Rheological properties and concentration evolution of thickened tailings under the coupling effect of compression and shear

Cemented paste backfill(CPB)is a key technology for green mining in metal mines,in which tailings thickening comprises the primary link of CPB technology.However,difficult flocculation and substandard concentrations of thickened tailings often occur.The rheological properties and concentration evolution in the thickened tailings remain unclear.Moreover,traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties.An experiment of flocculation condition optimization based on the Box-Behnken design(BBD)was performed in the study,and the two response values were investigated:concentration and the mean weighted chord length(MWCL)of flocs.Thus,optimal flocculation conditions were obtained.In addition,the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear,compression,and compression-shear coupling experimental conditions were tested and compared.The results show that the shear yield stress under compression and compression-shear coupling increases with the growth of compressive yield stress,while the shear yield stress increases slightly under shear.The order of shear yield stress from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Under compression and compression-shear coupling,the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases,while concentration increases slightly under shear.The order of concentration from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Finally,the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.

Antiplane shear crack in a prestressed elastic medium based on the couple stress theory

A prestressed elastic medium containing a mode-Ⅲcrack is studied by means of the couple stress theory(CST).Based on the CST under initial stresses,a governing differential equation along with a mixed boundary value problem is established.The singularities of the couple stress and force stress near the crack tips are analyzed through the asymptotic crack-tip fields resulting from the characteristic expansion method.To determine their intensity,a hypersingular integral equation is derived and numerically solved with the help of the Chebyshev polynomial.The obtained results show a strong size-dependence of the out-of-plane displacement on the crack and the couple stress intensity factor(CSIF)and the force stress intensity factor(FSIF)around the crack tips.The symmetric part of the shear stress has no singularity,and the skew-symmetric part related to the couple stress exhibits an r^(-3/2)singularity,in which r is the distance from the crack tip.The initial stresses also affect the crack tearing displacement and the CSIF and FSIF.

Wave-current bottom shear stresses and sediment re-suspension in the mouth bar of the Modaomen Estuary during the dry season

On the basis of the measurement data pertaining to waves, current, and sediment in February 2012 in the mouth bar of the Modaomen Estuary, the Soulsby formulae with an iterative method are applied to calculating bottom shear stresses （BSS） and their effect on a sediment resuspension. Swell induced BSS have been found to be the most important part of the BSS. In this study, the correlation coefficient between a wavecurrent shear stress and SSC is 0.86, and that between current shear stresses and SSC is only 0.40. The peaks of the SSC are consistent with the height and the BSS of the swell. The swell is the main mechanism for the sediment re-suspension, and the tidal current effect on sediment re-suspension is small. The peaks of the SSC are centered on the high tidal level, and the flood tide enhances the wave shear stresses and the SSC near the bottom. The critical shear stress for sediment re-suspension at the observation station is between 0.20 and 0.30 N/m2. Tidal currents are too weak to stir up the bottom sediment into the flow, but a WCI （wave-current interaction） is strong enough to re-suspend the coarse sediment.

Research on Measurement of Bed Shear Stress Under Wave-Current Interaction

The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave-current effect, and confirm that the method of measuring bed shear stress under wave-current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave-current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided.

Modelling erosion of a single rock block using a coupled CFD-DEM approach

Rock block removal is the prevalent physical mechanism for rock erosion and could affect the stability of dam foundations and spillways.Despite this,understanding of block removal is still inadequate because of the complex interactions among block characteristics,hydraulic forces,and erosive processes acting on the block.Herein,based on a previously conducted physical experiment of erosion of a single rock block,the removal processes of two different protruding blocks are represented by a coupled computational fluid dynamics-discrete element model(CFD-DEM)approach under varied flow conditions.Additionally,the blocks could be rotated with respect to the flow direction to consider the effect of the discontinuity orientation on the block removal process.Simulation results visualize the entire block removal process.The simulations reproduce the effects of the discontinuity orientation on the critical flow velocity inducing block incipient motion and the trajectory of the block motion observed in the physical experiments.The numerical results present a similar tendency of the critical velocities at different discontinuity orientations but have slightly lower values.The trajectory of the block in the simulations fits well with the experimental measurements.The relationship between the dimensionless critical shear stress and discontinuity orientation observed from the simulations shows that the effect of block protrusion becomes more dominant on the block incipient motion with the increase of relative protrusion height.To our knowledge,this present study is the first attempt to use the coupled finite volume method(FVM)-DEM approach for modelling the interaction behavior between the block and the flowing water so that the block removal process can be reproduced and analyzed.

Size-dependent effect on biaxial and shear nonlinear buckling analysis of nonlocal isotropic and orthotropic micro-plate based on surface stress and modified couple stress theories using differential quadrature method

The size-dependent effect on the biaxial and shear nonlinear buckling analysis of an isotropic and orthotropic micro-plate based on the surface stress, the modified couple stress theory （MCST）, and the nonlocal elasticity theories using the differential quadrature method （DQM） is presented. Main advantages of the MCST over the classical theory （CT） are the inclusion of the asymmetric couple stress tensor and the consideration of only one material length scale parameter. Based on the nonlinear von Karman assumption, the governing equations of equilibrium for the micro-classical plate consid- ering midplane displacements are derived based on the minimum principle of potential energy. Using the DQM, the biaxial and shear critical buckling loads of the micro-plate for various boundary conditions are obtained. Accuracy of the obtained results is validated by comparing the solutions with those reported in the literature. A parametric study is conducted to show the effects of the aspect ratio, the side-to-thickness ratio, Eringen＇s nonlocal parameter, the material length scale parameter, Young＇s modulus of the surface layer, the surface residual stress, the polymer matrix coefficients, and various boundary conditions on the dimensionless uniaxial, biaxial, and shear critical buckling loads. The results indicate that the critical buckling loads are strongly sensitive to Eringen＇s nonlocal parameter, the material length scale parameter, and the surface residual stress effects, while the effect of Young＇s modulus of the surface layer on the critical buckling load is negligible. Also, considering the size dependent effect causes the increase in the stiffness of the orthotropic micro-plate. The results show that the critical biaxial buckling load increases with an increase in G12/E2 and vice versa for E1/E2. It is shown that the nonlinear biaxial buckling ratio decreases as the aspect ratio increases and vice versa for the buckling amplitude. Because of the most lightweight micro-composite materials with high strength/weight and stiffness/weight ratios, it is anticipated that the results of the present work are useful in experimental characterization of the mechanical properties of micro-composite plates in the aircraft industry and other engineering applications.

Size-dependent thermomechanical vibration characteristics of rotating pre-twisted functionally graded shear deformable microbeams

A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).

Size dependent free vibration analysis of functionally graded piezoelectric micro/nano shell based on modified couple stress theory with considering thickness stretching effect

Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.

Upper crustal anisotropy from local shear-wave splitting and crust-mantle coupling of Yunnan,SE margin of Tibetan Plateau

The upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less than that from Pms splitting analysis, indicating that the crustal anisotropy is contributed mostly from mid-lower crust. The fast polarization directions are mostly sub-parallel to the maximum horizontal compression directions while the stations near fault zones show fault-parallel fast polarization directions, suggesting both stress and geological structure contribute to the upper crust anisotropy.Comparing fast polarization directions from shear wave splitting of local earthquakes and Pms, large angle differences are shown at most stations, implying different anisotropy properties between upper and mid-lower crust. However, in southwestern Yunnan, the fast polarization directions of Pms and Swave splitting are nearly parallel, and the stress and surface strain rate directions show strong correlation, which may indicate that the surface and deep crust deformations can be explained by the same mechanism and the surface deformation can represent the deformation of the whole crust. Therefore,the high correlation between surface strain and mantle deformation in this area suggests the mechanical coupling between crust and mantle in southwestern Yunnan. In the rest region of Yunnan, the crustmantle coupling mechanisms are supported by the lack of significant crustal anisotropy with Ne S fast polarization directions from Pms splitting. Therefore, we conclude that the crust and upper mantle are coupled in Yunnan, SE margin of Tibetan Plateau.

Coupling characteristics of stress and strain at different layers of different sub-regions in Yunnan and its adjacent areas

In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By using the cross-correlation method, 64 splitting events of 16 stations are processed. We also collect the splitting results of eight earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas. The orientations of maximum principal compressive stress of three sub-regions in this area are derived from the CMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axis azimuth-averaging method. The principal strain rate at each observatory is deduced from the observations of Crustal Movement Observation Network of China during the period from 1999 to 2004. In addition, the data of Pn aniso- tropy and SKS splitting of Yunnan and its adjacent areas are also collected. We have discovered from this study that the continental lithosphere, as a main seismogenic environment for strong earthquake, can be divided into blocks laterally; the mechanical behavior of lithosphere varies with depth and can be divided into different layers in the vertical orientation; the information of crustal deformation obtained from GPS might be affected by the type of blocks, since there are different types of active blocks in Yunnan and its adjacent areas; the shear wave splitting in this region might be affected mainly by the upper crust or even the surface tectonics.

Interaction of Streamwise and Wall-Normal Velocities in Combined Wave-Current Motion

The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity components has been compreheusively examined. Different from previous researches which attributed the deviation of velocity from the classical log-law to the wave Reynolds stress, i.e. - ρ uv^- only, this study demonstrates that the momentum flux caused by mean velocities, i.e., u^- and v^-, is also responsible for the velocity deviation, and it is found that the streamwise velocity for a flow in the presence of non-zero wall-normal velocity does not follow the classical log-law, but the modified log-law proposed in this study based on simplified mixing-length theorem. The validity of the modified log-law has been verified by use of available experimental data from published sources for combined wave-current flows, and good agreement between the predicted and observed velocity profiles has been achieved.

Couple stress nanofluid flow through a bifurcated artery—Application of catheterization process

In this article,we are exploring the hemodynamics of nanofluid,flowing through a bifurcated artery with atherosclerosis in the presence of a catheter.For treating obstruction in the artery,one can use the catheter whose outer surface is carrying the drug coated with nano-particles.The resultant solvent is considered as blood nano-fluid.Blood being a complex fluid,is modeled by couple stress fluid.In the presence of nano-particles,the temperature and the concentration distribution are understood in a bifurcated stenotic artery.The concluded mathematical model is governed by coupled non-linear equations,and are solved by using the homotopy perturbation method.Consequently,we have explored is the effects of fluid and the embedded geometric parameters on the hemodynamics characteristics.It is also realized that high wall shear stress exists for couple stress nano-fluid when compared to Newtonian nano-fluid.which is computed at a location corresponding to maximum constriction(z=12.5)of the artery.

The Effects of Post-Stenotic Dilatations on the Flow of Couple Stress Fluid through Stenosed Arteries

The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized and the expressions for the resistance to the flow, velocity, pressure drop, wall shear stress have been derived. The effects of various parameters on these flow variables have been investigated. It is found that the resistance to the flow and pressure drop increase with height of the stenosis and decrease with post stenotic dilatation. Pressure drop decreases with couple stress fluid parameter for both stenosis and post stenotic dilatation. Further, the wall shear stress increases with height of the stenosis and couple stress parameter but decreases with post stenotic dilatation and couple stress fluid parameter.

弹性支撑功能梯度压电多孔微圆柱壳的自由振动分析

旨在研究热-力-电载荷下弹性支撑功能梯度压电多孔微圆柱壳的自由振动。首先,建立弹性支撑功能梯度压电多孔微圆柱壳动力学模型;然后,应用三阶剪切变形壳体理论和修正的偶应力理论,推出弹性支撑功能梯度压电多孔微圆柱壳模态频率的解析解;最后,通过数值算例分析了微圆柱壳模态频率的影响因素。结果表明:Pasternak弹性支撑比Winkler弹性支撑更有利于提高微圆柱壳的模态频率;改变弹性支撑的刚度系数、轴向力、外加电压、孔隙分布、材料体积分数指数和结构尺寸可调节微圆柱壳的模态频率;孔隙体积分数越大,温度或轴向力对模态频率的影响越大,而电压对模态频率的影响则越小;不同材料指数下,增大孔隙体积分数对模态频率的影响趋势不同;弹性支撑会减弱温度、轴向力和电压对模态频率的影响,对薄圆柱壳或短圆柱壳模态频率的影响较为显著。

不同加载角压剪耦合作用下岩石强度与渗透性演变特征

华北型石炭-二叠纪煤系基底普遍发育奥陶系灰岩含水层,煤炭开采受到底板承压含水层突水灾害和水资源流失的双重威胁,压剪耦合下岩石水力特性是大倾角承压水上开采底板岩层阻水性能评价的基础。综合采用理论分析及离散元数值计算等方法,建立了不同压剪比例下莫尔圆旋转的岩石失稳判据,揭示了压剪耦合作用下岩石强度衰减机制,提出了综合裂隙角度、裂隙扩展速度、改进体积应变等指标的应力阈值确定方法,明晰了不同加载角、渗透压差及围压条件下岩石微裂纹扩展及渗透性演化特征。主要结论如下:压剪耦合作用下岩石承载能力降低表现在强度降低与弹性模量增大2个方面;岩石弹性模量随加载角增大呈现先缓慢增大(0°~15°)后迅速增大(15°~30°)再减小(30°~45°)趋势,但仍大于初始值;岩石强度和加载角呈线性负相关关系,降低幅度和围压成正比,2 MPa围压下强度降低速度是无围压的1.9倍,由等效内摩擦角控制;随着加载角的增大岩石破坏程度降低、峰后应力由脆性跌落向塑性转变;压剪耦合作用下拉伸裂隙诱导起裂及拉剪复合裂隙主导非稳定扩展解释了不同压剪比例条件起裂应力、损伤应力阈值非线性演化的内在机制;渗透率回弹位置处于起裂与损伤应力阈值之间并接近后者,随着加载角的增大,拉剪复合裂隙(优势渗流路径)分布较为集中;岩石强度随渗透压差增大而降低,降低速率和加载角呈负相关关系;岩石峰值渗透率随着加载角的增大而减小,降低趋势随着渗透压差的增大由线性向非线性转变;加载角较大时,渗透压差与围压对岩石强度及渗透性控制作用减弱。

机械应力调控血管平滑肌细胞的凋亡

背景:随着生物力学的发展,其在心血管疾病中的研究也日益广泛,通过研究血管的力学特性可以有效地揭示动脉粥样硬化、再狭窄等心血管疾病的发病机制,开发心血管疾病治疗的新思路和新方法。目的:综述机械应力刺激对血管平滑肌细胞凋亡的研究现状,寻找临床治疗潜在靶分子和信号通路,以期改善临床动脉粥样硬化及再狭窄等心血管疾病的临床治疗效果。方法:检索1992年1月至2023年5月在中国知网、PubMed及ScienceDirect数据库收录的文献。中文检索词为“血管平滑肌细胞,机械应力,剪切力,牵张力,凋亡”;英文检索词为“vascular smooth muscle cell,mechanical stress,shear stress,stretch stress,apoptosis”,最终纳入63篇文献进行综述分析。结果与结论:①血管平滑肌细胞的生理性和病理性凋亡都是为了适应血管力学变化而发生的适应性重构。不同部位的平滑肌细胞承受不同的力学刺激,其发病机制也不同。②低剪切力、生理剪切力和高剪切力可通过直接与平滑肌细胞表面分子、受体及蛋白等作用调控凋亡信号分子和抑制增殖实现对血管平滑肌细胞凋亡的调控,该部分未对促进增殖的研究进行综述。③低牵张力、生理牵张力和高牵张力可导致平滑肌细胞凋亡,但仍存在争议。平滑肌表面存在多种力学感受分子(如整合素及受体络氨酸激酶等)可以将力学信号转导为细胞内的化学信号(如Hippo通路),启动平滑肌细胞的凋亡信号,调控平滑肌细胞的凋亡。④总之,不同力学刺激通过多种信号分子,启动多个信号通路共同作用,调控平滑肌细胞的凋亡,例如剪切力主要通过刺激分泌前列腺素、转化生长因子等影响Fas/FasL、Akt通路;而牵张力主要通过Yes相关蛋白等调控YAP通路和Notch通路等。这些分子在不同的作用时间,或不同作用强度下可能发挥相反的双向作用,比如,小鼠血管平滑肌细胞受到10%生理牵张1 h时,其增殖增加;然而,人的血管平滑肌细胞牵张12 h后可以减少其增殖。临床可以通过寻找其关键作用时间点干扰力学转导关键分子,达到预防和治疗临床心血管疾病的目的。

Layerwise third-order shear deformation theory with transverse shear stress continuity for piezolaminated plates

Regarding laminated structures,an electromechanically coupled Finite Element(FE)model based on Layerwise Third-Order Shear Deformation(LW-TOSD)theory is proposed for sta-tic and dynamic analysis.LW-TOSD ensures the continuity of in-plane displacements and trans-verse shear stresses.The current LW-TOSD can be applied to arbitrary multi-layer laminated structures with only seven Degrees of Freedom(DOFs)for each element node and eliminates the use of the shear correction factors.Moreover,a shear penalty stiffness matrix is constructed to sat-isfy artificial constraints to optimize the structural shear strain.A dynamic finite element model is obtained based on LW-TOSD using the Hamilton's principle.First,the accuracy of the current model is validated by comparing with literature and ABAQUS results.Then,this study carries out numerical investigations of piezolaminated structures for different width-to-thickness ratios,length-to-width ratios,penalty stiffness matrix,boundary conditions,electric fields and dynamics.

BOTTOM SHEAR STRESS UNDER WAVE-CURRENT INTERACTION

The present work adopts the COHERENS-SWAN model developed by the first author through coupling three-dimensional hydrodynamic model （COHERENS） and third-generation wave model （SWAN）. Inside the COHERENS-SWAN, the SWAN is regarded as a subroutine and the time- and space-varying current velocity and surface elevation are obtained from the COHERENS. Wave-enhanced bottom shear stress, wave induced surface mixing length and wave dependent surface drag coefficient have been introduced into the COHERENS. Secondly, as wave-enhanced bottom shear stress （＂bottom shear stress＂ described as BSS sometimes in this article） is concerned, a modified bottom shear stress Grant and Madsen model which introduces random wave field is given and introduced to COHERENS-SWAN. COHERENS-SWAN is also adopted to simulate three-dimensional flow in the Yellow River Delta with wave-current co-existing. Four numerical experiments were given to study the effects of wave-current interaction on enhancing bottom shear stress. The simulated current velocities, wave height and wave period match well with field measurement data. The simulated significant wave height and wave period for the case with considering the effects of current can give better agreement with measurement data than the case without involving the effects of current. The introduction of random wave generates lower the bottom shear stress than the case without introducing it. There are obvious differences between bottom shear stress of two way interaction and one way interaction. Velocity field obtained by the COHERENS-SWAN is reasonable according to previous studies and measurements.

Stiffness Degradation of Undisturbed Saturated Soft Clay in the Yangtze Estuary Under Complex Stress Conditions

Stiffness degradation will occur due to the generation of accumulated pore pressure in saturated soft clays under cyclic loading. The soil static-dynamic multi-purpose triaxial and torsional shear apparatus in Dalian University of Technology was employed to perform different types of test on the saturated soft marine clay in the Yangtze Estuary. Undisturbed samples of the clay were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. Investigated were the effects of the initial orientation angle of the major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and continuous rotation of principal stress axes on the stiffness degradation. It is found that the degradation index decreases （or degradation degree increases） significantly with increasing initial orientation angle of the major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of the major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident and this trend is more clearly reflected by the results of the cyclic torsional shear tests than those of the cyclic coupling shear tests. At the same cycle number, the degradation index obtained from the cyclic torsional shear test is higher than that from the cyclic coupling shear test. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of the soil more than the cyclic torsional shear does.Based on a series of experiments, a mathematical model for stiffness degradation is proposed and the relevant parameters are determined.

Critical Cyclic Stress Ratio of Undisturbed Saturated Soft Clay in the Yangtze Estuary under Complex Stress Conditions

There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index dis-tinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus de-veloped by Dalian University of Technology in China was employed to perform different types of tests on saturated soft marine clay in the Yangtze estuary. Undisturbed samples were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consoli-dation parameters. The effects of initial orientation angle of major principal stress, initial ratio of deviatoric stress,initial coefficient of intermediate principal stress and stress mode of cyclic shear on the critical cyclic stress ratio wereinvestigated. It is found that the critical cyclic stress ratio decreases significantly with increasing initial orientation angle of major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientationangle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate prin-cipal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic cou-pling shear test is lower than that from the cyclic torsional shear test, indicating that the stress mode of cyclic shear has an obvious effect on the critical cyclic stress ratio. The main reason is that the continuous rotation in principal stressdirections during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does.