考虑残余应力的砂岩损伤理论模型

Damage constitutive relation of sandstone considering residual stress

采用自行研制的重力恒载蠕变渗流实验系统开展了砂岩恒定围压下的循环加载试验,得到不同围压下砂岩的应力应变过程。考虑岩样加载过程中的非线性变形特性,假定了轴向应力是轴向应变和球形应力函数;利用热力学基本原理,分析岩样损伤演化过程中能量耗散及转化关系;将受载岩样应力分为有效弹性部分和损伤部分,弹性部分受载损伤演化,损伤部分最终演化为残余应力;基于损伤力学基本原理,理论推导建立了三轴压缩情况下考虑残余应力的砂岩损伤本构关系,并对理论模型进行实验验证。研究结果表明所建立的损伤本构模型能很好地反映岩石受载损伤全应力应变过程,也能反映出围压对岩石损伤能量耗散的影响规律,随着围压的增大,砂岩需要损伤演化消耗的机械能也越大。

Applying the CSCG-160 creep-seepage testing system which designed and manufactured by CUMTB, the experiments of sandstone with loading-unloading test under constant confining pressure were conducted, and the strain-stress curves under different confining pressures were obtained. Taking the nonlinear deformation properties of rock into consideration, a hypothesis that axial stress is function of axial train and spherical stress was put forward. Based on the principle of thermodynamics, the energy dissipation and conversion during the damage process of sandstone under different load conditions was analyzed. Divided the stress of sandstone damage with load increase into two parts, one is the equivalent elastic part, and the other is damage part. The equivalent elastic part will damage with outside load, and the damage part will finally be the residual stress. According to the above two hypothesizes and using the basic theory of damage mechanics, a damage constitutive relationship of sand stone under triaxial compression was established theoretically, and the curves of theoretical fitting and experimental results were compared. The results indicate that the damage constitutive can describe the whole stress-strain process of sandstone under triaxial compression, and damage dissipation energy rate will be affected by confining pressure. With the increase of confining pressure, the damage dissipation energy rate increases. © 2015, China Coal Society. All right reserved.