| In this paper, the typical diseases in hydraulic structure engineering are simulated by FDTD method of GPR’s electromagnetic wave based on Yee grid, and the forward modeling graphic feature of typical diseases are analyzed with actual engineering detection. The main contents are presented as follows:(1) The electromagnetic fundamental of GPR is elaborated detailedly, the operating principle and system constitutes are analyzed. The conventional processing flow of GPR data is discussed. The applicative condition of various conventional treatment of data and processed effect are elaborated through actual examples. The radar images are enhanced in order to improve image quality and be recognized easily.(2) According to Maxwell curl equations, the3D FDTD form and2D FDTD form of Yee grid is deduced. The characteristics of Maxwell equations are deeply analyzed. The numerical simulation of GRP detection and the characteristics of boundary conditions are analyzed. The applicability of conventional simulation methods of absorbing boundary condition is discussed. Several conventional linear prompting functions are compared and the simulated images’ characteristics of typical prompting functions are studied.(3) The categories of typical diseases in hydraulic structure engineering are analyzed. The factors and characteristics of typical diseases,such as cracks, cavities and holes, are discussed. The features of forward modeling images of common disease in hydraulic structure engineering are analyzed. The mapping characteristics of different interval rebars and defects under steel fabric in reinforced.concrete are analyzed, and reference of GPR detection on reinforced concrete and image explaining are provided. Based on GPR numerical simulation method, the experiments of hole model and crack model are setted up. The actual measured2D reflective images and simulated images are compared and the feasibility of simulation method that mentioned in this paper is validated.(4) The GPR detection is applied in practical engineering. Through GPR detection technique, the health status of Mawei east levee in Wuxi and Zhenru Port levee in Shanghai have been prospected. And the feasibility of GPR detection in practical engineering is illustrated by comparing with detecting images and simulated images. |
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