| With the rapid development of my country’s economy,railway transportation volume is increasing year by year.Some existing railway lines can no longer meet the transportation needs.In order to solve this problem,it is necessary to rebuild existing railway lines or add second lines.The construction of the second line of the railway is often restricted by geographical conditions,and some protection and reinforcement measures are required.As a new type of retaining structure,the pile-slab wall has large lateral resistance,convenient construction,and small amount of masonry.It can block and protect the slope without being restricted by height.It is used in slope and road engineering applications.widely used.When the newly-built line is close to the existing embankment pile-slab wall laying,due to the restriction of the terrain,a new pile-slab wall slope must be installed between the existing pile-slab walls,and the two are arranged side by side to jointly bear the new load.At present,the effect of widening the slope on the force of the new pile-slab wall and the existing pile-slab wall structure,the load transfer mechanism when the two work together is still unclear.Therefore,relying on the newly built Zhongwei-Lanzhou Railway(Gansu section)to introduce the Lanzhou hub supporting project,carry out model test research on the synergy mechanism of the new-old combined embankment pile-slab wall,relying on theoretical analysis and using a combination of model test and numerical simulation.Analyze the influence of the load on the new pile-slab wall and the existing pile-slab wall structure when the subgrade is loaded,and study the load sharing when the two work together.The main research contents and results are as follows:(1)Check the literature,understand the research status of the pile-slab wall and composite retaining structure at home and abroad,and summarize the functioning mechanism of the pile-slab wall.Based on the Rankine earth pressure theory and the Coulomb earth pressure theory,the calculation method of the earth pressure behind the middle wall of the railway retaining wall is obtained,and the design of the pile-slab wall is studied.(2)Relying on the typical sections of actual projects,according to the similarity theory,the geometric similarity ratio between the model and the prototype was 1:8.The indoor model test was carried out.It was found that when the top surface of the roadbed was loaded,the soil of the cantilever section of the new-old composite pile-sheet wall The pressure increases first and then decreases along the top of the pile.The soil pressure of the old pile and the new pile reaches the maximum at 0.48 m and 0.78 m away from the top of the pile respectively.The soil pressure borne by the newly-built pile-sheet wall is directed to the existing pile In the process of slab-wall transfer,the two eventually bear almost half of the combined structural load;the pile body bending moments of the old pile-slab wall and the new pile-slab wall both increase first and then decrease along the pile top.The maximum bending moment of the pile body of the pile-sheet wall is 2.1m from the top of the pile,and the maximum bending moment of the old pile-sheet wall is 1.35 m from the top of the pile.When the track and train loads are applied after the new pile-slab wall,the displacements of the tops of the old piles and the new piles are both within the allowable range.(3)Establish the three-dimensional elastoplastic finite element model of the test model,study the development law of soil pressure distribution,internal force and deformation of the newly-built pile-slab wall and the existing pile-slab wall under the condition of hierarchical loading,and compare the actual measurement of the model test under the design load It is found that the earth pressure behind the wall,the internal force and deformation of the pile body obtained by the numerical simulation are basically consistent with the laws of the numerical simulation results,which verifies the correctness of the numerical model. |
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