应力释放法在隧洞开挖模拟中若干问题的研究

Study of some problems about application of stress release method to tunnel excavation simulation

根据快速拉格朗日法的基本原理,讨论了在其中实现应力释放法的理论根据。通过不同侧压系数下脆性岩体中圆形隧洞开挖卸荷过程的应力释放法模拟和真三维模拟,分别讨论了应力路径问题、模拟空间效应时最终计算结果的准确性及其工程应用问题。在未包含断层、软弱带等特殊地质条件的情况下,分析得到以下结论:(1)应力释放法模拟中,围岩经历的应力路径与真三维模拟不同,故只能用前者来近似模拟开挖问题;(2)不同的应力路径将导致不同的最终结果,在一定的近似程度要求及计算工作条件下应力释放法模拟的最终结果可近似真三维的模拟结果,且对于圆形隧洞问题,当侧压系数从1.0开始增大或减小时,这种近似误差将减小,并最终趋于稳定;(3)在工程应用中,由应力释放法可得到收敛约束法中的GRC曲线,从而使得它在工程应用中发挥重要的作用。

Based on the theory of fast Lagrangian analysis of continua, the theoretical basis of the stress release method is discussed. Through the analysis of a case in which the excavating and unloading process of a circular tunnel is simulated by using the stress release method and the three-dimensional simulating method respectively; the problems including the differences of stress paths, the accuracy of the calculating results and the applicability of the stress release method are discussed. Firstly, the results indicate that the stress paths are different in these two methods. So, the stress release method can simulate the excavation in tunnel engineering only in some limitation. Secondly, as to the material with the nonlinear mechanical property, the different stress paths induce the different results. But, the results from the two methods are equal approximately if the required conditions are satisfied and the error magnitude will decrease with the increase or decrease of the confining-pressure coefficient from 1.0. Finally, GRC in the convergence-confinement method can be obtained simply through the stress release method; and it indicates the importance of this method in the corresponding application.