脉动孔隙水压下三轴加压对煤岩损伤变形的影响  

Effect of triaxial compression on damage deformation of coal rock under pulsed pore water pressure

作　　者：朱红青[1,2] 张民波[2,3] 朱帅虎[2] 顾北方 申翔[2] 

机构地区：[1]中国矿业大学(北京)煤炭资源与安全开采国家重点实验室,北京100083 [2]中国矿业大学(北京)资源与安全工程学院,北京100083 [3]武汉工程大学资源与土木工程学院,湖北武汉430073

出　　处：《岩土力学》2015年第8期2137-2143,共7页Rock and Soil Mechanics

基　　金：国家自然科学基金重点资助项目(No.U126214)

摘　　要：为研究脉动孔隙水压作用下低透性松软煤岩在不同三轴加压条件下的损伤变形规律,采用RLW-2000M煤岩流变仪进行了不同轴压和围压系列下的试验研究。结果表明:煤岩破坏的应变曲线具有先疏后密再疏的变化规律,且累积应变和残余应变随着围压的增加而减小,而随着轴压的增加而增大;平均单次耗散能随着围压的增加而减小,随着轴压的增加而增加,其关系符合指数函数变化特征;采用累积耗散能计算了煤岩破坏过程中的损伤变化特征,并采用Logistic方程逆函数对其进行了拟合分析,得到了煤岩损伤演化模型,为预测煤岩破坏周期提供了依据。研究结果为具有不同地应力条件下的低透气性松软煤层施工脉动水力压裂提供了一定的理论依据。To study damage deformation behaviour of low permeability soft coal rock subjected to the triaxial compression and pulsed pore water pressures, a series of experiments is conducted under different axial compressions and confining pressures using the RLW-2000 coal/rock rheometer. The results show that the general trend of stress-strain curve exhibits characteristically from sparse to dense and then back to sparse. In addition, both the cumulative and residual strains decrease with increasing confining pressure, however it is opposite with the increase of axial pressure. Meanwhile, the average dissipated energy of a cycle declines with the increase of confining pressure when the axial pressure is constant, but it increases with the increase of axial pressure when the confining pressure is constant. Moreover, the relationship between the average dissipated energy of a cycle and the confining pressure or axial pressure fits the exponential function. Finally, the overall trend of damage in the process of coal failure is calculated on the basis of the relationship between accumulated energy dissipation and damage, and the inverse function of Logistic equation is applied to fit the damage trend. Then the damage evolution model is obtained, which provides the basis for predicting the damage cycle of coal. The present results provide a theoretical evidence for the pulsed hydraulic fracturing on the low permeability soft coal seams under different ground stresses.

关 键 词：脉动孔隙水压 轴压 围压 残余应变 能量耗散 损伤 

分 类 号：TU457[建筑科学—岩土工程]