Abstract: When metro tunnel crosses hourglass type Karst of firstclass terrace in Wuhan area, countermeasures should be adopted. Hence, the dimension, vertical distribution law, filling and developing law of the Karst are summarized, and the collapse mechanism and risk of hourglass type Karst are analyzed based on Karst surveying, design and treatment of Hongjianlu Station and sections ahead of and behind on Wuhan Metro Line No. 6. According to the features of shallow Karst in Wuhan, the Karst treatment idea of filling grouting after curtain grouting of rock 15 m below rockface is summarized. The measures, i.e. rock curtain grouting, Karst cave filling grouting, underground diaphragm wall bracket, soil layered jet grouting reinforcement, etc., are adopted for metro station, and those, i.e. rock curtain grouting, Karst cave filling grouting, sandy soil separation pile, etc., are adopted for tunnel sections. Furthermore, new technologies of Karst grouting with tube pore forming, slurry flow monitoring, etc. are also adopted in Karst grouting of Line No. 6, and the slurry proportions and end slurry standard are discussed. The applicable results verify the feasibility of the Karst treatment idea and measures.

Key words:

Wuhan area, firstclass terrace, Karst treatment, curtain grouting, filling grouting