Field Test And Theoretical Research On Bored Pile Retaining Wall In High Slope Of The Sichuan-Tibet Railway

The traditional retaining structure is difficult to meet the requirements of construction and normal use in high-cold-anoxic and high-slope areas.Bored pile retaining wall has the advantages of mature construction technology and high degree of mechanization.It is widely used in building foundation pit.But it is not common in railway engineering practice.Its stress mechanism and deformation characteristics are not yet clear.In response to the above problems,relying on the Sichuan-Tibet Railway,the research has been conducted through theoretical analysis,field tests,and numerical simulations.Mainly done the following work:1.Combined with the design process of the retaining structure of railway subgrade in China,this paper proposes a support structure that combines the bored pile with the retaining wall.This paper discusses the interaction theory between the retaining structure and the soil.Detailed description of the design and calculation method for the retaining structure.Using elastic foundation beam method,the cantilever section and anchor section are subjected to force analysis based on cantilever beam and elastic foundation beam respectively.2.By the field test,during the excavation process,the longer the cantilever segment of a bored pile,the greater the bending moment of the pile,and the deeper the position of maximum positive moment.At the same time,the horizontal deformation of the pile is also growing.After the completion of the construction,the stress of the soil around the pile was redistributed,and the stress and deformation of the retaining structure gradually stabilized.3.The bending moment of the pile is a parabolic type with “small on both sides and large in the middle”.Near-zero value at the bottom of the pile.The earth pressure before the pile is greater than the earth pressure behind the pile at the same depth,indicating that the soil before the pile has a good anti-slip effect.The earth pressure between the piles is lower than the earth pressure behind the piles,which verifies the existence of horizontal soil arches behind the piles.4.Through numerical simulation analysis,during the excavation process,the maximum shear force of the cantilever section increases,and the maximum shear force position is near the excavation floor of the corresponding working condition.The shear distribution of the anchor section proves the effect of the soil resistance before the pile.The zero shear force is the same as the depth position of the maximum bending moment.