Research On Influence Of Large Section Rectangular Pipe Jacking On Surrounding Soil And Underground Pipelines

In recent years,the pipe jacking method has been widely used in municipal engineering,geotechnical engineering and other related fields,and rectangular pipe jacking has more advantages than circular pipe jacking in underground crossing passage,underground utility tunnel and other aspects.Rectangular pipe jacking construction is often concentrated in prosperous urban areas,and the construction must cause disturbance to surrounding soil and existing underground pipelines.Therefore,it is of certain engineering significance to carry out relevant research on soil and pipeline displacement caused by pipe jacking construction.Based on an underground utility tunnel project in Guangzhou,this paper analyzes the formation deformation and its influence on the adjacent underground pipelines during the jacking process,and uses finite element software to establish comparative working condition models with different parameters for analysis.The main research contents are as follows:1.This paper introduces the general situation of the project of large-section rectangular pipe jacking through large-diameter water diversion steel pipe,carries out deformation monitoring on the actual construction process and collates relevant monitoring data.The MIDAS-GTS NX finite element software is used to establish the numerical model.Comparing the simulation results with the measured data,it is found that the measured results are slightly larger than the simulation results,but the laws are basically the same.2.According to the actual engineering conditions,a three-dimensional finite element model is established.Based on the established numerical calculation model,the displacement laws of soil and underground pipelines during jacking are analyzed.The results show that the surface settlement gradually increases with the increase of jacking distance,and reaches a stable level after the nose leaves the observation surface for a certain distance,and basically does not change.The maximum value of surface settlement appears above the pipe jacking axis,which conforms to Gaussian normal distribution law.The vertical displacement of soil on top of pipe jacking increases with the increase of depth,but the influence range gradually decreases,showing a narrow and deep trend.3.Through three-dimensional numerical simulation,the influence of different grouting pressure,support pressure,soil material parameters and other factors on surface deformation is analyzed.The results show that the support pressure and grouting pressure have influence on the surface deformation,and the increase of the support pressure leads to the decrease of the surface settlement in front of the excavation.For the earth's surface behind the excavation surface,too much or too little support pressure will lead to an increase in the earth's surface settlement.Increasing the grouting pressure is beneficial to reduce surface settlement,but it may cause surface grouting and uplift.In addition,the larger the soil elastic modulus and cohesion,the smaller the surface settlement caused by pipe jacking construction.4.Through three-dimensional numerical simulation,the influence of different grouting pressure,support pressure,soil material parameters,pipeline material parameters,pipe jacking and the relative position of pipelines and other factors on the displacement of underground pipelines is simulated and analyzed.The results show that the influence law of grouting pressure and supporting pressure on underground pipelines is the same as that on surface deformation.The greater the elastic modulus and internal friction angle of the soil under the pipeline,the smaller the vertical displacement and horizontal displacement of the pipeline.Under the same diameter,the vertical displacement of the underground pipeline with rectangular section is larger than that of the underground pipeline with circular section.The larger the wall thickness and pipe diameter of the outer pipe,the smaller the horizontal and vertical displacement of the pipeline.The vertical displacement of the pipeline decreases with the increase of the included angle between the underground pipeline and the pipe jacking in the range of 0 ?90,but the affected range of the pipeline gradually increases.If the condition requires an oblique angle,it is recommended that the included angle between the pipe and the tunnel be 40 ? 70.