Analysis On Ultimate Bearing Capacity Of Asphalt Pavements With Semi-rigid Base Based On Strain

Existing design methods of the asphalt pavement takes the deflection value as acontrol index of the pavement thickness design. The deflection value has a directrelationship with the accumulative frequency of equivalent standard axle load duringthe design life of the pavement. Research shows that, due to limitations on allowablebearing capacity of a pavement structure, excessive axle loading may damage thepavement material at one time, which will speed up the destruction of the pavementstructure. The designed deflection value is mainly used to characterize the overallstiffness of pavement structure under repeated standard axle load, which is differentfrom the effect of fracture under one axle load. Therefore, it is necessary to propose amore effective control index to analyze the fracture failure of the asphalt pavementlayer.This thesis made a comparison of conventional asphalt pavement design indexes(such as road surface deflection, compressive strain on top of subgrade soil, shearstress within granular base etc.) in many aspects. And the perspective that the tensilestrain value at bottom layers of pavement structure should be the control index ofultimate bearing capacity of asphalt pavements was put forward.Based on the test purpose and requirements, the experiment scheme was designedto investigate the fracture strain values of asphalt mixture and cement stabilizedspecimens (including the selection of raw materials, grading requirements and ten silestrength test method) in this thesis. In accordance with the established test procedurefor the experimental study, the test results was analyzed.Then, according to the multi-layer elastic layered system theory, typical structureof semi-rigid base course asphalt pavement was applied to analyze the trend of tensilestrain value at the bottom layers of pavement structure under different contact statesand load conditions, in order to determine the maximum value. Based on the abovetest results of fracture strain values of asphalt mixture specimen and cement stabilizedmacadam specimen, the rationality and applicability of the control index of strainvalue were further confirmed. Finally, appropriate measures to reduce cracks were proposed after determiningthe ultimate bearing capacity of pavement structure.