Research On The Influence Of New Bridge Pile Foundation Construction On The Deformation Of Adjacent Existing Tunnels

With the development of the city and the large-scale construction of urban rail transit,subway has become an important traffic support for large and medium-sized cities.At the same time,high-speed railway improves the travel efficiency of passengers between cities,reduces the time cost of passengers' travel,and plays an increasingly important role in the context of urban integration construction.With the construction of rail transit facilities,there are many engineering examples of high-speed railway bridges crossing existing urban subway lines.The construction of the new bridge will inevitably cause the redistribution of the stratum stress,the deformation of the stratum and the existing structure,which have a negative impact on the operation safety of the existing metro line.Therefore,it is of great practical significance to study the construction of the new high-speed railway bridge crossing the existing metro line.Taking the Huangcun railway station Yihezhuang section of Daxing Metro as the project background,the influence of new construction on the existing shield tunnel is studied by numerical simulation.The main research results are as follows:(1)The geological and hydrological conditions of the new project are investigated in detail.According to the relative position of the new project and the existing section tunnel,the risk factors of the project are analyzed.The current situation of the existing tunnel and track structure is investigated,which provides necessary basis for numerical simulation.(2)The numerical model is established by ANSYS.The vertical and horizontal deformation of the existing tunnel and track structure caused by the construction is calculated,and the deformation law of the existing structure is analyzed.The results show that the existing tunnel and track structure are uplifting due to the soil unloading caused by the excavation of bridge piles and the excavation of foundation pit of pile caps.The deformation of the existing structures increases with the construction stage.The construction stage of bridge superstructure causes the settlement of newly-built piles,which further causes the settlement of the existing tunnel.Due to the closer distance between the newly-built structures and the right line tunnel,and the denser distribution of pile groups on one side of the right line tunnel,the deformation of the right line tunnel and track structure is larger than that of the left line.(3)The key construction stages of deformation control were summarized.The construction of piles has the greatest influence on the existing structures in the stage of bridge foundation construction,which is the key stage of the uplifting deformation control of the existing structures.The existing structures has a large vertical deformation in the stage of the bridge superstructure construction,and the direction of deformation changes from uplifting state to sinking state,so the stage of the bridge superstructure construction is the key stage of the settlement control of the existing structures.(4)The whole process of monitored data in the construction process was analyzed.The actual deformation data of the existing tunnel and track structure was compared with the numerical simulation results.The results show that the deformation curve of the existing structure obtained by numerical simulation is basically consistent with the measured data,which proves the correctness of the numerical simulation method.(5)The control measures and construction process of the existing structure deformation in the construction of crossing project are described.The deformation control measures of the existing track structure are put forward.The track geometry is ensured to meet the operation requirements by setting gauge pull rod,anti derailment guard rail and strengthening monitoring.