Research on progressive failure and the establishment of analytical method based on constitutive

1.应变软化弹粘塑性模型的推导在Adachi-Oka应变软化模型的基础上，针对软岩提出了既能描述时间相关性又能描述应变软化的弹粘塑性模型。在模型的推导过程中，采用了三个新的假设。即应力历史的新定义、时间度量的引入和抗剪强度随时间的衰减。2.弹粘塑性模型的有效性研究时间相关行为包括应变率依赖性、蠕变和应力松弛三个方面。将该模型应用于砂岩的排水三轴剪切试验和砂岩的排水三轴蠕变试验。3.模型地基渐进破坏分析在上述模型的基础上，对模型地基渐进破坏进行了有限元分析。结果较好地模拟了先在局部发生，然后逐渐扩展到其他地方的渐进破坏机理。软岩边坡开挖渐进破坏的有限元分析通过考虑软化应变、强度随时间的退化以及土体的初始k_0应力状态，对边坡开挖进行弹塑性有限元分析，研究边坡开挖引起的渐进破坏。结果表明，随着土体的破坏，土体逐渐屈服，土体中的应力随着变形而重新分布。

1.The derivation of elasto-viscoplastic model with strain-softeningBased on Adachi-Oka's model with strain softening, and elasto-viscoplastic model which can both describe the time dependency and strain-softening, is proposed for soft rock. In the derivation of the model, three new assumption are adopted. That is, the new definition of stress history, the introduction of time measure and the decline of shearing strength with time.2.Investigation of the validity of the proposed elasto-viscoplastic modelThe time dependent behavior includes three aspects as strain rate dependency, creep and stress relaxation. The proposed model is applied to the drained triaxial shearing tests of Ohya-stone and the drained triaxial creep tests of Ohya-stone. It is found that the model can well simulate the all aspects of time dependent behavior.3.Analysis of progressive failure on model groundBased on above mentioned model, a finite element analysis of progressive failure on model ground is carried out. As a result, the mechanism of progressive failure that occurs at first in local point and develops to other place progressively is well simulated. The validity of the model in boundary problems is proved.4.Finite element analysis of progressive failure on soft-rock-slope excavationBy considering the strain-softening, the deterioration of strength with time and the initial k_0-stress state in the ground, a finite element analysis of elasto-plasticity is carried out for the excavation on slope to investigate the progressive failure caused by slope excavation. As a result, it is found that the ground yields progressively with the deterioration and the stress in the ground redistributed with deformation.