共查询到20条相似文献，搜索用时 15 毫秒
1.
现有的饱和软黏土循环荷载累积孔压显式模型未能反映路基土体单元在土体自重作用下主应力轴的偏转现象。在确定饱和软黏土固结时间的基础上,在固结压力分别为100、150、200 kPa下,对软黏土进行主应力轴偏转角为15°、30°、45°的不排水循环加载试验,得到了固结围压、主应力轴旋转角及动应力比对循环累积孔压影响的规律。基于第一次循环加载累积孔压变化规律和修正动偏应力水平,建立了能考虑恒定主应力轴偏转角循环加载下累积孔压显式模型,并利用恒定主应力轴偏转角循环加载试验结果验证了模型的合理性。建立的循环荷载下饱和软黏土累积孔压显式模型参数易于确定,参数具有明确的物理意义且能考虑主应力轴的恒定偏转现象。 相似文献
2.
Influence of pore pressure on plastic deformation and strength of limestone under compressive stress
This study is devoted to experimental investigation of effects of pore pressure on plastic deformation and failure of a water-saturated limestone. The experimental study is composed of three different groups of laboratory tests. The basic mechanical behavior of the rock is first characterized by drained triaxial compression tests on water-saturated samples without pore pressure. The results are compared with those obtained in a previous study from triaxial compression tests on saturated samples with a constant pore pressure. In the second group, water injection tests under a confining pressure of 20 MPa and different values of deviatoric stress are realized to study the effect of pore pressure increase. Finally, undrained triaxial compression tests are carried out for investigating the coupling effect of plastic deformation and pore pressure variation. Based on experimental data, the validity of effective stress concept for plastic yielding and failure strength is discussed.
相似文献3.
Experimental study of poromechanical behavior of saturated claystone under triaxial compression 总被引：1，自引：1，他引：0
This paper presents experimental results of drained and undrained triaxial compression tests of saturated Meuse–Haute/Marne claystone. The emphasis is to study the evolution of pore pressure with growth of microcracks and the effect of pore pressure on mechanical behavior. Basic mechanical responses are first investigated through drained triaxial compression tests, showing nonlinear stress strain relations, volumetric dilatancy and pressure sensitivity. In undrained triaxial compression tests, the pore pressure exhibits a transition from increase to decrease due to the transition from volumetric compressibility to dilatancy caused by the growth of microcracks. The failure surfaces, determined by total stress and Terzaghi’s effective stress under undrained condition, are compared with the one under drained condition. 相似文献
4.
减饱和法是一种通过减小饱和砂土地基中水的饱和度来处置可液化砂土地基的方法。基于单相流-固耦合理论,将减饱和砂中水-气两相流体等效为单相流体,提出一种可以考虑加载过程中孔隙流体体积模量变化的减饱和砂土静态液化的单相流改进算法,用其进行单调荷载作用下三轴不排水压缩试验数值模拟研究,分析了不同饱和度条件下的减饱和砂土的不排水反应并与饱和砂土三轴不排水试验结果进行对比。研究结果表明,单相流改进算法能够很好地反映减饱和法的抗液化特性。此外,对比不同数值分析方法模拟结果,得出以下结论：采用单相流简化算法分析减饱和砂土的不排水反应时,因为不考虑加载过程中的孔隙流体体积模量变化,所以初始的流体体积模量取值会影响减饱和砂土的强度,初始围压为100 kPa、饱和度为96%的减饱和砂土在单调荷载作用下,气体体积模量取值从100 kPa增加至200 kPa时,减饱和砂试样的峰值偏应力会减小约30%,孔隙压力会增加约40%;通过对比同等条件下的单相流改进算法和两相流算法的应力-应变关系曲线以及饱和度和体积应变变化曲线,两者结果相近,误差在5%以内。综上所述,单相流改进算法是一种较为合理而简洁地模拟减饱和砂土静态液化的计算方法。 相似文献
5.
在三轴条件下,对饱和土（砂土和黏土）进行排水与不排水条件下的冲击试验及冲击后再固结试验,对比研究了不同渗透性土在不同排水条件下的冲击动力响应和冲击后再固结性状。结果表明：饱和黏土不排水冲击时的孔隙水压力随冲击击数增加而升高并逐渐稳定,排水冲击时的孔隙水压力则是先达到峰值然后有所下降;砂土不排水冲击时的冲击能量对孔隙水压力影响最明显;饱和砂土不排水冲击时的轴向应变与冲击击数呈近似线性关系,饱和黏土冲击及饱和砂土排水冲击则呈近二次曲线关系;饱和砂土不排水冲击后再固结阶段的孔隙水压力立即消散为0,同时体变迅速增大到一定值;饱和黏土在冲击后再固结阶段的孔隙水压力在一定时间内逐渐消散完毕,同时体变逐渐增大;饱和黏土排水冲击时,冲击阶段产生的体变占冲击引起总体变的39%～49%,冲击后再固结阶段产生的体变占51%～61%;砂土和黏土的总体变均表现为排水冲击明显大于不排水冲击,改善冲击时的排水条件有利于提高加固效果。 相似文献
6.
在精准温控动三轴试验系统上开展了不同温度及不同升温路径饱和黏土剪切试验研究,探讨了不同温度对饱和软黏土不排水剪切特性的影响,分析不同升温固结方式对饱和软黏土孔压发展、体变、强度以及模量的影响规律。试验结果显示：在4～76 ℃试验研究范围内,环境温度升高导致饱和软黏土的不排水剪切强度有所减少,但温度升高对土体模量增加影响明显,温度T和模量ET关系可用ET = 2.69T 0.3表达;升温变化时正常固结黏土产生超孔隙水压力并随着温度增大而增大,升温热固结后土的剪切强度将明显提高,且排水状态下升温固结对土剪切强度增长小于升温完成后再固结情况;土体从26 ℃分别升高20、40 ℃时,升温引起的超孔压比分别为0.41、0.61,剪切峰值强度分别增加8.23%、22.37%。研究表明：升温幅值增大会使土体热固结程度越大,升温分级越多,热固结也越充分,其对应的体变、强度增长率则越大;同时最终温度及热固结路径对其剪切相转换特征存在影响,升温越高、热固结路径越多其剪胀性越明显,但温度变化范围、固结分级、热固结路径总体上对孔隙水压力的发展基本不产生影响。 相似文献
7.
饱和软粘土在不排水循环荷载作用下孔隙水压力模型的建立 总被引：3，自引：0，他引：3
通过应力控制式循环三轴试验,研究了饱和软粘土在不排水循环荷载作用下的性状。在考虑影响循环 特性因素的基础上,建立了一种适合上海地区饱和软粘土孔隙水压力的增长模型。 相似文献
8.
通过一系列不排水动三轴试验探究了饱和黄土振动液化过程中孔隙水压力和累积耗散能量的演化模式,并讨论了围压、动应力幅值和固结应力比对其演化过程的影响。结果表明：饱和黄土的孔隙水压力和耗散能量随着循环荷载作用逐渐累积。固结围压抑制孔隙水压力增长而消耗更多能量;更大的动应力幅值使得孔隙水压力增长更快而消耗能量更少;等压固结下,孔隙水压力增长至围压从而触发初始液化,而偏压固结下,通常先达到振动液化应变标准而孔隙水压力并没有增长至围压水平,并且固结应力比越大,液化时孔隙水压力越小,消耗能量也更少。归一化孔隙水压力u/σ0’与累积耗散能量W/Wf之间关系受围压、循环应力比和固结应力比影响较小,可统一用双曲线模型表示。 相似文献
9.
通过固结不排水三轴压缩试验,分析了围压、固结比和干密度等因素对饱和粉土静态液化特性的影响。试验结果表明,在干密度较小时,饱和粉土的偏应力-应变曲线呈现明显的硬变软化型,随轴向应变增大超静孔隙水压力增加、有效应力减小而发生静态液化,当干密度达到1.58 g· cm-3时,饱和粉土的偏应力-应变曲线表现出硬变硬化现象,超静孔隙水压力为负值或接近0,饱和粉土不再发生静态液化,即饱和粉土存在静态液化的干密度临界值;其他条件不变,随着围压、固结比或干密度的增大,偏应力峰值和残余强度均增大,静态液化势降低;根据有效应力路径建立了流滑面以作为饱和粉土稳定区与非稳定区的分界面。 相似文献
10.
In this paper the Discrete Element Method (DEM) is coupled with the Lattice-Boltzmann Method (LBM) to model the undrained condition of dense granular media that display significant dilation under highly confined loading. DEM-only models are commonly used to simulate the micromechanics of an undrained specimen by applying displacements at the domain boundaries so that the specimen volume remains constant. While this approach works well for uniform strain conditions found in laboratory tests, it doesn’t realistically represent non-uniform strain conditions that exist in the majority of real geotechnical problems. The LBM offers a more realistic approach to simulate the undrained condition since the fluid can locally conserve the system volume. To investigate the ability of the DEM-LBM model to effectively represent the undrained constraint while conserving volume and accurately calculating the stress path of the system, a two dimensional biaxial test is simulated using the coupled DEM-LBM model, and the results are compared with those attained from a DEM-only constant volume simulation. The compressibility of the LBM fluid was found to play an important role in the model response. The compressibility of the fluid is expressed as an apparent Skempton’s pore pressure parameter B. The biaxial test, both with and without fluid, demonstrated particle-scale instabilities associated with shear band development. The results show that the DEM-LBM model offers a promising technique for a variety of geomechanical problems that involve particle-fluid mixtures undergoing large deformation under shear loading. 相似文献
11.
《Engineering Geology》2007,89(1-2):144-154
This paper presents the results of an experimental investigation carried out to study thermally induced volume changes under drained heating condition and thermally induced excess pore water pressures under undrained heating condition of soft Bangkok clay. The clay was heated up from room temperature (25 °C) to 90 °C using a modified oedometer and a triaxial test apparatus, respectively. The clay was found to exhibit temperature induced volume changes and temperature induced excess pore water pressures, in the range of temperatures investigated, depending mainly on the stress history. A theoretical microstructure mechanism that can interpret the thermally induced volume change behaviour at different stress conditions is presented in this study. Furthermore, the thermally induced excess pore water pressure behaviour at different stress conditions is explained using the unloading–reloading hysteresis of the typical soil consolidation curve. The results of this study provide additional data that can enhance the understanding of the thermo-mechanical behaviour concepts of saturated clays. 相似文献
12.
土体的力学特性往往因应力状态和应力路径而异。为了探讨垂直加载和等剪路径下饱和土的力学特性,制备饱和重塑黄土试样,通过固结不排水（CU）和常剪应力排水剪（CSD）三轴试验,分别测定并绘制其应力-应变曲线、孔隙水压力变化曲线和应力路径曲线。试验结果表明,饱和重塑黄土在2种路径下有明显不同的变形特点:CU路径下的应力-应变曲线皆呈弱软化型,孔隙水压力先快速上升后逐渐趋于稳定;CSD路径下维持偏应力为一常量,施加孔隙水压力后的很长时间内试样变形很小,当孔隙水压力增大至试验围压的60%~75%时,试样迅速破坏。CSD路径无偏应力峰值,文中根据轴应变随平均有效应力变化曲线定义了等效峰值破坏线。通过对比发现,2种路径下饱和重塑黄土的有效峰值强度指标差异明显,而有效残余强度指标相近,表明有效残余强度指标是重塑黄土内在属性,受应力路径的影响不大。该研究结果可为实际工程选取正确的应力路径试验提供参考。 相似文献
13.
循环荷载下饱和黄土不排水强度退化规律试验与理论研究 总被引：1，自引：0，他引：1
循环荷载作用下饱和黄土的不排水抗剪强度会出现退化。退化主要由两方面的原因引起：一是超孔隙水压力的产生而导致有效应力的降低;二是塑性残余变形的累积导致土体内部结构发生了改变。首先基于静三轴不排水剪切试验结果,提出了饱和黄土不排水强度比随超固结比以及初始剪切变形变化规律的拟合公式。在此基础上,引入似超固结比的概念来考虑超孔隙水压力的影响,应用拟合公式来考虑剪切变形的影响,最终推导出了饱和黄土不排水强度的退化公式,与试验结果的对比证明了理论公式预测结果的合理性。 相似文献
14.
利用GDS空心圆柱仪进行了一系列主应力方向角?d变化的轴向、扭转、内压和外压四向耦合不排水循环剪切试验。在均等固结条件下,着重研究了循环加载方向角?d0对饱和粉土动力特性的影响。试验结果表明：饱和粉土的双规准化孔压发展模式与?d0无关,但受循环应力比CSR的影响;广义剪应变的发展模式不受?d0的影响。在循环剪切过程中,循环加载方向的变化对粉土的不排水动强度有显著影响,饱和粉土的动强度CRR随着?d0的增大呈现出先减小后增大的变化趋势,且当?d0=45°时CRR最小。同时,建立了反映?d0与CSR影响的孔压、变形的模型,并给出了相应的动强度表达式。 相似文献
15.
OuyangZhihua ElsworthDerek ShengJianlong 《中国地质大学学报(英文版)》2005,16(1):58-65
The undrained change in pore fluid pressure that accompanies dike intrusion may be conveniently represented as a moving volumetric dislocation. The concept of a dilation center was developed to represent the field of undrained pressure change in a saturated linear elastic medium. Since instantaneous pore fluid pressures can be developed to a considerable distance from the dislocation, monitoring the rate of pressure generation and subsequent pressure dissipation in a fully coupled manner enables certain characteristics of the resulting dislocation to be defined. The principal focus of this study is the application of dislocation-based methods to analyze the behavior of the fluid pressure response induced by intrusive dislocations in a semi-infinite space, such as dike intrusion, hydraulic fracturing and piezometar insertion. Partially drained pore pressures result from the isothermal introduction of volumetric moving pencil-like dislocations described as analogs to moving point dislocation within a semi-infinite saturated elastic medium. To represent behavior within the halfspace, an image dislocation is positioned under the moving coordinate frame fixed to the front of the primary moving dislocation, to yield an approximate solution for pore pressure for constant fluid pressure conditions. Induced pore pressures are concisely described under a minimum set of dimensionless parameter groupings representing propagation velocity, and relative geometry. Charts defining induced pore fluid pressure at a static measuring point provide a meaningful tool for determining unknown parameters in data reduction. Two intrusive events at Krafla, Iceland are examined using the type curve matching techniques. Predicted parameters agree favorably with field data. 相似文献
16.
Wang Jun Wu Lei Cai Yuanqiang Guo Lin Du Yunguo Gou Changfei Ni Junfeng Gao Ziyang 《Acta Geotechnica》2021,16(4):1161-1174
In certain field conditions such as offshore projects under wave loads or embankments under traffic loads, both the vertical and horizontal stresses are variable. However, previous investigations rarely considered the variation in horizontal stress. To better understand the characteristics of natural saturated soft clay, a series of monotonic and cyclic triaxial tests with a K0-consolidation state were carried out under a variable confining pressure (VCP) stress path. The development of axial strain, pore water pressure and effective stress path is analysed. The results show that with the increase in η (the ratio of the variation in the mean effective principal stress to that of the deviatoric stress), the undrained shear strength (qf) decreases continuously. The pore water pressure generation is slightly improved under a stress path with increasing confining pressure. Based on the test results, a unified formula was established to predict the pore water pressure under VCP stress paths. The unique p–q–e relationship of normally consolidated clay in monotonic VCP triaxial tests was also demonstrated. Under VCP stress paths, the amplitude of the pore pressure increases, and the effective stress path tilts more sharply to the right. Moreover, a unified formula was established that can provide a good reference for predicting effective stress paths under cyclic VCP triaxial tests.
相似文献17.
决定饱和岩土材料变形的有效应力 以及孔压系数B的表达式主要有2种不同的形式,为辨析其合理性,分析了不排水条件下,孔压增量和净围压增量作用下固相与骨架的体积压缩系数之间的关系,以及分别由孔压增量和净围压增量作用引起的液相、固相和骨架的体积增量,指出了 和B的两种形式的表达式在推求过程中各自存在的问题,并通过不排水和排水条件下的变形等效关系,建立了新的有效应力 和孔压系数B的表达式。 相似文献
18.
Yu Haizhen Zhao Wenguang Wang Ren Li Jianguo He Yang 《中国地质大学学报(英文版)》2005,16(4):340-344
INTRODUCTION Theexploitationofoffshorenaturalresourcesin thetropichaspresentedgeotechnicalengineerswith theproblemofdealingwithinsitucarbonatesedi mentsinharshconditionsforwhichfewengineering dataareavailable.Thecarbonatesedimentsaresub jectedtolargestaticstressesduetotheweightof foundationstructuresaswellascyclicstressesdueto waveaction,andinsomecases,earthquakeloading.Ithasbeenprovedthatthenatureofcyclicstresschangesoccurringintheseabeddepositduetowave loadinginvolvesacontinuousrotationo… 相似文献
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M. Monfared J. Sulem P. Delage M. Mohajerani 《Rock Mechanics and Rock Engineering》2011,44(6):735-747
Some aspects of the thermal behavior of the Opalinus claystone are investigated through laboratory tests conducted on a new
hollow cylinder triaxial apparatus specially designed for studying the thermo-hydro-mechanical behavior of very low permeable
materials. Two hollow cylinder samples are first resaturated under isotropic stress state equal to the mean effective in situ
one in order to minimize swelling and induced damage during the resaturation phase. Two drained heating–cooling cycles are
performed on the first sample of Opalinus claystone. During the first cycle, a thermo-elasto-plastic response similar to that
of plastic clays with low overconsolidation ratio is obtained. The thermal hardening of the sample is demonstrated by the
quasi-reversible behavior of the sample during the second heating–cooling cycle. An undrained heating test performed on the
second sample of Opalinus claystone induces an excess pore pressure in this sample. This induced pore pressure is attributed
to the higher thermal expansion coefficient of pore water compared to that of the solid phase. It is shown that the excess
pore pressure generated in the sample by undrained heating cannot be modeled by considering the free water thermal expansion
coefficient. The thermal expansion coefficient of the Opalinus claystone water is back-analyzed from the experimental results
which show a higher value than free water. 相似文献