System Identification Method For Backcalculating The Voids Beneath Rigid Pavement Slabs Based On GPR

Void is a quite universal disease in use of Cement Concrete Pavement. Void reinforcement should be completed timely, otherwise it will result heavy damage to the structure of pavement, even endanger the quality and safety of access. Accurately identifying void is the premise and basis of selective maintenance. Detecting voids beneath rigid slabs based on GPR has become a hotter issue in recent years. But it has been limited to qualitative detection because of the difficult of theoretical model and signal analysis. Method for backcalculating the thickness of voids beneath rigid pavement slabs based on GPR is studied, so that tentative study on quantitative detection voids can be realized. The research contents and results of the paper as follows:(1) Based on electromagnetic theory, models of radar wave propagation in pavement structure with air-filled voids and water-filled voids were established, and simulated signal was obtained based on the model. The precise theoretical model was provided for backcalculating parameters of voids beneath rigid pavement.(2) Based on the theory of system identification and sensitivity analysis,the method for backcalculating the thickness of voids beneath rigid pavement slabs was presented, and the backcalculation program was developed in this paper, so that the model parameters to achieve the efficient adjustment process the automation of adjusting parameters was realized.(3) Based on the above model and inversion method, inversion method for the thickness of voids beneath rigid pavement was established. Aim at the three special shapes of rectangular, circular and cross, the thickness of air-filled and water-filled voids were backcalculated. Evaluation results show that it is feasible of determining the thickness of voids beneath the rigid pavement based on the inversion method.The feasibility study of quantitative detection the thickness of voids beneath rigid pavement slabs based on GPR was carried out, and it provided theoretical basis for the further study on quantitative detection voids with general shape in engineering practice.