脉动孔隙水压下低透性松软煤岩损伤变形的实验分析

Experimental analysis of damage deformation of low permeability and soft coal under pulsating water pressure

为了研究脉动水压作用下低透气性松软煤岩损伤变形特征,采用RLW-2000M微机控制煤岩流变仪对标准原煤样进行了不同上限水压实验。结果表明:在脉动水压作用下,煤样疲劳破坏应变曲线具有三阶段特征:压密耦合阶段应变曲线在初期循环加、卸载过程中将产生较大变形,不容易形成滞回环曲线;弹性耦合阶段应变曲线呈现出稳定的滞回环曲线进行变化;屈服变形阶段经历几次较大的变形以后,煤样将产生疲劳破坏。采用能量耗散的观点对弹性耦合阶段的变形状态进行了判定,判定结果表明该阶段煤体单元在脉动水压的每次循环作用下都将产生一定的塑形变形和损伤。最后基于Logistic方程建立了煤岩损伤破坏数学模型,并采用最小二乘法进行拟合分析确定了未知参数。

In order to study damage deformation of low permeability and soft coal under pulsating water pressure, the experiment of different maximal pulsating water pressure acting on standard raw coal was done by using the RLW- 2000M coal rheometer controlled by microcomputer. The results show that the strain curve can be characterized by three phases when the samples are damaged by pulsating pore-pressure. In the initial stage, that is compaction couplingphase, the strain curve will generate large deformation in the process of loading and unloading, so the hysteresis loop curve will not be formed. In the elastic coupling phase, the strain curve demonstrats a stable hysteresis loop curve. In the yield deformation phase, coal will generate fatigue failure after several large deformation. The deformation state of elastic coupling phase was determined by using energy dissipation, and the results show that the coal unit producesplastic deformation and damage after a cycle of pulsating water pressure. At last, on the basis of Logistic equation, the mathematical model of coal damage was established and the unknown parameters were calculated by fitting analysis.