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Статті в журналах з теми "Triaxial loading path":
1
Vaid, Y. P., and S. Sasitharan. "The strength and dilatancy of sand." Canadian Geotechnical Journal 29, no. 3 (June 1, 1992): 522–26. http://dx.doi.org/10.1139/t92-058.
Анотація:
The effects of stress path and loading direction in the triaxial test on strength and dilatancy of sand are investigated. It is shown that the unique relationship observed between peak friction angle and dilation rate at peak in conventional triaxial tests is followed regardless of stress path, confining stress at failure, relative density, and the mode of loading (compression or extension). Key words : sand, peak friction angle, dilatancy, stress path, triaxial test.
2
Atkinson, J. H., and D. B. Clinton. "Stress Path Tests on 100 mm Diameter Samples." Geological Society, London, Engineering Geology Special Publications 2, no. 1 (1986): 133–37. http://dx.doi.org/10.1144/gsl.1986.002.01.28.
Анотація:
AbstractThe use of stress path tests is discussed in relation to geotechnical design, and a description is given of the triaxial test stress path apparatus developed at The City University.Test results are presented from a series of triaxial tests following stress paths commonly encountered in engineering design problems. These are compared with the results of conventional triaxial tests.The stress-strain behaviour and pore pressure response of soil are shown to be very much dependent on the stress path followed, and the advantages of using stress-controlled loading in triaxial tests is demonstrated.
3
Wang, Zhaofeng, Guangliang Feng, Xufeng Liu, and Yangyi Zhou. "An Experimental Investigation on the Foliation Strike-Angle Effect of Layered Hard Rock under Engineering Triaxial Stress Path." Materials 16, no. 17 (August 31, 2023): 5987. http://dx.doi.org/10.3390/ma16175987.
Анотація:
Deep underground engineering encounters substantial layered hard rock formations, and the engineering triaxial stress path involves an increase in maximum principal stress, constant intermediate principal stress, and a decrease in minimum principal stress. However, previous research has focused on rock layer angles under conventional triaxial stress conditions, disregarding the influence of foliation strike angles in engineering triaxial stress scenarios. This study experimentally investigates the effects of foliation strike angles on layered hard rock under an engineering triaxial stress path. To account for the brittleness of layered hard rock, we propose a specific small sample-processing method tailored to the foliation strike angle. True triaxial loading tests are conducted on steep, thin slate samples with two different loading orientations, accompanied by acoustic emission monitoring. Results indicate that the strength under a traditional true triaxial compression condition is similar for specimens with 90° and 0° strike angles. Stress–strain curves show that larger deformations occur perpendicular to bedding planes, while surface fractures propagate exclusively along the bedding planes. Mechanical responses differ significantly between specimens subjected to the engineering triaxial stress path at 0° and 90° strike angles compared to conventional true triaxial loading tests, with a lower bearing capacity and differentiated intermediate and minimum principal strains in the 0° case. Conversely, the 90° case exhibits a higher bearing capacity, consistent deformation, and more acoustic emission events. Numerical simulations comparing plastic zone sizes during actual underground excavation support these conclusions. These findings highlight the effects of foliation strike angles, favoring the 90° strike-angle configuration for excavation activities and providing enhanced stability in the surrounding rock mass.
4
Gautam, Rajeeb, and Ron CK Wong. "Transversely isotropic stiffness parameters and their measurement in Colorado shale." Canadian Geotechnical Journal 43, no. 12 (December 1, 2006): 1290–305. http://dx.doi.org/10.1139/t06-083.
Анотація:
Drained stress path triaxial tests and confined torsion tests were conducted on Colorado shale core samples to investigate transversely isotropic stiffness parameters at small strain deformation. Nonlinear plastic behaviour occurred along the primary loading path even at strains less than 0.01%. Nonlinear, hysteric behaviour was only observed during the loading–unloading path. However, the shale material displayed transverse isotropy in deformation, and very small or nondetectable Poisson's ratios in vertical and horizontal directions. This special response alludes to the postulate that the Colorado shale could be approximated by a transversely isotropic elasticity model at small strain levels with negligible yielding.Key words: anisotropy, elasticity, stiffness, triaxial test, torsion test, shale.
5
Xiao, Bin, Peijiao Zhou, and Shuchong Wu. "Creep Characteristics of Reconstituted Silty Clay under Different Pre-Loading Path Histories." Buildings 14, no. 5 (May 16, 2024): 1445. http://dx.doi.org/10.3390/buildings14051445.
Анотація:
Due to the long-term deformation settlement of foundations, issues such as damage and functional failure of buildings and structures have long been a concern in the engineering field. The creep of soil is one of the primary causes leading to long-term deformation of foundations. In this paper, the consolidation deformation, creep characteristics, and creep model of reconstituted saturated silty clay were studied using the isotropic consolidation creep test and triaxial compression creep test. The results show that for the isotropic consolidation creep test, although the applied load adopted different stages of loading, as long as the final applied confining pressure was the same, the number of stages applied by the confining pressure had little effect on the final isotropic consolidation deformation of the sample and the triaxial undrained shear strength after creep. However, for the triaxial shear creep test, it was found that under the same final deviatoric stress, the final deviatoric strain of the sample was closely related to the number of loading stages of deviatoric stress. The test showed that the more loading stages with the same deviatoric stress, the smaller the final deviatoric strain, and the triaxial undrained shear strength of the sample after creep increased. In addition, it was reasonable to set the pore pressure dissipation of the sample at 95% ((u0 − u)/u0 = 95%) as the time (t100) at which the primary consolidation of the soil sample was completed. The isotropic consolidation creep curves and the triaxial compression creep curves showed certain non-linearity. Then, the logarithmic model and the hyperbolic model were used to fit the creep curves of the samples. It was found that the hyperbolic model had a better fitting effect than the logarithmic model, but for the triaxial compression creep test, the creep parameters of the sample changed greatly. Therefore, studying the creep characteristics of soil under different pre-loading steps is of significant engineering importance for evaluating the long-term deformation of underground structures.
6
Chen, Rui, and B. Stimpson. "Triaxial stress relaxation tests on Saskatchewan potash." Canadian Geotechnical Journal 32, no. 1 (February 1, 1995): 11–21. http://dx.doi.org/10.1139/t95-002.
Анотація:
Relative to the study of creep, the stress relaxation phenomenon has been overlooked in research on salt rocks, especially with respect to the behavior of salt in deep underground mining environments. In the laboratory tests described in this paper, deformational properties of potash were first studied by performing reverse-loading tests that approximately simulate in situ loading paths during excavation of underground cavities. Potash relaxation properties were then investigated by multiple-stage, repeated relaxation tests along the reverse-loading path. Results show that potash behavior along a reverse-loading path is highly stress rate dependent and is reflected in the dependence of the initial axial deformation modulus, ductile point, and post-yield behavior on the rate at which the deviatoric stress is applied to the specimen. The inserted relaxation phases did not significantly affect the subsequent behavior of the potash, and therefore inserted relaxation tests are useful for investigating time-dependent behavior at various stages of deformation. A linear relationship exists between normalized stress drop and logarithm of time, which might imply that potash has no creep limit. Finally, an attempt was made to extend a uniaxial strain hardening constitutive law postulated by another researcher to include confining pressure, and the experimental data were found to approximately fit the proposed constitutive model. Key words : potash, stress relaxation, triaxial tests, constitutive model.
7
Zhang, Shu Chao, Shao Hui He, Pei Wang, and Lin Li. "Axial Unloading Test of Soil Based on the GDS Triaxial Apparatus." Applied Mechanics and Materials 638-640 (September 2014): 407–11. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.407.
Анотація:
Normal triaxial apparatus is suited to the loading stress path test, some stress path triaxial apparatus can be used to unload radial load smaller than the axial load, but it is difficult to unload axial load smaller than the radial load or even unload the axial load to zero. Using the iso-diameter headgear, different axial-radial unload ratio tests were done on the GDS triaxial apparatus, and the axial load was unloaded smaller than the radial load. During the test, it was found there are some deficiencies in the GDSLAB system. The results conformed to the characteristics of unloading test, which well verified the correctness of the test method and test results.
8
Kim, In Tai, and Erol Tutumluer. "Unbound Aggregate Rutting Models for Stress Rotations and Effects of Moving Wheel Loads." Transportation Research Record: Journal of the Transportation Research Board 1913, no. 1 (January 2005): 41–49. http://dx.doi.org/10.1177/0361198105191300105.
Анотація:
The latest research findings on stress rotations caused by moving wheel loads and their effects on permanent deformation or rut accumulation in pavement granular layers are presented. Realistic pavement stresses induced by moving wheel loads were examined in the unbound aggregate base and subbase layers, and the significant effects of rotation of principal stress axes were indicated for a proper characterization of the permanent deformation behavior. To account for the rutting performances of especially thick granular layers, a comprehensive set of repeated load triaxial tests was conducted in the laboratory. Triaxial test data were obtained and analyzed from testing aggregates under various realistic in situ stress paths caused by moving wheel loading. Permanent deformation characterization models were then developed on the basis of the experimental test data to include the static and dynamic stress states and the slope of stress path loading. The models that also considered the stress path slope variations predicted the stress path dependency of permanent deformation accumulation best. In addition, multiple stress path tests conducted to simulate the extension–compression–extension type of rotating stress states under a wheel pass gave much higher permanent strains than those of the compression-only single path tests. The findings indicated actual traffic loading simulated by the multiple path tests could cause greater permanent deformations or rutting damage, especially in the loose base or subbase, when compared with deformations measured from a dynamic plate loading or a constant confining pressure type laboratory test.
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Newson, T. A., M. C. R. Davies, and A. R. A. Bondok. "Selecting the rate of loading for drained stress path triaxial tests." Géotechnique 47, no. 5 (October 1997): 1063–67. http://dx.doi.org/10.1680/geot.1997.47.5.1063.
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Wang, Xiaoliang, Zhen Zhang, and Jiachun Li. "Triaxial behavior of granular material under complex loading path by a new numerical true triaxial engine." Advanced Powder Technology 30, no. 4 (April 2019): 700–706. http://dx.doi.org/10.1016/j.apt.2018.12.020.
Дисертації з теми "Triaxial loading path":
1
Ding, Yanzheng. "Une analyse d’images pour l'identification microstructurale en 3D d’un kaolin saturé sous chargement mécanique." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0051.
Анотація:
L'étude de la microstructure des argiles remaniées et saturées est cruciale pour la compréhension de leur comportement mécanique et des mécanismes de déformations volumiques. Cette thèse vise à identifier en 3D les mécanismes locaux qui s'activent au niveau de la microstructure en lien avec le chargement mécanique des milieux argileux. D'abord le comportement mécanique du Kaolin K13 est étudié à l'échelle de l'éprouvette sur deux chemins de chargement : œdométrique et isotrope. Ensuite, un protocole d'observation a été mis en place pour l'acquisition des images tridimensionnelles en utilisant la microscopie électronique à balayage (MEB) couplée à la Sonde Ionique Focalisée (FIB). La reconstitution des images obtenues par FIB-MEB nous permet d'accéder à la géométrie 3D d'un sous volume de l'échantillon. La deuxième partie consiste à développer une approche d'analyse quantitative en 3D permettant d'identifier les propriétés de la microstructure sur les différents chemins de chargement étudiés. La morphologie des pores est étudiée en utilisant les paramètres : flatness, élongation et sphéricité. L'orientation des pores et des particules a été d'abord identifier sur des images 2D représentants des coupes dans l'échantillon et étendue au 3D sur l'ensemble du volume et ceci sur les deux chemins de chargement. Les résultats obtenus dans le cadre de ce travail de thèse ont permis de mettre en évidence l'apport des images 3D à la compréhension de la microstructure des argiles remaniées saturéesAbstractMicrostructure investigation is essential for a better understanding of the mechanical behaviour and volumetric deformation mechanisms of remolded and saturated clays. The goal of this thesis is to identify in 3D the local mechanisms which can be activated at the microstructural level in relation to the mechanical loading of clayey meida. The mechanical behaviour of Kaolin k13 is firstly studied at on two loading paths - oedometric and isotropic. Then, an observation protocol was established for the acquisition of three-dimensional images using Scanning Electron Microscopy (SEM) coupled with Focused Ion Beam (FIB). The reconstruction of the images obtained by FIB-SEM allows us to study the 3D geometry of a sub-volume of the sample. The second part consists of developing a quantitative analysis approach in 3D to identify the microstructure properties on different loading paths. The pore morphology is studied using parameters such as flatness, elongation, and sphericity. The orientation of the pores and particles was first identified on 2D images representing cross-sections in the sample and extended to 3D throughout the entire volume for both loading paths. The results obtained in this thesis highlight the contribution of 3D images for a better understanding of the microstructure of saturated remolded clays
Частини книг з теми "Triaxial loading path":
1
Zhou, W., J. Liu, Gang Ma, X. Ma, Xiaolin Chang, and C. Zhang. "The Influence of Rolling Resistance on Granular Responses Under Triaxial Loading Paths." In Springer Proceedings in Physics, 209–16. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1926-5_24.
2
Yang, Sheng-Qi. "Triaxial Strength and Deformation Failure Behavior of Coarse Marble Under Six Different Loading Paths." In Mechanical Behavior and Damage Fracture Mechanism of Deep Rocks, 149–75. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7739-7_6.
3
Duan, Shuqian, Zhongsui Cao, Jiecheng Xiong, Bei Cao, and Chenyang Li. "Investigation on Applicability of Common Failure Criteria of Interlayer Staggered Zone Under Unloading Conditions of High Geostress." In Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230745.
Анотація:
Based on the experimental results obtained from the undrained triaxial unloading tests of interlayer staggered zone (ISZ), the validity and applicability of five conventional strength criteria are investigated to describe the unloading failure and strength parameters of ISZ through the assessment indexes of the sum of absolute deviation. It is indicated that Mogi-Coulomb criterion has relatively low sum of absolute deviation and Euclidean norm, thus it has a preferable applicability to the description of the strength property of ISZ unloading failure, not only for the stress path of the axial and confining pressure unloading, but also for the course of loading axially and unloading of confining pressure. Considering the influence of the intermediate principal stress and the non-linearity of the Parabolic criterion with relatively high sum of absolute deviation and Euclidean norm, it is more complicated to calculate the derivative with less applicability. Mohr-Coulomb criterion may not be favorable to fit experimental results under higher confining pressure, and hence not be the best choice. Hoek-Brown criterion and Drucker-Prager criterion need to be carefully considered as the two criteria tend to cause the regression result to lack fidelity and cannot describe the strength property of unloading failure of ISZ. Although the above five strength criteria seem to be with high correlations (R2 ≥ 0.95), the fitting deviations vary widely. Therefore, the correlation coefficient does not fully demonstrate the reliability of the criteria, which is suggested to combine with the least sum of absolute deviation to evaluate the applicability of unloading failure criteria of ISZ. The research lays the foundation for the selection of the plastic potential function and the solution of partial differential equations in the follow-up research.
4
Ma, Xiaodong, Bezalel C. Haimson, and John W. Rudnicki. "True triaxial failure stress and failure plane of two porous sandstones subjected to two distinct loading paths." In Porous Rock Fracture Mechanics, 285–307. Elsevier, 2017. http://dx.doi.org/10.1016/b978-0-08-100781-5.00013-0.
Тези доповідей конференцій з теми "Triaxial loading path":
1
Zhang, Q., Y. X. Shen, M. H. Wang, X. J. Wang, and X. J. Li. "Study on the Generalized Zhang-Zhu Strength Criterion Considering Different Loading Paths of True Triaxial Tests." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0608.
Анотація:
ABSTRACT Rocks in true triaxial stress states (σ1> σ2> σ3) have received much attention with the construction of deep underground engineering. True triaxial tests accurately reflect the triaxial stress state of rocks and have been widely used in the developments and validations of the three-dimensional strength criteria. Different loading paths are arranged to assess the deformation and failure properties of rocks as the development of true triaxial tests. In this study, the loading paths of the true triaxial tests are summarized as the traditional loading path, Lode angle loading path, and mean stress loading path. The ratios of σ2 and σ3, Lode angle, and mean stress can be regarded as invariants for three loading paths, respectively. The alternative expressions of the generalized Zhang-Zhu strength criterion of different loading paths are obtained by combining the three invariants. The expressions incorporate the properties of three loading paths to represent the correlations between σ1 and σ3 in simple forms. Finally, the typical rock data of three loading paths are collected to investigate the characteristics of the triaxial test data and the alternative expressions. The results show that the alternative expressions accurately predict the rock strength for different loading paths and reflect the effect of invariants of the loading path on rock strength. Adoption of three loading paths is discussed, and it is noted that the appropriate loading paths should be selected according to laboratory conditions and research priorities. INTRODUCTION With the extensive utilization of underground space, mineral, and environmental resources, the construction of deep underground engineering has been rapidly developed (Xie et al., 2017). Deep underground engineering is confronted with a complex environment such as high ground stress, high ground temperature, and strong disturbance (He et al., 2005; Qian and Zhou, 2018; Zhu et al., 2019). The mechanical behavior of deep rock is significantly different from that of shallow rock. Numerous studies indicated that the stress of deep rock presents a three-dimensional (3D) unequal characteristic (σ1>σ2>σ3) (Haimson and Rudnicki, 2010; Zhu et al., 2013; Zhu et al., 2017; Cai et al., 2021), which is defined as true triaxial stress state. Therefore, the strength characteristics of the rock cannot be effectively reflected by conventional triaxial tests (σ1>σ2=σ3) because the effect of σ2 is neglected (Zhang et al., 2013; Ma et al., 2017; Lu et al., 2020). It is important to study the mechanical properties of rock under true triaxial stress states.
2
Albinmousa, Jafar, Syed Haris Iftikhar, and Mustafa Al-Samkhan. "Modeling Multiaxial Fatigue Damage Using Polar Equations." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70998.
Анотація:
It is estimated that more than 70% of failures in engineering components are associated with fatigue loading. Therefore, fatigue is a major design tool for mechanical components. These components are usually subjected to multiaxial cyclic loading. In fact, multiaxial state is very common as tension specimen is under triaxial strain state even though its stress state is uniaxial. There are three approaches to modeling fatigue damage: stress, strain and energy. Critical plane concept is established based on the fact that fatigue cracks initiate at specific plane(s), therefore, multiaxial fatigue damage parameter is evaluated at these plane(s). Critical plane fatigue models such as Fatemi-Socie is among the popular strain-based models. Because it was shown to provide estimation mostly within two factors of life for different materials and different multiaxial loading conditions. This paper presents a new method for analyzing critical plane damage parameters. Using plane stress-strain transformation, maximum values of normal and shear stresses and strains from hysteresis loops are obtained at 360 planes. Plotting these values on polar diagrams shows that multiaxial cyclic responses represent polar curves that can successfully be fitted with definitive known polar equations. In principle, this means that both critical plane and fatigue damage can be determined analytically for a given loading path. However, fitting constants must first be determined. A systematic analysis is performed on different experimental data that were obtained by testing two extruded magnesium alloys at proportional and 90° out of phase loading paths. A closed-form solution for Fatemi-Socie damage parameter is presented for these two loading paths.
3
Zhuo, Renyan, Xinfang Ma, Yushi Zou, and Shicheng Zhang. "Experimental Study on the Mechanical Properties of Matrix and Laminae Planes in Shale." In GOTECH. SPE, 2024. http://dx.doi.org/10.2118/219339-ms.
Анотація:
Abstract The mechanical properties of laminae planes have an essential effect on the nucleation and propagation of hydraulic fractures. Previous studies mainly focused on the strong anisotropic mechanical characteristics of laminae shale. However, the effective experimental data on the mechanical properties of matrix and laminae planes is generally limited. Therefore, a series of rock mechanics tests were conducted on laminae shale to study the difference in mechanical properties between matrix and laminae planes. The tested shale samples were subsurface full-diameter cores from the Fengcheng Formation in Mahu Sag. Specimens with different laminae orientations were drilled in directions perpendicular and parallel to laminae planes. The triaxial compression strength tests, direct shear tests, and Brazilian tests were carried out on the specimens. The results showed that the tensile strength, shear strength, cohesion, and friction angle of the specimens loaded parallel to laminae planes were lower than those of the shale matrix. It demonstrated that the laminae planes are weak planes of shale in terms of mechanical strength. However, the normal stiffness and shear stiffness of the laminae planes were higher than those of the shale matrix, indicating that laminae planes are not prone to elastic deformation. Two types of failure modes were observed in the Brazilian test. For the specimens loaded parallel to laminae planes, the fractures propagated along the loading diameter without branching fractures. For the specimens loaded perpendicular to laminae planes, the fractures deviated from the loading diameter and suppressed the propagation of main fractures, which resulted in secondary fractures along the laminae planes. It was concluded that the laminae planes, as the weak planes of shale, lead to the mechanical properties changing with the loading direction relative to the direction of laminae planes and also change the propagation path of the fractures. For fractures propagating along the normal or oblique direction of the laminae plane, the propagation pathways usually offset to the direction of laminae planes or direction parallel to laminae planes, which produces curved propagation pathways and branch fractures. The mechanical properties of laminae planes in shale provide necessary data support for numerical simulation of hydraulic fracture propagation, fracture geometry prediction, and fracture initiation pressure prediction.
4
Winhausen, L., K. Khaledi, M. Jalali, and F. Amann. "Insights into the Anisotropic, Hydro-Mechanical Behavior of Opalinus Clay Through Experimental and Microstructural Investigations." In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-2075.
Анотація:
ABSTRACT: For analyzing the influence of structural anisotropy on the hydro-mechanical behavior of a clay shale, we performed three consolidated, undrained triaxial compression tests with different geometric specimen configurations. Opalinus Clay specimens were tested with bedding plane orientations of 30°, 60°, and 90° with respect to the horizontal. Results indicated different peak strengths at failure with highest and lowest values for the 90° and 30°-specimens, respectively. Failure occurred at different mean effective stresses with different magnitudes of pore water pressure built up. The 30°-specimen showed a decreasing effective mean stress up to and beyond failure compared to the initial effective consolidation stress of 10 MPa, while the 90°-specimen increased in effective mean stress during undrained loading. Dilation was found to be highest in the 30°-specimen and lowest in the 60°-specimen, demonstrated by both the effective stress path and the post-experimental microstructural analysis of the shear zones. The macroscopic shear band formed parallel to the bedding plane orientation for the specimen loaded in 60°-orientation. Here, only minor microstructural fabric changes such as increased porosity or deformed grain structures were observed, which verifies the minor volume changes inferred from the effective stress path. 1. INTRODUCTION Anisotropic rocks play an important role for engineering applications in the subsurface. Transversal isotropy is commonly associated with layered sedimentary or metamorphic rock such as sand- and siltstones, mud- or clay rocks, shales, slates and schists. Clay-rich rocks are currently investigated for their application as geological barriers in nuclear waste repositories in many countries (e.g. Belgium, Canada, France, Germany, Japan, Switzerland, United Kingdom and the United States). The hydro-mechanical response around a repository tunnel during and after the excavation is influenced by the anisotropy of the rock. The anisotropy ratio, i.e., the ratio between rock properties parallel and normal to the plane of transversal isotropy, has been investigated in a variety of experimental studies (e.g. Wild and Amann, 2018; Minardi et al., 2021). However, these two endmember orientations, i.e., 0° and 90° between the loading direction and the plane of anisotropy, cover only a minor portion of geometrical constellations around the full tunnel circumference (Fig. 1.). For the majority of geometric constellations the plane of structural anisotropy, i.e., the bedding or foliation, is oblique to the tangential stress orientation. Favorable boundary conditions for a nuclear waste repository include tectonically-inactive sites, where the bedding is oriented (sub-)horizontally and the major principle stresses are oriented vertically and horizontally. Fig. 1. shows the anticipated geometric constellation in a sub-horizontal layered clay shale at large depth. Although stress rotation may take place during excavation, this simplified sketch suggests that the two endmember constellations, where maximum load is oriented parallel (P-configuration) and perpendicular (S-configuration) to the plane of anisotropy, are limited at the roof/top and the side walls of the tunnel, respectively. All other constellations represent an oblique orientation of the tangential stress in respect to the bedding plane orientation (further referred to as Z-configuration).
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Knippel, E. P., A. P. Villaquiran Vargas, Q. Xiong, and J. C. Hampton. "Capturing Elastic Properties and Their Dependencies as a Precursor to Understanding Damage." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0764.
Анотація:
ABSTRACT Experimental rock mechanics testing provides an effective method for measuring physical properties, their dependencies, and their evolution due to the addition of localized microcracks in a controlled laboratory environment. In order to understand the contributions of microcrack parameters to first order changes in compliance, the behavior of initial undamaged properties of a material must be thoroughly understood as a function of stress, load path, and load history. To that end, we perform a comprehensive study of elastic properties and their dependence on testing parameters for a variety of materials exhibiting linear, nonlinear, and varying levels of anisotropic elastic stiffnesses. We utilize a programmatically controlled triaxial testing apparatus to perturb specimens instrumented with strain gauges and ultrasonic transducers. Elastic moduli are then measured along multiple discrete loading paths as a function of stress, with the upper limit calculated through an experimental derived failure envelope. Once the experimental results of those effects are isolated, we will then be able to assess the accuracy of limiting the modeled damage related changes in compliance to solely crack density, length, and orientation in a homogenized medium. INTRODUCTION The relationship between stress and strain is a constitutive law governed by properties intrinsic to a material. This is often assumed to be linearly elastic, where strain increases constantly with stress and deformation fully recovers once the applied stress is released. This is not always the case and is readily observed in experimental data, however the relationship is close enough for undamaged materials that the assumption is still valid in a variety of applications (Jaeger et al. (2007)). As stress and strain are both second order tensors, a fourth order tensor is required to relate these properties. This compliance tensor contains 81 components, however due to symmetry this can be reduced to 36 similarly to how both stress and strain contain six independent coefficients out of the total nine. For layered and isotropic materials, the number of independent coefficients can further be reduced. The compliance tensor for layered or vertically transversely isotropic (VTI) materials contain eight independent coefficients. Materials that are isotropic in all directions contain three independent coefficients. These coefficients can be calculated through experimental testing, where applied stress is manipulated along various load paths and resulting strain measured. There exists dynamic elastic moduli as well, measured through the use of ultrasonic transducers, where high frequency and low strain amplitude ultrasonic waves propagate through the material. The differences between static (low frequency and higher strain amplitude) and dynamic (high frequency and low strain amplitude) stress-strain perturbations often result in subtle differences between the moduli, though typical relationships between dynamic and static elastic moduli have been studied extensively and is out of the scope of this paper. VTI samples with non-uniform static elastic moduli are expected to have similar differences in velocity and dynamic moduli.
Звіти організацій з теми "Triaxial loading path":
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Vankirk, George, Andreas Frank, Michael Roth, Brett Williams, and William Heard. Residual strength of a high-strength concrete subjected to triaxial prestress. Engineer Research and Development Center (U.S.), January 2024. http://dx.doi.org/10.21079/11681/48055.
Анотація:
This study investigates simplified mechanical loading paths that represent more complex loading paths observed during penetration using a triaxial chamber and a high-strength concrete. The objective was to determine the effects that stress-strain (load) paths have on the material’s unconfined compressive (UC) residual strength. The loading paths included hydrostatic compression (HC), uniaxial strain in compression (UX), and uniaxial strain load biaxial strain unload (UXBX). The experiments indicated that the load paths associated with nonvisible microstructural damage were HC and UX—which produced minimal impact on the residual UC strength (less than 30%)—while the load path associated with visible macro-structural damage was UXBX, which significantly reduced the UC strength (greater than 90%). The simplified loading paths were also investigated using a material model driver code that was fitted to a widely used Department of Defense material model. Virtual experiment data revealed that the investigated material model overestimated material damage and produced poor results when compared to experimental data.