基于Hoek-Brown准则的隧道围岩屈服接近度分析

为了建立Hoek-Brown准则围岩稳定性评判标准,通过理论分析,推导了Hoek-Brown准则和Mohr-Coulomb准则的关系以及Hoek-Brown准则参数表征的屈服接近度(YAI)函数;通过FLAC3D建立隧道三维数值模型,编制相应Hoek-Brown屈服接近度YAIhb的程序,分析了材料参数和应力变化的影响.结果表明:①自编程序计算的YAIhb=1区域与FLAC3D计算的塑性区分布范围相同,验证了程序的正确性,并且屈服接近度能够表征各单元的屈服程度,优于塑性区判定标准.②随着地质强度指标GSI的增大,YAIhb逐渐减小,两者之间的关系采用3次多项式进行拟合的精度较高;YAIhb随岩石单轴压缩强度σci的增大而减小,采用指数方程对两者的关系进行拟合,能得到较高的相关系数;随着单元损伤的加剧,其屈服接近度逐渐增大,表征单元破坏程度增大,YAIhb和岩体损伤指标D之间符合双曲线分布规律.③最大主应力σ1增大引起YAIhb减小,两者表现出显著的线性关系;中间主应力σ2增大引起YAIhb呈现先增大后减小的趋势,可用3次多项式曲线对其关系进行拟合;YAIhb随着最小主应力σ3的增大而线性增大.

Yielding approach index for surrounding rock mass of tunnel based on Hoek-Brown criterion

In order to build an assessment standard for surrounding rock mass with the Hoek-Brown criterion, firstly, the relationship between Hoek-Brown criterion and Mohr-Coulomb criterion is theoretically analyzed; the yielding approach index (YAI) described by Hoek-Brown criterion parameters is obtained; secondly, the three dimensional calculation for tunnel is founded by FLAC3D, the program of yielding approach index for Hoek-Brown criterion (YAIhb) is compiled; the impacts of material parameters and stress variation to the YAIhb are analyzed, which show that: (1) the areas of YAIhb=1 calculated by the self-compiled program are the same with the plastic areas calculated by FLAC3D, which validates the correction of the self-compile program, and moreover the YAIhb can reflect the yield degree of each element which is superior to the plastic zone distribution standard; (2) with the increase of geological strength index GSI, YAIhb reduces gradually, and the relationship between GSI and YAIhb can be described precisely by the cubic-polynomial equation; with the increase of rock uniaxial strength σci, YAIhb increases gradually in the exponential form; with the damage of element increase, the YAIhb increases gradually, which shows the failure degree of element increases, the relationship between YAIhb and damage index D is in accordance with the hyperbola principle; (3) the increase of maximum principal stress σ1 will lead to the decrease of YAIhb, and their relationship is in accordance with the linear principle; the increase of intermediate principal stress σ2 will lead to the variation of YAIhb in the form of first increase then decrease; and their relationship in accordance with the cubic-polynomial principle; YAIhb increases linearly with the increase of minimum principal stress σ3.