煤岩组合体峰前轴向裂纹演化与非线性模型

随着中国煤炭开采深度逐渐加深,煤岩组合体的力学特性与应力–应变关系显得越来越重要。煤岩组合体的原生裂纹和煤岩体之间的界面对其力学性质有较大影响。为了探知裂纹和界面的影响,主要研究了轴向裂纹应变随应力、应变的演化特征,并基于工程应变和自然(真实)应变的概念,建立轴向裂纹闭合模型(axial crack closure model,简称ACCM)及轴向裂纹扩展模型(axial crack propagation model,简称ACPM),最后建立了峰前应力–应变关系模型。分析发现,轴向裂纹应变与轴向应变关系可分为4个阶段,即初始阶段、稳定阶段、缓慢增长阶段和快速增长阶段,轴向裂纹应变与轴向应力关系与之类似。轴向裂纹闭合模型、轴向裂纹扩展模型与峰前应力–应变模型均能够较好地与试验数据吻合,能够描述应力–应变关系的非线性特点。

Evolution of pre-peak axial crack strain and nonlinear model for coal-rock combined body

With the gradual deepening of coal mining layer in China, fundamental understanding of mechanical characteristics and constitutive relationship of the coal-rock combined body is increasingly significant. The original crack and interlayer between coal and rock have a major influence on the mechanical properties of the coal-rock combined body. In order to investigate the influence of crack and interlayer, the evolution characteristics of axial crack strain along with axial strain and axial stress are studied, and based on the concept of engineering strain and natural (true) strain, the Axial Crack Closure Model (ACCM) and the Axial Crack Propagation Model (ACPM) are established. Finally the constitutive model for pre-peak stress-strain curve is proposed. It is found that on the basis of the axial crack strain changing along with the axial strain, there are 4 stages in the whole process: initial stage, stable stage, slow-growth stage and rapid-growth stage. The characteristics of the axial crack strain evolving with the axial stress are similar to those changing with the axial strain. The ACCM, ACPM and axial stress-strain model are found to fit with the experimental data well, and they can describe the nonlinear characteristic of stress-strain relationship.