| Cement Asphalt Mortar(CA)layer plays the role of supporting the track slab and buffering high-speed train load in a ballastless track structure.Under the long-term effect of a complex environment and train load,the CA mortar layer will develop the void disease,which deteriorates the smoothness of the track and lowers the train’s running quality.Therefore,this thesis investigates the development law of CA mortar layer void under the combined action of train and vehicle-induced pore water pressure,to provide theoretical support for the maintenance and repair of ballastless track of high-speed railway.The specific research contents and results are listed as follows :(1)For CRTSI slab ballastless track,based on fluid mechanics theory and fluidsolid coupling method,the integrated simulation analysis model of track slab-CA mortar layer-cavity-water-base slab is established,and the modeling method is carried out to verify the correctness of the model.Among them,the change of hydrodynamic pressure gradient along the transverse position is more obvious,and the amplitude of hydrodynamic pressure increases with the increase of water filling amount.The hydrodynamic pressure can reach 52.891 MPa when the water filling percentage is very near 100%.(2)Based on the integrated simulation analysis model,the influence of train speed,cavity size,plane position,and water filling on the hydrodynamic pressure in the cavity is studied.When the water is full,the hydrodynamic pressure increases linearly with the train speed,and the growth rate is 0.75 MPa/(10km/h).When the void plane is located in the rail area,the sensitivity of hydrodynamic pressure change is larger than that in other areas.With the increase in void height,the hydrodynamic pressure decreases.When the void height exceeds 15 mm,the change rate of hydrodynamic pressure is-7.16 MPa/mm.The transverse and longitudinal length ratio of void has little effect on the change of hydrodynamic pressure amplitude.When the water is not full,the change of the hydrodynamic pressure amplitude is opposite to that of the full water state.When the vehicle speed reaches more than 300 km / h,the hydrodynamic pressure tends to be a fixed value related to the water filling amount.The variation of hydrodynamic pressure amplitude with void height and plane position is consistent with that of the full water state.When the longitudinal and transverse length of the void is relatively small,the variation law of the hydrodynamic pressure amplitude is the same as that of the full water state,but when it increases to 2.4 times,the hydrodynamic pressure increases exponentially.(3)Based on the XFEM method(extended finite element method),a hydraulic fracturing model of void edge cracks under vehicle-induced water pressure is established.The correctness of the modeling method is verified by the existing test results.The propagation law of a single crack at different initial positions and different initial angles and the propagation law of two cracks at different initial distances and initial angles are studied.Under the condition of full water,when the hydrodynamic pressure exceeds 52.891 MPa,the edge cracks begin to expand;the void location has little effect on the crack propagation path.The crack extends to the acute angle,but the crack at the edge of the void has a tendency to turn to the center of the void(d=0.25m),and the farther the distance,the earlier the crack turns.With the decrease of crack spacing,the mutual interference between cracks becomes greater and greater,and the interference force suppresses the intersection;with the increase of the initial angle θ,the two crack directions change from opposite to opposite,and the intersection is more likely to occur.Therefore,to avoid the expansion and intersection of cracks at the edge of the cavity and aggravate the cavity,the detection of water content in the cavity and the elimination of water in the cavity should be paid attention to in the actual track structure maintenance operation. |
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