Model Test Study On Influence Of Adjacent Buried Pipeline Induced By Construction Of Subway Tunnel Shield In Sand

It will be inevitably have a certain impact on the safe use of the pipeline network system because of the soil disturbance caused by the subway tunnel shield construction.Which caused the gas leak,water pipe burst and other safety incidents have occurred.Based on Dalian subway tunnel project.the influence of ground displacement and pipeline deformation induced by shield construction are studied by combining model test and theoretical analysis.Which takes into account pipeline material and section characteristics,tunnel depth and section characteristics,soil conditions and pipelines and tunnels locations.And finally the pipeline safety control standard about the largest surface displacement based on the permissible stress of the pipeline is put forward.Firstly,the ground loss and displacement caused by tunnel construction were studied based on the model test.The results show that the ground displacement curve in sand is generally subject to the Gaussian distribution.With the increase of the buried depth,the ground displacement changes from the Gaussian line to the chimney shape.Displacement distribution curve of longitudinal and horizontal are similar,and it can be assumed that the longitudinal ground displacement is shifted forward by the semi-lateral displacement distribution curve.Based on the principle of statistical analysis,the law of ground loss along depth was summarized.The results show that the ground loss increases from the surface to the power function.With the increase of the depth,the settling groove width coefficient increases to a certain value while the maximum displacement continues to grow.Based on the Gaussian distribution model,the method of calculating the horizontal ground displacement was proposed considering ground loss,and combining the law of distribution and time history of longitudinal ground displacement,the prediction formula of ground displacement of any place in tunnel tunneling process was obtained.Then,based on the model test,the pipeline deformation and mechanical properties of different tunnel buried depth,pipeline depth and pipe tunnel space location were studied.The results show that there is a critical value of pipeline depth and tunnel depth ratio to maximize the displacement of the pipeline,and the critical value of the tunnel depth is between 1/4 and 3/8.The time history characteristic of pipeline and ground is the same,and the distribution characteristic is different.The width of pipeline displacement distribution is almost the same under the conditions of vertical pipeline and tunnel and parallel pipeline and tunnel.The pipeline displacement increases as the angle of the pipeline and tunnel decreases.When the pipeline is perpendicular to the tunnel,the pipeline has the greatest stress and corner at the maximum displacement,which is possible the most dangerous condition.The pipeline stress and the subsoil pressure were analyzed.The results show that the separation degree of the pipeline and soil is obviously larger when the vertical distance between pipeline and tunnel is small.Therefore,the degree of deformation of pipeline is weakened.Finally,based on the Winkler foundation model,the transfer matrix method of pipeline displacement by using two-stage analysis method and Fourier transform was established.The relationship between the maximum stress and the displacement of the pipeline was established.And finally the pipeline safety control standard about the largest surface displacement based on the permissible stress of the pipeline was put forward.The present method was compared with the experimental results,and the results show that the decrease of the pipeline displacement and the stress results from the separation of the soil and pipeline.Based on the coordination of pipe and soil deformation,the present method belongs to the upper limit calculation method cause of taking into account the most unfavorable situation.The geological condition of typical sand was selected,and the important factors influencing the interaction between soil and pipeline were analyzed.And the maximum surface displacement control standard of several commonly used pipelines were given,and each applicability was analyzed.