基于黄土联合强度的黄土隧道围岩应力及位移研究

Stress and displacement of surrounding rock of loess tunnels based on joint strength

隧道围岩应力及位移计算问题是隧道工程界中传统研究课题之一,但黄土抗拉强度在黄土隧道围岩应力及位移计算中存在的影响需要进行合理性评价。基于建立的可综合考虑黄土抗拉和抗剪特性的联合强度,开展了极限应力平衡分析,重新推导了强度破坏曲线的主应力表达式;然后重新确定了轴对称圆形隧道条件下黄土围岩塑性区半径;最后得到了隧道周边黄土围岩位移表达式。研究结果表明:在围岩塑性区应力计算与比较中,基于联合强度确定的围岩塑性区应力小于基于传统的Mohr-Coulomb理论确定的围岩塑性区应力,而塑性区半径和隧道周边围岩位移相对较大;基于拉强度建立的联合强度理论克服了Mohr-Coulomb理论高估黄土抗拉强度的缺陷,可以合理评价黄土隧道围岩应力及位移。

The stress and displacement of surrounding rock of tunnels are one of the traditional research subjects in the tunnel engineering.However the impact of tensile strength on stress and displacement of the surrounding rock of structured loess tunnels needs to be evaluated reasonably.Based on the theory of joint strength considering the tensile and shear properties of loess simultaneously,the principal stress expression for the strength failure curve is re-determined to analyze the ultimate stress equilibrium.Then,the radius of the plastic zone of the surrounding rock of loess under the axisymmetric circular tunnel is re-determined.Finally,the expression of the displacement for the surrounding rock around the tunnel is obtained.The results show that the plastic stress in the surrounding rock determined by the joint strength theory is smaller than that determined by the traditional Mohr-Coulomb theory,and the radius of the plastic zone and the displacement of the surrounding rock around the tunnel are relatively large.The joint strength theory based on tensile strength overcomes the defect of Mohr-Coulomb theory overestimating the tensile strength of loess,and it can reasonably evaluate stress and displacement of the surrounding rock.