The Thermal Stress Study Of Void Beneath Slab On Cement Concrete Pavement

In recent years,the cement concrete pavement as a high grade pavement has been widely used.The void that beneath the slab has a negative impact on the pavement performance and generates a high maintenance cost.The void beneath slab is affected by traffic load and thermal stress.the thermal stress of cement concrete pavement is studied deeply in this dissertation.By using large-scale finite element software ANSYS to simulate and calculate the concrete pavement,analyzing the thermal stress condition of concrete pavement voids and not voids separately,Considering the various parameters under the condition of combination on the influence of the thermal stress of cement concrete pavement.Specifically,the content of this paper is the following:(1)Analyzing the void state analysis of cement concrete pavement,especially the formation mechanism,influence factors and test methods of void beneath slab.(2)Discussing thermal field and warping deformation theory.(3)Establishing a three-dimensional finite element model.In the process of establishing the model,selection of parameters and elements,partition of the meshes and the application of the constraint conditions are carried out.(4)The influence of the temperature gradient is the most significant among the factors,which affect the temperature stress,the second is the thickness of the surface layer,the least significant is modulus.Therefore,we can take some effective measures to minimize the temperature gradient of the road surface,so as to avoid the occurrence of the early destruction of the road.(5)The influence of the variation of thermal gradient on the cement concrete pavement slab corner thermal stress was analyzed.The thermal stress depends on the thermal gradient,which has no direct relation with the road surface or inside temperature.With the increase of thermal gradient of cement concrete pavement,the thermal stress of slab corner increases gradually.(6)Study on the influence of the area of void beneath slab corner on the thermal stress.The change of the temperature stress is obvious when from no void to void.And with the increase of the void area.the temperature stress change is small,change rate is less than 3%.Due to the road surface and base void,making the link between the board and the foundation becomes weak,bound to deformation decreases and the temperaturestress reduces.So,temperature stress of pavement voids is less than condition of pavement not voids.(7)General the tensile strength of the cement is relatively weak,When the temperature gradient is negative temperature gradient,the slab corner is subjected to tensile stress,at this time,concrete pavements are easily damaged.(8)Discussing the influence of the surface layer modulus on the cement concrete pavement thermal stress.With the increase of surface layer modulus,the thermal stress increases.When the modulus of the cement concrete pavement increases,the rigidity is improved,the binding force of concrete enhancement,lead to stress increased.Under the premise of ensuring the carrying capacity of pavement,the modulus should not be too large.