Research On Optimization Of Semi-flexible Pavement Structure Based On Crack Resistance

The semi-flexible pavement material is a pavement material which is composed of a cement-based grouting material with special properties in a high-interconnected void asphalt mixture,which has high bearing capacity and outstanding anti-rutting characteristics.However,compared with the asphalt pavement,the semi-flexible pavement material has a large rigidity and has a problem of cracking.Therefore,in this paper,for the problem that the semi-flexible pavement material is easy to crack,the semi-circular bending experiment of three different maternal semi-flexible mixtures is designed and the fracture parameters are obtained.And by means of the fracture theory in fracture mechanics,the simulation analysis of the fracture process and structural crack resistance optimization of semi-flexible materials is carried out.Based on the fracture energy and fracture toughness of fracture mechanics,the experimental results of the crack resistance of the material are evaluated.The rotary compacted test piece of SBS modified asphalt,SBS+MA100 interface enhancer and SBS+MA100 interface enhancer+fiber three types of large-void parent asphalt mixture was designed and fabricated.The grouting was cured and cut into semi-flexible materials.Semicircular test piece.The incision depth of the test piece was prefabricated to 8 mm,12 mm,and 15 mm,respectively,and the slit width was 2 mm.From the energy point of view,the experimental method of the crack resistance of the material is designed by the semi-circular bending experiment with slit.The failure process and failure modes of three types of semi-flexible materials at room temperature(25 ° C)and low temperature(-10 ° C)were analyzed.It was found that semi-flexible materials have certain viscoelastic properties at room temperature.Through the integral fitting and fitting analysis of the semi-circular bending force-displacement curve,it is concluded that the semi-flexible material of SBS+MA100 interface enhancer+fiber has the highest fracture energy and fracture toughness,which is suitable for the selection of engineering materials and the need for crack resistance.In order to verify the accuracy of the modulus parameters of SFP semi-flexible materials for 3D road model simulation,a two-dimensional finite element model based on the semi-flexible specimen dimensions of real semicircular bending experiments was constructed.With the extended finite element(XFEM)module in the software,initial cracks of length 8mm,12 mm,and 15 mm are inserted into the model to form a two-dimensional model with pre-cuts.The input of the existing semi-flexible material creep experiment is used to obtain the converted Prony parameters and the fracture energy parameters obtained by the semi-circular bending experiment.The forcedisplacement curve of the loading point of the SCB finite element model under controlled displacement loading is obtained by simulation.Then analyze and compare the SCB force-displacement curves obtained by finite element simulation and laboratory experiments,compare the shape,trend and envelope area of the curve,and obtain the simulation-experiment curve of the transient modulus E0 of the semi-flexible mixture at around 3500 MPa.The combination is better,so the modulus parameters of the macroscopic three-dimensional road structure model for semi-flexible pavement are confirmed,and the credibility of the model calculation results is improved.Combining the practical conditions of the semi-flexible pavement engineering and the advantages of the extended finite element method in simulating the crack propagation problem,the paper uses the Abaqus software and its XFEM module to adopt the optimized semi-flexible material modulus parameters,considering the initial existence of the road structure base layer.The crack does not extend to the state of the surface layer,and a threedimensional extended finite element model of the crack propagation of the semi-flexible pavement structure is established.The model analyzes the expansion of the base reflection crack under traffic load,and studies the influence of the thickness and combination form of the semi-flexible pavement structure and the base layer modulus on the reflection crack propagation under dynamic load.Finally,based on the angle of crack resistance,the stress intensity factor and J integral of the crack tip are used as the control indexes,and combined with the semi-flexible pavement test section of different structural combinations actually constructed by the project,the thickness of the surface layer of the semi-flexible pavement should be kept at 6 ~8cm.With the help of the grey correlation degree theory,the factors affecting the crack expansion are sorted and compared,which provides a reference for the future use of semi-flexible pavement.