Reasonable thickness of metro station with single arch large-span in upper-soft and lower-hard stratum

摘要

Based on the Junfeng Road station of Qingdao metro engineering, this paper studies the reasonable thickness of overburden rock stratum above the mining tunnel of single arch long-span station by theoretical analysis, numerical calculation and feedback analysis on field monitoring. Results show that stress release and transfer caused by tunnel excavation in upper-soft and lower-hard stratum distribute mainly in the surrounding rock stratum and have less impact to soft stratum. With the same thickness of overburden, the safety margin drops with the decreasing of surrounding rock strength and increasing of thickness of overburden rock; the thickness of overburden rock in Junfeng Road station tunnel is reasonable, but the excavation method of upper, middle and lower bench which contains 9 excavation parts is conservative, and the excavated parts and support measurements should be optimized to realize informationalized design and construction.