The Influence Of The Void Beneath Slabs Of Cement Concrete Pavement To The Load Transfer Of The Joint And Fatigue Cracking Damage

Void beneath slabs, as one of the major diseases of cement concrete pavement, is ubiquitous in our country. For its effect on pavement performance and life is very serious, research on void is very necessary.In order to establish a more reasonable and effective pavement maintenance & rehabilitation scheme to prolong the road service life and to provide important theoretical basis for road reconstruction and overlay, the confirmation of the location and size of the void is not enough, therefore, further study on void is necessary after mastering different evaluation methods. This paper, based on pavement mechanics finite element software KENSLABS, focus on the correlation between void beneath slabs and cement concrete pavement fatigue and the influence of void to load transfer, did the following research work:(l).Established a numerical model of dual plate cement concrete pavement with dowel bars when void occurs in the seam.Considering board weight and temperature, t his paper expounds the influence of the change of void height (i.e., the initial clearanc e) of two void forms to the load transfer capacity, compares the influence of the diame ter, spacing, looseness and supporting modulus of the dowel bar to the load transfer ca pacity, analyzes the optimization of dowel bar non-uniform layout to the load transfer system.The results showed that,as the void height increases.the load transfer coefficie nt will increase when void occures at both sides of seam,and decrease when void occu res at one side.But when the load transfer coefficient gets stabilized and when void oc cures at both sides, the absolute value of the maximum deflection increases;under diff erent void forms, all the dowel bar parameters have linear correlation with the load tra nsfer coefficient, among which the dowel bar looseness have the most significant infl uence.Under different pavement forms, the non-uniform layout of the dowel bars can i mprove the load transfer coefficient,and reduce the maximum shear force.The evaluati on of the load transfer capacity of the bottom slab void should consider load transfer c oefficient and the absolute value of the maximum deflection of the plate simultaneous ly, the evaluation of the optimization of dowel bar non-uniform layout to the load tran sfer system should consider load transfer coefficient and the shear force of dowel bar simultaneously.(2).Established a numerical model of the wheel load damage in the case of concrete pavement with void beneath slabs to explain the impact of changes in void height and void area of design life, the study uniaxial axle load, repeat every day affect the role of the number of panel thickness and flexural strength of concrete parameters on cement concrete pavement design life, and using the two-factor analysis of variance to shed light on a clear influence of the heavy weight of each factor. The results showed that when the void get smaller, with void height increasing, pavement design life of decay will sooner achieve relatively stable, and the extent of damage is relatively small. Change of Void height to the design life of the panel is much stronger than the void area. The uniaxial axle load, repeat every day affect the role of the number of panel,thickness and flexural strength of concrete parameters all have Logarithmic linear relationship of the pavement design life. The uniaxial axle load with respect to the number of daily repeated action, the panel flexural strength compared to the thickness of the concrete slab at the end of the design life of cement concrete pavement with void, impact is more significant. This paper may provide some theory evidence of the repair, maintenance and design optimization to the cement concrete pavement with void beneath slabs.(3). Referenced domestic and international literatures extensively. As for the aspect of void recognition, this paper summarized different methods which are based on the deflection index for voids beneath cement concrete pavement and analysed the applicability and limitations of each method. On the basis of void prevention, this paper introduced the principle and process of two kinds of pavement treatment means, meanwhile, summarized the previous experience and proposed an effective pavement voids preventive measures combined with the results in this paper.