空间随机性围岩隧道纵向差异变形设计值确定

隧道沿纵向的差异变形是引发衬砌破损和开裂渗漏病害的主要原因之一,而围岩空间分布的变异性则是隧道纵向差异变形预测不准的主要因素。本文根据围岩弹性模量空间变异性的随机分布统计规律特征,选择截断式正态分布进行拟合,建立了考虑围岩空间随机分布的三维随机有限元数值模拟方法,对隧道纵向差异变形进行预测,并引入可靠度理论,提出隧道纵向差异变形的概率可靠度设计值确定方法。通过案例分析发现:围岩弹性模量空间随机性与纵向差异变形值有明显的正相关性,围岩弹性模量空间随机统计函数的变异系数越大,差异变形量就越大,采用传统均匀法计算的误差就越大;差异位移值可近似分为近指数型离散阶段、波动性离散阶段、非线性离散阶段、单一化线性离散阶段4个阶段,其对应的临界变异系数分别为15.94%、23.02%、56.30%。

Method for Determining Design Value of Tunnel Longitudinal Differential Deformation Considering Spatial Variability of Surrounding Rock

The longitudinal differential deformation of tunnel is one of the main causes of lining damage, cracking and leakage, and the variability of surrounding rock spatial distribution is the main factor of inaccurate prediction of longitudinal differential deformation of tunnel. Therefore, according to the statistical characteristics of random distribution of surrounding rock elastic modulus spatial variability, the truncated normal distribution is selected for fitting, three-dimensional stochastic finite element numerical simulation method considering the spatial random distribution of surrounding rock is established to predict the longitudinal differential deformation and the reliability theory is introduced to determine the design value of probabilistic reliability of longitudinal differential deformation of tunnel. Through case analysis, it shows that: the spatial randomness of elastic modulus of surrounding rock has obvious positive correlation with the longitudinal differential deformation value. The larger the coefficient of variation of the spatial random statistical function of elastic modulus of surrounding rock is, the larger the differential deformation is, the larger the error of traditional uniform method is. The differential deformation can be approximately divided into near exponential discrete stage, fluctuating discrete stage, nonlinear discrete stage and single discrete stage The critical coefficients of variation are 15.94%, 23.02% and 56.30% respectively.