循环加卸载下饱和类岩石材料能量演化和损伤特性分析

Energy Evolution and Damage Characteristics of Saturated Rock-Like Material Under Cyclic Loading and Unloading

为了研究循环荷载作用下饱水岩石的能量演化和损伤特性,利用水泥砂浆材料开展分等级循环加卸载试验和等荷载幅值循环加卸载试验,对比分析饱和类岩石材料在不同循环加卸载方式下的弹塑性应变、弹性模量、能量密度、损伤变量随循环次数的变化规律。结果表明:两种循环加卸载作用下,饱和类岩石材料的初始循环残余塑性应变均较大,分别占总残余塑性应变的61%和76%;分等级循环加卸载作用下,弹性模量随循环等级的升高先增大后逐渐减小,输入能密度和弹性能密度随循环等级的增加不断增大,耗散能密度先减小后逐渐增大,耗能比曲线呈现出"勺"形演化特征;等荷载幅值循环荷载作用下,弹性模量随循环次数先增大后缓慢降低,3种能量密度在损伤稳定发展阶段基本保持定值,材料破坏阶段耗能比迅速增大;基于耗散能定义的损伤变量,分等级循环荷载作用下,随循环等级的增加损伤变量变化曲线呈"上凹"形上升;等荷载幅值循环荷载作用下,损伤变量随循环次数的增加呈线性增长,且累积总应变能是分等级循环加卸载的34.5倍,损伤破坏程度更大。

In order to study the energy evolution and damage characteristics of saturated rock under cyclic loading, graded cyclic loading and unloading tests and equal amplitude cyclic loading and unloading tests were carried out with cement mortar materials. The change laws of strain characteristics, elastic modulus, energy density and damage variables of saturated rock-like material under different cyclic loading and unloading methods were compared and analyzed. The results show that the initial cyclic residual plastic strain of saturated rock-like material is large under the two cyclic loading and unloading, accounting for 61% and 76% of the total residual plastic strain respectively. Under graded cyclic loading and unloading, the elastic modulus first increases and then decreases with the increase of cyclic grade, the input energy density and elastic energy density increase with the increase of cyclic grade, the dissipative energy density first decreases and then increases, and the energy consumption ratio presents a spoon shape. Under the equal amplitude cyclic loading, the elastic modulus first increases and then decreases slowly with the number of cycles. The three energy densities basically maintain constant values in the stage of damage stable development, and the energy consumption ratio increases rapidly in the stage of material failure. Based on the damage variable defined by dissipative energy, under the action of graded cyclic loading, the change curve of damage variable increases in a concave shape with the increase of cyclic level. Under equal amplitude cyclic loading, the damage variable increases linearly with the increase of the number of cycles, and the cumulative total strain energy is 34.5 times higher than that under graded cyclic loading and unloading, with a more sufficient damage degree.