Study On The Influence Of Shield Tunneling On Existing Pipelines

Subway projects are mostly constructed in the prosperous areas of the city,where the surrounding buildings(structures)are densely distributed especially various pipelines buried underground.Thus it is inevitable that the existing underground pipeline to some extent will be affected by the construction of the subway.Based on the project of Zhengzhou City Metro Line 3 from Erqiguangchang Station to Shunchengjie Station,this paper,combining the actual engineering geology and hydrology conditions,uses FLAC 3D software to establish a three-dimensional numerical model and study the influence of the construction of the shield tunnel on the surface and pipeline by the construction process simulation and on-site monitoring.The main research contents and conclusions are as follows:1?By means of comparing the numerical simulation results with the measured data,the reliability of the numerical simulation calculation is verified.At the same time,it is found that the surface lateral settlement groove curve is approximately Gaussian distribution after the construction of the left tunnel,and the maximum settlement of the surface is near the left tunnel axis.The surface horizontal subsidence groove curve is a single peak curve after the construction of the right tunnel,and the maximum settlement of the surface is still near the axis of the left tunnel,but it is no longer symmetrical about the axis of the left tunnel.The law of the settlement of soil layers in different depths is similar to the surface,and the greater the depth,the larger the settlement.The tunnel construction has a certain range of influence on the pipeline in front and behind the excavation face.However,after tunnel construction,the settlement of each part of the pipeline is relatively uniform,and there is no significant difference in settlement.The settlement of the surface and pipeline is further increased after the construction of the right tunnel.Its growth rate is not as large as that caused by the left tunnel construction,but the influence of the secondary construction of tunnel on the surrounding layer and pipeline cannot be ignored.2?On the basis of verifying the reliability of numerical simulation calculation,the sensitivity analysis of two construction parameters,the speed of tunnel excavation and the rate of stress release,is carried out.It is found that the influence of them on surface depends on its location,and the closer to the axis of the left tunnel,the bigger the affection of the speed of tunnel excavation and the rate of stress release on the settlement of the surface.The bigger the speed of tunnel excavation and the rate of stress release,the bigger the settlement of the surface and pipeline.Therefore,the speed of tunnel excavation should be strictly controlled in engineering to reduce the impact on the pipeline near the tunnel.3?Through the comparative analysis of surface and pipeline settlement caused by 11 different working conditions,it is found that the surface and pipeline settlement caused by the construction sequence of the left tunnel first tunneling and the right tunnel tunneling is the smallest.4?Combining the actual construction conditions of the tunnel,the construction control technology is collated and summarized,including the pressure control of the shield soil warehouse,the speed control of the excavation,the direction control of the excavation,the grouting control,the control of the amount of soil discharged,and the improvement of the slag soil to provide some reference for other similar subway projects.