Journal articles on the topic 'Triaxial stress'
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1
Serna Moreno, María del Carmen, Sergio Horta Muñoz, and Alberto Ruiz Gracia. "Design of Triaxial Tests with Polymer Matrix Composites." Polymers 14, no. 4 (February 21, 2022): 837. http://dx.doi.org/10.3390/polym14040837.
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Multiaxial testing in composites may generate failure modes which are more representative of what occurs in a real structure submitted to complex loading conditions. However, some of its main handicaps include the need for special facilities, the correct design of the experiments, and the challenging interpretation of the results. The framework of this research is based on a triaxial testing machine with six actuators which is able to apply simultaneous and synchronized axial loads in the three space directions. Then, the aim was to design from a numerical point of view a triaxial experiment adapted to this equipment. The methodology proposed could allow for an adequate characterization of the triaxial response of a polymer-based composite with apparent isotropic behaviour in the testing directions. The finite element method (FEM) is applied in order to define the geometry of the triaxial specimen. The design pursues to achieve homogeneous stress and strain states in the triaxially loaded region, which should be accessible for direct measurement of the strains. Moreover, a fixing system is proposed for experimentally reproducing the desired boundary conditions imposed on the numerical simulations. The procedure to determine the full strain tensor in the triaxially loaded region is described analytically and with the help of FEM virtual testing. The hydrostatic component and the deviatoric part of the strain tensor are proposed for estimating the susceptibility of the polymer-based composite to fail due to the triaxial strain state imposed. Then, the loading scenarios that cause higher values of the deviatoric components in the triaxially loaded region are considered to be more prone to damage the region of interest. Nevertheless, the experimental failure is expected to be produced in the arms of the specimen which are uniaxially loaded, since in all of the loading cases the simulations show higher levels of stress concentration out of the triaxially loaded region. Thus, although the triaxial strength could not be accurately determined by the proposed tests, they can be utilized for observing the triaxial response before failure.
2
Li, Rong Jian, Xi An Li, Gao Feng Che, Wen Zheng, and Wen Jun Chen. "A Simple and Practicable Approach on Implementing for the Reduced Triaxial Extension by the Conventional Triaxial Apparatus." Advanced Materials Research 250-253 (May 2011): 2089–92. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.2089.
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Stress path is one of the very important factors of soil strength. It is significant to study the strength and reveal the importance of the impact of sand in different stress path conditions. Firstly, an ameliorating approach on implementing for the reduced triaxial extension by the conventional triaxial apparatus was discussed. Then, In order to study shear behaviors of the eolian sand under different stress path, two monotonic shearing tests with the conventional triaxial compression and the reduced triaxial extension stress path were performed and analyzed. The test results not only indicate that the amelioration on conventional triaxial apparatus is simple, practicable and inexpensive, but also reveal the difference of strength’s parameter between the reduced triaxial extension and conventional triaxial compression stress path. In sum, the stress path has important effect on the strength of the eolian sand.
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Stone, B. M., I. J. Jordaan, J. Xiao, and S. J. Jones. "Experiments on the damage process in ice under compressive states of stress." Journal of Glaciology 43, no. 143 (1997): 11–25. http://dx.doi.org/10.3189/s002214300000277x.
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AbstractDuring ice-structure interaction, ice will fail in a brittle manner dominated by two processes. The first corresponds to the formation of macrocracks and the consequent spalling-off of large ice pieces. The second includes an intense shear-damage process in zones, termed critical zones, where high pressures are transmitted to the structure. The shear-damage process results in microstructural changes including microcrack formation and recrystallization. A range of tests on laboratory-prepared granular ice have been conducted to determine the fundamental behaviour of ice under various stress states and stress history, particularly as it relates to changes in microstructure. The test series was designed to study three aspects: the intrinsic creep properties of intact, undamaged ice; the enhancement of creep and changes in microstructure due to damage; and the effects of different stress paths. Tests on intact ice with triaxial confining pressures and low deviatoric stresses, aimed at defining the intrinsic creep response in the absence of microcracking, showed that an accelerated creep rate occurred at relatively low deviatoric stresses. Hence, a minimum Creep rate occurred under these conditions. Recrystallization to a smaller grain-size and void formation were observed. Ice damaged uniaxially and triaxially prior to testing showed enhancement of creep under both uniaxial and triaxial loading conditions Creep rates in triaxially damaged ice were found to be non-linear with high deviatoric stresses, corresponding to a power-law dependence of creep rate. Uniaxially damaged specimens contained microcracks parallel to the stressed direction which tended to close under triaxial confinement. Damage under triaxial conditions at low confining pressures produced small recrystallized grains near zones of microcracking. At high confining pressures, a fine-grained recrystallized structure with no apparent cracking was observed uniformly across the specimen. The recrystallization process contributes significantly to the enhanced creep rates found in damaged specimens.
4
Stone, B. M., I. J. Jordaan, J. Xiao, and S. J. Jones. "Experiments on the damage process in ice under compressive states of stress." Journal of Glaciology 43, no. 143 (1997): 11–25. http://dx.doi.org/10.1017/s002214300000277x.
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AbstractDuring ice-structure interaction, ice will fail in a brittle manner dominated by two processes. The first corresponds to the formation of macrocracks and the consequent spalling-off of large ice pieces. The second includes an intense shear-damage process in zones, termed critical zones, where high pressures are transmitted to the structure. The shear-damage process results in microstructural changes including microcrack formation and recrystallization. A range of tests on laboratory-prepared granular ice have been conducted to determine the fundamental behaviour of ice under various stress states and stress history, particularly as it relates to changes in microstructure. The test series was designed to study three aspects: the intrinsic creep properties of intact, undamaged ice; the enhancement of creep and changes in microstructure due to damage; and the effects of different stress paths. Tests on intact ice with triaxial confining pressures and low deviatoric stresses, aimed at defining the intrinsic creep response in the absence of microcracking, showed that an accelerated creep rate occurred at relatively low deviatoric stresses. Hence, a minimum Creep rate occurred under these conditions. Recrystallization to a smaller grain-size and void formation were observed. Ice damaged uniaxially and triaxially prior to testing showed enhancement of creep under both uniaxial and triaxial loading conditions Creep rates in triaxially damaged ice were found to be non-linear with high deviatoric stresses, corresponding to a power-law dependence of creep rate. Uniaxially damaged specimens contained microcracks parallel to the stressed direction which tended to close under triaxial confinement. Damage under triaxial conditions at low confining pressures produced small recrystallized grains near zones of microcracking. At high confining pressures, a fine-grained recrystallized structure with no apparent cracking was observed uniformly across the specimen. The recrystallization process contributes significantly to the enhanced creep rates found in damaged specimens.
5
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.
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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.
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Sakane, Masao, Hiroki Kobayashi, Ryohei Ohki, and Takamoto Itoh. "Creep Void Formation and Rupture Lifetime in Multiaxial Stress States." Key Engineering Materials 795 (March 2019): 159–64. http://dx.doi.org/10.4028/www.scientific.net/kem.795.159.
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This paper discusses creep void formation and rupture lifetimes in multiaxial stress states for a SUS 304 stainless steel at elevated temperatures. Biaxial and triaxial tension creep tests were performed using a cruciform and a cubic specimen, respectively. These two types of the specimens were designed to achieve uniform equi-biaxial and equi-triaxial stress distributions by a finite element analysis in the gage parts. Void formation at grain boundaries was observed by intermitting biaxial creep tests and by interrupting triaxial creep tests. Creep rupture lifetimes were also obtained in biaxial and triaxial creep tests. Biaxial stresses increase the void formation but give a little influence on a creep rupture lifetime in the correlation with von Mises equivalent stress. Triaxial stresses also increase the void formation and drastically reduce a creep rupture lifetime in the correlation with von Mises equivalent stress. Evident void formation in an equi-triaxial stress condition demonstrates that von Mises equivalent stress is not a suitable measure to evaluate creep damage development in multiaxial stress states. A new equivalent stress is proposed to evaluate creep rupture lifetimes in biaxial and triaxial stress states.
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Černý, Miroslav, Petr Šesták, and Jaroslav Pokluda. "Stress Coupling Effect on Ideal Shear Strength: Tungsten as a Case Study." Advances in Materials Science and Engineering 2016 (2016): 1–5. http://dx.doi.org/10.1155/2016/5317985.
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Mechanical response of a perfect bcc tungsten crystal to a multiaxial loading was investigated from first principles. The multiaxial stress state consisted of the shear stress and a superimposed compressive triaxial stress with various levels of differential stresses. The studied shear system was 111110. Results obtained within a relatively wide range of the compressive stresses showed that increasing hydrostatic triaxial stress (with zero differential stresses) increased the shear strength almost linearly. On the other hand, triaxial stresses with greater portion of the differential components did not have such a simple effect on the shear strength: we found a certain optimum value of the superimposed triaxial stress yielding the maximum shear strength. Any change (both increase and decrease) in the triaxial stress then reduced the ideal shear strength value.
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Andreghetto, Dionatas, Lucas Festugato, Gustavo Miguel, and Andressa Silva. "Automated true triaxial apparatus development for soil mechanics investigation." Soils and Rocks 45, no. 2 (April 19, 2022): 1–10. http://dx.doi.org/10.28927/sr.2022.077321.
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Soil mechanical fully understanding requires considering a three dimensional approach, including soil response under the second principal stress and its potential anisotropy. In order to achieve such soil mechanical understanding, a true triaxial apparatus might be used. Therefore, in the present research an automated true triaxial apparatus was developed comprising its cubical cell, data acquisition and stress control systems. The manufactured apparatus was validated by means a laboratory test campaign where true triaxial test responses were compared to standard drained triaxial tests. True triaxial and standard drained triaxial tests were carried out on both naturally and artificially cemented soils. Results were gathered and compared. A soil mechanical compatibility was observed when test results of the newest true triaxial equipment were compared to test results obtained from a well validated standard triaxial apparatus. Thereby, the present paper reports an affordable successful true triaxial apparatus development demonstrating its efficiency for regular soil mechanical tests. Finally, a full stress rosette was established for a uniform fine sand where some small anisotropy was detected.
9
Cui, Feng-kun, Huai-shuai Shang, Tie-jun Zhao, Guo-xi Fan, and Guo-sheng Ren. "Mechanical and Failure Criteria of Air-Entrained Concrete under Triaxial Compression Load after Rapid Freeze-Thaw Cycles." Advances in Materials Science and Engineering 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/6786270.
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The experiment study on the air-entrained concrete of 100 mm cubes under triaxial compression with different intermediate stress ratioα2=σ2D : σ3Dwas carried out using a hydraulic-servo testing system. The influence of rapid freeze-thaw cycles and intermediate stress ratio on the triaxial compressive strengthσ3Dwas analyzed according to the experimental results, respectively. The experimental results of air-entrained concrete obtained from the study in this paper and the triaxial compression experimental results of plain concrete got through the same triaxial-testing-system were compared and analyzed. The conclusion was that the triaxial compressive strength is greater than the biaxial and uniaxial compressive strength after the same rapid freeze-thaw cycles, and the increased percentage of triaxial compressive strength over biaxial compressive strength or uniaxial compressive strength is dependent on the middle stress. The experimental data is useful for precise analysis of concrete member or concrete structure under the action complex stress state.
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Goudar, D. M., M. S. Hossain, Christopher E. Truman, Ed J. Kingston, and David John Smith. "Uncertainties in Triaxial Residual Stress Measurements." Materials Science Forum 681 (March 2011): 498–503. http://dx.doi.org/10.4028/www.scientific.net/msf.681.498.
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Residual stress measurement techniques using mechanical strain relaxation depend on a number of physical quantities and are therefore sensitive to errors associated with the measured data. The resulting stress uncertainties can easily become significant and compromise the usefulness of the results or lead to misinterpretation of the behaviour of the residual stress distributions. It is therefore essential to develop an error analysis procedure for the measurements undertaken. Error analysis procedures for the deep hole drilling (DHD) method are developed to consider triaxial residual stresses. A modified deep hole drilling method, called the incremental deep-hole drilling (iDHD), was applied to measure the near yield residual stress distributions in a cold water quenched aluminium 7010 alloy forged block. The experimental results are used to illustrate the errors.
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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.
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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.
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Gross, Todd, Jordan Kusch, and Igor Tsukrov. "Determination of Triaxial Tensile Failure Surfaces for Curing Epoxy Resins." Key Engineering Materials 577-578 (September 2013): 257–60. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.257.
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Microcracking is often observed in the resin pockets of as-cured 3D woven composites with significant through-the-thickness fiber constraint. The resin is subjected to a triaxial tensile stress during cooling due to thermal expansion mismatch and shrinkage during curing. However, the temperature dependence of the failure surface for resins subjected to triaxial tensile stress is not known and there is no standard measurement method for applying a triaxial tensile stress. We have developed a novel method for measuring the triaxial tensile failure stress surface by confining the shrinkage of the resin to tubes of different thicknesses and made of materials with different thermal expansion coefficient. The difference in thermal contraction and shrinkage between the resin and the confining tube subjects the resin to a triaxial tensile stress during cooling and curing. We vary the stress-temperature state by selecting tubes with different coefficient of thermal expansion. We infer the stress in the resin from the deflections of the tube measured by a high resolution dilatometer assuming that the tube is a linear elastic, thick-walled pressure vessel.
13
HAN, BO, HANGZHOU LI, HONG-JIAN LIAO, and ZHENGHUA XIAO. "STUDY ON STRESS-STRAIN RELATIONSHIP OF LOESS BASED ON TWIN SHEAR UNIFIED DAMAGE CONSTITUTIVE MODEL." International Journal of Modern Physics B 22, no. 31n32 (December 30, 2008): 5838–43. http://dx.doi.org/10.1142/s021797920805125x.
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To investigate the change of loess stress state, a series of triaxial shear tests were performed on normal consolidation and over consolidation loess. From the test results, the stress-strain relationships of loess were obtained and discussed. Based on unified strength theory, the statistical damage constitutive equation was obtained under triaxial stress state assuming distribution statistical probability of micro-units strength. Then the proposed formulation was adopted to study on stress-strain constitutive relationships of loess and to simulate consolidation undrained triaxial test and consolidation drained triaxial test for normal consolidated and over-consolidated specimens. Compared between experimental and theoretical results, it was shown that the proposed constitutive model can well describe stress-strain relationship of loess, whatever the characteristic of strain softening or stain hardening.
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Chen, Youliang, Qijian Chen, Yungui Pan, Peng Xiao, Xi Du, Suran Wang, Ning Zhang, and Xiaojian Wu. "A Chemical Damage Creep Model of Rock Considering the Influence of Triaxial Stress." Materials 15, no. 21 (October 28, 2022): 7590. http://dx.doi.org/10.3390/ma15217590.
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In order to accurately describe the characteristics of each stage of rock creep behavior under the combined action of acid environment and true triaxial stress, based on damage mechanics, chemical damage is connected with elastic modulus; thus, the damage relations considering creep stress damage and chemical damage are obtained. The elastic body, nonlinear Kelvin body, linear Kelvin body, and viscoelastic–plastic body (Mogi–Coulomb) are connected in series, and the actual situation under the action of true triaxial stress is considered at the same time. Therefore, a damage creep constitutive model considering the coupling of rock acid corrosion and true triaxial stress is established. The parameters of the deduced model are identified and verified with the existing experimental research results. The yield surface equation of rock under true triaxial stress is obtained by data fitting, and the influence of intermediate principal stress on the creep model is discussed. The derived constitutive model can accurately describe the characteristics of each stage of true triaxial creep behavior of rock under acid environment.
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Rossato, Gianni, and Paolo Simonini. "Stress–strain behaviour of sands in triaxial and direct simple shear tests." Canadian Geotechnical Journal 28, no. 2 (April 1, 1991): 276–81. http://dx.doi.org/10.1139/t91-033.
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The behaviour of a natural sand in triaxial compression and direct simple shear tests was compared by means of dimensionless analysis of parameters controlling the evolution of stresses and strains. The secant triaxial compression and direct simple shear moduli were interpreted in a dimensionless form. A criterion based on the equivalence between major principal strain in the two tests was considered to compare the results. Key words: sand, stress–strain behaviour, triaxial test, direct simple shear test, shear modulus, triaxial compression modulus.
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Masuda, Tomokazu, Hiroyuki Toda, and Toshiro Kobayashi. "Notch Effects on Impact Tensile Properties in A6061-T6 Aluminum Alloy." Materials Science Forum 449-452 (March 2004): 137–40. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.137.
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The strain rate sensitivity of a A6061-T6 aluminum is examined as a function of triaxial stress. The triaxial stress state is changed by changing the notch acuity of notched specimens. Under the high strain rate conditions, increasing triaxiality increases flow stress. Plastic constraint factor decreases in notched specimens under high strain rate conditions. Reduction-of-area in notched specimen increases with increasing strain rate. The relaxation of plastic constraint takes place under high strain rate in the notched specimens. The effects of triaxial stress and strain rate on the fracture surfaces are discussed.
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Kirkgard, M. M., and P. V. Lade. "Anisotropic three-dimensional behavior of a normally consolidated clay." Canadian Geotechnical Journal 30, no. 5 (October 1, 1993): 848–58. http://dx.doi.org/10.1139/t93-075.
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An experimental study is presented of the influence of the intermediate principal stress on the stress–strain, pore-pressure, and strength characteristics of a normally consolidated, natural anisotropic clay, San Francisco Bay Mud, under undrained conditions. Consolidated undrained triaxial compression tests and triaxial tests with independent control of all three principal stresses on cubical specimens were performed. The stress–strain behavior and the pore-pressure characteristics as well as the effective stress failure surface can be described as being cross-anisotropic. Key words : anisotropic soils, clays, deformation, shear strength, triaxial tests.
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Dai, Jiahui, Chao Liu, Minghui Li, and Zhenlong Song. "Influence of principal stress effect on deformation and permeability of coal containing beddings under true triaxial stress conditions." Royal Society Open Science 6, no. 2 (February 2019): 181438. http://dx.doi.org/10.1098/rsos.181438.
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In situ stress is generally an anisotropic/true triaxial stress ( σ 1 > σ 2 > σ 3 ). Bedding weakens the continuity and integrity of coal. It is critical to understand the mechanical behaviour and gas migration of coal under true triaxial stress conditions. We performed experiments of cubic coal samples to investigate the permeability evolution and mechanical behaviour of coal under true triaxial stress conditions by using newly developed true triaxial geophysical apparatus. We analysed the effect of principal stresses on deformation and permeability characteristics of coal containing bedding planes. The results show that volumetric strain, stress states and bedding directions determine the permeability comprehensively. The variable quantity of strain was the largest in the direction normal to the bedding plane. The expansion or compression degree was characterized by the difference between the major and minor principal strain ( ɛ 1 − ɛ 3 ). Essentially, this represents the difficulty degree with regard to coal being compressed at the initial stress state and the deformation degree in ɛ 1 and ɛ 3 direction. The variation of ( ɛ 1 − ɛ 3 ) was consistent with that of permeability. Under an identical true triaxial stress condition, permeability was smaller when larger stress was applied in the direction normal to the bedding plane. Additionally, stress level in the direction parallel to the bedding planes and the directions between stresses in the direction parallel to the bedding planes and the flow direction also affect the permeability and strain. By solving lateral expansion coefficient, coal also exhibited anisotropic properties.
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Hu, Liangming, Shuyu Li, Junfu Zhu, and Xu Yang. "Mathematical Model of Constitutive Relation and Failure Criteria of Plastic Concrete under True Triaxial Compressive Stress." Materials 14, no. 1 (December 29, 2020): 102. http://dx.doi.org/10.3390/ma14010102.
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To establish the mathematic model of the constitutive relation and failure criteria of plastic concrete under true triaxial compressive stress, uniaxial compressive strength and true triaxial compressive strength of plastic concrete under three kinds of confining pressures with a size of 150 × 150 × 150 mm3 and a curing age of 540 days were tested, and the elastic modulus of plastic concrete with a size of 150 × 150 × 300 mm3 and a curing age of 90 days was tested. Based on the database, under uniaxial compressive stress tests and true triaxial compressive stress tests, the mathematic model of constitutive relation and the failure criteria of plastic concrete were investigated. It was observed that the strength of plastic concrete increased with confining stress. The mathematic model of constitutive relation in the form of the quartic polynomial is in good agreement with measured data. The general equations of failure criteria based on the octahedral stress-space under true triaxial compressive stress in the form of quadratic polynomial are well-fitting with experimental data. The mathematic model of constitutive relation and failure criteria of plastic concrete could provide the basis for a numerical simulation analysis of plastic concrete under true triaxial compressive stress, as well as promote the engineering application of plastic concrete.
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Xia, Wei, Erlei Bai, Jinyu Xu, and Gaojie Liu. "Experimental Study on the Strength and Deformation Characteristics of Concrete under True Triaxial Compression after Sulfate Attack." Advances in Civil Engineering 2021 (April 14, 2021): 1–15. http://dx.doi.org/10.1155/2021/5548313.
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To explore the mechanical properties of concrete under true triaxial static compressive load after sulfate attack, uniaxial static compression test and true triaxial static compression test at four stress ratios were carried out on concrete specimens immersed in 15% sulfate solution for 0–120 days by the integrated true triaxial static and dynamic load testing system, and the variation of performance indicators such as the strength and deformation of concrete under the coupling action of sulfate attack and complex stress state was analyzed. The results show that the uniaxial compressive strength of concrete increases at the beginning and then decreases with the increase of sulfate attack time and reaches the peak on the 30th day, with an increase rate of 16.57%; the strength of concrete under triaxial compression increases significantly, and the maximum triaxial compressive strength is 3.18 times of uniaxial compressive strength under the combination of 0-day sulfate attack and 0.2 : 0.8 stress ratio; and the deterioration of concrete under sulfate attack is more prominent at high confining pressure, and as the sulfate attack worsens, the sensitivity of triaxial compressive strength of concrete to lateral compressive stress is reduced. In conclusion, triaxial compression can significantly enhance the ductility of concrete by playing a role in restraining the deformation and cracking of concrete after sulfate attack.
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Johnson, Clarence E., Alvin C. Bailey, and Thomas R. Way. "A Shearing Strain Model for Cylindrical Stress States." Transactions of the ASABE 62, no. 1 (2019): 225–30. http://dx.doi.org/10.13031/trans.12725.
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Abstract. A shearing strain model for soil was developed that includes soil behavior under compressive normal and shear stresses great enough to attain maximum compaction. The model was developed for a clay and a clay loam from triaxial data with various stress loading paths. This model relates the ratio of maximum shear stress acting on the cylindrical sample (tmax) to major principal stress (s1), to the ratio of maximum natural shearing strain to natural volumetric strain occurring after shear stress is initiated. The model accurately describes the shearing distortion of triaxial soil samples under cylindrical stress loading prior to yielding by plastic flow. This model predicts soil shearing strain for input stress states that realistically represent field conditions. Keywords: Principal stress and strain, Shearing strain, Shear stress, Soil compaction, Soil parameters, Triaxial tests.
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Liu, Jun Xin, Zhong Fu Chen, and Wei Fang Xu. "Study on Character of Triaxial Extension Strength of Compacted Clay." Advanced Materials Research 243-249 (May 2011): 2183–87. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2183.
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For soils, failure occurs with lower deviatoric stress under the same pressure (the first invariant of stress tensor) in TXE compared with the strength of the triaxial compression, which is indicated that the strength of soils strongly depends on the third invariant of stress deviator; Although in the traditional Mohr-Coulomb criterion it can be reflected in difference of strength between triaxial extension and compression under the same pressure, it’s nothing to do with the pressure for the strength ratio between triaxial extension and compression. By TXC and TXE, changes of deviatoric stress and the ratio with the pressure were studied
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Wang, Ziyi, Hengyu Su, Chang Luo, Shu Ma, and Heng Ding. "Particle Flow Simulation of Failure Process of Defective Sandstone under Different Intermediate Principal Stress under True Triaxial Action." Processes 10, no. 10 (October 7, 2022): 2028. http://dx.doi.org/10.3390/pr10102028.
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In order to explore the mechanical response characteristics of fractured sandstone under true triaxial different medium principal stresses, matdem particle flow software was used to study the mechanical response characteristics, fracture mechanism and damage evolution characteristics of sandstone specimens under the conditions of 30 MPa, 40 MPa and 50 MPa respectively. The simulation results are verified by true triaxial test. The results show that under true triaxial stress, the increase of medium principal stress is beneficial to increase the strength of sandstone. The fracture degree of the specimen increases with the increase of the intermediate principal stress, and finally the interlacing macroscopic cracks are formed. When the intermediate principal stress is perpendicular to the fracture strike, the fracture mode of sandstone is that the macroscopic fracture plane is perpendicular to the fracture strike, and the fracture mechanism of sandstone under true triaxial compression is mainly shear failure, accompanied by tensile failure. With the increasing of the intermediate principal stress, the fractal dimension of the fracture of sandstone specimen increases significantly and the degree of fracture deepens. Combined with the true triaxial test results, the rationality of particle flow simulation test is proved.
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Atkinson, J. H., J. S. Evans, and D. Richardson. "Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay." Geological Society, London, Engineering Geology Special Publications 2, no. 1 (1986): 139–44. http://dx.doi.org/10.1144/gsl.1986.002.01.29.
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AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.
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Han, Bo, Hong Jian Liao, Hang Zhou Li, and Zheng Hua Xiao. "Experimental Study on Shear Strength Characteristics and Stress-Strain Relationship of Loess." Key Engineering Materials 535-536 (January 2013): 574–77. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.574.
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This paper mainly concerns the non-linear strength characteristics of the loess. A series of consolidated undrained triaxial tests(CU test) and consolidated drained triaxial tests (CD test) of normal consolidation and over consolidation loess specimens are carried out by using the normal triaxial apparatus of strain control. The stress-strain relationship curves and strength characteristics of loess are investigated and analyzed. The results show that the stress-strain relationship obtained by CU tests appears strain softening, while the stress-strain relationship for CD tests appears strain hardening. Different failure modes have different stress-strain relationships. Furthermore, the results also show that the peak strength, residual strength and residual strength ratio change with the different confining pressure. Based on the triaxial shear tests of normal consolidated loess, the influences of over-consolidated loess on the stress-strain relationships and strength characteristic are discussed. Several conclusions obtained in this paper can be referenced for the loess experimental study.
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Chen, Qingqing, Yuhang Zhang, Tingting Zhao, Zhiyong Wang, and Zhihua Wang. "Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour." Materials 14, no. 5 (February 26, 2021): 1099. http://dx.doi.org/10.3390/ma14051099.
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The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.
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Ye, Peihuan, Yuliang Chen, Zongping Chen, Jinjun Xu, and Huiqin Wu. "Failure Criteria and Constitutive Relationship of Lightweight Aggregate Concrete under Triaxial Compression." Materials 15, no. 2 (January 10, 2022): 507. http://dx.doi.org/10.3390/ma15020507.
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This paper investigates the compression behavior and failure criteria of lightweight aggregate concrete (LAC) under triaxial loading. A total of 156 specimens were tested for three parameters: concrete strength, lateral confining pressure and aggregate immersion time, and their effects on the failure mode of LAC and the triaxial stress-strain relationship of LAC is studied. The research indicated that, as the lateral constraint of the specimen increases, the failure patterns change from vertical splitting failure to oblique shearing failure and then to indistinct traces of damage. The stress-strain curve of LAC specimens has an obvious stress plateau, and the curve no longer appears downward when the confining pressure exceeds 12 MPa. According to the experimental phenomenon and test data, the failure criterion was examined on the Mohr–Coulomb theory, octahedral shear stress theory and Rendulic plane stress theory, which well reflects the behavior of LAC under triaxial compression. For the convenience of analysis and application, the stress-strain constitutive models of LAC under triaxial compression are recommended, and these models correlate well with the test results.
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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.
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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.
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Pincus, HJ, S. Aversa, and F. Vinale. "Improvements to a Stress-Path Triaxial Cell." Geotechnical Testing Journal 18, no. 1 (1995): 116. http://dx.doi.org/10.1520/gtj10128j.
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Drnevich, VP, S. Ampadu, and F. Tatsuoka. "An Automated Stress-Path Control Triaxial System." Geotechnical Testing Journal 12, no. 3 (1989): 238. http://dx.doi.org/10.1520/gtj10975j.
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Haider, Giasuddin M., J. G. Sanjayan, and P. G. Ranjith. "Complete triaxial stress–strain curves for geopolymer." Construction and Building Materials 69 (October 2014): 196–202. http://dx.doi.org/10.1016/j.conbuildmat.2014.07.058.
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Johnston, A. I., Trevor R. Finlayson, and J. R. Griffiths. "Triaxial Residual Stress Measurement Using Neutron Diffraction." Materials Science Forum 27-28 (June 1988): 465–70. http://dx.doi.org/10.4028/www.scientific.net/msf.27-28.465.
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Toyeb, Muhammad. "ANALISIS BALIK KUAT GESER TANAH TERSTABILISASI SEMEN DENGAN METODE NUMERIK." Racic : Rab Construction Research 5, no. 1 (June 29, 2020): 48–57. http://dx.doi.org/10.36341/racic.v5i1.1315.
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Shear strenght is a parameter to soils strenght analysis. Shear strenght can be obtained from laboratorium test that interpreted as stress and strain. Soil tests had done on soil stabilization of cement with mixing 5%; 10%; 15% of content. Soil tests were used by triaxial test of unconsolidated undrained (triaxial UU) with cell pressure at 50; 100; 200 kN/m2 and unconfined compression test. The test specimens were disturbed soil samples which compacted and remolded, and then carry out curing for 0; 3; 7; 14; 28 days. The laboratory test results were back analysis in Plaxis 2D by using Mohr-Coulumb and Hardening Soil model later. The Mohr-Coulumb and Hardening Soil model had deviator stress results was almost equal to the test results of triaxial UU and unconfined compression test. Especially of strain by Mohr-Coulumb model, shew the lower strain than be showed by triaxial UU test and unconfined compression test. The Hardening Soil model, provides fluctuating strain results of triaxial UU test because it is affected by the application of cell pressure (σ3) and it provides greater strain results from unconfined compression test.
Keywords: Triaxial UU, Unconfined Compresssion, Stress and Strain, Plaxis 2D
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Mpawenayo, Régis, and Pierre Gerard. "Prediction of unsaturated shear strength from microstructurally based effective stress." E3S Web of Conferences 92 (2019): 07005. http://dx.doi.org/10.1051/e3sconf/20199207005.
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This work aims at investigating the adequacy of microstructurally based effective stress to predict the shear strength of unsaturated soils over a wide range of suction. For that purpose, shear strength data are acquired on a silty clay soil through two types of unsaturated triaxial tests: suction controlled triaxial tests and unconsolidated triaxial tests at constant water content. The microstructure of the soil is determined with Mercury Intrusion Porosimetry and is directly used in different expressions of microstructurally based effective stresses available in the literature. The large range of suction tested allows to determine the most consistent expression of the effective stress to reproduce the experimental observations.
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Su, Li Jun, Hong Jian Liao, and Jian Hua Yin. "Numerical Modeling of the Constitutive Relationship of a Soft Rock Using a 3-D Elastic Visco-Plastic Model." Key Engineering Materials 261-263 (April 2004): 723–28. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.723.
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In this paper, a diatomaceous soft rock is studied. Triaxial tests had been conducted on this soft rock. From the test results, it is found that the stress-strain curve of this soft rock has a notable strain-softening tendency. In order to study its time-dependent stress-strain behavior, a constitutive model that can describe not only the strain-hardening behavior, but also the strain-softening behavior must be constructed. Based on Perzyna’s fundamental assumptions of the elastic visco-palstic theory, a visco-plastic flow rule, and Yin and Graham’s 3-D elastic visco-palstic constitutive model (3-D EVP model), the constitutive formulation under a triaxial stress state is obtained in this paper. The derived formulation can be used to simulate the time-dependent stress-strain behavior of both consolidated undrained and consolidated drained triaxial tests of soils and rocks. In this paper, the constitutive formulation is used to simulate the time-dependent stress-strain behavior of consolidated undrained triaxial tests of the soft rock studied in this paper. The simulated results are compared with the triaxial test results. The comparison of the results shows that model predictions agree well with measured results. This demonstrates that the EVP model can be used to describe the time-dependent stress-strain behavior of the soft rock studied in this paper.
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Su, San Qing, Bo Tuan Deng, Jun Feng Hou, and Zhen Lv. "Experimental Study on Shear Strength of Intact Loess at Different Stress Paths." Advanced Materials Research 368-373 (October 2011): 2891–94. http://dx.doi.org/10.4028/www.scientific.net/amr.368-373.2891.
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The conventional triaxial compression(CTC), triaxial compression(TC) and reduce triaxial compression(RTC) of ordinary loess in Xi，an Ba He was conducted with GDS stress path tests and the strength behavior and deformation capacity of loess was studied. The experimental results showed that the larger the initial moisture content, the smaller the shear strength. The strength characteristic of loess varied under different stress path. Relationships between σ and ε was strain hardening model. The peak strength of CTC is larger than that of TC and the peak strength of RTC was smaller.
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Szypcio, Zenon. "Stress-Dilatancy for Soils. Part II: Experimental Validation for Triaxial Tests." Studia Geotechnica et Mechanica 38, no. 4 (December 1, 2016): 59–65. http://dx.doi.org/10.1515/sgem-2016-0031.
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Abstract Different forms of the stress-dilatancy relations obtained based on the frictional theory for the triaxial condition are presented. The analysed test data show that the shear resistance of many soils is purely frictional. The angle Φ0 represents the resistance of the soil as a combined effect of sliding and particle rolling on the macro-scale during shear at the critical frictional state. The stress-plastic dilatancy relations differ not only for triaxial compression and extension but also for drained and undrained conditions. The experiment investigated shows the correctness of the frictional state theory in the triaxial condition.
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Shen, Wei, Guang-Jian Liu, Lin-Ming Dou, Si-Yuan Gong, and Hu He. "Influences of True Triaxial Loading-Unloading Stress Paths on Mechanical Properties and Wave Velocity of Coal Samples subject to Risk of Rock Burst." Shock and Vibration 2021 (September 14, 2021): 1–14. http://dx.doi.org/10.1155/2021/4074159.
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To study fracture evolution and peak stress in burst risk coal samples (BRCSs) under true triaxial loading and unloading conditions, experimental and numerical research was applied to BRCSs under true triaxial stress paths entailing “x-direction displacement fixed, y-direction loading, z-direction unloading.” Both the experimental and the numerical results demonstrated that the peak stress borne by the BRCSs was not only affected by the initial stress but also had a negative exponential relationship with the ratio of the unloading rate and the loading rate (RURLR); therefore, peak stress equations of BRCSs under true triaxial loading and unloading conditions were established. The triaxial stress-time curves obtained by experiments and simulations exhibited an “elasticity-yield-destruction” phase, and the characteristics of the yield phase were determined by the RURLR. A typical BRCS was selected for velocity tomographic imaging to analyze the fracture evolution characteristics under true triaxial loading and unloading. The results showed that when the BRCS was subjected to a triaxial state of stress, the high- and low-velocity regions existed alternately due to the presence of the crack; during the elastic phase, the crack closed during loading in the previous phase was reopened upon unloading, so that the velocity of the sample decreased and a wide range of low-velocity regions could be formed; when entering the yield phase, the original crack continued to expand into a hole-through crack, leading to wider extreme values and ranges of these low- and high-velocity regions; at the breaking phase, multiple microcracks were generated around the hole-through cracks, decreasing the overall velocity, and showing point distributions characteristics of high- and low-velocity regions. Overall, many low-velocity regions with similar normal directions to the unloading direction were formed; these correlated well with macrofractures (postfailure).
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Deng, Zhiheng, Jingkai Zhou, Beiquan Chen, Xiaoyan Wen, and Bing Liu. "Triaxial Compression Performance Research of Steel Slag Concrete on the Unified Strength Theory." Applied Sciences 11, no. 1 (December 24, 2020): 128. http://dx.doi.org/10.3390/app11010128.
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To better explore the mechanical properties of steel slag concrete (SSC) under triaxial compression, true triaxial tests were performed on SSC with three replacement ratios (30%, 70%, 100%) by a servo-controlled setup (TAWZ-5000/3000). Through the test, failure modes, peak stress, and corresponding strain of SSC are obtained. Results show that the failure modes of SSC are plate-splitting and slant-shear. Compared with the corresponding uniaxial strength, the triaxial compressive strength of SSC is significantly improved and is influenced by the stress ratio and the replacement ratio. Finally, based on unified strength theory, the strength failure criterion formula of SSC with different replacement rates under triaxial compression is given.
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Zhang, Dongjie, Fei Luo, Zhanyuan Zhu, Jiaming Liu, Jing Li, Bailin Li, and Tianlang Xue. "Study on Mechanical Properties of Gravelly Sand under Different Stress Paths." Advances in Civil Engineering 2021 (February 17, 2021): 1–21. http://dx.doi.org/10.1155/2021/8898814.
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To investigate the strength and deformation characteristics of gravelly sand on the Qinghai-Tibet Plateau under different stress paths, a series of triaxial shear tests was conducted under confining pressures of 50–400 kPa in four types of stress path conditions of conventional triaxial compression (CTC) (drained and undrained), triaxial compression (TC), and reduced triaxial compression (RTC). We can see from the test results that gravelly sand samples show strain hardening and shear contraction under the CTC (drained), TC, and RTC during the shearing process but exhibit strain softening under the CTC (undrained). To explore the microscopic deformation mechanism of gravelly sand, a characteristic angle θ was defined to reflect the relative movement of soil particles. The relationship between principal stress ratio σ1/σ3 and characteristic angle θ and that between void ratio e and characteristic angle θ were derived. Subsequently, the relationship expression of stress ratio η (q/p) and void ratio e was established, and the trend of void ratio e with the stress path was studied. To describe the strain hardening and strain softening characteristics of gravelly sand in different stress paths, a new dilatancy equation was obtained by introducing the characteristic state stress ratio Mc into the dilatancy equation of the modified Cam-Clay model based on the state-dependent dilatancy theory. Finally, an elastoplastic constitutive model of gravelly sand was established by applying a nonassociate flow rule. All model parameters can be determined by triaxial shear tests under different stress paths, and the comparison results show that the proposed model can well reflect the mechanical behaviors of gravelly sand under different stress paths.
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Narayanasamy, R., V. Senthilkumar, and K. S. Pandey. "Some Aspects on Hot Forging Features of P/M Sintered High-Strength Titanium Carbide Composite Steel Preforms Under Different Stress State Conditions." Journal of Engineering Materials and Technology 129, no. 1 (May 6, 2006): 113–29. http://dx.doi.org/10.1115/1.2400261.
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Experiments were carried out to evaluate the hot forging features in the high-strength sintered Powder Metallurgy TiC composite steel performs under different stress states, namely, plane and triaxial stress. Cylindrical compacts with aspect ratios 0.45, 0.75, and 1.25 were prepared, sintered and forged at the temperatures of 1120°C+10°C. The investigation suggests that the experimentally determined relative density has a straight line relationship with the new geometrical shape factor (ρ0∕ρth)(h0∕hf)(3D02∕(2Db2+Dc2)). The measured barrel radius of curvature is found to have a circular arc because the above relation is a straight line one. Relationship is established between the measured barrel radius and the stress ratio parameters namely (σθ∕σz), (σz∕σm) and (σeff∕σz) under plane stress and triaxial stress state conditions. An attempt is also made to establish a relationship between the various stress ratio parameters namely (σθ∕σz), (σz∕σm), and (σeff∕σz) under plane stress and triaxial stress state conditions and the relative density.
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Negussey, D., and Y. P. Vaid. "Sand deformation under proportional loading." Canadian Geotechnical Journal 23, no. 2 (May 1, 1986): 155–63. http://dx.doi.org/10.1139/t86-025.
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A fundamental experimental study of sand behaviour under low stress ratio proportional loading wherein all strain components are contractant is presented. Experimentally observed behaviour under stress conditions of the triaxial test led to a coherent framework for representing proportional loading stress–strain response. The stress–strain relationship formulated incorporates relative density as an inherent independent state variable and does not require appeal to material isotropy. Key words: triaxial test, proportional loading, sand, relative density, energy density, stress increment, strain increment.
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Matsuoka, Hajime, De'an Sun, Akiteru Kogane, Nobuhiko Fukuzawa, and Wataru Ichihara. "Stress–strain behaviour of unsaturated soil in true triaxial tests." Canadian Geotechnical Journal 39, no. 3 (June 1, 2002): 608–19. http://dx.doi.org/10.1139/t02-031.
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A suction-controlled true triaxial apparatus for unsaturated soil was developed from the existing true triaxial apparatus for sand by attaching a device to supply matric suction to specimens. Using the developed apparatus, true triaxial tests (σ1 [Formula: see text] σ2 [Formula: see text] σ3; where σ1, σ2, and σ3 are the three different principal stresses) on an unsaturated silty soil were carried out under constant suction using the negative pore-water pressure method (s = uw > 0; ua = 0) for applying the matric suction, s (s = ua uw; where ua is the pore-air pressure and uw is the pore-water pressure). It was found that the true triaxial test results under three different principal stresses are uniquely arranged on the "extended spatially mobilized plane (extended SMP)" for frictional and cohesive materials that is modified from the original SMP for frictional materials by introducing "a bonding stress, σ0 (= c·cotϕ, where c is cohesion and ϕ is the internal friction angle)." It was also found that the shear strengths of the unsaturated silty clay obtained by the true triaxial apparatus nearly agree with the extended SMP failure criterion (Î1Î2/Î3 = constant, where Î1, Î2, and Î3 are the first, second, and third invariants of the translated stress tensor). The measured stress-strain-strength behaviour of the unsaturated soil in three-dimensional (3D) stresses can be well simulated by an elastoplastic model with the transformed stress based on the extended SMP criterion and a special hardening parameter.Key words: failure criterion, shear strength, special shear test, suction, stress path, unsaturated soil.
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Shi, Jun Wei. "Experimental Research on Deformation Properties of Gangue-Paste Filling Material in Mine." Advanced Materials Research 734-737 (August 2013): 746–50. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.746.
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According to the mechanical properties of paste filling body under special environment such as high temperature high humidity high stress and high airtight) in gob, mechanical properties of gangue-paste filling body was studied with the method of field core and laboratory test. The complete stress-strain curve of filling body under the condition of uniaxial and triaxial and the ultimate compressive strength under different confining pressure station were obtained through uniaxial and triaxial compression test. Six stages of uniaxial compression complete stress-strain curve (compression stage, elastic deformation stage, non-stable developing stages, plastic hardening stage, stress softening stage and residual deformation stage) were improved and developed. The deformation characteristics of filling body under triaxial compression were different from that under uniaxial compression. Namely the deformation of filling body under triaxial compression only appeared two deformation stages: linear deformation stage and plastic hardening stage, but had no softening stage basically under different confining pressures, which was benefit for controlling the ground subsidence and preventing the ground buildings.
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Zhao, Jin Bin, Hui Meng Zhao, Xiao Liu, and Jie Meng. "Dynamic Feature Analysis for Silty Sand." Advanced Materials Research 1089 (January 2015): 223–27. http://dx.doi.org/10.4028/www.scientific.net/amr.1089.223.
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Dynamic shear modulus is proportional to average principal stress.Cyclic varied surrounding pressure isn't proportional to cyclic varied pore water pressure.The dynamic triaxial test with cyclic surrounding pressure can apply cyclic surrounding pressure.The dynamic triaxial test with cyclic surrounding pressure can apply cyclic surrounding pressure in addition to the cyclic deviator stress and it can simulate the coupling of cyclic shear stress and it can simulate the coupling of cyclic shear stress and cyclic normal stress in an earthquakes.
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Syed, Amer, Yukie Tanino, Jacob M. LaManna, David L. Jacobson, Daniel S. Hussey, Eli Baltic, and Genoveva Burca. "A portable triaxial cell for beamline imaging of rocks under triaxial state of stress." Measurement Science and Technology 32, no. 9 (June 1, 2021): 095403. http://dx.doi.org/10.1088/1361-6501/abeb94.
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Vaid, Y. P., and S. Sivathayalan. "Static and cyclic liquefaction potential of Fraser Delta sand in simple shear and triaxial tests." Canadian Geotechnical Journal 33, no. 2 (May 8, 1996): 281–89. http://dx.doi.org/10.1139/t96-007.
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The potential for static and cyclic liquefaction of the sand that underlies the highly seismic Fraser Delta is assessed under simple shear test conditions, typical of an earthquake shaking. A comparison of liquefaction potential is also made between simple shear and conventional triaxial stress conditions. It is shown that the liquefaction potential of sand is profoundly influenced by the stress path. The reduction factors currently applied to the cyclic triaxial resistance for representing simple shear response may involve a large degree of conservatism in design. A direct measurement of soil behaviour under stress conditions typical of earthquake loading may thus have large economic benefits. Key words: sand, liquefaction, static, cyclic, triaxial, simple shear.
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Song, Zhenlong, Minghui Li, Guangzhi Yin, Pathegama Ranjith, Dongming Zhang, and Chao Liu. "Effect of Intermediate Principal Stress on the Strength, Deformation, and Permeability of Sandstone." Energies 11, no. 10 (October 10, 2018): 2694. http://dx.doi.org/10.3390/en11102694.
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Although the mechanical behaviors and flow aspects of sandstone have been previously investigated, studies of the effect of the intermediate principal stress (σ2) on the strength, deformation, and permeability of sandstone are lacking. In this work, the mechanical behaviors and permeability of sandstone under true triaxial stress conditions were investigated using a newly developed true triaxial geophysical apparatus. The experimental results showed that with increasing σ2, the peak strength, octahedral effective normal stress, and octahedral effective shear stress of the sandstone increased, and the rate of increase decreased. This is because a larger intermediate principal stress coefficient b has an inhibitory effect on rock strength. In our study, as the ratio of σ2/σ3 increased, the specimen entered compressive strain in the σ2 direction during the first stress drop. The stress and strain path deviations occur during rock failure. The amount of deviation increased as the σ2 increased before the peak stress. This phenomenon indicates that elastic mechanics are not suitable for understanding this sandstone rock during its failure. The permeability evolution of the sandstone under true triaxial stress conditions was measured and analyzed to investigate the effect of σ2. During the complete true triaxial stress-strain experiments, the variation we found in gas seepage velocity could be divided into two stages. Before the first pressure drop, the gas seepage velocity was mainly affected by volume strain. After the first pressure drop, the seepage velocity was affected by the deviator strain, which can change the seepage channels.
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Sun, De'an, Tugen Feng, and Hajime Matsuoka. "Stress–strain behaviour of weathered weak rock in middle-sized triaxial tests." Canadian Geotechnical Journal 43, no. 10 (October 1, 2006): 1096–104. http://dx.doi.org/10.1139/t06-057.
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A middle-sized triaxial test apparatus for a specimen 20 cm in height and 10 cm in diameter was developed to measure the deformation and strength of weak rock or gravel. High-quality undisturbed samples of a weathered weak rock were taken from a dam site by a core drilling method. To avoid damage to the structure of the weak rock due to saturation of specimens as a result of measuring volume change through the water change in a burette, the lateral deformation of specimens was directly measured in the unsaturated condition using three rings mounted on the specimen. Using the developed triaxial test apparatus, isotropic compression tests and consolidated–drained triaxial compression tests were performed on unsaturated or saturated undisturbed samples under confining pressures of 49, 98, 196, 392, 539, and 683 kPa. The test results show that the stress–strain relationship of the weathered weak rock under both unsaturated and saturated conditions is strongly influenced by the confining pressure when the confining pressure is less than 392 kPa, and the stress–strain behaviour becomes similar to that of normally consolidated clay when the confining pressure is greater than 392 kPa. Comparison of results of triaxial tests on unsaturated and saturated specimens shows that the saturated samples become somewhat weak. The test results also show that the bonding and stress history largely influence the stress–strain relationship at small strain levels.Key words: weathered weak rock, microstructure, undisturbed sample, deformation, strength, triaxial test, unsaturated sample.
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Xiao, Taoli, Mei Huang, and Min Gao. "Triaxial Permeability Experimental Study on Deformation and Failure Processes of Single-Fractured Rock Specimens." Shock and Vibration 2020 (July 16, 2020): 1–12. http://dx.doi.org/10.1155/2020/7329825.
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A series of rock-like specimens with specific sizes and fracture inclinations was created in the laboratory. The different effects of seepage pressure on the deformation and failure characteristics between a conventional triaxial compression test and a triaxial permeability test were studied using a servo-controlled testing machine. Furthermore, the change in the permeability of single-fractured specimens was explored based on a triaxial permeability test. The results were as follows. Compared with those observed in the conventional triaxial compression test, the peak stress and corresponding axial strain decrease under seepage pressure in the triaxial permeability test, while the deformation modulus increased. With the increase of fracture length, the peak stress of specimen decreases due to the seepage pressure and the specimen showed tensile failure horizontally. The failure mode of the single-fractured specimens was changed by the seepage pressure. A closed relationship was observed between the failure modes and the permeability-stress curves. A shear failure along the crack surface will occur when the permeability abruptly changed later than the peak stress point. The dramatic change in the permeability indicated that the permeability channel was extended or new seepage paths were created. These conclusions can provide a valuable theoretical reference for the numerical simulation of excavation and design in stability analysis of jointed rock masses.