Laboratory investigation on the compressibility of Singapore marine clays     

Myint Win Bo  Victor Choa  Jian Chu  Arul Arulrajah 《Marine Georesources & Geotechnology》2017,35(6):847-856

The compressibility characteristics of Singapore marine clay in reconstituted and undisturbed states were studied using oedometer, constant rate of strain, Rowe cell, and isotropic consolidation tests. The intrinsic compression curve of the reconstituted clay was found to be similar to that proposed earlier with some minor deviations at low vertical stresses of less than 100?kPa. The field and laboratory compression behaviors were found to be similar, hence the laboratory curve could be used as a reference for interpreting the field behavior. Factors affecting the measurements of compression index and yield stress were discussed. As the coefficient of lateral earth pressure at the top upper clay was close to 1, the compression curves of vertically and horizontally trimmed samples were almost similar. The yield stress was mainly controlled by the strain rate; i.e., the higher strain rate resulted in the higher yield stress. Constrained modulus as derived from cone penetration tests and flat dilatometer tests were also examined and compared with laboratory test results. The in situ tests showed the decrease in constrained modulus with depth and generally the dilatometer test was found to register a higher modulus value.  相似文献   

Experimental study on the unconfined compressive strength of carbon fiber reinforced clay soil     

Lei Gao  Qiuyue Zhou  Xiangjuan Yu  Kexiong Wu  Ali H Mahfouz 《Marine Georesources & Geotechnology》2017,35(1):143-148

To study the effect and mechanism of carbon fiber reinforced clay, a series of unconfined compression tests for clay reinforced with carbon fiber have been performed under the conditions of controlled water content and dry density. The carbon fiber is mixed into soil with the quality percentage of 0.01, 0.02, 0.03, 0.05, 0.1, 0.15, 0.25, 0.35, and 0.5%, then a certain quality of water was added in the soil to achieve the optimum soil water content. Ten groups of samples were tested by the unconfined compression experiment. The results showed that the incorporation of carbon fiber elements can effectively improve the unconfined compressive strength and brittle failure mode of soil. The soil is strengthened at the beginning and then weakened with the increased incorporation of carbon fiber, the effect is especially significant when the mix percentage becomes 0.1%. The interaction at the interface between carbon fiber surface and soil matrix is analyzed by using scanning electron microscopy (SEM). It is found that the enhancement mechanisms of carbon fiber reinforced soil are one-dimensional reinforcement of a single carbon fiber thread and three-dimensional reinforcement caused by fiber network respectively.  相似文献   

Influence and countermeasure of specimen misalignment to small-strain behavior of soft marine clay     

Guan-Lin Ye  Chao-Jun Wu  Jian-Feng Wang  Jian-Hua Wang 《Marine Georesources & Geotechnology》2017,35(2):170-175

Triaxial test with local displacement transducers is an effective technique to obtain the small-strain stiffness of soils. Many previous studies provided feasible solutions for reducing or avoiding potential sources of error in conventional triaxial tests. However, little literature gave out detailed explanations on how to identify those potential errors from the measured testing data and corresponding solutions. Therefore, nowadays, it is still not easy for a new user to gain proficiency in such kind of advanced tests. In this article, by conducting triaxial tests featured with Hall effect transducer on Shanghai soft marine clay, it is found that the influence of the specimen misalignment to the measured small-strain stiffness cannot be neglected. The typical symptom of specimen misalignment, namely the tilting of specimen, was described carefully. An improved connection between top cap and load cell was applied to overcome the problem. The new connection can reduce the disturbance to specimen in terms of both force and displacement. It can be applied to both isotropic and anisotropic consolidated triaxial tests.  相似文献   

Effects of cyclic confining pressure on the deformation characteristics of natural soft clay     

《Soil Dynamics and Earthquake Engineering》2015

To investigate the coupling effects of cyclic deviator stress and cyclic confining pressure on the deformation behavior of natural soft clay under partially-drained conditions, a series of one-way cyclic triaxial tests with and without cyclic confining pressure were carried out. Test results show that, at the same amplitude of cyclic deviator stress, the increase of cyclic confining pressure amplitude will accelerate the accumulation of both permanent volumetric and axial strain significantly. The comparison between test results for different amplitudes of cyclic confining pressure shows that tests with a cyclic confining pressure corresponding to a stress path of η^ampl=p^ampl/q^ampl=1 lead to a 1.4 times larger permanent volumetric strain and a 1.2 times larger permanent axial strain compared to the conventional cyclic triaxial tests with constant confining pressure (η^ampl=1/3). In case of η^ampl=2 the permanent strains are found to be even 2.0 or 1.5 times larger compared to the standard tests. Finally, an empirical formula is proposed for the prediction of permanent axial deformations of natural soft clays under partially-drained conditions, considering the effects of cyclic confining pressure.  相似文献   

循环荷载作用下广西红黏土动力特性试验研究          下载免费PDF全文

穆坤  郭爱国  柏巍  孙志亮  臧濛 《地震工程学报》2015,37(2):487-493

针对广西上林县原状红黏土开展一系列循环加载动三轴试验,分析天然含水率、围压与固结应力比等对红黏土动力特性,包话动应力-动应变关系、动弹性模量以及阻尼比等的影响来研究循环荷载作用下红黏土的动力特性。试验结果表明:广西原状红黏土动应力-动应变关系曲线接近双曲线;由于初始剪应力的影响,达到相同的动应变,在均压固结下所需的动应力比在偏压固结下所需动应力要小;动弹性模量随着动应变的增加而减小,且减小幅度随应变增加逐渐减小,初始应力状态对动弹性模量的影响最为显著;固结应力比、围压、含水率和振动次数等对阻尼比均有影响,综合反映在阻尼比随动应变增加而减小,阻尼比离散性较大,取值范围在0.05~0.20之间。利用Konder双曲线模型对试验数据进行拟合,得到相关参数,可为广西地区原状红黏土动力特性设计和数值计算提供一定的理论和参数支持。  相似文献   

袋内材料对土工袋动力特性参数影响的试验研究   总被引：1，自引：0，他引：1  

李玲君  刘斯宏  徐小东  张雨灼  李栋 《岩土力学》2015,36(1):131-136

土工袋加固地基技术已普遍应用于房屋地基、边坡加固等工程中。大量研究表明,土工袋具有显著的减振消能效果。为了进一步探讨不同的袋内充填土体材料对土工袋减振消能效果的影响,通过对不同粒径、级配、黏粒含量的填充土体材料及装有相应填充土体材料的土工袋进行水平循环剪切试验,研究袋内填充土体材料与动剪切模量及等效阻尼比2个参数的关系。试验结果表明,土体装入土工袋后,动剪切模量降低,等效阻尼比增大;当填充土体材料及土工袋内土体材料粒径相对较小、级配均匀、黏粒含量高时,等效阻尼比和动剪切模量较大。总体而言,粒径和级配对土工袋减振消能效果影响不大。  相似文献   

结构性软黏土损伤变量与扰动度的相关性研究     

张彤炜  徐海波  邓永锋 《岩土力学》2015,36(4):958-964

取样与施工过程会对天然沉积结构性软黏土产生扰动,使土体的工程性质发生演化,一些学者分别以扰动度和损伤变量两个特征参数对该问题进行了较为深入的研究,但扰动度与描述土体应力状态的损伤变量之间的相关性目前仍未明晰。为此,以连云港天然沉积结构性软黏土进行不同应力路径下快速加载试验模拟土体应力损伤,对损伤后土体进行固结试验和无侧限抗压强度试验,结合张孟喜提出的损伤变量以及两种常用的扰动度（变形和强度）的定义,评价了损伤后土体的损伤变量和扰动度,探讨二者间关系。结果表明,损伤后土体压缩曲线屈服前的斜率并未产生明显改变,即损伤变量与按变形定义的扰动度间关系不明显;而损伤变量与以强度定义的扰动度之间存在线性递增关系,说明了当土体沿着某一路径加载时,越接近破坏线,其损伤程度越高,土体的强度也随之降低。  相似文献   

干湿循环对填埋场压实黏土盖层渗透系数影响研究     

万勇  薛强  赵立业  杜延军  刘磊 《岩土力学》2015,36(3):679-686

针对干湿循环作用下填埋场封场覆盖系统压实黏土防渗失效等问题,系统开展了干湿循环作用下（室内模拟填埋场气候环境）压实黏土渗透特性及微观结构特征试验研究,探讨了干湿循环次数、压实度、试样尺寸对压实黏土渗透系数影响并从微观层次揭示其防渗失效内在本质。研究结果表明：干湿循环前,相同压实度的大、小两种尺寸渗透试样所测渗透系数基本相同,经3次干湿循环后,不同尺寸、不同压实度黏土渗透系数增加量却存在明显差异。干湿循环作用下,小尺寸高、低两压实黏土试样均只收缩不开裂,并且高压实黏土微观结构损伤大于低压缩黏土,其渗透系数的增加量也大于小尺寸低压实黏土。而大尺寸试样裂隙发育与现场压实黏土裂隙发育相似,高压实黏土内部裂隙体积小于低压实黏土,其渗透系数的增加量也小于低压实黏土。同时,大尺寸试样内部大量未闭合宏观裂隙致使其渗透系数增加量大于同等压实度条件下小尺寸试样渗透系数增加量。室内小尺寸试样无法体现干湿循环作用下压实黏土层内部干缩裂隙对其渗透性能的影响,因此,其渗透试验结果不宜作为评价压实黏土长期防渗性能的评价指标。  相似文献   

考虑循环软化特性的饱和软土弹塑性本构关系研究   总被引：1，自引：0，他引：1  

程星磊  王建华 《岩土力学》2015,36(3):786-794

将软化指数关系与非等向硬化模量场理论相结合,研究了可描述循环荷载作用下饱和软土软化特性的增量弹塑性模型。该模型借助硬化模量的插值和映射中心的移动,在偏应力空间中构造硬化模量的演化规则;通过在弹塑性模量插值函数中引入初始弹塑性模量软化系数,模拟循环荷载作用下软土的刚度软化特性;通过引入硬化模量调整系数,增强循环加载时应力-应变曲线的滞回特性;再通过引入反映应变累积速率和大小的模型参数,描述循环加载时软土的应变累积特性。利用Idriss提出的指数关系式近似拟合软化系数随应力循环次数的变化关系,并通过引入循环应力参数建立了循环软化系数与静应力水平和循环应力水平的关系。阐述了确定模型参数的方法,并利用模型预测了相关试验结果,通过预测结果与试验结果的对比,验证了该模型描述循环荷载作用下软土软化特性的可行性。  相似文献   

软土中浅埋法向承力锚位移破坏标准模型试验     

王建华  李一峰  程星磊 《岩土力学》2015,36(Z1):277-280

为确定浅埋软黏土中法向承力锚的位移破坏标准,利用实验室自行开发的电动伺服加载控制装置,对埋置在饱和软黏土中深度为3倍锚板宽度、系缆力角度为30°的法向承力锚模型进行了荷载和位移控制的静力加载试验。依据试验结果,以极限承载力与锚板宽度为参考,对锚板法向荷载与位移进行归一化处理,通过归一化曲线确定了法向承力锚的位移破坏标准,即破坏位移约为0.38倍锚板宽度。另外,依据锚板的尺寸、埋深及试验土体的强度条件,利用经验公式对锚的极限承载力进行了计算。结果表明,以该位移破坏标准确定的极限承载力与经验公式计算结果基本一致,两者相差均不超过10%,初步验证了该位移破坏标准的合理性。  相似文献