基于双参数屈服函数的黏土和砂土非正交单屈服面模型  

A non-orthogonal single yield surface model for clays and sands based on a two-parameter yield function

作　　者：李海潮[1] 童晨曦 马博 张升[1,2] LI Haichao;TONG Chenxi;MA Bo;ZHANG Sheng(School of Civil Engineering,Central South University,Changsha,Hunan 410075,China;National Engineering Laboratory for High Speed Railway Construction,Central South University,Changsha,Hunan 410075,China)

机构地区：[1]中南大学土木工程学院,湖南长沙410075 [2]中南大学高速铁路建造技术国家工程实验室,湖南长沙410075

出　　处：《岩石力学与工程学报》2020年第11期2319-2327,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金优秀青年科学基金项目(51722812);湖南省然科学基金杰出青年科学基金项目(2017JJ1033);湖湘高层次人才聚集工程(2018RS3016)。

摘　　要：假定任意加载时刻土体的应力点始终位于下加载面上,并且基于临界状态土力学框架建立适用于黏土和砂土的非正交单屈服面模型。该模型具有形式简单且易于理解的优点,其所采用的硬化法则能够考虑应力水平和密度等因素对下加载面演化规律的影响,适用于超固结黏土和密砂应变软化和剪胀特性的理论描述。该硬化法则同时包含应力状态参量Ip和密度状态参量Ie,其中Ip可用于描述p-q平面当前有效平均主应力p与临界状态有效平均主应力pcs之间的相对位置;而Ie则用于描述e-lnp平面当前孔隙比e与临界状态孔隙比ecs之差。当土体由于剪切达到临界状态时,状态参量Ip和Ie均趋近于0。另一方面,该模型所采用的广义塑性势函数可以由一个与修正剑桥模型剪胀方程类似的高阶剪胀方程积分得到,其所包含的与土体剪胀特性有关的材料参数α可以由试验得到的剪胀曲线拟合得到。进一步引入材料参数δ,可以由广义塑性势函数得到适用于不同类型岩土材料的双参数屈服函数。调整δ的取值,可以分别得到相关联(δ=0)和非相关联(δ≠0)的塑性流动法则。土体的塑性流动方向m和加载方向n之间的偏差将随着δ增大而增大,此时应变矢量不再垂直于物理屈服面。该模型充分考虑了屈服面几何形状对模型计算结果的影响,将计算结果与黏土和砂土的试验结果进行对比分析,可以看出,该模型能够对黏土和砂土的力学特性进行统一的描述;此外,适当的调整屈服面的几何形状能够显著的提高模型的计算精度。A non-orthogonal single yield surface model for clays and sands is proposed based on the critical state soil mechanics,while,and a state-dependent hardening rule including parameters of I_p and I_e is developed for the sub-loading surface by considering the effects of the stress level and the relative density.The proposed model is quite simple in the formula and is capable of describing the strain-softening and dilative features of over A non-orthogonal single yield surface model for clays and sands is proposed based on the critical state soil mechanics,while,and a state-dependent hardening rule including parameters of I_p and I_e is developed for the sub-loading surface by considering the effects of the stress level and the relative density.The proposed model is quite simple in the formula and is capable of describing the strain-softening and dilative features of over consolidated clays and dense sands.In the p-q plane,the relative position between the current mean effective stress p and the critical state mean effective stress p_c_s is represented by the pressure state parameterI_p,while the void difference between the current and critical states in the e-ln p plane is captured by the density state parameterI_e.Both I_p and I_e will approach zero once the material enters the critical state due to yielding.On the other hand,the generalized plastic potential function adopted in the proposed model is integrated by a high-order dilatancy rule,which is extended from the modified Cam-clay dilatancy rule.The plastic potential function contains a dilatancy related parametera,whose value can be determined by fitting dilatancy curves with the high-order dilatancy rule.Besides,a two-parameter yield function can be developed by introducing an extra parameterdinto the proposed plastic potential function.Adjusting the value ofd,both associated(d(28)0) and non-associated(d10) plastic flow rules can be obtained.The deviation between the plastic flow direction(m) and the loading direction(n) increases as the parameterdincreases

关 键 词：土力学 双参数屈服函数 黏土 砂土 状态参量 连续方程 

分 类 号：TU43[建筑科学—岩土工程]