结构性黄土深埋盾构隧道围岩力学特性研究

盾构施工会破坏黄土结构性,为探求黄土结构性变化对盾构隧道围岩力学特性的影响,引入应力比结构性参数对摩尔-库伦强度准则和芬纳公式进行修正,通过建立黄土围岩和管片之间力和位移的连续条件,对围岩塑性区半径进行了求解,并对解析解进行了对比验证,最后分析了关键参数对围岩力学性态的影响。结果表明:(1)太沙基土压力公式计算结果介于解析解上限值与下限值之间;(2)随着应力比结构性参数的增大,对应的塑性区半径和围岩压力值在不断减小;(3)随着覆跨比的增加,塑性区半径不断减小,围岩压力值不断增大,当黄土结构性比较强时,隧道覆土厚度达到一定值之后围岩压力解析公式才适用;(4)围岩压力和塑性区半径与开挖半径近似呈线性正相关关系。

Research on the Mechanical Properties of Surrounding Rock of Deep Shield Tunnel in Structural Loess

The structural properties of loess will change due to the shield construction. In order to explore the influences of variate structural properties on the mechanical properties of surrounding rock of shield tunnels, the structural parameters of stress ratio were introduced to modify the Mohr-Coulomb strength criterion and Fenner formula. By establishing the continuous conditions of force and displacement between loess strata and segments, the radius of plastic zone of surrounding rock was solved, and the analytical solutions were compared and verified. Finally, the influences of key parameters on the mechanical form of surrounding rock were analyzed. The results show that: (1) The calculation results of the Terzaghi surrounding rock pressure formula are between the upper limit and the lower limit of the analytical solution; (2) With the increase of the structure parameter of stress ratio, the corresponding plastic zone radius and surrounding rock pressure value are continuously decreasing; (3) With the increase of thickness span ratio, the radius of plastic zone decreases and the value of surrounding rock pressure increases. When the structural properties of loess are relatively strong, the analytical formula of surrounding rock pressure is applicable after the cover depth reaches a certain value; (4) The surrounding rock pressure and the radius of the plastic zone are approximately linearly positively correlated with the excavation radius.