岩石试件非线性黏弹塑性蠕变模型分析

Analysis of Nonlinear Visco-elastic-plastic Creep Model for Rock Specimen

建立了非线性黏弹塑性蠕变模型,并建立了模型的本构方程。通过引入岩石的流变指数建立的非线性黏弹塑性蠕变模型,较好地反映了岩石试件的3阶段蠕变过程,充分描述岩石加速蠕变特性;同时,得出岩石试件在恒应力状态下的蠕变变形、蠕变速率和蠕变加速度的解析表达式。通过分析得到:岩石试件在恒应力下,岩石试件在经过一定时间后进入加速蠕变阶段,这一时间的长短与岩石试件的力学性质有关,特别与岩石的流变指数有很大的关系;岩石的流变指数是岩石的一个重要指标,它对岩石蠕变增长快慢程度有着重要的影响,岩石的流变指数越大,岩石越容易进入流变加速阶段,越容易失稳。

This paper constructs a nonlinear visco-elastic-plastic creep model and its constitutive model. By introducing rock rheologic index, this creep model demonstrates 3 phrases of rock creep process and states accelerated creep characteristic. It also presents analytic expressions of creep deformation, creep rate and creep acceleration under invariable stress state. Analysis resuhs are shown as follows. Under constant stress, rock specimen begins to accelerate creep after period of time and this duration depends on mechanics properties of rock specimen, especially on rhologic index. Rhologic index is an important parameter of rock and significantly influences creep increment speed. The bigger rhologic index is, the more easily rock starts creep and instability.