Preliminary Study On Uniformity Mechanical Model Of Asphalt Pavement Structure Damage Based On The Mohr-Coulomb Criteria

Pavement structural mechanics analysis is a traditional research topic in road engineering,the predecessors have done a lot of work. But with the increase of wheel load, and diversification of pavement structure combination form,theory for some phenomenon of pavement structure damage can not explain the traditional damage of pavement structure. Such as: a lot of Top-Down crack of pavement surface damage produced in the round, is Top-Down crack pressure cracking tensile stress generated? Why after the grass-roots strength improved significantly faster the pavement surface asphalt layer damage soon?Studying the pavement structure of complex stress state needs new ideas. The M-C criterion is commonly used in geological engineering and the strength criterion of rock and soil mechanics, this paper attempts to explain the complex asphalt pavement stress from the angle of cross discipline,the stress of the main stress distribution and the M-C criterion based on the traditional model of pavement structure.The main work includes:Based on the elastic layered system theory and using the simplified model of the asphalt pavement structure, the influence of base modulus on asphalt pavement structure damage are analyzed,APPD that is the control index of a pavement structure is established.The unified mechanical model of pavement structure damage are initially proposed citing 6 highway asphalt pavement.Its stress distribution and failure mechanism of the different pavement structure were studied by finite element.Compared with the actual pavement damage, several pavement structure strength requirements of material are analyzed to verify. The stress states of asphalt pavement with high modulus basement are calculated with finite element models in which the parameters input are arranged with Uniform Design method. Combine with Mohr circle method and APPDI,stress system is applied to analysis the calculation results. The positions of Mohr circles for different nodes of two-dimensional stress systems are contrasted.Biaxial compression/tension phenomenon on pavement surface is discovered, in which casethe stress circle extends into both positive and negative σ space.Major research content and achievements:1)Preliminary study of the unified mechanical model of pavement structure damage, it was found that the maximum tensile stress and shear stress is not the first position of whole pavement structure damage.As a control index of pavement, tensile stress or shear stress structure is not reasonable.This paper proposes a new control index of APPDI to explain the mechanism of pavement structural damage.2)Analysis of three kinds of typical asphalt pavement structure, damage of structure patterns are from the control index of APPDI. Flexible base asphalt pavement performance is in bottom layer tensile stress of the bottom layer of bending failure; Performance of semi rigid base asphalt pavement for shear in the vicinity of the wheel track edge 1~5cm deep pressure stress damage(rutting) shear and wheel about 20 cm is at the depth of 7~12cm characterized by compressive stress damage(reflex crack); Rigid base asphalt pavement performance for the surfaces of wheel tracking edge is the shear failure(Top-Down crack) of tension compression symbiotic performs as the top-down extension; Three kinds of typical pavement damage the structure of the surface layers trength of materials is analyzed, and then given material intensity range.3)Though effects material parameters of APPDI cohesion c and the ultimate tensile strength of T, the influence of component failure and pavement structure of asphalt pavement are analyzed.The results show: Biaxial compression/tension phenomenon makes it possible there are at least two stress paths for pavement material to reach the strength envelopes under fatigue loadings. Biaxial compression/tension phenomenon is one of the key reasons for both TOP-DOWN cracking and rutting. Under fatigue loading, the positions of Mohr circles on different stress state under the pavement have great influence on fatigue life of pavement.Because the strength envelopes can be determined by cohesive, c, and tension strength, σt,both of them can be used as alternative design parameters together for evaluating pavement material anti-shear characteristic.