The Research On Slab Corner Breakage Of Cement Concrete Pavement In The Condion Of Soft Contact

In recent years,with the growth of traffic volume,construction mileage and service life,the phenomenon of structural damage on cement concrete pavement is more and more serious.The pavement base will be softened gradually and the condition of soft contact and cavity beneath slab will be produced under the influence of factors such as soaking and scouring.The breakage of slab and dislocation will be caused.The condition of soft contact means that strength of pavement base is decreased,support capacity for the slab is decreased and the cavity beneath slab is not produced after pavement base is soaked and scoured.The biggest contributing factors are that the anti-scouring ability of pavement base is insufficient and the softening and cavity of pavement base are not taken into consideration in the structure design of cement concrete pavement,and a thin thickness of surface layer is designed.The mechanical characteristics and deformation performance of cement concrete pavement are researched when vehicle load acts on the void cement concrete pavement by ANSYS in this paper.Three kinds of models are established when the pavement base contacts with slab completely,pavement bases is softened and cavity beneath slab is produced.The load stress of slab angle bisector and deflection of slab angle vertex are selected,and it is analysed that the change regularity of load stress and deflection is produced by slab.In order to perfect the existing design theory of cement concrete pavement thickness,the method is put forward that the load stress and deflection of slab corner are controlled in the condition of soft contact.The main conclusions in this paper are as follows.(1)In the condition of the pavement base contacting with slab completely,it is analyzed that the influence on load stress and deflection of concrete pavement on the condition of different surface layer thickness,different base course thickness and different load weight.The calculations results indicate that the slab is pressed near the corner of slab and tensed in the other positon of slab.And increasing the thickness of slab is more effective than increasing the thickness of pavement base to control load stress and deformation of pavement slab.(2)In the condition of pavement base being softened,it is analyzed that the influence on load stress and deflection of concrete pavement on the condition of different surface layer thickness,different soft size and different soft elasticity modulus.The calculations results indicate that phenomenon of obvious stress concentration is produced in the corner of slab when the pavement base is softened.And the value of load stress and deflection is higher than the condition of the pavement base contacting with slab completely.(3)In the condition of cavity beneath slab,it is analyzed that the influence on load stress and deflection of concrete pavement on the condition of different surface layer thickness,different cavity size and different load weight.The calculations results indicate that phenomenon of obvious stress concentration is more obvious than the condition of pavement base being softened.And the value of load stress and deflection is largest in the three states.(4)In the condition of three states,it can reduce the maximum tensile stress and deflection of pavement slab by increasing slab thickness and improve stress state of pavement slab.(5)The load stress and deflection of slab corner are taken into account in the condition of soft contact to design thickness of cement concrete pavement.It indicates that increasing design thickness of pavement slab can increase slab rigidity and reduce the deflection of slab corner.Breakage of slab and dislocation is avoided and service life of cement concrete pavement is prolonged.