Study on Reasonable Pile Length for Steel Pipe Pile Reinforcement at Base of New Loess Tunnel
The open tunnel and shallow buried section of the new loess tunnel in collapsible loess areas have high collapsibility and low bearing capacity,and the tunnel base bearing capacity cannot meet the design requirements,so steel pipe piles are often used for the base reinforcement.To investigate the reasonable length of the steel pipe pile,this paper established a 3D finite element analysis model of a new loess tunnel to study the stress and deformation of the tunnel surrounding rock and the composite foundation under four working conditions of the pile lengths of 4 m,6 m,8 m,and 12 m.The study results showed that the longer the steel pipe pile,the smaller the value of stress stability and final deformation of the surrounding rock and composite foundation.But when the steel pipe pile length was larger than 6 m,the reinforcement effect of the steel pipe pile on the tunnel base was similar,and the value of the stress stability and final deformation of the surrounding rock and composite foundation was identical.So,the suggested reasonable length range of the steel pipe pile is 6-8 m.
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