| The paper focuses on problems about the applicability,structural response and slope reinforcement effect of the "double row bored pile + plant bar retaining wall" retaining structure in the aeolian sand high steep slope cutting engineering.In the project of DK104+810~DK104+832.5,DK39+602.25 ~ DK39+653.75 section of the Lalin Railway cutting engineering,a large number of data were measured in the field.The current paper analyzed the force and deformation law of double-row piles,the distribution characteristics of soil pressure and the slope deformation characteristics during the action of pile-soil by using combination methods of numerical simulation(main research method)and theoretical calculations.Then,the topics were discussed in terms of the mechanism of pile-soil interaction,design method,force and deformation law of different structural forms and design parameters of double-row pile structure.The main research contents and results can be drawn as follows:1.The results obtained through numerical calculation and theoretical calculation of single row pile retaining structure of field test section were compared with the field test results.It is shown that the values of the force and deformation of piles from numerical calculation in the current study are closer to the measured data compared with the conventional theoretical calculation results by considering the soil inhomogeneity,structural form,slope shape and other factors.The post-pile soil pressure nephogram accurately reflects the post-piling soil arching effect.This result suggests that the calculation result obtained from the current numerical calculation method can be considered to truly reflect the actual stress state of the structure.2.Under the premise that the number of piles per unit width,the soil parameters of the slope,and the relevant parameters of the structure are unchanged,change single-row pile structure to double-row pile rigid frame structure for 3D simulation calculation,the results show that compared with single row piles,double row piles are improved to varying degrees in the aspects of bending moment,deformation of pile body,deformation of post-pile slope and deformation of pre-pile foundation surface,strengthening the reinforcement of soil between piles,measures should be taken to strengthen the soil body in the passive area before the pile,the surface sand soil behind the pile and the end connecting steel bar during the construction,the distribution characteristics of pile body pressure change,the front pile bears the thrust action,and the back pile bears the resistance action,which should be taken into account in the theoretical calculation.3.Based on the conventional cantilever frame calculation model,consider the factors such as loose sand,low strength and stress characteristics of piles,specific calculation model,load calculation method,distribution method and distribution form are proposed,and the calculation results can reflect the stress characteristics of double-row pile more truly,which has a high reference value in the design of double-row pile structure in similar projects.4.Through the establishment of different 3D simulation models,the influence of design factors such as pile layout,pile spacing,row spacing,pile diameter,tie beam stiffness and connection stiffness on double-row pile structure is systematically analyzed,and design Suggestions are given:rectangular pile layout should be preferred,the spacing of the piles should be 2D~3D,the spacing should be 3D~4D,and the pile diameter should be 1.0m~1.5m.Measures should be taken to ensure the connection rigidity between the bored pile and the tie beam.The beam stiffnessc can be appropriately increased to reduce displacement of the structure.The back pile diameter can be appropriately reduced to reduce the project cost.According to the engineering characteristics and requirements of the project,the parameters should be reasonably selected in order to achieve the purpose of reasonable structural stress and economic cost. |
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