共查询到18条相似文献，搜索用时 156 毫秒
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含气软黏土广泛分布在世界五大洲,大量离散气泡的存在对软黏土的不排水抗剪强度具有强化或损伤作用,然而目前仍缺乏能综合考虑气相强化与气相损伤竞争机制的含气土不排水剪切强度解析表达式。结合临界状态土力学理论,基于笔者提出的含气土屈服函数,建立了v-lnp¢ 空间下临界状态线截距与土体含气特性(uw 0,y0)的数学关系,进而推导了含气软黏土在三轴应力状态下不排水抗剪强度su的理论显式表达式。同时,采用所提出的含气软黏土不排水抗剪强度理论计算公式,分别对比了3种典型的含气软黏土在不同含气特性下的不排水抗剪强度理论预测与试验结果,包括马来西亚高岭土、Combwich 黏土和高岭黏土。另外,对比分析了4种不同的含气软黏土不排水抗剪强度理论计算模型的预测误差百分比,证明了提出的基于改进的含气软黏土本构模型的不排水抗剪强度理论计算式的合理性,能够更加准确地同时考虑含气软黏土的气相强化与气相损伤双重效应。 相似文献
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《岩土力学》2015,(9):2442-2450
临界状态是土的重要破坏特征,是当今许多土本构模型建立的基础。由于工程和试验中不能忽略时间因素,临界状态实际上是土在一定的时间作用下或者说一定的加载速率作用下表现出的破坏规律。率相关本构模型作为考虑了时间对土应力-应变关系影响的本构模型,理应可以描述临界状态。通过使用较为常用的率相关本构模型——过应力弹黏塑性模型对三轴不排水和排水剪切进行预测,探讨了这些模型对临界状态的描述情况。预测结果表明:(1)第1类过应力弹黏塑性模型(该模型认为屈服面是黏塑性体积应变率的等值面)计算所得的三轴不排水应力路径在临界状态线的下方出现应变软化,并且应力路径趋向于坐标原点,不能终止于临界状态;(2)第2类过应力弹黏塑性模型(认为屈服面是黏塑性标量因子的等值面)在对高应变率三轴排水剪切进行预测时,所得的最终应力比超过临界状态应力比;(3)第3类过应力弹黏塑性模型,亦即时间UH模型(认为屈服面是统一硬化参量变化率的等值面,并认为土产生应力塑性变形)在三轴不排水和排水剪切条件下均能较好反映临界状态。通过3种模型的公式分析了前述预测结果产生的原因。 相似文献
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为探究伊犁地区高易溶盐含量黄土的临界状态特性,针对不同易溶盐含量的非饱和伊犁原状黄土,开展了控制吸力和净围压的三轴固结剪切试验。研究结果表明：在常吸力固结剪切条件下,非饱和伊犁原状黄土的强度随含盐量的增加存在峰值;含盐量一定,不同吸力非饱和土的q-p或e-p临界状态线均为平行直线,q- 临界状态线可归一为饱和土临界状态线表示的一条直线,其斜率随含盐量的增加呈幂函数降低;非饱和土e-p临界状态线的斜率 大于饱和土的斜率 ,两者均随含盐量的增加先减后增,相同有效净平均应力下非饱和土和饱和土的临界状态孔隙比之比 与气体饱和度1- 可以归一化;q-p平面上初始屈服曲线和后继屈服曲线均可近似假定为对称于 线的椭圆,吸力和应力对屈服曲线的硬化作用是等向的。 相似文献
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为了研究非饱和黄土在有效应力空间的屈服特性,利用真三轴仪对非饱和原状黄土进行了不排水等向净应力压缩固结和不同中主应力参数b值的剪切试验,研究了真三轴压缩条件下非饱和黄土的有效应力屈服变化规律。研究结果表明：有效应力比随着中主应力或净围压的增大而减小,中主应力的增大作用对有效球应力的影响大于广义剪应力;由有效应力比?体应变关系曲线确定的剪缩屈服曲线在有效应力空间具有良好的规律性,屈服点的有效屈服应力随着中主应力和初始吸力的增大而增大;π平面上的有效应力屈服强度面和强度破坏面与SMP强度准则稳合较好,有效球应力和初始吸力越大,屈服强度面和强度破坏面越大。提出了真三轴条件下弹性剪应变和塑性剪应变的计算公式,通过分析有效应力与塑性应变关系得出有效应力空间中不同子午平面内的塑性势面呈椭圆形,且随着中主应力的增大,椭圆屈服面增大。 相似文献
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《岩土力学》2021,(2)
为了研究非饱和黄土在有效应力空间的屈服特性,利用真三轴仪对非饱和原状黄土进行了不排水等向净应力压缩固结和不同中主应力参数b值的剪切试验,研究了真三轴压缩条件下非饱和黄土的有效应力屈服变化规律。研究结果表明:有效应力比随着中主应力或净围压的增大而减小,中主应力的增大作用对有效球应力的影响大于广义剪应力;由有效应力比-体应变关系曲线确定的剪缩屈服曲线在有效应力空间具有良好的规律性,屈服点的有效屈服应力随着中主应力和初始吸力的增大而增大;π平面上的有效应力屈服强度面和强度破坏面与SMP强度准则稳合较好,有效球应力和初始吸力越大,屈服强度面和强度破坏面越大;提出了真三轴条件下弹性剪应变和塑性剪应变的计算公式,通过分析有效应力与塑性应变关系得出有效应力空间中不同子午平面内的塑性势面呈椭圆形,且随着中主应力的增大,椭圆屈服面增大。 相似文献
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考虑温度影响的非饱和土本构模型 总被引：1，自引：1，他引：0
首先建立了反映温度对非饱和土前期固结压力影响的加载-升温(loading thermal, LT)屈服线,而后基于真强度概念并结合潜在强度的确定方法推导出不同温度下非饱和黏土临界状态应力比的理论计算公式;将LT屈服线与反映常温下吸力对土体前期固结压力影响的加载-湿陷(loading collapse, LC)屈服线结合,建立了加载-升温-湿陷(loading thermal collapse, LTC)屈服面,该屈服面综合考虑了温度和吸力对土前期固结压力的影响;最后在临界土力学框架内建立了一个考虑温度影响的正常固结非饱和土本构模型,并将其扩展到超固结非饱和土。与巴塞罗那模型相比,所提出的模型仅增加了一个参数来反映非饱和土的前期固结压力随温度升高而降低的特性。模型能够综合描述温度、吸力以及不同超固结程度对土应力、应变的影响,方便于数值计算和有限元分析。模型预测和试验分析表明,某一固定吸力下升温会使正常固结非饱和土强度提高;对于超固结非饱和土,升温或湿化均会破坏土体超固结,降低软化和剪胀的效果。 相似文献
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连云港软黏土的不排水强度试验研究 总被引：1，自引：0，他引：1
对连云港软黏土不扰动样和重塑样进行三轴CU对比试验研究。结果表明,不扰动样的不排水强度包线是由以屈服压力为界的双折线组成,而重塑样的不排水强度包线可以用通过圆点的直线表示。屈服前阶段,不扰动样由于受结构性影响产生的抵抗作用,其不排水强度包线高于重塑样;屈服后阶段,不扰动样的不排水强度包线介于具有不同初始含水率的重塑样的包线之间。通过对比分析,发现不扰动样与重塑样的不排水强度包线存在差异的主要原因是由于试样的不同初始含水率引起的。不扰动样在屈服后阶段的含水率变化规律与不排水强度增长规律与重塑土相一致,采用Burland提出的孔隙指数Iv,可将不同初始含水率重塑样及屈服后阶段不扰动样的压缩性状较好地归一化。 相似文献
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堆石料的临界状态与考虑颗粒破碎的本构模型 总被引：4，自引：1，他引：3
高应力水平时堆石料的颗粒破碎对其强度和变形机制有重要影响。临界状态土力学理论对重塑土的应力-应变关系的描述较为成功,但目前颗粒破碎对堆石料的临界状态的影响及其数学描述鲜有研究。对堆石料进行了固结应力从0.4 MPa到4 MPa的18组固结排水和固结不排水常规三轴压缩试验,以及6组等向压缩试验。试验结果表明：在排水条件和不排水条件下,不同的固结应力试样都趋于临界状态;堆石料的临界状态在q-p′平面和e-lgp′平面均为非线性变化。基于此试验结果,通过引入状态参数,在广义塑性力学的理论框架下,建立了考虑颗粒破碎的堆石料本构模型,并给出了模型参数的确定方法。与长河坝料的试验进行了对比,结果表明所建议的本构模型可以较好地模拟堆石料从低围压0.4 MPa到高围压 3.5 MPa下的应力-应变特性 相似文献
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结构性土颗粒间的胶结使试样剪切破坏最终应力比高于相应重塑土,也限制了试样剪切时体积应变的自由发挥。在考虑结构垮塌为主的结构性土统一硬化(UH)模型基础上,将应力空间中静止的临界状态线扩展为动态的移动临界状态线。据此,通过建立新的屈服面方程并修正剪胀方程,将结构性土统一硬化(UH)模型扩展为胶结结构性土统一硬化(UH)模型。相对于原模型,新模型增加了1个模型参数,即初始胶结应力,反映土颗粒之间的初始胶结作用。通过4种结构性土试验数据与模型预测对照表明：所提模型能够较合理地描述结构性土等向压缩、常规三轴排水与不排水剪切等特性。 相似文献
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常规剑桥模型和修正剑桥模型是以正常固结和弱超固结土的三轴试验现象为基础建立起来的,且试样的初始应力状态为各向等压的球应力状态,将模型应用于K0固结状态的原状土必然引起不可忽略的系统误差。基于原状土K0固结线与等倾线之间的关系,在常规剑桥模型的基础上推导并得到了基于K0线的原状土剑桥模型和修正剑桥模型。在主应力空间中,该模型以K0固结线而不是以等倾线为轴线,因而能反映原状土的结构性和各向异性。既有试验数据的验证表明,与常规剑桥模型和修正剑桥模型相比,该模型能更合理的描述原状土的屈服和强度特性。 相似文献
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The cyclic behavior of soil–structure interface can be very important in dynamic problems. The cyclic behavior of soil–structure interface may be nonlinear, which includes hysteresis, hardening, degradation, and particle breakage. The breakage of granular soil particles during shearing of granular soil–structure interface is associated with cyclic degradation and can be critical to the dynamic behavior of soil–structure system. The critical state soil mechanics concept formerly used to simulate the nonlinear monotonic behavior of granular soil–structure interface was modified and extended to describe the cyclic behavior, especially soil‐particle breakage and degradation during cyclic shearing. Soil‐particle breakage was assumed to relate to the energy consumption during cyclic shearing and the critical state line of the soil–structure interface was assumed to translate with the consumption of shearing energy during cyclic shearing as the threshold value is attained. The model was formulated in the framework of generalized plasticity and is capable of describing the salient features of granular soil–structure interface under cyclic loading. Most of the model parameters have straightforward physical meanings and are calibrated using monotonic or cyclic interface test results. The proposed model was calibrated and validated against published test results. The dependency of interface behavior on stress path and cyclic degradation can be successfully described by the proposed model. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
14.
Estimation of critical state-related formula in advanced constitutive modeling of granular material 总被引：1，自引：0，他引：1
Different critical state-related formulas, for the critical state line and the critical state-dependent interlocking effect, have been proposed in constitutive modeling of granular material during last decades, which rises up a confusion on how to select an appropriate model in the geotechnical applications. This paper aims to discuss the selection of these critical state-related formulas and parameters identification. Three formulas of critical state line together with two formulas of critical state-dependent interlocking effect are combined to propose six elasto-plastic models. Drained and undrained triaxial tests on four different granular materials are selected for simulations. In order to eliminate artificial errors, a new hybrid genetic algorithm-based intelligent method is proposed and used to identify parameters and estimate simulations with minimum errors for each granular material and each model. Then, the performance of each CSL and each state parameter is evaluated using two information criteria. Furthermore, the performance was evaluated by simulating three footing tests using finite-element analysis in which the models are implemented. All comparisons demonstrate the incorporation of nonlinear critical state line combined with the state parameter e/e c in constitutive modeling can result in relatively more satisfied simulated results. 相似文献
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The stress–strain behaviour of a soil is crucial to the recognition of the mechanism of slope failure. Triaxial tests, composed of isotropically consolidated drained (ICD) and undrained compression (ICU) tests and anisotropically consolidated constant deviatoric stress path (CQD) tests, were carried out with the aim of investigating the stress–strain behaviour of loosely compacted volcanic-derived soils. The fact that the critical states are the same for ICU, ICD and CQD tests may show that the critical state is independent of the above three stress paths. The critical state line, as defined in critical state soil mechanics, is obtained from the e–log p′ and q–p′ plots based on the results of the above tests. The initial state of the consolidated specimens at initiation of failure may be classified as dilative or contractive in the light of the locations of the soil state relative to the critical state line. For contractional soils, the increased pore water pressure generated by rainfall infiltration leads to a contractive failure in a drained manner, giving rise to high excess pore water pressure. The excess pore water pressure caused by contraction cannot be dissipated instantly, resulting in a decrease in the shear resistance of the soil. The failure process is rapid. The failed soil mass is prone to flow after failure under the action of gravity due to its high moisture content and inflow of surface runoff and rainwater. For dilational soils, the increased pore water pressure resulting from infiltration leads to dilation, which reduces pore water pressure and thus increases the shear resistance of the soil. However, continued rainfall infiltration may be able to equilibrate the reduction in pore water pressure caused by dilation and, therefore, the dilation or displacement can continue. In Hong Kong, volcanic-derived soil is characterized by high permeability. Both the high permeability of volcanic-derived soil and a shallow failure surface make it possible for the reduction in pore pressure to equilibrate relatively quickly. Therefore, the failure is also rapid, at least for poorly compacted fill slopes. 相似文献
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结构性黄土临界状态力学性状 总被引：2，自引：0，他引：2
土颗粒之间的联结方式和排列方式是影响土的结构性的两个主要因素,而水和外力可以改变土颗粒间的联结方式和排列方式,破坏了土的结构性。当排列是影响黄土结构性的主要因素时,在外力的作用下,K0结构性黄土表现出临界状态力学性状。对饱和K0结构性黄土进行不同试验,应用临界状态土力学理论进行归纳,分析其规律,总结出在外力作用过程中K0结构性黄土的结构性特殊物理力学性质,为建立结构性土的本构模型提供有力的试验依据。 相似文献
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A constitutive model for dense gravelly soils was developed to reproduce their responses under cyclic loadings. Its application aims at nonlinear dynamic analyses of earth structures involving gravelly soils, such as rockfill dams and railroad ballasts. The framework of generalized plasticity was modified to incorporate the concept of stress distance for better simulation of unloading and reloading responses. It was then combined with the theory of critical state soil mechanics to develop the constitutive model. The model has the following important features: unified simulation of particle breakage through translating critical state line, smooth transition from unloading to reloading in the stress space, and proper modeling of cyclic hysteresis, cyclic densification, and cyclic hardening of dense gravelly soils. Most of the model parameters can be obtained through simple calculation using conventional triaxial test results, and their calibration process was discussed. The model was used to simulate the cyclic responses of three gravelly soils with satisfactory accuracy. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献