Three-dimensional Numerical Simulation And Construction Control Countermeasures Of Large Diameter Curved Pipe Jacking Crossing River

Pipe jacking construction,as a trenchless technology,has the advantages of high construction efficiency,low comprehensive cost and small environmental impact,but it can cause soil disturbance and then produce ground deformation.There are many rivers in southern China,and some underground pipelines inevitably need to go through the river.So the difficulty of pipe jacking construction is greatly increased.This thesis takes a pipe jacking project in HangZhou as the basis,using ABAQUS 3D finite element analysis software,the influence of lubrication slurry and pressurized slurry in mud cabin on the pipe and soil above pipe jacking is simulated and related parameters are optimized.The simulated results are then used to guide the construction and verified according to the actual monitoring results.From this,the following main conclusions can be obtained:(1)In the process of pipe jacking crossing the river,ground surface settlements on both sides of the river slope and at the bottom,and vertical lateral displacements of pipes are always larger than those in the river bank;increasing grouting pressure when pipe jacking crosses the river would have a larger influence on the displacements of soil and pipe;increasing the grouting pressure can effectively reduce the ground surface settlement and the vertical displacement of pipes,but the lateral displacement for the curved segments of pipes will increase and pipes will deviate away from the pipe center side direction.(2)Under the condition of the project,for pipe jacking across the river bank,the soil will be disturbed in the range of about 4D(outside diameter of the pipe jacking)in front of the pipe jacking.For pipe jacking across the river slope,the influencescope of the soil will extend to the 5D range in front of the head.The soil above the head of the pipe will settle rapidly along the top of the pipe,and the soil will settle slowly in the original position when pipes are further jacked about 3.75 D.(3)Control parameters of lubrication slurry grouting pressure and support pressure of mud cabin in the projected introduced in this thesis are suggested as: when the pipe jacking in the West Bank,the grouting pressure control in 0.19~0.22 MPa,support pressure control in 0.1~0.12MPa;at the top to the bottom of the river into the process,grouting pressure decreases to 0.16~0.19 MPa,support pressure gradually reduced to 0.06~0.08MPa;from the river to the East Bank of jacking pipes,the grouting pressure is gradually increased to 0.19~0.22 MPa,the support pressure is gradually increased to 0.1~0.12 MPa.