| With the economic development,the passenger and freight volume of my country’s railways continue to increase,and the passenger and freight volume of existing railways will not be able to meet the long-term needs in the future,and the expansion and reconstruction of existing railways is imperative.In the western mountainous areas,railway widening is often restricted by topography.If single-row piles are used for slope support,the size of the piles may be large enough,which consumes more materials,so consider the use of front and rear composite pile-slab walls for slope support.At present,the research on the mechanical mechanism of the composite pile-slab wall is obviously insufficient,especially in the interaction mechanism of the front and rear composite pile-slab wall.Therefore,this paper conducts on-site measurement of the new front and rear composite pile-slab wall project in the Xigu section of the Lanzhou hub of the Zhonglan Passenger Dedicated Railway Station.Finite element software is used for numerical simulation,and the force analysis of the front and rear composite pile-slab wall is carried out to study the force and deformation The mechanism,the conclusion is as follows:(1)Measure,record and organize the field data to obtain the earth pressure,bending moment and displacement of the front and rear piles,and organize and plot the stress,bending moment and displacement curves.The maximum bending moment of the rear piles appears above the bottom of the pile At position 1/3,consider that there is a sliding surface at this position,and the anchoring section is below the sliding surface.Comparing the left and right piles,the regularities of stress,bending moment and displacement are relatively consistent,but the values are different.When analyzing the reasons for the differences,it is considered that the difference between the adjacent piles at the other end of the composite pile is caused.(2)Midas GTS NX finite element software is used to numerically simulate the actual project according to the construction process and analyze the results.Considering the combined action of the soil pressure in front of the pile,the soil pressure behind the pile and the force of the beam,the stress distribution curve law of the back row of piles and the front row of piles in front of and behind the pile is analyzed,and the maximum value of the stress behind the back row of piles is compared with that of the front row of piles.The maximum value of the front stress of the row of piles is obtained,and the stress apportionment ratio of the rear row of piles in the front and rear composite piles is obtained.The stress distribution law of the left and right composite piles is relatively consistent,and the difference between the adjacent piles at the other end of the left and right composite piles leads to the difference in the stress value and the stress sharing ratio of the left and right composite piles.Correspondingly,the stress distribution patterns at the upper and lower ends of the left and right beams are also relatively consistent,and the stress values are different.The stress of the retaining plate is approximately symmetrical,and the stress difference between the left and right ends causes the deflection of the retaining plate.The displacement in the X direction of the front and rear rows of piles is regarded as rotating around a point respectively,and the displacement in the Y direction is similar to the displacement in the X direction.Only considering the rear-row piles as a single row of piles through the Lizheng software for safety checking,and drawing a safety conclusion,the safety of the composite pile-slab wall is also guaranteed.(3)In addition to actual working conditions,numerical simulations under six working conditions are also studied.By reducing the length of the bottom of the pile and the length of the cantilever end,and changing the connection method of the beam and the front and rear piles,the stress maximum value,the stress sharing ratio and the displacement under the seven working conditions are analyzed and compared.The position of the maximum stress is related to the position of the beam.The reduction of the cantilever end is more sensitive to the increase of the stress,and the fixed connection of the beam helps to reduce the stress.All working conditions are positively related to the advancement of the construction phase.From the fifth layer filling stage to the train loading stage,the stress sharing ratio of each working condition is relatively stable,and the stress sharing of each working condition during the train loading stage The ratio difference is not big,considering that the front row piles have a good stress sharing effect on the back row piles.The working condition where the end of the cantilever is reduced by 1m is more sensitive to the increase of the displacement.The zero point of the displacement is different from other working conditions,and the zero point of the displacement of other working conditions is more concentrated. |
