Analaysis On The Merchanical Response Of Semi-Rigid Base Pavement With Contact Model

The current Specifications for Design of Highway Asphalt Pavement (JTJ014-97) (SDHAP) is based layered elastic theory, which assumes that the interface between layers can transfer force and deflection fully. However, it is proved during engineering practice that the adhesion between the layers of the pavement structure is poor, the adhesion quality is between absolutely slippery and whole continuous, and the interface transfer force by contact. Then, the design point of pavement is not coincident with its active state, which will influence the accuracy of the performance's evaluation. It is better to use contact model to analysis the mechanical response of pavement than traditional continuous model.Generally, a uniform circular vertical contact stress is commonly assumed in representing wheel loads in pavement analysis procedures. However, experimental measurements have shown that a non-uniform rectangular vertical contact stress is more appropriate, especially when the vehicle is overloaded. The objective of the paper was to present the difference of mechanical response of two kinds of model applied different loads. To carry out this objective, three-dimensional (3D) finite element (FE) program is used to predict the mechanical response of semi-rigid base pavement. The 3D FE program permits to input non-uniform vertical rectangular contact pressure at various axle load and horizontal stress from the tires when vehicles start or brake. In these analyses, the deflection on the pavement surface, the maximum principal stress at the bottom of the asphalt layer and semi-rigid base, the minimum principal strain on the top of subgrade and the maximum shearing stress at the bottom of the asphalt layer were predicted. The remarkable difference is the maximum principal stress, which results from the traditional continuous model is too small to work the item about tensile stress of the existing SDHAP that the maximum principal stress at the bottom of the asphalt layer and semi-rigid base should never excess the permissible tensile stress of corresponding material. On the contrary, the maximum principal stress from the contact model is much bigger and morerational. From the predicted maximum principal stress at the bottom of the semi-rigid base when the percentage of overload increased, the service life of the semi-rigid base asphalt pavement was estimated. In addition, the horizontal stress has effect on the maximum shearing stress.According to the result of 3D FE program, it is better to use contact model to analyses the pavement structure, because it can better present the active state of the pavement than traditional continuous model.