随着技术的进步以及浅部矿产资源的枯竭，深部矿产资源开发与利用将成为常态。深部岩石的物理力学性质复杂，往往处于循环加卸载的应力条件。深部地下水的压力较大，是深部煤矿的重大安全隐患之一。顶板砂岩是工程最为常见的岩石种类之一，研究其力学性质及渗透规律对深部空间开发利用及矿产资源开采等都具有重要意义。以埋深约1 050 m的平煤12矿顶板砂岩为研究对象，采用循环加卸载声发射渗透实验对其渗透率演化规律进行研究。从应力-应变及损伤特征、耗散能密度占比、累计声发射事件数的增长速度、不同围压条件下的破裂面特征4个方面进行分析，总结了循环荷载下深部工作面顶板砂岩不同应力阶段的渗透率演化特征。实验结果表明:循环应力对深部顶板砂岩的作用可以分为压密作用与压裂作用两种机制，应力水平较低时主要起压密作用，应力水平增大到屈服强度的60%以上时则表现为压裂作用。岩样的渗透率在应力的压密作用下降低，在应力的压裂作用下升高。逐级增大的循环应力作用下，岩样的损伤以及耗散能密度占比均表现为先因压密作用减小，再由压裂作用而增大的演化规律，并且两者与渗透率演化呈正相关关系。整个实验过程中围压对岩样起压密作用，且随着围压的增大，渗透率减小的程度更大。顶板砂岩的破坏形式对破坏时的渗透率具有显著影响。岩样的破裂面角度随着围压增大而减小，岩样破坏时产生的贯通裂隙有轴向与横向两种形式，产生轴向贯通裂隙时的渗透率远大于岩样的初始渗透率，而产生横向贯通裂隙时的渗透率变化较小。综合五个岩样的渗透率演化情况，得到岩石渗透率在逐级增大的循环荷载下具有4个明显的阶段特征。渗透率在较低应力的循环中因压密作用减小;随着循环应力的增大，在压裂及损伤作用下增大;在应力达到岩样抗压强度发生破坏时因破裂面的产生骤增;破坏后因大幅下降的应力的压密作用再次降低。

Coal mass is often affected by consecutive loading-unloading cycles in coal mining,so the study of energy conversion and failure mechanism of coal mass under repeated loads has a guiding significance for understanding the mine dynamic disasters. By using MTS815. 03 servo experimental system,the uniaxial loading cycle tests were per- formed for the mechanism of energy accumulation,dissipation,and release in the failure process of coal sample under different loading rates,and the fragmentation distribution was also analyzed based on the theoretical analysis of energy and fractal. It provides a basis for the study of burst response and failure mechanism of coal and rock under cyclic loading. The experimental results show that the phasic characteristics of energy conversion are obvious,which can be divided into three stages:initial energy accumulation stage,accelerated energy accumulation stage and fast energy dis- sipation stage. The proportion of energy dissipation of coal samples encounters the course from high to low again to high. The elastic energy has an opposite trend of change,the proportion of elastic energy drops or the proportion dissi- pated energy increases at the later stage of loading,the coal samples enter the accelerated failure stage. The energy dis- sipation and the energy release are closely related with the loading rate. With the increase of loading rate,the propor- tion of elastic energy increases before the peak stress,sample is damaged severely after the peak stress and its macro failure mode transits from shear tension and splitting failure to ejection failure. Because more energy is stored in the coal sample body in the form of elastic energy before the coal sample is destroyed,and more energy is released after the rock is destroyed,which makes the coal sample destroyed more severely. The phasic characteristics of fractal fea- tures of coal samples are obvious under cycling loading and unloading and the self-similarity characteristics are obvious within the range of threshold,the fractal dimension is between 2-3,which increases linearly with the loading rate. The fractal dimension of fragments increases with the increase of loading rate,and the higher the broken degree of coal samples,the smaller the proportion of large fragments. In this case,the higher of the broken level of more fragments and the smaller the mass of single fragments is,the greater the risk of dynamic disasters of coal samples.