渗流水压力分级加载岩石蠕变特性研究

采用RLW-2000M微机控制煤岩流变仪,以细粒砂岩为研究对象,对三轴压缩条件下岩石渗流水压力分级加载蠕变试验进行了蠕变特性研究。重点分析了渗流水压力分级加载时蠕变条件下岩石的应变、渗流体积(体积速率)演化曲线,同时对不同渗流水压力分级加载条件下的岩石蠕变与渗透系数演化曲线进行了分析和对比。试验结果表明:分级加载渗流水压力作用下细粒砂岩的蠕变曲线符合蠕变演化三阶段特征;随着渗流水压的逐级加载,瞬时轴向、横向应变和瞬时泊松比呈增大的趋势;随着应变的累积,横向应变量大于轴向应变量呈扩容效应,直至发生蠕变破坏;分级加载渗流水压力作用下渗流体积曲线呈线性演化。研究认为:渗透系数先瞬时减小后增大,初始渗透系数都具有记忆性,即岩石孔隙通道具有记忆特征,孔隙通道经过变形→闭合→冲蚀→形成新通道过程。

Experimental study on creep of rocks under step loading of seepage pressure

The creep and damage of fine sandstone rock under gradual loading of seepage stress are investigated through a series of triaxial compression tests using RLW-2000M coal and rock computer-controlled rheological testing machine. The volumetric strain and seepage volume (volume rate) evolution curves of rock creep under different seepage stresses are highlighted. In addition, the transformation curves of rock creep and permeability coefficient under different seepage stresses are analyzed and compared. The results show that the porosity evolution has agreement with three stages in typical creep process. As the gradual loading of seepage water pressure, the instantaneous axial and transverse strains as well as Poisson's ratio have an increasing trend. With the accumulated strain, the transverse strain is greater than the axial one in company with expansion effect until the occurrence of creep damage. The seepage volume curve is linearly evolved under the gradual loading of seepage water pressure. It is conclued that the permeability coefficient decreases firstly and then increases. The initial permeability has a memory (a memory of rock pore channels) that pore channels are formed through the process of deformation-closing-erosion-new channel.