The Study Of The Technology Based On The Pile Foundation Underpinning Of Bridge With The Undercrossing Foundation PIT In The Condition Of Dynamic Load

With the development of urban construction, we often encounter the new buildings undercrossing the existing buildings or through the existing buildings nearby in the actual engineering design and construction. In order to ensure the normal construction engineering and safety of the existing buildings, we must adopt reliable treatment measures. Pile foundation underpinning technology as a kind of scientific method, has been widely used in practical engineering. For specific underpinning engineering, adopting what kind of underpinning form, relates to the success or failure of underpinning engineering.This paper is based on the project of Chengdu-Leshan passenger dedicated line, Ji changlu tunnel pass through the Cheng du city. The tunnel traverses under the railway bridge of west tie-line, the Lantian highway bridge and the Chengya highway bridge. Some piles and their foundations of the bridges intrude into the boundary of the tunnel. The technical scheme of pile foundation underpinning is used to solve the problem of the piles and the foundations. Pile foundation underpinning of the bridges is the technology emphasis and difficult point of this project. This paper studies the main contents include:(l)Adopt artificial-numbered excitation force as the dynamic load of the train, research the displacement of the line and pile foundation in different construction stages, and also in different speed of the train. Establish the limit speed of the train in the condition of different construction stages;(2) Research the displacement of the highway bridge pile foundation under the vehicle dynamic load, evaluate the safety of the highway bridge underpinning engineering;(3) Give out the settlement of bridge’s underpinning pile via numerical simulation, compare with the date of field measurement, evaluate the safety of the whole underpinning engineering construction;Through the above research, we obtain the limit speed of the train in u in different construction stages:(1)In the excavation stage of the soil around the pile foundation, the speed limit is70km/h.(2)After applying underpinning beam, speed limit is80km/h;(3)The stageof foundation pit excavation, the speed limit is80km/h. Numerical calculation data is compared with the measured data, the result proves the safety of the underpinning engineering construction.