| With the development and utilization scale of urban underground space expanding,the distance between new underground projects and existing underground pipelines is getting closer.The foundation pit dewatering and excavation will cause adverse effects on existing pipelines and even damage to the pipelines.The existing pipelines will also affect the distribution of soil stress field,and increase the uncertainties and risks of the project.Therefore,how to effectively control the deformation and ensure the safety of adjacent pipelines caused by dewatering and excavation has become a hot topic in underground engineering academic subjects.Theoretical calculation and numerical simulation are used to analyze the deformation response of the surrounding pipelines and soil by dewatering and excavation based on engineering examples under two different situations(the existing pipelines are located at the side or the bottom of the foundation pit).Research results can provide reference for the design and construction of similar projectsMajor work and innovation achievements are as follows:(1)Based on Pasternak elastic foundation beam theory,an analytical calculation method for the deformation of adjacent pipelines in sandy soil caused by single well dewatering is derived based on the two-stage stress analysis method,of which the validity is verified by comparing the results with finite element simulation and field test The effects of soil shear stiffness,dewatering depth,the distance from pipeline to the dewatering well and the depth of the pipeline on the stress and deformation of the pipeline are analyzed.(2)For foundation excavation with groundwater seepage,based on a foundation pit in Hangzhou,the finite element numerical simulation using the HSS model is established.The response laws of bottom heave,ground settlement,lateral displacement of support piles and pipeline deformation under different depth of waterproof curtain are studied(3)For deep foundation pit engineering with adjacent pipelines,based on the finite element numerical simulation,the distribution law of soil strain field behind the retaining wall are analyzed when the buried depth of pipelines,the distance between pipelines and the retaining structure,and the number of pipelines are different,as well as the response laws of ground settlement,lateral displacement of support piles and pipeline deformation.(4)For the pipeline lying under the foundation pit,the additional stress along the pipeline under the influence of excavation and dewatering is solved,and the analytical solution of pipeline deformation is obtained.Based on a foundation pit project in Hangzhou,the calculation is carried out and verified.Parameter analysis is carried out to analysis the influence of soil modulus,pipeline modulus,pipeline diameter,pipeline depth,relative position of pipeline and foundation pit and dewatering depth. |
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