Research On Void Beneath Curling Slab And Load Fatigue Stress In Rigid Base Cement Concrete Pavement

In china, the early damage of cement concrete pavement is more serious. The poorconstruction quality and the improper late maintenance, with no doubt, could cause thissituation. However, one deep reason of this early damage is that the curling deformationphenomenon under temperature gradient occurs on the cement concrete pavement, and thepavement structure design is lack of consideration for the influence of void beneath curlingslab. In this paper, the void law beneath curling slab under the couple action of traffic loadand temperature is deeply studied, the calculation formula of loading stress in the curling slabis firstly set up, and the calculation method of load fatigue stress is given, which have animportant practical significance and theoretical value for the design of cenment concretepavement.According to the disease investigation and using status of cement concrete pavement, thevoid beneath curling slab and working state of cement concrete pavement are analyzed. Using24h continuous FWD deflection testing method on the curling slabs, the void condition wasgiven. Deflection and temperature of road surface test shows that the damage of the concretepavement is related to void beneath curling slab cause by the changes of the temperaturegradient.Through the analysis of temperature distribution, temperature gradient status andtemperature distribution model, the prediction formula of curling deformation is derived in thepure bending condition under negative temperature gradient.The three-dimension temperature model is built by finite element software, and theinfluences of curling deformation are systematically analyzed under the weight, temperaturegradient, base modulus and thickness, slab length and thickness, and the interlayer state. Thevoid beneath curling slab analysis shows that the temperature gradient and base modulus havesignificantly influence on void size beneath curling slab. As the temperature gradient and basemodulus increases, the void size beneath curling slab increases. Finally, the curlingdeformation of pavement is verified by observation data in the test road.Through the finite element calculation under the couple action of traffic load andtemperature, the change law of warping cavity and load stress is studied. Through the regression analysis of calculation result, the formula of load stress with temperature gradient,base modulus, and slab thickness has established.Based on the probability distribution of the road temperature field and axle load, the leanconcrete base cement concrete pavement load fatigue stress model is is firstly andsystematically proposed. And the analysis shows that the cracking time of pavement surveyedis significantly reduced. And the service life analysis shows that the service life of ShuiNanRoad will significantly reduce due to the increasing of loading stress occurring in curling slab,and the void beneath curling slab caused by temperature gradient changes is the fundamentalreason for the failure of rigid base cement concrete pavement.