含水率对泥质粉砂岩强度损伤及声发射特征影响的研究

煤系沉积岩体原生及采动裂隙为水-岩作用提供了渗流通道，且受其组分和胶结类型等因素的影响，水作用下煤系沉积岩体力学性质改变显著。采用X射线衍射仪、无损浸水试验装置和煤岩力学性质测试系统，分析了泥质粉砂岩矿物组分，测试了其含水率随时间变化规律，并探讨了含水率影响下泥质粉砂岩强度损伤演化特征。研究结果表明:泥质粉砂岩中高岭石、伊利石和绿泥石等黏土矿物占矿物成分的62%;根据岩样含水率随浸水时间的变化趋势，将其划分为快速增长(0~25 h)、缓慢增长(25~85 h)及恒定(85 h~)3个阶段;由干燥到饱和，岩样的单轴抗压强度降低了47.72%，弹性模量降低了18.36%;随着含水率的增加，岩样破坏形式由剪切破坏逐渐向拉张破坏转化;应力、累计AE计数与时间变化关系曲线能阐明裂隙扩展的各个阶段，其中，裂隙不稳定扩展阶段和峰后阶段声发射活跃;除含水率1.6%的岩样外，声发射定位结果与岩样实际破坏迹线大致相符;加载初期，岩样内部在中心位置产生剪切裂隙并扩展，裂隙和能量逐渐向外围扩散，后期产生拉剪复合裂隙。研究成果对于煤矿地下水库坝体设计、富水巷道顶板岩层控制等工程中涉及的水岩作用问题研究提供了有益参考。

Experimental study on damage characteristics of siltstone under water action

The original interface and seepage channel of water rock interaction is provided by original and mining crack of rock in coal measure strata.Due to the mineral composition and cementation type and other factors,the mechanical properties of the rock in coal measure strata is changed significantly under the water action.The mineral compositions of pelitic siltstone,the moisture content of pelitic siltstone changes with soaking time and the evolution characteristics of strength damage of pelitic siltstone under the impact of moisture content were discussed by using X ray diffractometer,nondestructive immersion test equipment,mechanical properties and acoustic emission monitoring system.The results show that kaolinite,illite and chlorite constitute 62% of the mineral composition in pelitic siltstone.Rock samples are affected by water.With the change of time,the moisture content of rock samples is divided into three stages,including swift growth (0-25 h),slow growth (25-85 h) and constant stage (85 h-).From dry to saturated,the uniaxial compression strength of the rock sample is reduced by 47.72%,and the modulus of elasticity is reduced by 18.36%.With the increase of moisture content,the destructional forms of rock samples is gradually transformed from shear failure to tensile failure.Change relationship between stress and accumulated AE counts and time can elucidate the stages of crack development.Among these stages,acoustic emission signals of crack instability expansion stage and post peak are active.Except of rock whose moisture content is 1.6%,the result of acoustic emission localization is roughly consistent with the actual failure trace of rock samples.At the early stage of loading,shear cracks which are located inside the core appear and expanded.Crack and energy spread to the periphery.At the later stage of loading,tensile shear composite cracks occur.The research findings provide useful references to water rock interaction problem in engineering such as water conservation mining in coal mine,underground reservoir and water rich roadway.