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蠕变和应力松弛是岩石材料固有的时效特性,与岩石工程的长期稳定性密切相关。基于Rice不可逆内变量热力学理论对岩石蠕变和松弛本质上的一致性问题进行研究。给定余能密度函数和内变量演化方程建立基本热力学方程,通过不同约束条件构建黏弹–黏塑性蠕变和应力松弛本构方程。黏弹性本构方程具有普遍性,能包含经典元件组合模型的黏弹性本构方程;黏塑性本构方程考虑材料变形过程中的硬化效应,更加符合实际情况。蠕变和松弛是岩石材料在不同约束下的外在表现,但两者具有相同的非平衡演化规律,本质上具有一致性。蠕变与应力松弛本构方程基于相同的基本热力学方程,可以相互转化,且方程参数相同,因此可以通过蠕变方程和蠕变试验结果对材料的松弛特性进行分析。最后通过模型相似材料单轴蠕变加卸载试验和应力松弛试验对这一思想进行验证。
Creep and stress relaxation are inherent aging properties of rock materials and are closely related to the long-term stability of rock engineering. Based on Rice’s theory of irreversible internal variables thermodynamics, the inherent consistency of rock creep and relaxation is studied. Given the residual energy density function and the internal variable evolution equation, the basic thermodynamic equations are established, and the viscoelastic-viscoplastic creep and stress relaxation constitutive equations are constructed by different constraints. The viscoelastic constitutive equation is universal and can contain the viscoelastic constitutive equations of the classical component model. The viscoelastic constitutive equation considers the hardening effect in the material deformation process, which is more in line with the actual situation. Creep and relaxation are the external manifestations of rock materials under different constraints, but the two have the same non-equilibrium evolution law and are inherently consistent. Creep and Stress Relaxation The constitutive equations can be transformed into each other based on the same basic thermodynamic equations, and the parameters of the equations are the same. Therefore, the relaxation characteristics of the material can be analyzed by creep equation and creep test results. Finally, this idea is verified by uniaxial creep loading-unloading test and stress relaxation test of model similar materials.