考虑硬化软化和剪胀特性的绿泥石片岩力学模型

Mechanical model of chlorite schist considering hardening-softening and dilatancy characteristics

绿泥石片岩是一种典型的软岩,开挖过程中出现的围岩大变形和塌方对工程安全危害极大。为了深入研究绿泥石片岩的力学特征并建立其合理的力学模型,首先进行了不同围压下的三轴压缩试验,并考虑应力状态对塑性演化的影响,定义了新的内变量;分析了凝聚力和内摩擦角随内变量的演化规律,结果表明,凝聚力先近似呈线性减小,而后近似呈抛物线递减至残余破坏;而内摩擦角一直近似呈抛物线递增;研究了绿泥石片岩的剪胀特性,分析了剪胀角随内变量演化规律,结果表明,剪胀角与内摩擦角呈相反的演化趋势。考虑硬化、软化和剪胀特性,建立了绿泥石片岩的力学模型,对室内三轴压缩试验结果的模拟分析表明,该力学模型可以较好地描述绿泥石片岩的硬化、软化规律和剪胀等性质,为工程安全性分析提供了基本的力学模型,对于类似软岩力学性质的研究也具有重要的参考意义。

Chlorite schist is a kind of soft rocks,and its large deformation and collapse due to excavation are greatly harmful to engineering safety.In order to investigate the mechanical property of chlorite schist,triaxial compression test is conducted and a new internal variable is defined considering the influence of stress state on plasticity evolution.According to test results,evolution characteristics of cohesion and friction angle are that the cohesion decreases firstly approximately linearly and then parabolically,but friction angle always decreases approximately parabolically.Meanwhile,based on test data,evolution of dilatancy angle is opposite to that of friction angle.Finally,mechanical model of chlorite schist is proposed considering hardening-softening and dilatancy characteristics;and then it is applied to simulate the triaxial test;the result shows a good agreement with the test data.Effort of this paper offers a rational mechanical model for engineering safety estimation and an important reference for the mechanical investigation of other similar soft rocks.