Abstract

In situ soils of deep overburden layer of dam foundation are widely distributed in Southwest China, which are mixtures of gravel and silty clay in varying proportions and have cementation feature between soil particles. Based on a series of triaxial compression tests carried out on artificially cemented mixed soils (CMS) and remolded mixed soils (RMS) at confining pressures of 50, 100, 200 and 400 kPa with fine contents (silty clay) of 13%-70% in mass, a binary-medium constitutive model for artificially cemented mixed soils is proposed within framework of breakage mechanics theory for geological materials and homogenization theory. This model was formulated by regarding the soils as a binary medium consisting of bonded blocks (idealized as bonded elements) and weakened bands (idealized as frictional elements), whose deformation properties are described by the modified Duncan-Chang model and the Lade-Duncan elastoplastic model, respectively. The non-uniform distribution of stress and strain within a representative volume element can be given by introducing the structural parameters of breakage ratio and local stress coefficient. Comparisons of computed results with test results demonstrate that the binary-medium constitutive model can reflect mechanical properties of artificially cemented mixed soils well.

摘要

坝基深覆土层原位土广泛分布于西南地区，为砾石和粉质粘土不同比例的混合物，土粒间具有胶结特性。基于在 50、100、200 和 400 kPa 围压下对人工胶结混合土 (CMS) 和改造混合土 (RMS) 进行的一系列三轴压缩试验，细粒含量（粉质粘土）为 13%-70%在质量方面，在地质材料断裂力学理论和均质化理论的框架下，提出了人工胶结混合土的二元介质本构模型。该模型是通过将土壤视为由粘合块（理想化为粘合元素）和弱化带（理想化为摩擦元素）组成的二元介质，其变形特性分别由修正的 Duncan-Chang 模型和 Lade-Duncan 弹塑性模型描述。通过引入断裂率和局部应力系数等结构参数，可以得到具有代表性的体积元内应力和应变的非均匀分布。计算结果与试验结果对比表明，二元介质本构模型能较好地反映人工胶结混合土的力学特性。