正常固结非饱和黏性土的三剪边界面模型研究  

TRIPLE-SHEAR BOUNDING SURFACE MODELS FOR UNSATURATED CLAYS IN NORMAL CONSOLIDATION

作　　者：胡小荣[1] 蔡晓锋 陈昊 HU Xiao-rong;CAI Xiao-feng;CHEN Hao(School of Civil Engineering and Architecture,Nanchang University,Nanchang 330031,China;Zhongmei Engineering Group Ltd.,Nanchang 330001,China)

机构地区：[1]南昌大学建筑工程学院,南昌330031 [2]江西中煤建设集团有限公司,南昌330001

出　　处：《工程力学》2021年第6期175-190,共16页Engineering Mechanics

基　　金：国家自然科学基金项目(10862004,11362016)。

摘　　要：将三剪统一强度准则分别与非饱和土的单应力变量理论和双应力变量理论相结合提出了正常固结非饱和黏性土的三剪强度准则,在此基础上采用等量代换法与坐标平移法分别推导出可以反映土体全应力状态效应的三剪破坏应力比。将该三剪破坏应力比引入非饱和黏性土修正剑桥模型的屈服面方程以确定初始边界面,采用径向映射法则确定后续边界面,根据插值函数得到加载面上的塑性模量,据之建立了非饱和黏性土单应力变量和双应力变量下分别采用等量代换法和坐标平移法的4个三剪弹塑性边界面模型并对这4个模型做了单调和循环压缩荷载试验验证。结果表明,所建模型均能较好地反映土的变形特征,但相比之下,双应力变量下建立的模型相对单应力变量下建立的模型更接近试验结果,采用等量代换法建立的模型相对坐标平移法更接近试验结果的特点。真三轴数值模拟结果表明,单调加载时,相同应力条件下中主应力影响系数增大会引起非饱和土强度增大;循环加载时,最小主应力或中间主应力的增大均会引起土体抗剪强度的增大,且荷载振幅越大,非饱和土的轴向应变随之增大。比较4个边界面模型在真三轴应力状态的模拟结果表明,单调加载时,非饱和黏性土在双应力变量下的模拟抗剪强度值相对较大;循环加载时,单应力变量下所得塑性变形相对较大。The triple-shear unified failure criterion for unsaturated clays is proposed by combining the triple-shear unified strength theory,the single stress variable theory and the double stress variable theory,so that the two triple-shear failure stress ratios which can reflect the effects of full stress states acting on the soils are deduced with the methods of equivalent substitution and coordinate translation.The triple-shear failure stress ratios are then interfered with the yield function of the modified Cambridge model for unsaturated clays to determine the initial bounding surface,and the subsequent bounding surfaces are formulated by the radial mapping method,and the moduli of plasticity on the loading surface are obtained by employing the interpolation function.Based on that,the four triple-shear bounding surface models in elasto-plasticity for unsaturated clays are established according to the theories of single stress variable and double stress variable together with the methods of equivalent substitution and coordinate translation respectively,and are verified with monotonic and cyclic compression tests on several clays.The results show that all the four models can well reflect the mechanical characteristics of the selected unsaturated clays.Comparatively,models of the double stress variables can give closer approximations to the tests than models of the single stress variable,and models with the equivalent substitution method can also give better fits to the tests than models with the relative coordinate translation method.Results of the true triaxial numerical simulations on unsaturated clays show that under monotonic loading,the strength of the unsaturated clays increases with the influence coefficient of the intermediate principal stress under definite stress conditions.Simulations also show that under cyclic loading,the shear strength of the unsaturated clays increases with the minimum principal stress or intermediate principal stress,and a greater amplitude of load vibration leads to a larger axial str

关 键 词：非饱和黏性土 三剪统一边界面模型 三剪统一强度准则 单应力变量 双应力变量 

分 类 号：TU432[建筑科学—岩土工程]