo de atrito estático em interfaces de contato entre concreto e areia." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-17072006-111343/.
Full textAbstract:
Esta tese apresenta os princípios e a formulação de um modelo não-linear de atrito estático em interface de concreto areia. A hipótese básica para desenvolvimento das equações consiste na ocorrência do atrito de deslizamento (atrito verdadeiro), do atrito de rolamento (rearranjo das partículas) e da dilatância (variação de volume durante o cisalhamento). A solução analítica do modelo considera o efeito da rugosidade da superfície de contato, da curva granulométrica da areia e do seu estado de compacidade inicial. Foram realizados ensaios de cisalhamento direto com carga normal constante em interface de contato entre concreto e areia com seção de 500 mm x 500 mm com o objetivo de permitir a calibração do modelo proposto. É discutida e sugerida a incorporação da equação constitutiva desse modelo em análises de interação solo-estrutura via método dos elementos finitos. Sua aplicabilidade é demonstrada através da análise 1D e 2D de estacas de atrito executadas em areia e submetidas a carregamentos de compressãoThis thesis presents the principles and formulation underlying a concrete-sand interface nonlinear static friction model. The basic hypothesis employed in the development of the model equation takes into account the interface sliding friction (true friction), a rolling friction (particle rearrangement) and dilatancy(volume variation during shear). The model analytical solution considers the effect of roughness of the contact surface, the grain size distribution and its initial state of compactness of the sand. To calibrate the proposed model, a direct shear stress test under constant load was carried out along a 500mm x 500mm section concrete-sand interface. Furthermore, a discussion and suggestion of the inclusion of the model constitutive equation applied to the analysis of soil-structure interaction using the finite element method are presented. The applicability of the proposed model is proven through the analysis of 1-D and 2-D skin friction piles made of sand mass subjected to compression load
21
Nouailletas, Olivier. "Comportement d'une discontinuit?? dans un g??omat??riau sous sollicitation chemo-m??canique : exp??rimentations et mod??lisations." Thèse, Universit?? de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/110.
Full textAbstract:
R??sum?? : Ces travaux de th??se s'int??ressent ?? l'??tude du comportement d'une discontinuit?? dans un g??omat??riau sous sollicitations chemo-m??caniques ?? l'??chelle du laboratoire. Des essais de traction-compression cyclique ??tudient la refermeture d'une fissure. Ils indiquent que les d??formations in??lastiques seraient gouvern??es en partie par les frottements g??n??r??s lors du r??-embo??tement des l??vres de la discontinuit??, non correspondantes du fait des contraintes internes. Des joints rocheux alt??r??s chimiquement sous sollicitation tangentielle sont ??tudi??s au travers d'essais de cisaillement direct : le comportement des joints d??grad??s est profond??ment modifi?? du fait de la diminution des propri??t??s m??caniques du mat??riau de part et d'autre de la discontinuit?? et de l'accentuation de la non-correspondance des profils rugueux. Le comportement d'une discontinuit?? est mod??lis??e par le couplage d'un mod??le ??lasto-plastique endommageable continu avec une r??solution discr??te du probl??me de contact/frottement (code calcul aux ??l??ments finis Cast3M). Les r??sultats num??riques confirment les ph??nom??nes constat??s exp??rimentalement.//Abstract: To probate the technology of CO[indice inf??rieur 2] geological storage, the integrity of the site must be assure over time. This industruial problematic involves the study of the mechanical properties alteration of geomaterials in the presence of CO[indice inf??rieur 2]. The scenario at the origin of this thesis illustrates the possibility of a CO[indice inf??rieur 2] leakage on a fault located in the caprock. This geological problem is complicated by the many parameters to consider: in situ temperature and pressure, scale effect, heterogeneities of the geomaterial, geofluide composition, chemical reactions ... These works focus on the behavior of a discontinuity in a geomaterial solicited chemomechanically at the laboratory scale. They were realised in cotutelle between SIAME laboratory at the University of Pau and Pays de l'Adour (France) and the laboratory of rock mechanics and engineering geology from the University of Sherbrooke (Quebec, Canada). The first part of the experimental program was defined to characterize the reclosing of a crack under cyclic uniaxial stress. The second experimental campaign has studied the shear behavior of a rock joint chemically degraded. The data obtained were used to model the behavior of a discontinuity by the finite element method. The mechanical behavior of a crack under normal stress is assessed with cyclic tension-compression tests. Stress curve showed hysteresis during opening and closing cycles of a discontinuity in concrete, it indicated inelastic deformations The analysis of displacement field by image correlation indicated that theses deformations were partially governed by the friction generated during the closing of the discontinuity lips. Frictional phenomena are due to asperities mismatching induced by the internal stresses in the concrete. The shear behavior of a rock joint chemically damaged was studied through direct shear tests. Rough surfaces were immersed in acid solution during 6 hours at constant pH. Digitalization of these surfaces befor and after immesion, with a lase profilometer, indicates little modifications of the geometry induced by dissolution of material. Results of tests pointed out significant modifications for altered joints illustred by a of the peak shear strength and an increased of contractancy. They are induced by: 1) the mismatch enhancement of the rough profiles of the discontinuity and, 2) the degradation of the mechanical properties of the material on both sides of the discontinuity due to the chemical attack. Numerical contribution of the thesis lies in modeling the behavior of a discontinuity by the coupling of an continuous elastic-plastic damaged model with a discrete resolution of the contact/friction problem. The model is developed with the finite element code Cast3M. Geometries lips discontinuities are modeled directly from the roughness profiles from experimental scans. The numerical results correctly represent the friction phenomena observed experimentally. Finally, a model of the shear test altered joints is performed by coupling the mechanical model with chemical damage model.
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Cocheteau, Natacha. "Caractérisation et modélisation d'une adhérence moléculaire renforcée." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4700/document.
Full textAbstract:
Le collage par adhérence moléculaire est un collage basé sur la mise en contact de deux surfaces sans l'utilisation de colle ou matériaux additionnels. Ce procédé de collage est utilisé dans de nombreuses applications, notamment dans les domaines de l'optique terrestre et spatiale. Bien qu'un prototype ait déjà passé avec succès l'environnement spatial - où les contraintes d'utilisations sont différentes de celles rencontrées sur Terre - la spatialisation de cette technologie nécessite une caractérisation plus fine du procédé ainsi qu'une amélioration de la tenue mécanique des interfaces adhérées afin de valider les normes de l'Agence spatiale Européenne. Pour répondre à cette problématique de spatialisation de la technologie, des essais mécaniques ainsi que des analyses chimiques ont été réalisés dans le but d'étudier l'influence de certains paramètres du procédé ) sur la tenue mécanique et l'énergie de collage. Ces essais ont également été réalisés afin de comparer les deux matériaux étudiés : le verre de silice et le Zérodur vis-à-vis de l'adhésion. A l'issue de ces essais, les paramètres à appliquer permettant de doubler la tenue mécanique des interfaces adhérées ont été déterminés. Parallèlement, une loi phénoménologique reliant l'énergie de collage aux précédents paramètres du procédé a été développée ainsi qu'un modèle macroscopique visant à décrire l'intensité d'adhésion. Ces deux modèles une fois couplés permettent de modéliser le comportement normal de l'interface en fonction des paramètres du procédé. Enfin, ces deux lois sont implémentées dans un code éléments finis afin de simuler la propagation de la fissure lors de l'essai de clivage au coinDirect bonding consists in joining two surfaces without the use of any adhesive or additional material. This process is used in several applications, particularly in terrestrial and spatial optics. Although a prototype passed with success spatial environment - where constraints involved are very different from those encountered on Earth - this technology requires a more detailed characterization and an improvement of the mechanical strength of bonded interfaces in order to validate the European Space Agency standards. To address this issue, mechanical tests (double shear tests, cleavage tests and wedge tests) and chemical analysis (wetting tests and XPS spectroscopy) were performed in order to study the influence of some process parameters (roughness, relative air humidity during room temperature bonding, the annealing temperature and time) on the mechanical strength and the bonding energy. These tests compared the two materials used: fused silica glass and Zerodur glass. As a result of these tests, optimal parameters doubling the mechanical strength were also obtained. In the same time, a phenomenological law relating the bonding energy to the previous parameters is developed as well as a macroscopic model to describe the adhesion intensity. Both models when coupled describe the normal behavior of the bonded interface depending on the process parameters. Then, the both laws are implemented in a finite elements model in order to simulate the crack propagation during the wedge test
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Lin, Yu-Chun, and 林郁鈞. "Numerical simulation in direct shear test using bonded particles." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/36549517862215088518.
Full textAbstract:
碩士國立中央大學
土木工程學系
102
Direct shear testing is among the most common laboratory tests for obtaining the engineering properties of soils. However, the microscopic behavior during direct shear test of this type of material is not always easy to monitor. Previous studies have found that the non-uniformity of the stress can be developed along the failure plane have been brought up by previous study. Therefore, a discrete element method is employed and the PFC2D is used to simulate the direct shear test in this study. Since prior researchers have been observed the influenced of the microscopic parameters and the microscopic behavior of the dry granular material during the direct shear test, I simulate the direct shear test by bonded-particle and investigate the related of the particles microscopic parameters and the macroscopic cohesion and friction angle in this study. I also monitor stress and porosity distribution, and bond break condition during direct shear test as well as analyze the variations of average stress, stress path and major principal plane along the pre-determined failure plane were also observed. The following summaries are addressed: (1) smaller particles size has stronger cohesion and smaller friction angle, and greater bond forces have stronger cohesion; (2) the dilation of the overall particle assembly comes from the right of the upper shear box and left of the lower shear box; (3) most breaks of the bonds locate on the shear zone, and the number of normal bonds breaks exceeds that of the shear bonds breaks; (4) the directions of major principal plane ranges from 50 and to 60 degrees in the counterclockwise direction until the test specimen reaches failure; (5) the coefficients of variation of the horizontal and vertical stress become larger when near approaching the failure, and the coefficient of variation of the shear stress becomes smaller and more stable.
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Ye, Jhen-You, and 葉真有. "A study of geogrid interface shear behavior by large-scale direct shear test." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21664813673372125079.
Full textAbstract:
碩士國立暨南國際大學
地震與防災工程研究所
97
The interface friction coefficient between different soils and geosynthetics by obtaining from large-scale direct shear test has been widely used in designing of reinforced earth structure. Most of the direct shear tests are usually performed the geogrid and same soil at upper and lower layer of shear box. The lack of research by using direct shear test to observe the shear band of soil particles. Therefore this study adopt a transparent large-scale direct shear box with five opening size of grid and four different soil particle size to observe the flow characeteristics of soil particle at interface shear band by using a digital camera. Recording interface friction changes and analyize the change of different geogrid characteristics and between soil particles. The testing results show gravel particles and geogrid have good interaction behavior. Failure surface of shear band will be far away from the location of geogrid and interface area. The bandwidth is about (9.2mm-26mm)、(8.7mm-13.4mm) that is measured at Vietnam sand. The interface shear band bandwidth is about (4mm-6mm) at Ottawa sand and gravel. Observation of Ottawa sand interface shear band bandwidth about (1.2mm-2.6mm),effect of sand particle size on the interface shear band with the scope of the smallest. The result of interface shear observation use four different soil particle size and five different kinds of type geogrid of the above mentioned, the interface shear band ranked in descending order are as follows: gravel＞Vietnam sand＞Ottawa sand. Understandably, the different soil particle size can show the different interface behavior, despite in reinforced soil condition or in unreinforced soil condition, gravel specimen has more visible shear band than Vietnam sand and Ottawa sand. Under the same conditions, the gravel has the higher shear strength more than Vietnam sand and standard sand, soil dilation behavior also more pronounced. This study is to explore Interface shear observation and to understand the soil in the geogrid rib development, in this test can found that geogrid surface and geogrid rib tensile strength with soil particle mobile has the quite Obviously influence.
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Tseng, Hsiao-Chian, and 曾孝欽. "Development of a Multi-Purpose Shear Test System for Soft Rocks-Direct shear and Simple Shear Apparatus." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/11754689634744927071.
Full textAbstract:
碩士國立交通大學
土木工程系
91
Development of a Multi-Purpose Shear Test System for Soft Rocks - Direct Shear and Simple Shear Apparatus Student: Hsiao-Chian Tseng Advisor： Dr. Jyh-Jong Liao Dr. Yii-Wen Pan Department of Civil Engineering National Chiao Tung University Abstract Due to the low strength and high deformability of poorly cemented sedimentary rocks, the conventional soil or rock mechanics test equipments are not suitable for determining the mechanical properties of those rocks. In order to propose reasonable engineering approaches in the soft rock area, the mechanical behavior of the rocks has to be investigated in details. To study the mechanical behavior of soft rocks, we need to develop a test system, which is appropriate for testing soft rocks. The geotechnical group, NCTU, aims to develop a multi-purpose shear test system for soft rocks. The system can perform direct shear test, simple shear tests, torsional shear tests, and triaxial tests. This thesis has designed and built a servo-controlled shear apparatus including direct shear test and simple shear test apparatus. The maximum normal and shear capacity of the system are 20 tons and 10 tons, respectively. The equipment was designed to conduct direct shear and simple shear tests under various conditions including constant normal force, constant normal displacement, and constant stiffness, especially for soft rock specimen. A series of experiments were carried out to verify the design objectives. It was confirmed the designed equipment could be operated according to the designed purposes. Keywords : soft rock, direct shear, simple shear, multi-purpose shear test system.
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Sung, chiu-yen, and 宋丘言. "Discrete Element Modeling of Granular Material in Direct Shear Test." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/31759052501309765061.
Full textAbstract:
碩士國立中央大學
土木工程研究所
100
Direct shear test has been among common laboratory tests to obtain the engineering properties of soils, especially for dry granular soils. In this study, the microscopic parameters to describe the force-displacement relationship between particles are compared to the macroscopic engineering properties of the particle assemblies. It was found that the friction angle of the particle assembly is related to the contact normal and shear stiffness and the particle friction from a microscopic point of view. Dilation of the particle assembly is also observed in the discrete element model. Basically the dilation of the overall particle assembly comes from the dilation of the particles in the shear zone. Furthermore, the non-uniformity of stress states along the predetermined failure plane is examined. As the normal stress increases, the stress state in the middle of the predetermined shear plane also becomes less complicated with pure compression loading, while for the smaller normal stress, the stress states are combinations of compression and extension loading. The variations of stress path somehow also explains why a direct shear test can overestimate the strength of a granular material, since a compression loading test can yield the highest strength comparing to other test types.
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Pi-Chih, Hsieh, and 謝碧枝. "The Study of Direct Shear Test Method on Unsaturated Soil." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/06429798274174156312.
Full textAbstract:
碩士明新科技大學
土木工程與環境資源管理系碩士班
101
The ground water exists in nature environment. The soil below ground water table, immerged in water long period of time, is called saturated soil. Due to capillary effect, rainwater infiltration and evaporation, the soil underground water table exhibits native pore water pressure, it is called unsaturated soil. The research of traditional soil mechanics on saturated soil had well developed and results were vigorous. Because of expensive equipment, difficulty of test technics and sensitive of test precision, the study in the field of unsaturated soil is still limited. Minghsin University of Science and Technology locate at Hukou terrace, the ground water table is at -5 meters below ground surface. The soil above the ground water table, dried and wetted altered frequently, is in unsaturated condition. This study tries to apply traditional direct shear test method and contact filter paper method to remodel lateritic soil sample. The relationship between unsaturated soil shear strength and matric suction is studied. The results show that the direct shear behavior of unsaturated soil reveal shear dilation properties, the lower of soil water content, the larger of dilatancy angle. The relative shear strength shows the same effect. Soil matric suction is inverse proportion to soil moisture content. The relationship between soil matric suction and unsaturated soil shear strength is increased nonlinearly. The suggest test method successes apply in unsaturated soil.
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Nien, Wei-Tung, and 粘為東. "Using PFC2D to Simulate the Shear Zone in a Direct Shear Test and its Application." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/30094935235602572839.
Full textAbstract:
碩士臺灣大學
土木工程學研究所
98
Engineers are accustomed to using finite element method (FEM) to simulate the failure problem in sand. In this way, however, they are unable to solve the case with rapture and rolling. In order to analyse the real stress and strain situation in soil, more and more researchers choose to use distinct element method (DEM) to simulate the physics experiment and field problem. Nevertheless, the shear zone localization is still a significant issue to be further studied. In order to localize the shear zone, this research simulates the most basic soil experiment, direct shear test, by using a DEM software PFC2D, trying to propose a method which can point out the shear zone location. According to a structural geologic analysis method recommended by Ramsay and Huber (1983), this study defines the homogeneous strain in the soil by ellipticity R. R is a relative physical quantity to shear strain γ which is more familiar to engineers. Then this study set many grid points in the direct shear test simulation, separating the simulating soil into several squares with same area size. Every square is a shear strain calculating unit named grid square. The shear strain can be regarded as homogeneous if the grid square is small enough, and then the shear strain of the grid square can be represented by the ellipticity R. Combining two definition mentioned above, we can calculate the shear strain of every single grid square. Then, it is clear to localize the shear zone by giving every square different color related to its shear strain. Finally, this study also localize the shear zone in the fault sand box simulation and land slide simulation, and compare the result in the fault sand box in this study with the research studied by Chung (2007). No program can calculate the ellipticity in PFC2D, so in this study matrix calculating software MatLab is used to develop a program that can solve this problem. The simulation results indicate that the shear zone in the direct shear test is horizontal and its shape looks like lens. Also, particle rolling inside the shear zone can be observed. In the fault sand box simulation, the result demonstrates the development of the shear zone and the fault tip of tri-shear zone. In the land slide simulation, the result demonstrates the development of sliding surface and the appearance of tension crack.
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Chi, Yu-Cheng, and 紀有政. "A Study of Unsaturated Consolidated Drained Shear Strength for Weathered Mudstone by Direct Shear Test." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/76817869175221745719.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程研究所
103
In the dry season, mudstones are just as hard as rocks. In the raining season, however, mudstones absorb excessive water, causing mudstones to swell and disintegrate. As a result, slopes are uncovered. Between underground water and topsoil are unsaturated mudstones. With its matric suction, the unsaturated mudstones stabilize soil firmly in the dry season. However, mudstones lose matric suction in the raining season due to the infiltration of rainwater. As a result, mudstones lose shear strength. With the decreased shear strength, the shallow layer of slope collapses or slides. This study gathered soil samples from a slope nearby the mire volcano in Moon World, Tainliao District, Kaohsiung. Several tests were conducted to identify the basic physical properties of soil samples with emphasis on the characteristics of the weathered mudstone in Tianliao District. Therefore, in-situ moisture content was simulated; remolded specimens were reproduced; the relationship between the matric suction, saturation, and moisture content of weathered mudstone was analyzed using soil water characteristic curve; saturated consolidated drainage direct shear test was conducted using the modified direct shear apparatus developed by National Kaohsiung First University of Science. Five levels of matric suction, namely, 50, 100, 150, 250, and 350kPa, were designated for the unsaturated consolidated drainage direct shear test in which net normal stress was set as 100, 200, and 400kPa, respectively. The test was designed to identify the rise and fall of shear strength due to the changes of moisture content in connection with the varying matric suction of the weathered mudstone in Tianliao District. Gathered from the surface layer of weathered soil, the soil samples were considerably porous with a few soil particles. According to the soil water characteristic curve, the soil has an unsatisfactory water-keeping effect. According to the consolidated drainage test, the sample soil has 43.4kPa of effective cohesion force and 22.6° of inner friction angle. Moreover, the unsaturated consolidated drainage test indicated that the inner friction angles within all levels changed slightly. Using average inner friction angle 23.5° as the shear strength, this study concluded that the matric suction could change the moisture content of the soil samples, causing the soil shear strength to increase as the matric suction increases. Moreover, a non-linear relationship between matric suction and total cohesion force was identified through the test. Based on the non-linear relationship stated above, the angle〖 ϕ〗^b corresponding to the increased matric suction decreased significantly.
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Chen, Yen-Hsu, and 陳彥旭. "Assessment of Shear Strength of Vegetated Slopes and Measurement of Direct Shear Test on Sites." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04186999620063199482.
Full textAbstract:
碩士中國科技大學
土木與防災設計研究所
102
Combined direct shear measurement of the rooted soil can meet the needs of the field and laboratory. Therefore, the field direct shear measurement has multi-purpose properties. In the current study, the soil specimens were collected from fields. The direct shear tests were the proceeded and the relationship between the shear strength and the lateral displacement was determined simultaneously. After the test, the number of roots on the shear plane was counted and then the plant roots were extracted to make a direct tensile test. According to the data obtained from experiments, the statistical analysis was performed to obtain the parameters for the specific mechanics of the plant roots. Because the field plants exist in the poor-drained sandy and non-uniform grained soils, the roots of the plants on the field soils appear more complicated and differed in mean length with an acrylic box. Under the same parameters for the specific mechanics of the plant roots, the result was found to be different between the shear strength increment calculated by the root strength model and measured by the tests with various soil conditions.
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Gao-zhi-hua and 高志華. "To investigate the feasibility of using the large size simple shear test device to replace the direct shear test device." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/08868719282222088171.
Full textAbstract:
碩士朝陽大學
營建工程系碩士班
87
Abstract Gravel formation is widely distributed in the central region of Taiwan. The difficulties of under ground excavation in gravel layers will be encountered in the construction of several large transportation projects. In the design of lateral earth pressure for the supporting system of under ground excavation, he shear strength parameters are the most important property to be obtained. Therefore, how to find out the mechanical strength parameters of gravel layer promptly and correctly is one of the most important research topic in geotechnical engineering. Previous study indicates that the distribution of stress and strain is more uniform in a simple shear device then in a direct shear device. Therefore, a new apparatus which can perform tilt table test, direct shear test, as well as simple shear test was designed in this study to investigate the influence of testing methods on the shear strength of gravel, and the feasibility of using direct simple shear test instead of direct shear test for obtaining the shear strength parameters of gravel. Results of this study indicate that at low normal stresses, due to the effects of stacking the shear strength of samples with largest grain diameter equal to 3-inches is higher than the strength of sample with smaller grain size. However, this trend is less significant at higher normal stresses. It also shows that for duplicated samples under the same normal stress, because the simple shear test does not force the sample to be failed along a pre-defined failure plane, the shear strength obtained from simple shear test is less scatter then results from direct shear test.
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Lin, Yi-Pei, and 林宜霈. "A study of the shear strength of unsaturated silty clay using the multistage direct shear test." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/03488004442505223897.
Full textAbstract:
碩士國立高雄第一科技大學
營建工程研究所
105
This study is application of the multistage direct shear test to reduce the cost and time associated with shear strength testing of unsaturated soils. In the saturated consolidated drainage direct shear test, in which net normal stress was set as 20kPa, 40kPa, 80kPa. The unsaturated consolidated drainage direct shear test, combined action of the net normal stress and the matric suction, the independent design panel used to control the matric suction. Six loading stages of matric suction, namely 25, 50, 100, 200, 250 and 300 kPa. The experimental results that under the control of single net normal stress and increasing matric suction, the change of water content of soil is influence of shear stress. The correlation coefficient (R2), at which the matric suction reaches the fourth loading stage is somewhat lower value, it can be relied upon in engineering practice.
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HUANG, JIAN-WEN, and 黃建文. "Study of geogrid/soil interaction behavior by large-scale direct shear test." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/99698164161058371718.
Full textAbstract:
碩士國立暨南國際大學
土木工程學系
96
Using Large-scale direct shear test to measure the different soils and geosynthetics related to the interface friction coefficient has been widely used in the design of the reinforced earth structure. Most of the direct shear tests are usually used on the shear box from top to bottom with same filling materials, but in the use of design and construction in field often have different needs change, from top to bottom shear boxes filled with different soil. So the interface of friction with two different layer types of soil is still a lack of research, this study will perform several series of large scale direct shear test to realize the interface behavior of geosynthetics and soil related with soil particle size, opening size of grid and passive resistance force. Test results show that Taichung Harbor Sand (upper box)/ concrete block (bottom box), the interface friction angle and shear strength are difference, related with the size of the grid opening, the grid number of horizontal opening, Soil and the geogrid system has more obvious acts, such as the shear stress to the displacement of shear increases, the interface will increase friction angle. The Taichung Harbor sand / clay test results also show that peak shear strength of pure sand all higher than any condition with different geogrids about 8 to 11 percent, and the peak shear strength of adding geogrid layer has no significant difference. The interface friction angle of geotextile and geomembrane, their peak shear strength are lower than pure soil about 7 ~ 43%, mainly reason is smooth suface. Base on the observation of gravel / clay and gravel /Taichung Harbor sand. The failure surface will be far away from the interface surface of soil when geogrid and soil particle has good interaction. The gravel/ concrete block tests showed that the main factor effect friction angle and shear resistance is interface roughness and it has similar shear strength under 50 kPa normal stress with none geosynthetic layer. In this study, the direct shear tests found horizontal rib of geogrid can develop passive resistance force. According to the previous research, the value from formula calculation is lower than the value from the measurement in this study. The passive resistance behavior also can be obviously found in this study.
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Chen, Tsung-Chia, and 陳聰嘉. "A study of interface shear behavior between PET geogrid and soil by conducting large-scale direct shear test." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/95775209924283937996.
Full textAbstract:
碩士國立暨南國際大學
土木工程學系
94
The reinforcing technique which has many advantages like high workability and low cost has been widely used in recent years.And the PET geogrid is the most prevailing reinforcing material in Taiwan nowadays. So far, HDPE or PP geogrid are often selected to discuss the interface friction angle in the large-scale direct shear test. However, the PET geogrid tests are relatively rare, so this study uses PET geogrids to test and discuss its interface friction properties. Because geogrid’s design applicability varies with field condition, this study uses large-scale direct shear test to discuss the interface friction properties between different factors of PET geogrids and three kinds of soil (Ottawa sand, gravel and laterite).Also, the relationship of gravel diameter and geogrid opening size, the influence of different lower shear box to test result, and whether the interaction between soil and geogrid using various lower box of the device exists or not are discussed in this article. From the test of Ottawa sand, the result shows that the geogrid's strength is not very influential to the test, but the opening size is. The smaller the geogrid’s opening size, the higher the interface friction angle. And the angle would be higher in sand/geogrid interface than in sand/sand one, however, it would be lower in gravel and laterite test.As to the relationship between gravel size and geogrid opening size, the test results show that if the ratio of particle size to opening size is greater than 20, the interlocking of particles would not be affected by the intervention of geogrid on interface. This study discuss if the interlocking exists in the soil of direct shear test, the result shows that under three different soil, the interlocking can be found, and the interface friction angle would be higher. This result demonstrates that the interlocking in the soil do exist in the direct shear test. When discussing the influence of different types of lower box to the test. The results show that soil disturbing would occur in the larger lower box, and the steel plate which replaces the lower box would lack interlocking mechanism. Thus the values from the test would be lower.
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Shi-Yun, Chi, and 蔡熙昀. "Analysis of Axially Loaded Cast-in-Situ Piles from Direct Shear Test Result." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/54457517256835937287.
Full textAbstract:
碩士國立臺灣科技大學
營建工程技術學系
82
In this study, the shear stress-displacement curves of direct shear test of undisturbed soil sample in Taipei Basin are collected, and a series of direct shear test for remolded soil sample against cement mortar is conducted in laboratory. Based on all tested data, both the exponential and hyperbolic functions are employed to simulate the non- linear shear stress- displacement curves, and the relationship between the depth and parameters of these mathematical curves are obtained. Finally, these mathematical functions are used to establish the t-z curves of pile shaft to provide the analytical curves in Reese load transfer method. From the experimental results of this research, no matter what kind of interface. as a result of migration of cement or bentonite particles, the shear strength of immediate soil increasing distinctly. Based on this fact and correlative research, it may be deducted that axially loaded bored pile would not fail at exactly the interface of shaft and soil particles, but fail at some distance away from the interface. It is believed that the shaft resistance is provided mainly from shear strength of surrounding soil. Supposing the disturbance of construction process of bored pile is neglected, this study uses hyperbolic model mentioned above to establish the t-z curves, Finally, selects fifteen pile loading tests with different diameter from Taipei Basin to test the applicability of t-z curve. After comparing the load- settlement curves obtained from calculated t-z curves and pile testing curves, it was found the coincidence is quite well.
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HSIAO, NIEN-HUNG, and 蕭年宏. "Transmission of sound waves and vibration waves in sand under direct shear test." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/pa8bxs.
Full textAbstract:
碩士國立中央大學
土木工程研究所
97
This research used wave signals measured from microphones and accelerometers to investigate transmission properties of sound waves and vibration waves generated by shock vibration or shear displacement in sand layer. This research carried out a series of constant loading shear tests by means of a modified direct shear apparatus. Set a microphone and a accelerometer in the direct shear box to measure sound pressure accelerate. Siluo sand was used in the tests and the shear stress was applied with air cylinder. The signals of vibration and sound wave were measured from the direct shear tests. The results showed that when the shear stress has reached 40%~50% of soil strength, the higher sound pressure would appear. Then of values of vibration and sound would become smaller with the increase of shear displacement. For the sand with higher relative density, the vibration and sound wave would be getting higher with the same normal stress. Under the same condition, higher shear stress increment will cause higher vibration and sound wave. In addition, field test was performed in this research. The sound and vibration waves were caused by the explosion of dynamite of 750 kg which was imbedded at depth of 80 m. The microphone and the accelerometer were set apart from the sound source of 20 m, and these sensors were imbedded at depth of 30 cm. From the results of the experiment, the sound and vibration waves were appeared at the same time. If the generated energy of slide or movement of sand is large enough, the sound waves may transmit away with the vibration waves to a farther distance simultaneously.
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Heng, kuo Shun, and 郭順恆. "The Development of a Cylindrical Direct Shear and Pull Out Test Apparatus for Geosynthetics." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/80929735738792938056.
Full textAbstract:
碩士國立屏東科技大學
土木工程研究所
83
A prototype cylindrical direct-shear and pull-out test apparatus was designed and constructed. For evaluating the frictional behavior between geosynthetics and other materials. The use cylindrical geometry is to utilize the axisymmetric characteristics of cylindrical elements in order to eliminate the necking phenomena of geosynthetics during direct-shear and pull-out tests. The apparatus consists of several parts: a cylindrical clamp ,a cylindrical shear box including an inner and an outer cells, a cylindrical pressure device comprising an inner flexible membrane and a supporting base with a cylindrical outer ring to from a water tank for testing saturated samples. A universal testing machine is used to provide a precisely strain and stress control loading. The geosynthetics test speecimen is placed between the inner and outer cylindrical cells. The test specimen is a cylindrical specimen with a diameter of 18 cm and 60 cm height. A series proving direct-shear and pull-out tests were performed. A nonwoven needle-punched geotextile, a woven fabric, and a poor graded white quartz sand were used for the tests. The results of the tests indicated that the shear resistance is greatly depend on the relative density of soil sample, and would increase. The required shear deformation for inducing peak shear resistance would increase as the confining pressure increases for the nonwoven geotextiles, however, confining pressure seems to have no significant effect on the behavior of the peak ultimate shear resistance for the woven fabric. Water contain of the soil has small influence on the shear resistance for the geotextiles. Due to low tensile strengths of the chosen fabrics , only few pull-out tests were performed and tensile break were all observed for the pull-out tests. Therefore, geotextiles having stronger tensile strength shouldbe used for the future investigations. Moreover few improvements are recommended for the current for future study.
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Ke, Chi-Ching, and 柯志青. "The numerical simulation of rock direct shear test and the uniaxial compressive strength under elevated temperature." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/39437592277477835024.
Full textAbstract:
碩士國立台灣工業技術學院
營建工程技術研究所
85
The mechanics behavior of rock may change due to temperature. The temperature influence of marble and serpentinite were investigated in the study. The uniaxial compressive strength of marble and serpentinite of two different thermal paths between room temperature and 300oC were analyzed, and the maximum strength were reached when the specimen was heated at 100oC. The strength of marble and serpentinite decreased when heated temperature increases over 100oC. Numerical simulation of rock direct shear test was tried in the study, and it shows that the numerical simulation of experimental work is possible if the input rock parameters are correct.
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Wu, Szu-Ting, and 吳思鋌. "The Mechanical Behavior of Concrete-Poorly Cemented Sandstone Interface under Constant Normal Stiffness Direct Shear Test." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/887v58.
Full textAbstract:
碩士國立交通大學
土木工程系所
92
The Mechanical Behavior of Concrete-Poorly Cemented Sandstone Interface under Constant Normal Stiffness Direct Shear Test Student: Szu-Ting Wu Advisor： Dr. Jyh-Jong Liao Department of Civil Engineering National Chiao Tung University Abstract The mechanical properties of soft rock are distinct those of hard rock or soil, so the failure mechanism of soft rock slope may be different. The existing study of the pile behavior is based on the experience of pile foundation and the theory of soil mechanics with the safety factor according to the uniaxial compressive strength and the interface roughness；Therefore, for large scale constructions, it is required for the Pile-load test results to get the more reliable pile-rock interaction. To estimate the shear strength of the interface of rock and concrete, it is more appropriate to adopt the results of constant normal stiffness direct shear test and the stiffness between pile shaft and soft rock. Hence, Direct shear test under constant normal stiffness is valuable to perform on the interface of concrete-soft rock. This thesis aims to investigate the mechanical behavior of Concrete-Poorly Cemented Sandstone Interface by direct shear test under constant normal stiffness. The experimental results show that normal stiffness and initial normal stress strongly influence the behavior. However, the influence of roughness of interface can be neglected in this study. Keywords : soft rock, normal stiffness, direct shear, interface.
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Chiou, Wen-roug, and 邱玟融. "A Preliminary Study on Numerical Simulation of Direct Shear Test and Calibration of Micro-Parameters of Soils Through Discrete Element Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/62939890123056494438.
Full textAbstract:
碩士國立雲林科技大學
營建工程系碩士班
95
In order to calibrate suitable micro-parameters for use in numerical analysis, the study herein had conducted a series of direct shear tests on the material strength data (i.e., macro-parameters). The micro-parameters included friction coefficient (fric) among soil grains, normal stiffness of contacts (Kn), and tangent stiffness of contacts (Ks), etc. Commercial software, PFC2D, by Itasca based on discrete element method has been adopted for the simulation of direct shear test in this study. Ottawa sand and Tzuo-swei sand were used for the testing. Problems encountered during the simulation process, including sample assembling, density controlling, vertical loading, and shearing, etc., are discussed in this paper. The study found the falling height and the soil grain friction coefficient would affect the density of soils. The lesser the friction coefficient or higher the falling height, the greater the density will be. Under the same normal pressure, the decrease in the tangent stiffness of contacts will result in a flatter stress-strain curve, as well as a smaller friction angle and the shear resistance. In spite of different definitions, the micro-parameters, fric and Ks, would result in similar effects on the material strength characteristics. The calibrated micro-parameters of the test sands would be used in the future for numerical simulations on more complicated engineering problems encountered in the field.
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Resketi, Nima Azimi. "Analytical and Experimental Studies on Interface between Different Mortars and Brick." Master's thesis, 2018. http://hdl.handle.net/10316/93192.
Full textAbstract:
Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeirosUsage of masonry materials in a country like Iran is still significantly high. As most of the failures during an earthquake in this system is failure caused by low ductility of cement mortars and also the high rate of carbon dioxide produced by cement. Experiences of Kermanshah earthquake in 2017 in Iran has doubled the importance of this issue. Hence, in the present investigation, an attempt to enhance the shear bond characteristics of structures constructed by masonry using green materials has been made. “Taftan” natural Pozzolan and two types of rice husk ash (RHA) was used in mix design of used mortars as a green material. In this investigation, a direct shear test (DST) device is modified and proposed to determine brick-mortar shear bond strength. The proposed method of applying DST has the advantageous of changing normal load and determine pure bond characteristics. For this purpose, two bricks bonded to each other by a mortar and subjected to the shear load. Tests were performed using DST for nine different types of mortars with different normal loads. The effect of increasing shear bond strength over time was also studied. Tests showed that using waste material like RHA in mortar is reasonable as its causes to the increase mortar plasticity and failure strain and also reduce the cost of mortar and its environmental effect.
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Louro, Raquel Alexandra Afonso Sabino de Sousa. "Compressibilidade e resistência ao corte de areias contaminadas." Master's thesis, 2017. http://hdl.handle.net/10316/83382.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia do Ambiente apresentada à Faculdade de Ciências e TecnologiaAo longo dos anos, a vertente ambiental está cada vez mais presente em todas as áreas em desenvolvimento da sociedade, particularmente as que envolvem as áreas das engenharias. Apesar das crescentes preocupações ambientais, continuam a existir casos em que, por acidente ou por ações humana consciente, os solos são contaminados com materiais derivados do petróleo. Assim, o tema dos solos contaminados é não só atual como uma emergência, quer do ponto de vista ambiental quer do ponto de vista da decisão sobre como utilizar estes materiais.Para ajudar a resolver este tipo de problemas, é necessário conhecer as características de um solo não-contaminado, e de um solo contaminado, através de ensaios laboratoriais. Realizaram-se ensaios de compressibilidade, através de testes com o edométrico, e resistência ao corte, realizados com a caixa de corte. As amostras eram preparadas por camadas de areia limpa intercaladas com os vários contaminantes: óleo novo de motor de carro (10W40), mistura de óleos usados de motores de carros e crude. No estudo da intervenção destes contaminantes nas propriedades da areia, foram tidas em conta a contaminação das percentagens de 6% e de 10% do peso seco da areia.Com base nos resultados dos ensaios realizados verificou-se que a presença de óleos, de uma maneira geral, aumenta a compressibilidade e diminui a resistência ao corte. Sendo por isso importante conhecer o tipo de solo que vai ser utilizado numa construção, de forma a prever a sua reação às cargas a que o solo vai estar sujeito, ou para o poder descontaminar da melhor maneira possível.
Over the years, the environmental dimension is increasingly present in all developing areas of society, particularly those involving engineering areas. Despite growing environmental concerns, there are still cases where, by accident or by conscious human actions, soils are contaminated with petroleum-derived materials. Thus, the issue of contaminated soils is not only current but also an emergency, from an environmental point of view and from the point of view of the decision on how to use these materials.To help solve this type of problem, it is necessary to know the characteristics of an uncontaminated soil, and contaminated soil, through laboratory tests. Tests of compressibility, through tests with the oedometric, and resistance to the cut, were carried out with the direct shear test. The samples were prepared by layers of clean sand interspersed with the various contaminants: new car engine oil (10W40), blend of used oils from car engines and crude oil. In the study of the intervention of these contaminants in the sand properties, contamination of the percentages of 6% and 10% of the dry weight of the sand was taken into account.Based on the results of the performed tests it has been found that the presence of oils, in general, increases compressibility and decreases the shear strength. It is therefore important to know the type of soil that will be used in a construction, in order to predict its reaction to the loads to which the soil will be subjected, or to be able to decontaminate in the best possible way.
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Mendes, Eduardo Manuel Andrade. "O fenómeno de consolidação na prática laboratorial." Master's thesis, 2016. http://hdl.handle.net/1822/49792.
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Dissertação de mestrado em Engenharia Civil (área de especialização em Perfil de Estruturas e Geotecnia)A perceção do comportamento de um solo é de extrema importância, pois é sobre este que são realizadas a grande maioria das obras de construção civil. No caso de solos finos, a consolidação é um dos principais fenómenos a ter em consideração. Este fenómeno é reproduzido e analisado laboratorialmente através de ensaios de consolidação, realizados em vários equipamentos distintos, com o objetivo de estimar o nível de assentamento e o tempo necessário para que esse esteja concluído. No entanto, é possível que a informação obtida a partir da realização desses ensaios não seja a mais precisa, quer devido aos procedimentos executados laboratorialmente, quer devido ao tipo de equipamento utilizado, o que condiciona diretamente as simulações numéricas realizadas, principalmente quando as mesmas são necessárias na calibração de modelos constitutivos avançados. Neste contexto, pretende-se com este estudo contribuir para a melhoria das boas práticas na realização de ensaios laboratoriais de consolidação, quantificando-se a influência do procedimento de ensaio em três equipamentos distintos (i.e., edómetro, célula de Rowe e caixa de corte), sobre um solo argiloso. No que diz respeito à célula de Rowe, pretende-se também proceder à sua implementação no Laboratório de Estruturas (LEST) da Universidade do Minho (UMinho). No edómetro, realizaram-se ensaios de modo a permitir a análise da reprodutibilidade do ensaio, da influência do incremento de carga aplicado, da influência do grau de saturação inicial do provete e da possibilidade de ocorrência de drenagem radial. Na célula de Rowe, realizaram-se trabalhos para a sua implementação no LEST. E ainda, analisou-se o processo de consolidação no ensaio de corte direto, com vista a identificar e limitar a ineficiência identificada por Pereira (2015).
The perception of the behavior of a soil is extremely important, because it is where the vast majority of building works is conducted. In the case of fine soils, consolidation is one of the main phenomena to be taken into consideration. This phenomenon is reproduced and analyzed in laboratory by means of consolidation tests, performed on several different equipments, and aiming to the estimating of the settlement level and the time required for its conclusion. However, it is possible that the information obtained from such tests is not the most accurate, either because of the procedures performed laboratory, or due to the type of equipment used, which directly affects numerical simulations results, especially when they are necessary for the calibration of advanced constitutive models. In this context, the objective of this study is to contribute to the improvement of good practices in laboratory consolidation tests. This is done by quantifying the influence of the test procedure in three different equipments (i.e., oedometer, Rowe cell and shear box) on a clayey soil. With regard to the Rowe cell, it is also intended to proceed to its implementation in the Structures Laboratory (LEST) at University of Minho (UMinho). The oedometer tests were performed to allow the analysis of the reproducibility of the test, the influence of the applied load increment, the influence of the initial degree of saturation of the sample and the possibility of radial drainage. Regarding the Rowe cell, work was carried out for its implementation in LEST. In addition, the direct shear test was analyzed to identify and solve the inefficiency identified by Pereira (2015).
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(8066420), Shahedur Rahman. "Improvement of Stiffness and Strength of Backfill Soils Through Optimization of Compaction Procedures and Specifications." Thesis, 2019.
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Vibration compaction is the most effective way of compacting coarse-grained materials. The effects of vibration frequency and amplitude on the compaction density of different backfill materials (No. 4 natural sand, No. 24 stone sand and No. 5, No. 8, No. 43 aggregates), were studied in this research. The test materials were characterized based on the particle sizes and morphology parameters using digital image analysis technique. Small-scale laboratory compaction tests were carried out with variable frequency and amplitude of vibrations using vibratory hammer and vibratory table. The results show an increase in density with the increase in amplitude and frequency of vibration. However, the increase in density with the increase in amplitude of vibration is more pronounced for the coarse aggregates than for the sands. A comparison of the maximum dry densities of different test materials shows that the dry densities obtained after compaction using the vibratory hammer are greater than those obtained after compaction using the vibratory table at the highest amplitude and frequency of vibration available in both equipment. Large-scale vibratory roller compaction tests were performed in the field for No. 30 backfill soil to observe the effect of vibration frequency and number of passes on the compaction density. Accelerometer sensors were attached to the roller drum (Caterpillar, model CS56B) to measure the frequency of vibration for the two different vibration settings available to the roller. For this roller and soil tested, the results show that the higher vibration setting is more effective. Direct shear tests and direct interface shear tests were performed to study the impact of particle characteristics of the coarse-grained backfill materials on interface shear resistance. A unique relationship was found between the normalized surface roughness and the ratio of critical-state interface friction angle between sand-gravel mixture with steel to the internal critical-state friction angle of the sand-gravel mixture.
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Haque, Rizwana. "THICKNESS VARIABILITY EFFECTS ON THE PROPERTIES OF UNSTABILIZED FULL DEPTH RECLAIMED AGGREGATES." 2014. http://hdl.handle.net/10222/50064.
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Inadequate financial allocation for road maintenance is a threat to the impaired rural highways in Atlantic Canada. The conventional means of pavement rehabilitation has been to place a hot mix asphalt concrete overlay on the existing worn out pavement which is only a short term adjustment. The purpose is to provide a smooth wearing surface at a low cost. This traditional way of pavement repair does not fix the damage embedded within the pavement structure. After a certain extent of time the cracks in the original pavement start to reflect to the smooth new wearing surface, causing deterioration on the overlay. The advanced approach which is becoming more popular is the application of Full Depth Reclamation (FDR). This technique helps to repair the extensively defective roads by pulverizing the flexible pavement along with a fraction of the underlying damaged base layer. Thus a damage free base layer can be obtained by stabilizing and recompacting the pulverized materials. FDR is a sustainable and an environmentally beneficial repair method as it re-uses the in-situ materials.
FDR process has been used around the world for over 25 years yet confronts some difficulties regarding the fluctuation in the strength of materials in various projects. It is inferred that some of these difficulties are due to the variability and poor quality in the restored materials. The variability in the recycled base layer is a result of currently utilizing a retroactive depth control method to attain a specific blend of asphalt concrete to granular base for the pulverized materials. Two FDR projects applying two different pulverization control methods (conventional retroactive and GPR depth control methods) were analyzed to investigate the improvements in consistency of the restored materials by using Ground Penetrating Radar (GPR). A wide range of asphalt concrete/base layer blend ratio was detected in retroactive control section, while consistent blend ratio was maintained in GPR survey by mapping the variability in the depth of pavement and sub-dividing the test sections accordingly.
A GPR controlled constant blend ratio during pulverization displayed improvements in consistency of materials, physical and mechanical properties and performance as anticipated. The materials obtained by using the conventional retroactive depth control method exhibited higher variability in grain size distribution, optimum moisture content, optimum density, California Bearing Ratio, resilient modulus and shear strength. All materials from both projects exhibited excessive air voids and inadequate fines content as the as-obtained particles acted as conglomerated particles and enough fines were not generated after the pulverization. It is recommended that efficient quality control, precise specifications and appropriate pulverization methods will provide more reliable and impressive FDR pavements.This thesis contains research on unstabilized full depth reclaimed aggregates properties