Study On The Stability Of Slope Pile-slab Subgrade In High-speed Railway

The development of high-speed railway put forward very high requirements to the subgrade which may be of "high stability, high precision and small residual deformation". Building the high-speed railway in slope soft soil section not only needs to overcome the unfavorable conditions in soft soil section but also needs to solve the problems of lack of lateral restraint on subgrade and the potential sliding surface. Therefore, the application of pile-slab embankment in slope soft soil section can effectively improve the vertical and lateral stability of the subgrade. Thus it is no wonder a new solution to solve the problems when building high-speed railways in similar conditions. Based on a comprehensive research on relative references, in this paper a deep research has been done on pile-slab embankment used in slope soft soil section. Details are as follows:(1) Definitions of stability coefficient of pile-slab in slope subgrade and limit basic principles have been analyzed; conditions and yield criterion acquired in the to limit analysis method have been proposed; A pile slab subgrade three-dimensional model have been built by using nonlinear finite element software and reasonably solve the problem of pile-soil, slab-soil contact and ground stress balance.(2) The paper studies the change law of stability coefficient, internal force and displacement of the slope’s sheet pile structure under vertical, horizontal and longitudinal load; Analysis of the main influencing factors of the mechanics characteristics of sheet pile structure under several conditions have been done to study the reasonability of structural type. It shows that application of the pile-slab in the slope subgrade allows a substantial increase in stability coefficient, and the sliding surface of slope has been effectively controlled; Vertical load is the main load of sheet pile structure. The bending moment and shear force in the middle of loading plate are greater and under vertical loads. Piles are mainly due to shear force of the axial force and the soil boundary increasing with the span and the height and decreasing with pile length, pile diameter and thickness.(3) Analysis of influences factors such as the weak layer thickness, position weak layer in the foundation, the impact of ground cross slope and embankment filling nature of the pile-plank embankment on slope stability have been done. The research shows that stability coefficient of the pile-slab in the slope subgrade increases with the weak layer thickness. And when the value of the thickness is larger than critical value, the stability coefficient stabilized; The impact that rock layer and weak interlayer on the embankment is very obvious; Stability coefficient decreases linearly with improving cross slope of the ground; Shear strength index of the subgrade has obvious influence of the stability of slop. However, improving the internal friction angle of the soil can be more quickly and effectively increase the stability of the subgrade.(4)The dynamic responses and stability of pile-slab in the slope subgrade under seismic wave load have been studied. The result shows that soil damping and the selection of model boundary conditions have a direct impact on the calculation. Damaging effects on subgrade of shear waves is much greater than the vertical ramp wave. The subgrade is easy to slide laterally and the shear failure occurs easily in pile-slab structure under seismic load, piles between embankment fill and the old subgrade surface bear larger shear force and bending moment, the lateral displacement of that piles is also large. So piles mentioned above will be easily destroyed. Bearing board bears greater shear force and bending moment only at mid-span. The vertical and lateral displacement is the same with the pile top.