Abstract: To avoid the risk of unstable tunneling parameters, poor muck state, and spewing of screw conveyor during shield tunneling in waterrich gravel stratum in Kunming, China, a series of tests and analysis are conducted on plasticfluidity of muck and shield tunnel parameters of Kumming metro line 4, and reasonable ranges for shield thrust, cutterhead torque, tunneling speed, and soil chamber pressure and solution for plasticfluidity index slump of muck are proposed. Further, the soil conditioning scheme of waterrick gravel stratum is improved using planning and solution method, and the rational water content and foam injection ratio for muck with different gradations are determined. The field application results indicate the good feasibility of improved soil conditioning scheme, providing guarantee for safe and efficient shield tunneling and followup shield crossing underneath Kunming metro line 2 with a short distance.

Key words: earth pressure balance shield, waterrich gravel stratum, tunneling parameters, soil conditioning