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1.
Constitutive model of saturated soft clay with cyclic loads under unconsolidated undrained condition
An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established. 相似文献
2.
Undrained anisotropy and non-coaxial behavior of clayey soil under principal stress rotation 总被引：2，自引：0，他引：2
In this study, a series of undrained tests were conducted on both intact and reconstituted clay using an automatic hollow cylinder apparatus. Monotonic shearing tests with fixed principal stress directions were carried out, pure and cyclic prin- cipal stress rotation tests were also performed. The non-coaxiality, defined as the non-coincidence of the principal plastic strain increment direction and the corresponding principal stress direction, of clayey soil was studied experimentally. The effects of the intermediate principal stress, shear stress level, and inherent anisotropy were highlighted. Clear non-coaxiality was observed during pure principal stress rotation, in both intact and reconstituted clay. The influence of the intermediate principal stress pa- rameter, shear stress level, and inherent anisotropy on the non-coaxial behavior of the clayey soil was found to be insignificant when compared with the sand. The non-coaxial behavior of the clayey soil depended more on the stress paths. Under undrained conditions, the contribution of elastic strain to the direction of the total principal strain increment cannot be ignored. 相似文献
3.
Failure criterion of saturated soft clay is studied under cyclic loads through different experiments. A large number of cyclic torsional shear and cyclic triaxial tests on saturated soft clay under unconsolidated undrained condition are conducted. From the test result analysis, it is seen that the failure of saturated soft clay under static and cyclic loads satisfies Mises criterion. The result from different test stress states is not related to the test stress states or confining pressures. It can be applied in general stress states. Then according to the Mises criterion, the equivalent relationship on failure moment between the test stress state and the general stress state can be established. So the cyclic mechanics characteristics of saturated soft clay at failure moment are clarified in this paper. Furthermore, a theory basis is provided for using pseudo-static elasto-plastic cyclic strength model to evaluate cyclic bearing capacity. 相似文献
4.
In this paper we propose a degradation model to describe the damage-dependent behavior of saturated soft clay under cyclic loading, which is then applied to the analysis of a caisson breakwater. The degree of damage and remolding of soft clay is quantified by a damage parameter related to the accumulated plastic deviatoric strain. Through the correlation between the maximum pore pressure and the undrained strength of soft clay, we obtain a damage-dependent degradation model that employs the post-cyclic undrained strength degradation coefficient in terms of the cyclic stress ratio and the number of cycles. Based on the Tresca yield criterion, the degradation model of undrained strength of soft clay is numerically implemented in the user interface USDFLD of ABAQUS. The performance of this model is verified by a comparison between numerical results (finite element method) and experimental data (cyclic triaxial test). The model is applied to the numerical simulation of a caisson breakwater resting on a partially sand-filled soft clay seabed under cyclic wave loading. The cyclic stress distribution, pore pressure development, and strength degradation of the seabed soil are presented to illustrate the applicability and efficiency of the model in the analysis of the interaction between offshore structures and soft ground. 相似文献
5.
回顾了基于CPTU测试成果确定粘土固结屈服应力和超固结比的方法,表明土的固结屈服应力和超固结比与CPTU测试参数之间不存在惟一的相关关系,仅仅针对某一地区的相关关系才是有效的.根据苏北里下河地区泻湖相沉积土的CPTU测试资料,对3种经验方法进行了比较.评价了固结屈服应力与CPTU测试参数现有经验关系的有效性,并且确定出适宜于里下河地区泻湖相沉积土的预测方法.结果表明:基于净锥尖阻力的相关关系比其他经验方法具有较高的精度,可以有效地预测该地区泻湖相沉积土的固结屈服应力和超固结比. 相似文献
6.
Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined. 相似文献
7.
Theone dimensionalinfinitesimalstrainconsolida tiontheorydevelopedbyTerzaghiassumedthattheper meabilityandcompressibilityoftheclayremainedcon stantduringconsolidationunderaparticularincrementofload[1] .So ,inpractice ,thetheorywasonlyapproxi matelysatisfying .Variousresearcheshavesoughttoex tendtheclassicaltheorytotakeaccountofthevariationofpermeabilityandcompressibilityduringconsolidationinoneormoreways .Thecompressibilityandcoefficientofpermeabilitywereassumedtobefunctionsofthede greeofsatur… 相似文献
8.
INTRODUCTION Adequate information on dynamic soil proper-ties, especially dynamic shear modulus and dampingratio, is essential for accurate computations of groundresponse and soil-structure interaction problems.Many experimental investigations carried out onsandy soils through resonant column test or improvedcyclic triaxial test in early studies (Hardin and Richart1963; Hardin and Black, 1968; Drnevich and Richart,1970; Seed and Idriss, 1971; Kokusho, 1980) showedthat the small … 相似文献
9.
In-situ vane shear test is frequently performed to determine shear strength for slope stability analysis in Tianjin New Harbor. However,the soil shear strength varies with the shear plane orientation. A possible means to reduce the effect of directional dependency of shear strength is to convert the in-situ vane shear strength into undrained shear strength parameters. A method of converting in-situ vane shear strength into undrained shear strength parameters is presented. The shear strength parameters determined for all of the in-situ vane shear strengths are subjected to statistical regression analysis to take into consideration the possible effect of non-homogeneity in the soft clay deposit. Using the regressed shear strength parameters, slope stability analyses are performed for five existing soil slopes. The results of stability analyses indicate that the safety factors obtained from the converted parameters reflect the state of the slopes analyzed much better than those obtained from in-situ vane shear strength and laboratory consolidated-undrained and unconsolidated-undrained strength parameters. It is concluded that the presented methsod of determining undrained shear strength parameters for in-situ vane shear strength is effective. 相似文献
10.
陈颖平 《辽宁科技学院学报》2011,13(4):25-26
对杭州某粘土进行循环荷载作用下的动强度研究,发现土体结构破坏与否对土的动强度有很大影响,尤其是在动应力较小的情况下。各固结压力下均存在着一个临界最小动应力比。 相似文献
11.
Initial fabric anisotropy can greatly affect the shear behavior of particulate materials during shear. The bedding plane effect induced by particle orientation is one of the main fabric anisotropic factors that may affect other factors. It is hard to experimentally examine the effect of bedding direction of particles on the shear behavior of particulate materials, such as sand. A 2D discrete element method (DEM) is employed in this paper to study the influence of different orientations of oval particles on the behavior of dense assemblies under simple shear. As well as the macroscopic shear behavior, the evolution of particle orientation, contact normal, and inter-particle contact forces within the samples with different initial bedding angles during shear have been extensively examined. It was found that the initial bedding direction of the particles has great influence on the non-coaxiality between the directions of principal stress and principal strain increment. The bedding direction also affects the strength and dilatancy responses of DEM samples subjected to simple shear, and the samples with larger bedding angles exhibit higher shear strength and larger volume dilation. A modified stress-force-fabric relationship is proposed to describe the effect of particle bedding direction on the shear strength of samples, and the new equation can better describe the stress-force-fabric relationship of assemblies with initial anisotropic fabrics compared with the existing model. 相似文献
12.
XIE Kang-he Ql Tian DONG Ya-qin 《浙江大学学报(A卷英文版)》2006,7(8):1358-1364
INTRODUCTION Conventional consolidation analysis based on Terzaghi’s one-dimensional theory neglects the non-linearity of soil for the sake of mathematical expediency, which is considered to be one of the theory’s shortcomings. Many researchers have pro-posed one-dimensional (1D) consolidation models where the coefficient of volume compressibility mv, coefficient of permeability kv, and coefficient of consolidation cv, vary with either depth or time. Schiffman (1958), Davis and Raymon… 相似文献
13.
通过对圆柱体直前缘表面裂纹在循环拉伸与循环扭转载荷共同作用下的扩展规律进行实验研究,分析了不同载荷曲线相位差、以及拉扭应力幅度对表面裂纹扩展路径、疲劳寿命和裂纹扩展速率的影响。结果表明:不同的相位差对裂纹扩展行为有着非常重要的影响。初始阶段的裂纹扩展主要受到剪应力幅度的影响,后继扩展则依赖于轴向应力幅度。拉应力和剪应力的增加均会增加裂纹扩展速率,但轴向应力幅度变化的影响大于剪切应力幅度。 相似文献
14.
The dynamic stress path of a rock and soil mass under seismic action has a crucial influence on its catastrophic behavior. In soil dynamics, earthquakes are commonly simplified as vertically incident shear waves and the seismic stresses in soil are estimated based on rigid foundation models. However, the great effect of P-waves should not be overlooked in strong earthquakes, which have happened frequently in recent years. The characteristics of the dynamic stress path under longitudinal waves with significant oblique incidence are still unclear. Analytical formulas for the seismic stresses at any depth of a semi-infinite elastic space under obliquely incident P-waves are derived, which degenerate into the traditional rigid foundation method in soil dynamics when both the incident angle and Poisson’s ratio are taken as zero. Here, we reveal the fundamental characteristics of a dynamic stress path under obliquely incident P-waves. The stress path is proved mathematically to be an oblique ellipse in the plane of normal stress difference and horizontal shear stress. We identify factors affecting the stress path, including the incident angle, Poisson’s ratio, and depth corresponding to unit wavelength. The possible variation in the range of an oblique elliptic stress path is systematically analyzed, which lays a theoretical foundation for further study of the dynamic response of sites under obliquely incident seismic waves. 相似文献
15.
The parameters obtained from oedometric consolidation tests are commonly used in the development of constitutive modeling and for engineering practice. This paper focuses on the influence of the natural deposition plane orientation on oe- dometric consolidation behavior of three natural clays from the southeast coast of China. Oedometer tests were conducted on intact specimens prepared by sampling at a series of angles relative to the natural deposition plane. For each specimen, yield stress, compressibility indexes, secondary compression, and permeability coefficients were determined. The influence of the sampling angle on these properties was investigated, revealing that yield stress, compression index, swelling index, creep index, ratio of secondary compression coefficient to compression index （Cae/JCc） and permeability coefficient were all dependent to some extent on the sampling angle. These findings indicate the role of the anisotropy due to the natural deposition on the oedometric con- solidation behavior. 相似文献
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17.
The variation of effective stress ratio of stratfied soil with semi-pervious boundaries and under cyclic loading was analyzed on the basis of Terzaghi's one-dimensional consolidation assumptions. A solution by Laplace Transform was obtained for the case when the soil was under time-varied loading. With numerical inversion of Laplace Transform, some useful results were obtained for several kinds of commonly encountered loadings. The results can be meaningful in engineering practice. 相似文献
18.
Considering the effects of particle crushing and intermediate principal stress on material yielding strength, the spatial mobilization plane(SMP) yielding criterion and state parameter model including a general critical state line are selected in the analysis of cylindrical cavity expansion.Meanwhile, combining Rowe's flow rule and Bolton's simplification to stress-dilatancy relationship to reflect soil shear dilatancy and softening behavior, this paper analyzes the problem of cylindrical cavity expansion i... 相似文献
19.
为了研究粘土与加筋材料接触面之间的力学特性,及砂对粘土与筋带接触面力学特性的改善情况,采用直剪试验方法对粘土与聚丙烯土工带polypropylene在粘土不同含水量条件下进行了不同法向荷载作用的直剪试验,讨论了法向应力、含水量对高液限粘土与筋带之间剪切特性的影响;设计了筋带砂粘土层状布置体系的加筋土结构模型,并根据设计的模型进行直剪试验.试验结果表明:粘土与筋带接触面之间的剪切强度随着法向应力的增加呈非线性增长;接触面的摩擦系数随着含水量的增加而减小,接触面的粘聚力随含水量的增加先增大后减小,粘土与接触面之间存在一个最佳的含水量,这个值要比粘土压实的最佳含水量低2%左右;筋带砂粘土层状布置体系表明砂对粘土与筋带的剪切特性起到明显的改善作用. 相似文献
20.
INTRODUCTION Since the development of the conventionalconsolidation theory by Terzaghi (1943) in 1923,many attempts have been made to present some solu-tions for the problems considering more realistic as-sumptions on the practical geotechnical engineering.Some efforts have been made to avoid limitation ofthe assumptions in the Terzaghi’s theory. During theconsolidation of soil, it is obvious that the coefficientof volume compressibility mv and the coefficient ofpermeability kv ar… 相似文献