| In recent years,the problem of water accumulation in the depressed bridge area is becoming more and more serious in the rainy season,the old rainwater regulation and storage facilities have gradually failed to meet the requirements of urban development.In order to solve the problem of ponding in the depressed bridge area,it is an important measure to build a new rainwater storage tank near the existing bridge.When the rainwater storage tank is built near the existing bridge,the excavation of foundation pit,the construction of support structure and the operation process of the storage tank may affect the safety of the existing bridge.In order to ensure the normal operation of the existing bridge during the construction of the storage tank structure,it is necessary to study such projects.In this paper,the following three parts of work are carried out in connection with a new rainwater regulation and storage tank project in xuyin Road,Tongzhou District,Beijing(1)In this paper,the supporting structure of the foundation pit of the new rainwater storage tank adjacent to the existing railway bridge excavation is designed,and the monitoring scheme in the construction process is designed in combination with the actual situation of the site project.Based on the measured data,the settlement of bridge pile foundation,the settlement of diaphragm wall support and the horizontal displacement of diaphragm wall top are analyzed.It is considered that for the foundation pit project with large length width ratio,it is feasible to adopt the support method of diaphragm wall and internal support when the adjacent bridge is under construction.Influenced by the corner effect of foundation pit excavation,the deformation monitoring of the support structure at the middle part of the long side of the foundation pit should be strengthened.The vertical settlement value of the road near the long side of the foundation pit is large,and corresponding measures should be taken to protect it.(2)The ABAQUS model is built for the new rainwater storage tank project,and the finite element numerical simulation is carried out for the excavation and construction process of the foundation pit of the rainwater storage tank.The comparison between the numerical simulation results and the actual monitoring data of the project verifies the rationality of the model.According to the analysis,with the increase of the excavation depth of the foundation pit,the horizontal displacement of the pile foundation gradually increases,and the displacement reaches the maximum below the maximum buried depth of the diaphragm wall support.Based on the established numerical model,the working condition is changed,and the influence rule of the excavation process on the adjacent pile foundation under different support conditions is verified.The results show that the foundation pit is carried out in the adjacent existing railway bridge During excavation,the structure of diaphragm wall and internal support should be adopted,which has little disturbance to the surrounding soil.(3)The anti floating structure of the new rainwater storage tank is designed,and the anti floating stability of the rainwater storage tank under extreme conditions is calculated.It is considered that the structural form of combining the side wall of the diaphragm wall with the rainwater storage tank is beneficial to increase the anti floating performance of the whole structure.This paper analyzes the influence of the structure of the rainwater storage tank on the adjacent pile foundation when the groundwater buoyancy changes.The results show that under the action of the groundwater buoyancy,the friction of the axial force of the pile body increases a little,but there is no slippage between the pile foundation and the soil in the whole process.The influence of the groundwater buoyancy on the pile foundation can be ignored. |
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