软弱破碎围岩隧道炭质页岩蠕变特性试验研究

采集贵广铁路天平山隧道典型软弱破碎围岩岩样，在室内开展三轴常规压缩和三轴压缩蠕变试验。基于岩石试验成果，分析炭质页岩的蠕变力学特性，低应力水平条件下岩石仅出现减速蠕变和等速蠕变阶段，在更高的应力水平条件下，岩石并未出现加速蠕变的现象，但围压在一定程度上提高岩石的屈服强度，弹性模量亦有随着围压增加而增大的趋势。据此，建立依托工程炭质页岩蠕变全过程的黏弹塑性应变软化蠕变力学模型，推导该蠕变力学模型在三维应力状态下的本构方程，并确定模型的参数，运用最小二乘法对模型的参数进行辨识。通过与试验曲线对比显示，所建蠕变模型能够描述依托工程炭质页岩的蠕变力学特征，可以用来研究该隧道软弱破碎围岩的蠕变性质和稳定性。

Experimental study of carbonaceous shale creep characters of weak broken surrounding rock tunnel

Typical rock samples of weak broken surrounding rock are collected from Tianpingshan Tunnel for Guiyang-Guangzhou railway. The conventional triaxial compression and triaxial compression creep tests are also carried out in the test room. Based on the results of rock tests, the creep characters of carbonaceous shale are studied. Only decelerating and steady creep stages appear under a low stress level. In the higher stress level, accelerating creep doesn’t appear. However, increasing confining pressure has raised the yield strength of the rock to some extent; and the elastic modulus also tends to increase. According to these, the viscoelastic plasticity strain softening creep model of the carbonaceous shale with whole creep process is established; and the constitutive function of this model is deduced under three dimensional stresses with its parameters confirmed. The creep parameters are identified by least square method. The comparison between creep model and test curve shows that the proposed creep model can reflect the creep characters of carbonaceous shale in background project; and it can be used to study the creep properties and stability of weak broken surrounding rock of this tunnel.