针对受载煤体卸压过程裂隙发育数据难以捕捉的现状，设计了受载煤体伪三轴瓦斯渗流实验，完成了受载煤体加载和卸载过程的应力-应变-渗透率动态监测。同时基于能量守恒定理，开展了卸载过程中不同卸载速率下的能量分配比较，阐释了卸载速率对裂隙发育和渗透率变化的控制作用，并通过煤样裂隙监测数据对比予以验证。研究结果显示，卸载过程中的煤体裂隙结构受卸载速率影响，围压卸载速率越高，I类和II类裂隙越发育(所占比率增高)，I类裂隙数量较原始数量增幅甚至超过1倍，II类裂隙数量提高74.13%;在卸载过程中渗透率曲线整体可分为3段:线性段、抛物线段和稳定段，而决定其3段曲线分布的关键因素是煤体弹性模量大小、加载强度和卸载速率;随着卸载速率的提高，煤体渗透率加大，线性段斜率和抛物线段曲率半径逐步增加，线性段斜率由0.054 8逐步升高至0.091 9，0.138 8和0.216 4，抛物线曲率半径逐步增大，顶点曲率半径分别达到1.232，1.334，1.863和2.014，渗透率稳定的应力临界点不断减小，由15.26 MPa降低至14.08，13.14和10.88 MPa;煤体渗透率的变化可以通过裂隙长度增量进行量化表征，相同实验条件下，渗透率增量与裂隙长度增量之间呈线性关系;统计数据显示，围压卸载速率越高，弹性能转化率越低，裂隙发育能耗越高，高速卸载(加卸比1∶8)可使煤体破裂能耗超过80%，而低速卸载(加卸比1∶1)的裂隙能耗仅有25.62%;比较研究发现，高速卸载过程中煤体能量释放的主体引发原有裂隙扩展，而不是导致新裂隙的萌生，裂隙发育能耗与卸载速率之间呈对数关系。

In view of the fact that the fracture development data in the unloading process of the loaded coal body was difficult to capture,a pseudo threeaxis seepage experiment was designed to complete the dynamic monitoring of stress-strain-permeability in the loading and unloading process of the loaded coal body.At the same time,based on the conservation of energy,the energy distribution states at different unloading rates during the unloading process were compared,and the effect of unloading rate on fracture development and permeability evolution was explained,and verified by coal sample fracture monitoring and comparison data.The results showed that the fracture structure was affected by unloading rates.The higher the unloading rate of confining pressure was,the more Class I and Class II fractures were developed (the ratio increased).Compared with the original number,the number of Class I fractures increased even more than one time,and the number of Class II fractures increased by 74.13%.During unloading,the permeability curve can be divided into three sections:linear section,parabolic section and stable section,and the distribution characteristics of those three curves were determined by the elastic modulus,loading strength and unloading rate of experimental coal samples.With the increase of unloading rate,coal permeability enhanced,the slope of linear section and curvature radius of parabolic section increased gradually,the slope of the linear segment gradually increased from 0.054 8 to 0.091 9,0.138 8 and 0.216 4,and the radius of curvature of apexes reached 1.232,1.334,1.863 and 2014,respectively.With the increase of unloading rate,the critical stress point of permeability stability decreased from 15.26 MPa to 14.08,13.14 and 10.88 MPa.Under the same experimental conditions,there was a linear relationship between the increment of permeability and the increment of fracture length.The statistical data showed that the higher the confining pressure unloading rate was,the lower the elastic energy conversion rate was,and the higher the energy consumption of fracture development was.The fracture energy consumption of high speed unloading (loading unloading ratio 1∶8) was more than 80%,while that of low speed unloading (loading unloading ratio 1∶1) was only 25.62%.According to comparative studies,it was found that the main body of energy release of coal body was consumed by the expansion events of original fracture group,rather than the initiation of new fracture group during coal mass high speed unloading,and there was a logarithmic relationship between energy consumption for fracture development and unloading rate,which provided data support for the quantitative study on energy consumption and fractures growth

1 受载煤体卸压损伤的力-能关系

2 受载煤体卸压实验测试

   2.1 实验煤样基本参数测试

   2.2 煤样受载测试

3 结果分析

   3.1 煤体应变比较与分析

   3.2 煤体渗透率比较与分析

   3.3 实验煤体前后裂隙结构比较

   3.4 煤体裂隙结构变化的能耗表征

4 结论