Studies On Lateral Resistance Of Ballast Bed In Cold Area Based On The DEM

With the advent of "economic globalization" and "One Belt And One Road",China’s railway develops rapidly.Railway coverage in cold ares is increasing.However,lateral stability studies on the railway ballast bed in these areas are relatively few,and the influencing factors of lateral resistance change are not well understood.Therefore,it is necessary to carry out studies on the lateral resistance change rule of ballast bed in cold areas and its microscopic mechanics.These studies are of important theoretical value and engineering significance for the railway traffic safety in cold areas.In this paper,the discrete element method(the DEM)is adopted,and the lateral resistance and its influencing factors of different sleeper types-frozen ballast bed in cold areas are explored.The main works are as follows:(1)The construction of the DEM model of irregularly shaped ballast.In order to better reflect the physical characteristics of ballast,the external contours of ballast are drawn by CAD,and spheres are filled in them to construct different shapes of ballast.(2)The DEM simulations of uni-axial compression tests on frozen ballast.The DEM models of uni-axial compression tests of frozen ballast are developed.The parallel bonding model is used to model the freezing effect of ice,and the contact-freezing DEM model of frozen ballast is established.The microscopic parameters of the frozen ballast under different freezing conditions are determined.(3)The DEM simulations of lateral resistance of full scale standard IIIc sleeper-frozen ballast bed.The DEM model of full scale standard IIIc sleeper-frozen ballast bed is developed,and the lateral resistances are simulated.The influences of different freezing temperatures,the shape of ballast shoulder and the action of cyclic loading are determined as well.(4)The DEM simulations of lateral resistance of full scale different sleepers-frozen ballast bed.The DEM models of full scale different sleepers-frozen ballast bed are developed,including different winged and double-block sleepers,and the lateral resistances are simulated.It turns out that the optimized winged and double-block sleepers have higher lateral stability.Based on the DEM calculations at the meso-scale,the lateral resistance of different sleepers-frozen ballast bed and the influencing factors are discussed.These studies provide a reference for the maintenance and optimization design of ballast bed in cold areas.