大直径盾构隧道与下伏溶洞安全距离

岩溶发育地区的溶洞与在建盾构隧道之间的安全距离是一个重要的工程问题,如果溶洞与盾构隧道之间的距离过小则会导致隧道的失稳。本文基于武汉和平大道南延线隧道工程,在岩溶隧道失稳判断依据的基础上,设计选取围岩级别、侧压力系数、隧道的埋深和溶洞的大小四个影响因素来进行正交实验,同时采用了数值模拟与回归分析相结合的试验分析方法,探讨了影响安全厚度的因素,最终建立了下伏溶洞与隧道安全距离的预测模型。研究结果表明：在大直径盾构隧道下伏溶洞情况下,隧道的埋深、侧压力系数、溶洞的直径、围岩水平对于隧道安全距离的影响程度依次增加。安全距离与围岩级别呈负相关关系,与侧压力系数、隧道的埋深和溶洞的直径呈正相关关系。另外,通过对比验证试验区段典型断面的工程实例,证明了该安全预测模型在工程设计中具有参考价值。

Analysis of safety distance between large diameter shield tunnel and underlying karst cave

The safety distance between karst cave and tunnel is an important problem in the construction of tunnel in karst area. If the distance between karst cave and tunnel is too small, it will cause tunnel instability. In view of this problem, based on the tunnel project of South extension line of Heping Avenue in Wuhan, based on the judgment basis of karst tunnel instability, four influencing factors, namely surrounding rock grade, lateral pressure coefficient, tunnel buried depth and karst cave size, are selected to design orthogonal experiment. The influence factors of safety thickness are discussed by combining numerical simulation and regression analysis, and the underlying karst cave and tunnel safety are established Full range prediction model. The results show that: the influence degree of each factor on the safety distance between tunnel and karst cave is as follows: tunnel buried depth, lateral pressure coefficient, cave diameter, surrounding rock grade. The safety distance between tunnel and karst cave is negatively correlated with surrounding rock grade, and positively correlated with lateral pressure coefficient, tunnel buried depth and karst cave diameter. The typical section of the test section is selected for comparison and verification of engineering examples, which proves that the safety prediction model has a certain reference value in the project.