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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.
There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index distinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus developed 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 consolidation 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 were investigated. 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 orientation angle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic coupling 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 stress directions during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does. 相似文献
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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
4.
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
5.
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
6.
The National Swimming Center built for the 2008Beijing Olympic Games applies the polyhedron spatialframe structure, which is based on the foam physicstheory[1]. Its simple geometry is a square box of 170m×170 m×29 m. It can hold 17 000 people, theroof o… 相似文献
7.
对调质42CrMo钢进行室温下各种应力循环和对称应变循环的低周疲劳实验,揭示材料的循环软化特性,棘轮变形和低周疲劳特性以及棘轮-疲劳交互作用。结果表明,调质42CrMo钢体现出明显的循环软化;在应力幅值或平均应力较高时,试样的棘轮变形较大,其破坏形式为延性破坏,而在应力水平较低时,材料的破坏由疲劳裂纹扩展所致的脆性断裂引起;材料在应力循环下的低周疲劳寿命由于有棘轮变形的产生而受到平均应力、应力幅值、最大应力和应变比等多种因素的影响。 相似文献
8.
Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio. 相似文献
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10.
研究了采用离心模型试验来研究波浪与土相互作用的方法,并针对渤海某油田的波浪及土质条件进行了试验研究.结果表明,在最大波高作用下,软粘土层的上部发生了软化,但这种影响随着深度的增加而逐渐减小;在波浪荷载的作用下,软粘土层下的粉砂层没有液化迹象. 相似文献
11.
斜拉桥索梁锚固区焊接集中,受力复杂,特别是在运营阶段循环应力作用下的疲劳性能值得关注。本文根据国内某大型斜拉桥中索梁锚固区构造,制作1∶1的索梁锚固区试验模型,进行静力与疲劳试验。根据试验实测数据,研究锚固区关键部位的静力及疲劳受力性能,从而对实桥索梁锚固区结构的可靠性做出评价。 相似文献
12.
LUO Yao-zhi ZHU Shi-zhe CHEN Xi 《浙江大学学报(A卷英文版)》2007,8(11):1731-1739
A new double-arch structure for the gate used as tidal barrage and sluice was adopted in Caoe River Dam in China. It was a spatial structure made up of the right arch, the invert arch, the chord, etc., and was designed to bear bilateral loads. To research the cyclic behavior of the new double-arch structure, a scale-model cyclic test was conducted. First, the test setup and test method were presented in detail, and according to the test results, the cyclic behavior and failure characteristics of this structure were discussed. Then by analyzing the test cyclic envelope curve, it was found the curve was divided into three stages: the elastic stage, the local plastic stage and the failure stage at the local yield point and structural yield point. The gate model has local yield strength and structural yield strength, with both their values being bigger than that of the designing load. Therefore, the gate is safe enough for the projects. At last, dynamic property of the gate was analyzed considering additional mass of the water. It was found that the tidal bore shock would not cause resonance vibration of the gate. 相似文献
13.
The fracture behavior of a ceramic reinforced metal-base coating prepared by high velocity arc spraying (HVAS)technology in three-point bending test was studied.Moreover,finite element analysis(FEA)was adopted to analyze the stress distribution in the crack front.It can be found that the crack norrnal to the interface in the coatings occurred at the location where a fixed moment of force was reached.So the critical moment can be taken as thecoating cracking criterion,which was confirmed by FEA results.In addition,the stress levels at three different locations where cracks occurred near the interface are almost the same.The results will provide reference for the design of coatings and the structure integrity evaluation of coating/substrate systems. 相似文献
14.
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
15.
通过对填充墙钢框架和同尺寸纯钢框架结构的数值模拟,从两种不同形式的框架结构在单调荷载作用下的荷载——位移曲线、低周反复荷载作用下的滞回曲线、骨架曲线及刚度退化曲线,分析得知填充墙钢框架体系是一种理想的抗侧力体系,其优势表现在该结构的耗能能力、极限承载能力、延性、变形恢复能力及抗侧刚度均优于纯钢框架。 相似文献
16.
为了确定正交异性钢桥面铺装受力状态并为设计提供参考,运用子模型有限元法分析了桥梁整体变形及局部轮载作用下铺装内部受力状态及应变分布特点.为优化设计铺装层结构,分析了铺装层模量对其应变状态影响.分析结果表明:大跨径钢桥整桥变形对铺装层受力状态影响很小,钢桥面铺装设计的控制受力因素是轮载局部作用下铺装层的横向应变,铺装层模量对铺装层的受力状态有显著影响,通过提高铺装层刚度过渡层的结构优化设计措施可以显著改善铺装层的受力状态,降低铺装层的应变水平.分别对环氧沥青混凝土、SBS改性沥青SMA和Rosphalt改性沥青混凝土的模量及疲劳性能进行了试验评价,可以为桥面铺装结构组合设计提供参考数据. 相似文献
17.
以浙江某高速公路路基工程为例,介绍高压旋喷注浆法加固软土地基的原理、施工工艺、施工方法、质量检测内容及质量控制措施,对处理后的软土地基进行详细的喷射固结质量检测,并列出质量检测的内容。 相似文献
18.
介绍了钢管混凝土柱-环梁中节点(环梁节点)在静载和低周反复荷载作用下的设计方法,其可靠性得到试验数据的证实。结果显示,在地震区推广应用钢管混凝土柱-钢筋混凝土环梁节点的结构体系具有较强的可行性。 相似文献
19.
为了研究沥青混凝土的疲劳特性,提出了基于双线性内聚力模型（CZM）的数值模拟方法．建立了疲劳损伤演化模型并将其与内聚力模型耦合,以反映沥青混凝土在循环荷栽作用下的软化行为．通过编制用户材料子程序。实现了疲劳损伤模型在有限元软件ABAQUS中的应用,并对劈裂疲劳试验进行了模拟．研究结果表明：模拟得到的疲劳寿命与实验室结果基本一致;疲劳损伤随加载次数的累积是非线性的,且损伤累积阶段是疲劳破坏的主要阶段;应力比增大时,损伤稳态发展阶段的寿命明显减小．可以发现提出的疲劳损伤数值模型是一种预估沥青混凝土疲劳损伤的有效方法． 相似文献
20.
The beam element in FLAC3D can be used to simulate the supporting arch in a tunnel. However, this approach has the shortcoming of its constitutive model, and the bearing capacity and surrounding rock supporting effect of the arch model will be significantly exaggerated. To simulate the supporting arch in tunnel engineering well, a new approach is proposed by improving the beam element. The yield criterion of the beam element subjected to compression-bending loads is established based on the now-available bearing capacity formulas of some typical compression-bending sections. In addition, the yield criterion is embedded in the FLAC3D main program by using the FISH language, and the modification of the beam model and the yielding failure simulation of the supporting arch are finally implemented. Compression-bending tests and roadway tunnel arch support example analysis were performed. The results are as follows: (1) the modified model showed the dependence of the bending moment and axial force on the yielding action of the beam element under compression-bending loads; (2) the implementation program is effective and sensitive; (3) the computing deviation caused by the shortcomings of the original beam element model was effectively suppressed, the mechanical behavior and surrounding rock supporting laws exhibited by the arch model were much closer to reality, and the calculation accuracy and design reliability were improved by the new simulation approach. 相似文献