岩石非线性蠕变损伤模型研究

Nonlinear Creep Damage Constitutive Model of Rock

对岩石蠕变3个阶段各自的力学状态特征进行分析,认为岩石处于衰减和稳态蠕变阶段时存在非线性硬化现象,此时可以认为岩石内部不产生损伤或者是损伤程度十分微小可以忽略不计;当岩石处于加速蠕变阶段时,岩石内部的损伤不断产生并加剧,呈现出较为明显的非线性特征;将一个非线性硬化函数和损伤演化方程引入到Maxwell蠕变模型中去,使其可以较好地描述蠕变的3个阶段.对向家坝水电站右岸地下厂房工程区的砂岩进行了三轴蠕变力学试验,依据典型的岩石全程蠕变试验曲线数据,对所提出的岩石非线性蠕变损伤模型进行了辨识,辨识的蠕变模型和试验结果具有较好的一致性.

Three stages of mechanical creep in rock were studied. There is nonlinear hardening during primary and steady-state creep. During these stages intrinsic damage to the rock is immaterial and may be neglected. During accelerated creep intrinsic damage becomes continuous and exacerbates the nonlinear characteristic of the response. The intrinsic damage to the rock is assumed to be exponential in time and stress level during accelerated creep. A damage evolution equation is proposed. Nonlinear hardening and damage are introduced into the Maxwell constitutive creep model. This proposed model can better describe the three typical stages of nonlinear creep in rock. Creep experiments were preformed on sandstone taken from the right bank, underground powerhouse of the Xiangjiaba hydro-power project. A servo-controlled theology testing machine was used for these tests, which determined the tri-axial accelerated creep curves of the rock. Creep parameters for the proposed model are identified from the data. The fit model agrees well with the test creeo data.