基于改进双剪统一强度理论的围岩松动圈分析

为了研究岩石应变软化、剪胀性质、中间主应力和拉压不等特性对围岩松动圈的影响,基于改进双剪统一强度理论,得到了隧道围岩松动圈半径、围岩应力及洞壁位移的解析表达式。通过与已有方法计算结果的对比,验证了该方法的可行性,并进一步分析了中间主应力大小以及软化程度对结果的影响。研究结果表明:(1)随着软化模量的降低,隧道围岩塑性区、松动区(圈)半径以及洞壁位移均逐渐减小;(2)中间主应力大小对隧道围岩弹塑性行为具有一定的影响,随着中间主应力系数b的增大,围岩的切向应力在塑性软化区、破碎区内变大,而在弹性区内减小,围岩的径向应力在3个区域内均增大;(3)隧道洞壁位移随着中间主应力系数b的增大而减小;(4)考虑中间主应力的影响以及围岩软化的程度,能够充分发挥围岩的强度潜能,合理指导隧道布置、支护设计与施工。该结果为隧道围岩松动破裂分析提供了理论依据,具有一定的工程参考价值。

Analysis on Loosen Zone of Surrounding Rock Based on Improved Double-shear Unified Strength Criterion

In order to study the influence of rock strain softening, expansion properties, intermediate principal stress and varying characteristics of tension and compression on the fractured surrounding rock, based on the improved double-shear unified strength criterion, this paper obtains an analytical solution for the radius of loosen zone, surrounding rock stress and surrounding displacements of a circular opening. The method is proved to be feasible by comparing the results with the existing methods, furthermore, the effect of intermediate principal stress and softening extent on the results is analyzed. The results show that: (1) with the reduction of the softening modulus, the radius of plastic zone, loosen zone(circle) and the displacement of tunnel wall decrease; (2) the intermediate principal stress has a certain influence on the elastoplastic behavior of the surrounding rock, with the increase of the intermediate principal stress coefficient b, tangential stress of surrounding rock increases gradually in plastic softening zone and loosen zone, but decreases in elastic zone, and radial stress of surrounding rock increases in three zones; (3) the displacement of tunnel wall decreases with the increase of the intermediate principal stress coefficient b; (4) the strength potential of surrounding rock can be fully realized after considering the effects of the intermediate principal stress and softening degree of surrounding rock, that we can provide reasonable suggestions for design and construction of tunnel supporting structure. The results provide theoretical basis for analysis of fractured circular openings and have a certain reference value in engineering projects.