真三轴应力条件下破断煤体力学响应及渗流特性试验研究

Experimental study on mechanical response and seepage characteristics of broken coal under true triaxial stress conditions

为探究煤炭深部开采过程中破断区域煤体的力学及渗流特性,利用多功能真三轴流固耦合试验系统,结合计算机断层扫描(CT)技术分析破断煤体破坏后的内部裂隙分布情况,获得不同中间主应力下破断煤体的强度特征、渗透率演化及破坏模式。研究结果表明:真三轴应力条件下破断煤体呈现出脆-延性破坏特征,随着中间主应力的增大,峰值强度呈现先增大后减小的变化趋势;破断煤体的渗透率在临近破坏前并未出现大幅增长,在进入峰后阶段总体呈下降趋势,且在峰前阶段变化更为明显;破断煤体破坏后的裂隙形式以剪切裂隙为主,宏观剪切破裂面呈现非对称分布特征。应根据现场煤层破断区域构造应力和裂隙结构的变化,调整煤层破断区域瓦斯抽采或破碎煤岩巷道注浆加固方案,保障深部煤炭安全开采。

In order to investigate the mechanical response and seepage characteristics of coal in broken areas during deep underground coal mining,the multi-functional true triaxial fluid-solid coupling apparatus was used.The distribution of internal fractures of broken coal after failure was detected and analyzed by using the computed tomography(CT)scanning system.The strength characteristics,permeability evolution,and failure modes of broken coal under different intermediate principal stresses were obtained.The research results show that broken coal presents brittle-ductile failure characteristics under true triaxial stress conditions,and the peak strength shows an ascending-then-descending trend with the increase of intermediate principal stresses.The permeability of the broken coal body does not increase significantly before failure and continues to decrease at the post-peak stage.Furthermore,the permeability varies more at the pre-peak stage.The macro-fracture forms of broken coal after failure are mainly shear fractures,and the macro-shear failure plane presents asymmetrical distribution characteristics.In order to ensure the safe mining of deep coal,attention should be paid to the change of tectonic stress and fracture structure in the broken coal seam area on site,and the gas drainage in the broken coal seam area or the grouting reinforcement scheme for the broken coal rock roadway should be adjusted.