Research On The Influence Of Foundation Pit Excavation On The Mechanical Behavior Of Adjacent Pipelines

The normal operation of the pipeline will be affected by the surrounding environment,and the effect of the construction of the foundation pit on the adjacent pipeline has become one of the important problems in urban construction.Therefore,it is of great significance to study the effect of pipeline in foundation pit excavation.And the current research on this subject is less,but also the lack of systematic.First of all,this paper studies the characteristics of the buried pipeline under the excavation of the foundation pit,and analyzes the common methods of solving the pipeline deformation:the elastic foundation beam method and the finite element method.The solution process of elastic foundation beam method and the development of finite element method are expounded,and the finite element method is used as the main analytical method.Secondly,based on the finite element method,a three-dimensional model is established in the software ABAQUS,and the mechanical effects of the unsupported foundation pit and the supported foundation pit on the adjacent pipeline are analyzed respectively.After the excavation of the unsupported foundation pit,the maximum force area of the pipeline is in the middle of the pipeline and at the edge of the foundation pit.The upper surface of the pipeline is pressed in the middle,and pulled at the edge of the foundation pit,but the lower surface of the pipeline is opposite.The overall displacement of the pipeline is manifested as subsidence while moving toward the internal of the foundation pit.After the excavation of the foundation pit,the deformation of the pipeline decreases with the increase of the elastic modulus and cohesion of the soil,and increases with the increase of the Poisson's ratio.The deformation of the pipeline decreases with the increase of the pipeline depth,and decreases with the increase of the pipeline wall thickness and the distance between the pipeline and the foundation pit.The width of the foundation pit has an obvious effect on the pipeline,and the deformation of the pipeline increases with the increase of the foundation pit.But the length of the foundation pit has no effect on the pipeline deformation.After the excavation of the supported foundation pit,the deformation law of the pipeline is similar to the unsupported foundation pit,but the overall deformation degree is small.After the excavation of the supported foundation pit,the effect law of the elastic modulus,cohesion,Poisson's ratio,wall thickness,the distance between the pipeline and the foundation pit and the size of the foundation pit are similar to the unsupported foundation pit.At the same time,it is found that the internal pressure of the pipeline has no effect on the deformation of the pipeline.The deformation of the pipeline increases with the depth of the foundation pit.The larger the thickness and elastic modulus of the underground continuous wall,the smaller the deformation ability of the pipeline.Thirdly,the effect of excavation on common parallel pipelines is studied.The results show that the overall deformation law of the parallel pipeline is similar with the single pipeline,but the distance between the parallel pipeline will affect the deformation of the pipeline.With the increase of the parallel distance,the deformation degree of the pipeline closer to the foundation pit is gradually increased,while the deformation of the pipeline far from the foundation pit is gradually decreased.In addition,the deformation of the parallel pipe decreases with the thickness of the pipeline wall and the distance between the pipeline and the foundation pit.The width of the foundation pit is positively correlated with the deformation of the pipeline,and the length of the foundation pit has no effect on the pipeline deformation.Finally,the effect of different supporting and excavating foundation pit on adjacent pipeline is analyzed.It is found that the lateral reinforcement of the pipeline can effectively reduce the pipeline deformation,the internal support of the foundation pit also has a positive effect on the pipeline protection,and bolt support is similar with internal support.Slope excavation can be very effective in reducing pipeline deformation,although the island excavation and the pot excavation method can affect the pipeline deformation to a certain extent,but the effect is not obvious.The research results in this paper provide theoretical guidance for the study of foundation pit and pipeline,and provide reference for engineering construction.