Evaluation Of The Base And Coordination Design Of Structures For Concrete Pavement In Hot-moist Regions

For various reasons, the use situation of cement concrete pavement built in early years isnot good in China, service life is greatly lower than designed service life. At present, the studyof the durability for concrete pavement in China mainly focus on surface layer, while thelong-term performance of concrete pavement is related to subgrade and base, fine subgradeand base are the premise which ensure normal operation of concrete pavement. With the rapiddevelopment of China economy, the traffic characteristics of rapid speed，heavy load and thelarge proportion of overload vehicles proposed more strict requirements to cement concretepavement. Therefore, for cement concrete pavements with different types of bases, choosingreasonable structure design index, conducting the combination design of the pavementstructure, increasing the long-term performance to improve the use of concrete pavementcondition, and prolonging service life are critical to concrete pavement for its faster and betterdevelopment.According to different traffic levels and different types of base, the use situation ofconcrete pavement with semi-rigid base and rigid base were investigated and analyzed inhot-moist regions. The influences of base cracking, cavity, interlayer combining status andbase stiffness on concrete pavement were analyzed. On the basis of the long-termperformance of base and climate characteristics in hot-moist regions, the reasonable base typeof concrete pavement was preliminarily recommended.Through laboratory experiments and mechanical analysis, the binding situation betweenthe base and concrete slab, the influence of base layer cracking on concrete pavement, theanti-brushing performance of base materials, as well as the deformation and strain of cementconcrete pavement with different kinds of base layer were studied. The results showed that thebinding status between the base and concrete slab is extremely important. The sliding frictioncoefficient of cement concrete slab at base interface is an important parameter for researchingtemperature stress, the length of slided and fixed area, joint, spacing, plate-end lapse andlongitudinal instability. Under normal conditions, the friction resistance of emulsified asphaltisolation layer is between0.76and0.87, while asphalt mixture functional layer of which isbetween0.71and1.10, and geotexitle isolation layer is between1.08and2.06. The constraintof the aggregate base to concrete is minimum, and concrete slab buckling deformation ismaximum, and the constraint of asphalt concrete base to concrete is medium, while leanconcrete’s constraint to concrete is maximum, almost no buckling deformation formed.Through analyzing the effect of long-term performance evaluation index of base course on cement concrete pavement, using grey relation analysis theory, this study establishedprediction model of evaluation index for long-term performance of base. the evaluationmethod of cement concrete pavement, which can be used for forecast evaluation of long-termperformance of base.By analyzing the effects of cavity on the concrete pavement stress, according to thecalculated value of the maximum stress and the maximum deflection of concrete pavement,the maximum amount of allowed cavity of concrete pavement under the consideration offatigue but without temperature stress was derived. On the condition of adverse loadingposition, the effects of crack(or not)of base, the width and the location of base crack on loadstress and temperature stress of cement concrete pavement were analyzed. The results showthat the presence of cracks damaged the integrity and continuity of the pavement structure, theload stress of pavement structure significantly increased. The functional layer cansignificantly reduce the maximum tensile stress of the slab, and the temperature stress of thepavement structure showing a decreasing trend. Taking full account of the mechanical andphysical properties of different types of base layer, and combining with the improvement ofthe functional layer, the appropriate types of base under different traffic level for hot-moistregions were recommended. Based on the requirements of the long-term performance of thebase, this paper proposed a structure design method for cement concrete pavementconsidering fatigue of both concrete surface layer and base layer.