Abstract:

The features and pattern of karst development in Wuhan area are analyzed on the basis of the karst investigation data and the karst encountered in the construction of Wuhan Metro. The treatment methods for the karst encountered in the construction of Wuhan Metro are also summarized. Conclusions drawn are as follows: 1) The karst in Wuhan area belongs to shallow karst, which develops mainly within the scope of 0~15 m below the rock surface; 2) The karst in Wuhan area takes the shape of karst caves, karst channels and karst troughs; 3) The rate of karst cave encountering in borehole drilling is about 50%, and the rate of linear karst is about 6%; 4) The deeper the karst caves, the smaller the karst cave filling rate; 5) The karst can be classified into 3 geological structural types, i.e., Type I, Type Ⅱ and Type Ⅲ, which correspond to 3 karst subsidence risk zones, i.e., high karst subsidence risk zone, medium karst subsidence risk zone and low karst subsidence risk zone; 6) Countermeasures, including karst cave filling by grouting, grouting curtain installed in rocks, isolation of soil layers, reinforcement by jetgrouting piles and extending the retaining structures into the rock, are taken to cope with the karst encountered in the construction of Wuhan Metro. 

Key words: karst development feature, geological structure, Metro works, karst treatment