K_0固结软土的循环剪切特性及其流变模拟

Cyclic shearing behavior of K_0-consolidated clay and its rheological simulation

对原状温州黏土进行了三轴不排水循环剪切试验,系统分析了黏土在循环剪切过程中应变和孔压的累积特性以及加载频率的影响。考虑到天然黏土不等向固结历史的影响,试验土样在循环剪切前均先K0固结至原位应力状态。研究表明,对于K0固结软黏土,以剪应变累积曲线出现拐点作为循环破坏标准较为合适,此拐点对应的单幅破坏峰值剪应变εs,tp大小基本恒定为3%,与加载频率、循环偏应力幅值等因素无关;循环荷载幅值一定时,荷载持续时间t对黏土的循环剪切性状起控制作用,可综合反映加载频率和振次的影响。根据黏性不排水循环累积效应与静力蠕变过程的相似性,按静力蠕变等效的思路,采用建立的各向异性弹黏塑性本构模型对其进行模拟分析,并通过试验验证了此流变等效方法的有效性。

Experimental researches are conducted on natural Wenzhou clay to study its undrained cyclic deformation,pore pressure behavior and effects of loading frequency.Taking the stress-induced anisotropy into account,all the specimens are initially restored to the in-situ stress state under K0 consolidation.The emergence of the inflexion points on the accumulative strain curves can be considered as a suitable failure criteron for K0-consolidated clay and the corresponding peak strains ？s,tp of all the tests are about 3%.For a given dynamic stress ratio,the stress duration t is a key factor which comprehensively reflects the effects of loading frequency and cyclic number.Finally,based on the similarity,the accumulation during undrained cyclic shearing is equivalent to a static creep process,and a proposed anisotropic elastic visco-plastic constitutive model is used for the simulation.The predicted results indicate that the creep equivalent simplification is suitable in practice,and that the accumulation behavior of natural clays can be fairly predicted.