The change of water environment in urban subway tunnel in loess stratum is mainly reflected in the fluctua-tion of groundwater level and the seepage of shield lining segments,which will further affect the surface settlement.Based on the background of a subway tunnel,the modified Mohr-Coulomb model (MM-C model) are used to describe the ground surface uplift and ssettlement under complex loading and unloading conditions.The results are as follows.The surface settlement increases by 24％ when the shield segment leakage ratio increases from 0.1 to 10.The maxi-mum surface settlement increases by 77％ when the number of segment leakage blocks increases from 1 to 6.The maxi-mum surface settlement enlarges by 1.2 times during 5 m groundwater level decline,and the surface settlement in-creased by about 7 mm with 1m water level decline.During the initial elevation of 5 m,the maximum surface settle-ment decreased by 37％.In order to control the surface from excessive uplift and settlement,the number of leakage blocks should not exceed 3,and the failure or leakage of arch bottom segments should be avoided.The recharge eleva-tion of groundwater level and the dewatering depth should be controlled within 3.0 m and 2.0 m respectively.
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