| The existing diseases of the cement pavement are mostly related to slab void,such as discontinuity of slabs,arching,fracture,pumping,and slab void evolution has played a catalytic action.At home and abroad,the research on the fatigue life of cement pavement with void time history evolution analysis is not thorough and perfect.Therefore,it has great scientific significance and application value which studying the evolution law and fatigue life of cement pavement slab under void deeply.This study set up the mechanical 3D model of cement pavement slab with void evolution under dynamic load,based on the orthogonal analysis of the position and shape of void,systematic analysis on mechanical properties of the cement pavement slab with void was made.The grey relational analysis method was used to explore the correlation degree of the seven parameters and the four parameters of the void slab under time history evolution innovatively.The theoretical model of cement pavement slab void evolution is verified by tests.The calculation method of the fatigue life of cement pavement under the action of the void evolution is proposed.Results show that:(1)Through the analysis of orthogonal combination calculation,it is found that when the location of the void is at the corner of slab is the most unfavorable mechanical position,and ellipsoidal is the closest to the bottom of the slab.The bottom plate influence range is void range outside the region in 400 mm.When the void radius reaches 2090 mm,the crack will occur.The influence of the void depth is 50% to the void radius.The possibility of the cement concrete pavement failure on the bottom of the slab is more than 3~6 times higher than that of the cement pavement with no void because of overload.(2)The correlation degree order of the different parameters for cement concrete pavement slab void under time history evolution: Dynamic elasticity modulus of surface 6>Dynamic load4>Surface plate thickness5>Vehicle speed3>Void radius1=Dynamic elasticity modulus of sub base7>void depth2。The grey relational analysis of the slab void under time history evolution about seven parameters and four parameters propose that the correlation degree of vehicle speed is greater than void radius,and the correlation degree of void radius is greater than void depth.(3)The stress value of the point in the void area is about 3~5 times of the stress value in the edge point in the sensitivity analysis of the parameters.After the full-scale transformation,it is equivalent to the location of the edge of the void area.When the load is located at the distance from the plate angle of 1800 mm,the stress value is almost zero in the void radius test.The test verified the conclusion that effect of void depth is little than void radius,and effect of dynamic load is little than void depth in the simulation.(4)According to the fatigue damage type constitutive equation with fatigue void damage variable,the calculation method of the fatigue life of cement pavement under the action of the void evolution is proposed:lgN_f=2.813=(((1-D)f_r)/σ)~122 .When the void radius is greater than 800 mm,the fatigue life of the pavement is plunged.When the void depth is 20 mm,decreasing rate of the fatigue life of cement pavement becomes larger under the void evolution.When the dynamic load increases to 180 kN,the fatigue life is reduced to almost zero.When the slab thickness is more than 280 mm,the fatigue life is greatly improved. |
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