Study on Surface Subsidence Law and Control Measures in Large Section Rectangular Pipe Jacking Method in Complex Environment

In order to study regularity and control measures of surface settlement during shallow large cross-section(6.9 m×4.9 m) rectangular pipe-jacking construction in the north second terrace area of Yongjiang river.The paper based on No.3 exit project of Jinhuguangchang station on Line 1 of Nanning Metro,three-dimensional model is set up by finite difference software FLAC3D to simulate pipe jacking construction process,and compared with actual monitoring results.Conclusions are drawn as follows:①the main disturbance range of soil in front of Pipe jacking machine is about 2 times of the tunnel width;②the surface transverse settlement curve presents normal distribution as the center of pipe axis,the impact range of surface transverse settlementis about 3 times of the tunnel width;③in order to ensure that the surface uplift and settlement are within the range of reasonable control through the pipe jacking head up slightly,add grouting sleeve plate,pipe section antifriction slip casting and reasonable jacking parameters.