冻结红层软岩的蠕变特性研究

为研究第三系红层软岩在低温下的蠕变特性。对冻结红层进行单轴蠕变试验，试验结果表明，在应力水平较低时，软岩只存在衰减蠕变，随着应力水平的增大，当超过流变长期强度时，出现了非稳定蠕变；同时，随着温度的降低，软岩的瞬时应变量和蠕变量都会明显减少，而长期强度则有较大幅度的增长，说明温度对软岩及冻结壁的流变性质影响十分显著。引入与时间和应力相关的非线性黏滞系数和时间开关函数，对西原模型进行改进，得到了可以描述加速蠕变的非线性流变本构模型，通过试验数据对冻结红层软岩的参数进行了辨识。将流变模型嵌入到abaqus有限元程序，并对井筒开挖进行数值模拟，获得冻结壁最大位移与时间曲线，通过与实测值进行比较，两者较为吻合。可见，建立的流变模型能够很好的描述冻结红层软岩的蠕变规律。

Research on the Creep Characteristics of Frozen Red- Bed Soft Rock

In order to investigate the creep characteristics of the red - bed soft rock of Tertiary at low tempera- ture, uniaxial creep tests were conducted. The tests results showed that only the attenuation creep can exist un- der low stress, and the instable creep appears when the stress exceeds the rheological long - term strength. At the same time, with the temperature reducing, the instantaneous strain and creep deformation of soft rock de- crease apparently, while there is a substantial increase of the long - term strength. It shows that the influence of temperature on the rheological property of soft rock and frozen wall is very significant. Nonlinear viscosity coeffi- cient related to the time and stress and the time switching function were introduced to improve the Nishihara mod- el, and the nonlinear rheological constitutive model which describes accelerating creep was obtained. The param- eters of frozen red - bed soft rock were identified by the tests data. Shaft excavation was simulated with introduc- tion of the model into ABAQUS finite element program, and the curve of maximum displacement of frozen wall with time was obtained. At last the comparison between the numerical solution and the measured value was con- ducted and the results are consistent relatively. The rheological constitutive model can establish a good descrip- tion of the Creep law of red - bed soft rock.