中文摘要：

岩石的裂纹闭合效应对于岩石的变形以及强度性质具有重要影响。主要研究了岩石内部微裂纹的闭合压密效应及其定量评价方法。首先,基于有效介质理论将岩石的轴向应变分为基质轴向应变和裂纹轴向应变两部分;然后通过3组岩石压缩试验资料,建立裂纹轴向应变随轴向应力变化的负指数模型。分析发现,负指数模型可以较好地描述岩石裂纹闭合压密阶段的非线性。裂纹闭合应变可以在一定程度上反映岩石内部的微裂纹数量（密度）,能够描述微裂纹密度在单轴、三轴压缩条件下的变化规律。

英文摘要：

The deformation and strength of rocks are significantly influenced by the crack closure behavior. In this study, the crack closure effect and its quantitative characterization are studied. First, based on the widely used effective medium theory, the axial strain is divided into the matrix axial strain and the crack axial strain. Three sets of test data are then used to establish a negative exponential model for the relationship between the crack axial strain and the axial stress. It is found that the crack closure behavior is well captured by the proposed model. The crack closure strain can be used to some extent to represent the microcrack quantity（or microcrack density） in the rock sample. The variation of the microcrack density under uniaxial and triaxial compressions is well described by using the crack closure strain.