Study On Deformation Failure Characteristics And Design Method Of Railway Stepped Reinforced Earth Retaining Wall

There is not well accepted method for the design of rail stepped reinforced soil retaining walls although their popular use in rail slope reinforcement practice.For this concern,the determination of the potential failure surface is the key issue.Some current specifications clearly addressed the shape and location of the potential failure surface but limit its use only in single walls with the height of no more than 10 m.Based on the actual construction site of step reinforced earth retaining wall in Dechang Station,this paper explores the influence of railway load and step width on deformation and failure characteristics of reinforced earth retaining wall through indoor model test and FLAC numerical simulation.The main research contents are as follows:(1)The model is designed with a large scale of 1:4 and the rail load is stimulated by a specific cycle of surcharge load.The shape and location of the potential failure surface are brought out by the analysis on the slope surface lateral displacements,the vertical settlement at the slope crust,also and the strain of the geogrid at different investigation points.(2)FLAC3D is used to validate the model test,and the numerical simulation program verified by the model test is used to analyze the influence of step width change on the horizontal displacement,vertical settlement of the top of the wall,the location and shape of the potential rupture surface of the reinforced earth retaining wall.(3)The design and calculation methods of reinforced earth retaining wall are systematically studied and analyzed.Based on the results of model test and numerical simulation,The potential failure surface form and design calculation method of railway reinforced earth retaining wall under different step widths are put forward.The results indicate that: the shape of the potential failure surface in the lower stage wall is similar to what in the “0.3H” method,but it has a deeper location and a more gentle inclination of the bottom part which indicate a larger unstable area;and that the shape of the potential failure surface in the upper stage wall is similar to the Ranking's active rupture,however it thrusts into the lower stage wall rather than thrusting out from the foot of the upper stage wall.It can be seen that with the increase of the step width,the maximum horizontal deformation value of the wall decreases gradually and the settlement value of the corresponding points tends to decrease,but the change trend is basically the same.The potential fracture surface forms of reinforced earth retaining walls with different stepped widths are also different.Therefore,the width of the step is the key factor to control the deformation and failure of the reinforced earth retaining wall.The result including the shape and the location of the potential failure surface may be taken as a reference for design of rail stepped reinforced soil retaining wall.