基于塑性体积应变的岩石损伤变形特性实验研究

为分析岩石塑性变形与损伤的关系,在定义岩石的初始损伤和临界损伤,提出塑性体积应变分析方法,从而以塑性体积应变为损伤变量,采用归一化方法建立岩石的损伤本构模型。采用递增循环加载实验确定岩石损伤本构模型中的弹性卸载模量和弹性应变比例系数两个参数。通过实验和理论分析得出:当荷载较小时,普通单轴压缩状态下岩石损伤随荷载的增加具有减小趋势,荷载超过一定数值后,岩石损伤才开始增加;单轴递增循环压缩状态下当循环荷载大于约35%峰值强度后,卸载后岩石的损伤具有增加的趋势,小于该荷载之前具有减小的趋势。整个加载过程的理论应力-应变曲线能很好地与实验结果相吻合,在循环加载区间理论结果还能体现出岩石实验结果中的回滞环。

Experiment Study of Rock Damage Deformation Characteristics Based on Plastic Volumetric Strain Analysis

In order to analyze the relationship between rock plastic deformation and damage, rock initial damage and critical damage were defined, and plastic volumetric strain analysis method was put forward, then rock damage constructive model was set up based on normalization and plastic volumetric strain by way of damage variable. Uniaxial incremental circulating compression experiment was carried out to determine two parameters: elastic unloading modulus and elastic strain proportional coefficient. Experimental results and theory analysis show that first, when load is small and increasing, rock's damage is decreasing in general uniaxial compression condition; when load surpasses a certain number, rock's damage begins increasing; second, when cyclic load is higher than 35% peak strength, rock's damage presents increasing trend after unload; when the cyclic load is lower than 35% peak strength, rock's damage decreases after unload. Theoretical stress-strain curve accords with experimental results well in loading condition and theoretical curve can embody hysteretic loop of experiment results in cyclic loading region.