The stress-induced evolution of coal fractures significantly affects permeability and, consequently, gas extraction efficiency. This study introduces a novel coal fracture evolution model based on assumptions of fracture morphology and log-normal distribution of fracture aspect ratio. This model offers a theoretical framework for understanding the fracture closure process, ultimately depicting fracture evolution as a combined result of elastic compression and closure. It predicts the decay curve of fracture porosity under hydrostatic pressure loading. We conducted uniaxial compression experiments for determining the mechanical parameters of the model and in situ CT experiments with confining pressure ranging from 0 to 25 MPa for validating the model. The findings indicate the following: (1) Initially, the decline in fracture porosity with stress is predominantly due to elastic compression, followed by a rapid transition to closure. (2) Sensitivity analysis reveals that an increase in two physical quantities—the cube root of the product of the peak aspect ratio and the square of the mean aspect ratio (x_c) and the bulk modulus of the coal matrix (K_m)—results in a decrease in the rate of fracture porosity decay with stress. (3) Tectonic action has a dual effect of augmenting x_c and diminishing K_m. We define the magnification of x_c and the divisor of K_m under a common term—scaling factor. When the scaling factor of x_c is less than that of K_m, the tectonic action promotes the decay of porosity with stress. Conversely, when the scaling factor of x_c is greater than that of K_m, the effect is reversed.

应力引起的煤裂缝演化显着影响渗透率，从而影响瓦斯抽采效率。本研究介绍了一种基于裂缝形态和裂缝纵横比对数正态分布假设的新型煤裂缝演化模型。该模型为理解裂缝闭合过程提供了一个理论框架，最终将裂缝演变描述为弹性压缩和闭合的综合结果。它预测了静水压力加载下裂缝孔隙度的衰减曲线。我们进行了单轴压缩实验来确定模型的力学参数，并进行了围压范围为0~25 MPa的原位CT实验来验证模型。研究结果表明：（1）最初，裂缝孔隙度随应力的下降主要是由于弹性压缩，随后迅速过渡到闭合。 (2) 敏感性分析表明，峰值纵横比与平均纵横比平方乘积的立方根(x _c )和煤的体积模量这两个物理量均有所增加基质 (K _m )——导致裂缝孔隙度随应力衰减的速率降低。 (3)构造作用具有增大x _c 和减小K _m 的双重作用。我们将 x _c 的放大倍数和 K _m 的除数定义在一个通用术语“缩放因子”下。当x _c 比例因子小于K _m 时，构造作用促进孔隙度随应力的衰减。相反，当 x _c 的缩放因子大于 K _m 的缩放因子时，效果相反。