SOLUTION AND ANALYSIS OF CIRCULAR TUNNEL FOR THE STRAIN-SOFTENING ROCK MASSES CONSIDERING THE AXIAL IN SITU STRESS AND SEEPAGE FORCE
摘要: 为了研究轴向应力和渗透力共同作用下软化围岩的应力与位移的变化及分布规律. 基于摩尔-库伦屈服准则及应力-应变软化模型并考虑轴向应力和渗透力的共同作用，将整个塑性区分为有限个同心圆环，以弹塑性交界面处的应力、应变为初始值，并采用微小径向应力增量逐步求出各个圆环上的应力应变及塑性区半径，据此重构了考虑渗透力和轴向力共同作用下软化围岩应力应变特性的逐步求解方法. 利用该方法，推导出软化围岩应力应变的解. 计算结果表明：在考虑轴向应力作用下，塑性区半径和隧道围岩位移都随着渗透力的增加而有所减小；当轴向应力为最小主应力时，渗透力的影响更为显著. 这说明渗透力的存在对于隧道围岩的应力应变分布以及塑性半径和围岩的位移有不可忽略的影响.Abstract: This paper presents an analysis for the distributions of stresses and displacements considering the effect of seepage force and the axial in-situ stress for strain-softening rock masses by using Mohr-Coulomb yield criterion. The plastic region is divided into a finite number of concentric rings. Using the stress and strain of the elastic portion of elastic-plastic interface as the initial value and the known differential increments of radial stress, the stress-strain increment can be obtained. Then, the stress and strain on each ring can be reduced. The displacement and plastic radius of surrounding rock can be gained. The derivations of the stress, strain and displacement solutions in strain-softening rock masses considering the influence of the axial in-situ stress and seepage force can be obtained by the use of reconstructed step-by-step solution. The theoretical results can be simplified into Wang's theory as well. The results calculated and analyzed by the approach of Matlab programming showed that the present theory developed in this paper is correct. This study found that the plastic radius and displacement of tunnel wall decrease while seepage force increases with the axial in-situ stress. And when the axial in-situ stress is the minor principal stress, the influence of seepage force is much more apparent. It can be found that the displacement of tunnel wall, the plastic radius and the distribution of stresses and strains are influenced by the consideration of seepage force.
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