循环孔隙水压力作用下砂岩变形损伤的能量演化规律

摘要

On the view of energy, energy absorption and release of the deformation and damage process of sandstone are studied under cyclic loading of pore water pressure.The results show that plastic-loop is divided into four stages during a single cycle; and energy absorption and release is also divided into four stages.In loading, energy absorption per unit volume and energy release per unit volume decrease and gradually tend to stabilization with the increase number of cycles and the greater lower limit of pore water pressure, the greater energy absorption per unit volume and energy release per unit volume are.Axial effective stress of demarcation points of energy absorption and release increases with the increase number of cycles.In unloading, energy release per unit volume decrease with the increase number of cycles; while energy absorption per unit volume increase with the increase number of cycles and the greater lower limit of pore water pressure, the smaller energy absorption per unit volume is.Axial effective stress of demarcation points decreases with the increase number of cycles.Plastic energy per unit volume decreases with the increase number of cycles which means that the deformation and damage of rock decreases under a single cycle of rock pore water pressure.At the early stage of the loop, the greater lower limit of pore water pressure is, the smaller plastic energy per unit volume is.%从能量的角度出发,分析砂岩在循环孔隙水压力作用下的变形损伤过程,并探讨在这一变形损伤过程中的能量吸收与释放的演化规律,结果表明:单个循环过程中岩石的滞回曲线分为4个阶段,同时单个循环过程中能量吸收与释放也分为4个阶段.在加载段,单位体积吸收能和单位体积释放能均随着循环次数的增加而减小且逐渐趋向于稳定,孔隙水压力循环下限值越大,单位体积吸收能和单位体积释放能均越大;能量吸收与释放分界点对应的轴向有效应力随着循环次数的增大而增大.在卸载段,单位体积释放能随着循环次数的增大而减小,而单位体积吸收能随着循环次数的增加而增大且孔隙水压力循环下限值越大,单位体积吸收能越小;能量吸收和释放分界点对应的轴向有效应力随着循环次数变化有逐渐下降的趋势.单位体积塑性能随着循环次数的增加而逐渐减小,即随着循环次数的增加,岩石在单个循环孔隙水压力后的损伤变形逐渐减小;在循环初期阶段,孔隙水压力循环上限值相同的情况下,下限值越大,单位体积塑性能越小.