| With the rapid development of our economy,people’s demand for power is increasing day by day,and construction of power tunnels has become the important part of underground project.The pipe jacking method has been widely used in urban underground engineering,but because of its different construction methods,it is very important to study the influence of pipe jacking method on surrounding soil and existing pipelines.Based on the cable tunnel overspan Xi ’an Metro Line 5 project,this paper adopts laboratory model test,numerical analysis and other research methods to study the deformation law of the existing underground subway tunnel and the stratum under the overspan construction of the power pipe jacking tunnel.The main research contents and achievements are as follows:1.Relying on the independently developed pipe-jacking system and non-contact laser displacement meter test system,this paper simulated the construction process of the pipejacking tunnel across the existing subway tunnel,so that the actual working conditions could be restored in the model test.The tube jacking system simulates the jack,cutting process and dumping process respectively through the power device composed of air compressor and cylinder,cutter head cutting parts and the rotating device composed of motor and screw rod.The non-contact laser displacement meter test system makes up for the relative lack of fixed position displacement meter at the test point in the test,so that the entire section corresponding to the laser displacement meter in the test can be coherent displacement monitoring,so as to accurately analyze the change law of surface displacement.2.Laboratory model test was used to study the construction deformation of the power pipe jacking tunnel over the existing subway tunnel under the condition of different burial depth,soil layer thickness and horizontal cross Angle between the pipe jacking tunnel and the existing subway tunnel.The test results show that the maximum settlement value of ground is inversely proportional to the thickness of soil covering the pipe jacking tunnel.The slower the subsidence attenuation of ground is,the width of settlement trough will increase and the influence range on the ground will also expand gradually.The maximum additional bending moment values of both tunnels occur in the middle of the tunnel.The smaller the horizontal crossing Angle between the pipe jacking tunnel and the existing tunnel is,the larger the affected scope of the existing tunnel is.Orthogonal crossing should be chosen as far as possible under the condition of comprehensive factors.The additional earth pressure above the existing tunnel is inversely proportional to the intersection Angle of the two tunnels and the thickness of the sandwiches.However,when the thickness of the sandwiches exceeds 2D,the additional earth pressure is almost zero.3.The finite element analysis software ABAQUS was used to conduct supplementary and comparative analysis on the displacement change rules of the strata not studied in the model test and the existing tunnel.The results show that the ABAQUS simulation results are in good agreement with the experimental results.During the construction of pipe jacking tunnel,the existing subway tunnel deforms in both vertical and horizontal directions,showing an upward uplift as a whole.In the vertical direction,the uplift in the middle of the tunnel is the largest,the uplift at the vault is greater than that at the bottom of the arch,and the displacement at the waist in the horizontal direction is greater than that at other positions. |
