岩溶地层盾构施工风险评估方法研究

Assessment method of tunnel shielding in Karst stratum

随着我国地铁建设多城市、大规模的开展,盾构施工会遇到各种特殊地质条件,大规模岩溶地层是一类典型城市地铁施工的不利地质条件。对地铁线路中的溶洞分布进行科学评判,以及对相应施工风险进行科学评估,有着重要的理论意义与工程价值。提出了对于城市地铁盾构区间大规模岩溶地层空间分布规律的网格化统计方法,将某城市地铁1275.7 m长区间的左、右两线,分别分为6、8个区段,以2m×2m的正方形网格进行溶洞网格化统计。对此14个区段的溶洞与隧道间距离、溶洞大小和溶洞分布密集程度等空间分布规律进行了统计分析,得到了R 1、R 4、L 1三段相对危险的结论。由此选取典型区段,对于不同工况下的单溶洞、多溶洞进行了数值模拟,并采用层次分析方法,构造风险指标体系,结合数值计算方法,对于施工风险进行了评判。提出的溶洞分布网格化统计规律分析-数值计算-层次分析法的复合风险评价方法,以网格化统计结合数值计算避免传统层次分析法专家打分的主观性,以层次分析法来综合化、系统化多工况数值计算的结果,对于土木工程风险评判方法有一定的参考性。

Karst strata is one of the typical risk resources for shield tunnelling,and is unavoidable China’s in city Metro construction considering the massive investment in recent years.The reasonable investigation on the Karst spatial statistical characteristics,and the scientific assessment on the construction risk are both important in theory research and for the engineering experiences.The gridding measure method is proposed which are used to illustrate the Karst cave spatial distribution in city Metro construction.The two tunnel lines of a Metro interzone,which length is 1275.7m,are divided into 6 and 8 subzones.All the Karst caves in the subzones are measured by 2 m×2 m square grid.The distance to the tunnel,the size,and the density of karst cave distribution of the 14 subzones are investigated.The construction risk of subzone R 1,R 4 and L 1 is higher than the one of the other subzones.The Karst cave scenarios in typical sections are numerically calculated.The risk index system is performed and the risk of the subzone is assessed by Analytical Hierarchy Process.A hybrid assessment method is proposed by this study,in which Karst cave gridding measurement,numerical calculation,and Analytical Hierarchy Process is included.The weakness of the Analytical Hierarchy Process is improved by gridding measurement and numerical calculation.The numerical calculation results are more systematic by the Analytical Hierarchy Process.The proposed method is helpful for the risk assessment in civil engineering.