Influence Of Open-cut Tunnel Construction On Pile Foundation Of Adjacent Bridge And Its Engineering Application

In recent years,with the development of society,the surface space has been insufficientto meet the needs of people for transportation and urban construction,more and more underground space and super high-rise buildings have been favored,and the construction of subway and bridge has become more important.The construction of bridge tunnel can effectively save the ground resources,cross the obstacle terrain,and divert and decompress the traffic congestion area.In the development of urbanization,the bridge and tunnel project occupies a great proportion,especially in the economically more developed area,the bridge and tunnel project is more than 50%,in the city with insufficient land expansion space,the tunnel excavation project will inevitably appear near the bridge and other building structures.The excavation process of foundation pit is the unloading process of soil,which will cause disturbance of soil around foundation pit to threaten the safety of nearby structure,and the engineering accidents such as structural overturning,pavement collapse,pipe network fracture and so on may follow.Therefore,it is very important to evaluate the safety of adjacent structures in the construction process.To ensure the safety of the impact of excavation process on the pile foundation of adjacent existing bridges and to provide ideas for similar engineering calculation,this paper combined with the actual construction project of tunnel construction in the first A section of Haibin Avenue(Tinghai Road-Xixiang Avenue),using finite element software Midas to establish three-dimensional finite element model for the excavation process of viaduct and tunnel foundation pit along the Yangtze River.The main points are as follows:(1)This paper summarizes the current research methods and experimental methods of foundation pit excavation deformation theory by scholars at home and abroad.Research status of excavation deformation on existing adjacent pile foundation affected by pile-soil interaction.(2)Through numerical simulation,a five-span continuous beam bridge is used as an example to study the sensitivity of adjacent bridges to pile foundation displacement,and the sensitivity coefficient of each evaluation index to pile foundation displacement in different control sections is obtained.Analyzing the most unfavorable settlement combination,the influence of uneven settlement under the most unfavorable settlement combination on thedeflection of the beam and the frame pier,the weak position which is greatly affected is obtained,so as to strengthen the monitoring pertinently,and determine the combination of the early warning value of settlement and the allowable limit value of settlement lateral displacement which can ensure the safety of bridge.(3)Simulate the whole process of foundation pit excavation dewatering support,evaluate the safety of bearing capacity of pile foundation and main beam under actual conditions,putting forward effective reinforcement measures and emergency plan for foundation pit engineering and bridge,controlling the influence on surrounding environment and ensuring construction safety.