Analysis On Design Of Underpinning Structure In Construction Of Underground Engineering

With large-scale, modernized development of city, the exploitation and construction of underground space has become a best strategy to solve the traffic jams. However, in the early city planning, the construction of underground engineering was not taken in account. This results in a problem that the route is always through the existing architectural construction partly or entirely under the metro construction. Going through the buildings must weaken or damage the bearing capacity of existing building foundation. Underpinning technology may solve this problem well.This article introduces the development and application of underpinning technology, summarizes the difficulties and key point of underpinning structure design, emphatically analyses the design and shear mechanism of nodes of underpinning beam and new underpinning pipe, illuminates the significances, details and methods of a third party monitoring during the underpinning.Reference to specifications and some details, the underpinning beam、new underpinning pipe and underpinning beam-pipe nodes in an underpinning engineering case of Chengdu-Mianyang-Leshan Railway airport road tunnel was designed respectively. What is more, the underpinning beam-pipe node was designed, which was the key point of whole underpinning engineering.Finally, based on general geotechnical engineering analysis software Midas/GTS, a finite element model of underpinning was build and jacking process of underpinning was simulated and analyzed. With the multistage loading regulations, the displacement changes of beam-pipe node and both sides of joist and the settlement of the new underpinning pipe were acquired under the various loading level. Therefore, this can provide the references and proposals for the deformation value controls.