Analysis Of Long-term Settlement Of Different Clear-distance Parallel Tunnels Under Subway Moving Loads

In recent years,the rapidly planned construction of the subway has become a efficient tool to solve traffic congestion in large cities.While constructing subways,the clear-distance between subway shield tunnels become smaller.After the subway is put into operation,the clear-distance will more significantly affects the response of the tunnel structure and the surrounding soil,and induce the uneven settlement of tunnel area.This article analyzes the tunnel structure and surrounding soil response of the different clear-distance parallel tunnels,and then predicts the longitudinal differential settlement of the different clear-distance parallel tunnels during the operation period.This article mainly includes:1)Taking the section tunnel near People’s Square of Shanghai Metro Line 1 as the engineering background,establish a subway train-tunnel-stratum finite element-infinite element coupling model,simulate train load with artificial excitation function,and adopt long-term longitudinal differential settlement reflecting dynamic deviator stress model,combined with the layered sum method to calculate the soil settlement.The results show that the tunnel structure,soil dynamic response law and the growth trend of longitudinal differential settlement of tunnel during operation are basically the same under all working conditions.The vertical acceleration of the tunnel structure is much greater than the horizontal acceleration,and the tunnel structure mainly presents a vertical response;with the increase of depth,the dynamic stress of the soil under the tunnel decays approximately logarithmically;the settlement growth during the metro operation period meets the exponential growth trend,and the longitudinal differential settlement of tunnel is mainly completed in the first 10 years after it was put into operation,and after 20 years of operation,the settlement has stabilized.2)Establish 14 parallel tunnels simulation models with different horizontal clear-distance to calculate the response of the tunnel structure,surrounding soil and the settlement of the soil.The results show that the clear-distance has a greater impact on the horizontal response of the tunnel structure,and less impact on the vertical response of the tunnel structure.With the gradual increase of the clear distance from 0.3 to 4.2 times the outer diameter of the tunnel,the maximum value of soil dynamic stress generally increases first and then decreases,and the minimum value of soil dynamic stress generally decreases;the total cumulative settlement during the tunnel operation period first decreases and then increase,and finally decrease to the settlement of single-line operation.The total accumulated settlement of the soil at the central axis of the model decreases approximately exponentially with the increase of the net distance.3)Establish 10 parallel tunnels simulation models with different spatial angles to calculate the response of the tunnel structure,the surrounding soil and the settlement of the soil.The results show that the spatial angle between tunnels has a certain effect on the horizontal and vertical response of the tunnel structure.As the spatial angle gradually increases from 0 to 90 degrees,the maximum dynamic stress of the soil generally increases first and then stabilizes;the total cumulative settlement first increases and then decreases;the change of the spatial angle has little effect on the minimum soil dynamic stress,and has a greater impact on the total cumulative settlement of the tunnel.