Controlling Technology Of Shield Construction In Subway Tunnel Crossing Saturated Soft Loess Strata

Strata subsidence has caused by the subway tunnel which using the shield construction crossing loess strata,has effect on both the around building’s safety and the speed of the shield construction. Being based on the theoretical of the surrounding rock mechanical properties, the deformation mechanism and the deformation of stratum subsidence mechanism of saturated loess subway tunnel, sum up the feasibility factors of the construction of the subway tunnel; Combined with the engineering, using the ANSYS to build the 3D model, FLAC3 D to numerical simulation of saturated loess tunnel shield construction, to research the regular of strata subsidence and uplift in different soil thickness, construction speed and the condition of the wall after grouting reinforcement,and put forward the subway tunnel’s construction settlement prediction and control measures. The research shows that:(1) The growth of the strata subsidence and uplift displacement is slowly when the excavation of tunnel boundary after 24 m; When to 42 m, the vault’s subsidence and uplift are maximum, 2.3719 cm and 2.5094 cm respectively. By comparing the results of the research and the engineering monitoring data,we can conclude that the shield method is adopted for the saturated soft loess strata subway tunnel, and conform to the requirements of the specification and the engineering practice.(2) When the soil thickness increased from 8 m to 16 m, the maximum of the earth’s surface subsidence decreased from 1.5057 cm to 1.1297 cm, the maximum of vault subsidence decreased from 2.6497 cm to 2.2537 cm, the subsidence is changing slowly after the soil thickness is 13 m, so the reasonable thickness is 10 m ~ 13 m.(3) When the construction speed increased from 0.5 m/d to 4 m/d, the maximum of the earth’s surface subsidence increased about 31.91%, the maximum of vault subsidence increased about 23.15%. Under the condition of meeting the project duration, the construction speed should be controlled within 2 m/d.(4) The grouting material elastic modulus is 0.46 MPa, 4.6 MPa, 46 MPa,, the maximum of the earth’s surface subsidence are 1.2855 cm, 1.2245 cm and 1.1736 cm, the maximum of the vault subsidence are 2.4655 cm, 2.3719 cm and 2.2886 cm.The research provides reference for similar engineering construction.