Research Of Asphalt Overlay Structure With Cracking Relief Layer On Existing Cement Concrete Pavements

Paving asphalt concrete overlay on existing cement concrete pavement, can notonly improve the condition of the road structure and the usability of the roadsignificantly, but also make full use of the existing cement concrete pavement, reducethe construction pollution caused by it, shorten the cycle of existing cement concretepavement reconstruction. All of these reflect good economic and social benefits. Butthe main problem is the reflective cracking emerged easily in asphalt overlay, whichcan greatly influence the life of the road after reparation.Reflective cracking is one of the main damages of asphalt concrete overlay onexisting cement concrete pavement, so far there is no ideal method to solve it, aimingat this problem, a method of using the graded crushed stone as cracking relief layer isproposed. The mechanisms of anti-reflective cracking of the graded crushed stonelayer are analyzed, multi-void structure of grading crushed stone layer can beeffective to block the extension path of crack-tip, weaken the tensile stress, tensilestrain of the delivery capacity and disperse, absorb loading stress and thermal stresscaused by the traffic load and ambient temperature changes.On the basis of introducing the current measuring method of resilient modulus ofgraded crushed stone, this paper proposed a new measuring method of resilientmodulus of graded crushed stone plate specimen, the formula with the new methodwas deduced, which was verified by the finite element method. This method providesa new choice to the measurement of resilient modulus of graded crushed stone.This paper established the structural mechanics analysis model of asphaltconcrete overlay with graded crushed stone cracking relief layer by the finite elementmethod, analyzed the asphalt concrete near seams overlay of stress conditions underthe effect of load and temperature, and studied the change rule and effect degree ofloading stress, thermal stress of asphalt concrete overlay followed by factors ofasphalt concrete overlay thickness, resilient modulus, graded crushed stone crackingrelief layer thickness, axle load, resilient modulus of base, to reveal the preventingreflective cracking mechanical mechanism of graded crushed stone cracking relieflayer material. These provide essential evidences in the design of asphalt concreteoverlay.Referred to graded crushed stone cracking relief layer anti-measures, the design method of asphalt concrete overlay on existing cement concrete pavement at homeand abroad was summarized, and the applicable design index and method for thesetting of graded crushed stone relief layer overlay structure was proposed.