基于弹塑性理论的软岩隧道最大变形量预测方法研究

Prediction Method of Maximum Deformation of Soft Rock Tunnel Based on Elastoplastic Theory

软岩隧道支护时机选择和安全评价过程中,隧道边缘最大变形量是一个重要的参数。为了准确预测隧道边缘最大变形量,基于松动圈剪切滑移理论,利用Hoek-Brown准则推导得到最小支护应力,将其带入到隧道边缘位移公式中,得到圆形隧道边缘最大变形量的理论解。利用现有研究成果对所提出的计算方法进行验证,并探究远场应力、岩体力学参数对最大变形量的影响规律,分别利用现有数值模拟方法和所提算法对2条隧道最大变形量进行计算。结果表明:所提算法的误差均小于5%,证明了所提估算方法的合理性与准确性。最大变形量与远场应力呈现正相关,与单轴抗压强度、参数mi呈现负相关。随着地质强度指标(GSI)的增加,敏感性均呈现减弱的趋势,当GSI较大时(超过40时),敏感性可近似忽略。最大变形量与弹性模量、泊松比呈负相关,随着地质强度指标GSI的增大,敏感性并未产生显著的改变。

The maximum deformation of tunnel edge is an important parameter in the process of supporting timing and safety evaluation of soft rock tunnel.In order to accurately predict the maximum deformation of the edge of the tunnel,based on the shear slip theory of the loose ring,the minimum support stress was derived by using Hoek-Brown criterion,which was brought into the displacement formula of the edge of the tunnel,and the theoretical solution of the maximum deformation of the edge of the circular tunnel was obtained.The existing research results were used to verify the proposed prediction method,and the effects of far-field stress and mechanical parameters on the maximum deformation were explored.The maximum deformation of two tunnels was calculated by using the existing numerical simulation method and the proposed algorithm.The results show that the error of the proposed algorithm is less than 5%,which proves the rationality and accuracy of the proposed estimation method.The maximum deformation is positively correlated with the far-field stress,and negatively correlated with the uniaxial compressive strength and parameter mi.With the increase of the geological strength index(GSI),the sensitivity shows a weakening trend.When the GSI is large(more than 40),the sensitivity can be approximately ignored.The maximum deformation is negatively correlated with elastic modulus and Poisson’s ratio.With the increase of geological strength index GSI,the sensitivity does not change significantly.