Karst geology and mitigation measures for hazards during metro system construction in Wuhan, China

Abstract

Karst geology is widely distributed in China; the great differences in natural conditions bring it an array of characteristics in different regions. There is a huge area of the buried karst in Wuhan, exhibiting a unique, but complicated engineering geological environment. This paper summarizes the geological conditions in Wuhan, with special focus on its karst geology. At present, a total of six karst belts have been detected, and they were divided into five structure types. For shield tunnelling in karst region, some problems such as water ingress or mud inrush, partial ground collapse, damage or failure of shield machine, and metro operation and management issues may be raised as a result of the activity of the karst geology. To prevent occurrence of possible hazards, a series of countermeasures suggested for hazard and risk mitigation were discussed in this paper. A case history, where the study section belongs to the Wuhan metro line 6, is referred to evaluate effectiveness of the adopted treatment measures. The feedbacks demonstrated that water ingress was successfully avoided, and ground deformation was effectively controlled in the study section throughout the construction phase. This study can provide significant reference information and experience for metro tunnel constructed in karst region.