Research on the Damage Characteristics of Double-Block Ballastless Track Bed Slab under Temperature and Vehicle Dynamic Loads

The concrete damaged plasticity model was adopted to describe the mechanical characteristics of double-block ballastless track bed slab.Setting the maximum damaged state of track bed slab under changing temperature as the initial condition and taking the rail supporting force obtained by vehicle-double-block ballastless track coupled dynamic simulation as an external excitation of track-subgrade structures,the damage evolution law of track bed slab and the influence of track bed slab on the mechanical behavior of structure were analyzed under the joint action of changing temperature and vehicle dynamic load.Results show that the track bed slab presents lateral bending deformation and produces damage which weakens the tensile capacity in temperature dropping process.While in the temperature rising process,the damage value of track bed slab remains unchanged and keeps around 0.23 due to the tension damage produced by temperature dropping is unrecoverable,but the elastic stiffness of track bed slab appears recovery phenomenon.As vehicle passes through the damaged track bed slab,the internal cracks of track bed slab take on open or closed alternatively.The elastic stiffness is partly recovered for a short time and the maximum amplitude of stiffness degradation factor is 0.057,while the damage value of track bed slab remains unchanged.The dynamic amplitude including displacement and acceleration of track bed slab,the dynamic stress of supporting layer and the surface of foundation bed are all increased,but the tensile stress is decreased,compared with the results of undamaged condition.The damaged plasticity model can well represent the softening and stiffness degradation behavior of concrete of track bed slab.