冻结砂土的应力-应变关系及非线性莫尔强度准则  

STRESS-STRAIN RELATIONSHIPS AND NONLINEAR MOHR STRENGTH CRITERION OF FROZEN SAND CLAY

作　　者：赖远明[1] 程红彬[1] 高志华[1] 张淑娟[1] 常小晓[1] 

机构地区：[1]中国科学院寒区旱区环境与工程研究所冻土工程国家重点实验室,甘肃兰州730000

出　　处：《岩石力学与工程学报》2007年第8期1612-1617,共6页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家杰出青年科学基金资助项目(40225001);中国科学院知识创新工程重要方向项目(KZCX3–SW–351);中国科学院知识创新工程重大项目(KZCX1–SW–04)

摘　　要：对于-6℃的冻结砂土进行一系列的试验,结果表明,当围压小于3.0MPa时,其应力–应变关系具有明显的应变软化现象;当围压大于3.0MPa时,其应力–应变关系则具有明显的应变硬化现象。针对广义的双曲线模型并不能很好地描述-6℃冻结砂土在围压大于3.0MPa时的应力–应变关系,邓肯–张模型也不能理想地反映围压小于3.0MPa时-6℃冻结砂土的应变软化特性,提出既能描述应变软化现象又能描述应变硬化现象的改进的邓肯–张模型。研究表明,其结果和试验结果吻合良好。由于压融现象的存在,当围压大于一定值后,冻结砂土的剪切强度随围压的增大而减小。如果用莫尔–库仑准则来描述冻结砂土的剪切强度,会产生较大的误差。为解决这一问题,提出非线性莫尔强度准则。研究结果表明,其精度较高,比莫尔–库仑强度准则能更好地描述冻结砂土的剪切强度。A series of triaxial compression tests were carried out on frozen sand clay with confining pressures from 0.0 to 18.0 MPa at -6 ℃. The experimental results indicate that the strain softening exists in the stress-strain relationships of the studied frozen sand clay when the confining pressures is below 3.0 MPa; and the strain hardening phenomenon appears in the stress-strain relationships when confining pressures is greater than 3.0 MPa. Since the general hyperbolic model cannot describe the strain hardening behavior; and Duncan-Chang model cannot describe the strain softening behavior of frozen sand clay; an improved Duncan-Chang model is proposed. This model can describe not only the strain softening behavior but also the strain hardening behavior of frozen sand clay. Moreover, its modeling precision is better than those of Duncan-Chang model and the general hyperbolic model. Due to pressure melting, shear strength of frozen sand clay nonlinearly changes with increasing confining pressures. In order to solve the problem that linear Mohr-Coulomb criteria can not exactly reflect theshear strength of frozen sand clay, a nonlinear Mohr criterion of frozen sand clay is presented. The results calculated by the nonlinear Mohr criterion of frozen sand clay illustrate that it has higher precision and can more exactly describe the shear strength of frozen sand clay than the linear Mohr-Coulomb criterion.

关 键 词：土力学 冻结砂土 应力-应变关系 改进的邓肯-张模型 非线性莫尔强度准则 

分 类 号：TU445[建筑科学—岩土工程]