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岩石材料的蠕变具有明显的非线性特征,在蠕变模型中考虑蠕变参数随应力、时间等因素而变化是解决非线性蠕变问题的方法之一。试验已经证实,应力、时间及渗流等外部条件会引起岩石某些力学参数的改变,因此,将蠕变参数视为变量符合岩石材料的本质属性。以西原蠕变模型为基础,研究了各蠕变参数与应力及时间的关系。根据试验结果,通过非线性最小二乘法从蠕变试验数据中求出不同应力作用下不同时刻的各个蠕变参数,再根据参数随应力、时间的分布规律经非线性拟合得到各蠕变参数与应力及时间的表达式,进而可得到变参数的蠕变方程。蠕变参数的变化是岩石非线性特征的充分体现,从损伤力学的角度来讲,蠕变参数的变化反映了岩石内部损伤不断加剧、累积,材料特性不断劣化的演变过程。
The creep of rock material has the obvious non-linear characteristic. It is one of the methods to solve the nonlinear creep problem that considering the variation of creep parameters with the stress and time in the creep model. Experiments have confirmed that external conditions such as stress, time and seepage can cause changes in some of the rock’s mechanical parameters. Therefore, considering creep parameters as variables complies with the essential properties of rock materials. Based on the original creep model of West China, the relationship between each creep parameter and stress and time is studied. According to the test results, various creep parameters at different moments under different stresses are obtained from the creep test data by non-linear least square method, and then each creep parameter is obtained through non-linear fitting according to the distribution law of stress and time And stress and time expressions, and then get variable parameters of the creep equation. The change of creep parameters is a sufficient manifestation of the nonlinear characteristics of rock. From the point of view of damage mechanics, the change of creep parameters reflects the evolution of the damage, accumulation and material properties of the rock.