Detection Of Ground Penetrating Radar In Homogeneous Earth Dam And Three-dimensional Forward Modeling

Ground penetrating radar(GPR)is a main method of engineering detection,but its application in dam disease detection is not mature due to the imperfect theory and detection technology,the limitation of detection depth and the influence of detection object on radar wave.Therefore,GPR technology in disease dam detection image feature analysis and the corresponding research achievements are less,and widely used in field detection is still a two-dimensional detection technique,the location of the disease in the homogeneous earth dam,form hard description,the corresponding disease spectrum feature analysis is also larger subjectivity and empirical.Starting from the physical model test of roller compacted homogeneous earth dam and three-dimensional forward modeling based on FDTD algorithm,this paper analyzes the position,shape and size of preset diseases in the model,and studies the second and three-dimensional detection technology and Matlab three-dimensional forward modeling of diseases of homogeneous earth dam.The main research contents are as follows:(1)The physical model of homogeneous earth dam was designed and fabricated,and the physical model was detected by radar.The radar waveform was processed by RADAN7,and the second and third-dimensional images of the cavity and metal diseases were obtained,which more directly demonstrated the homogeneous soil.The image characteristics of the dam disease detection radar waveform map,and the rationality and feasibility of the model design and line layout scheme are discussed by detecting the image results.(2)According to Maxwell's equation,the propagation principle of radar wave is studied.The special matching matrix on the cutoff boundary is used to derive the UPML absorbing boundary condition of TM wave in conductive medium and non-magnetic consuming medium under forward modeling.The UPML absorbing boundary is studied.The parameters are set in the homogeneous dam clay medium,and the relationship between the FDTD algorithm and the UPML difference formula is established.The UPML absorbing boundary conditions under the finite difference time domain are systematically combed and studied,which provides a Matlab programming.Theoretical basis.(3)FDTD algorithm was established based on Matlab programming under UPML absorbing boundary conditions of numerical model,constructs the three 1000 mm cube model,on the depth of 20 cm in diameter and height is 160 mm hollow cylinder and metal disease model,and the diameter and height are under 50 cm depth 160 mm cylinder cavity disease model of three-dimensional forward modeling,the analysis summarizes the characteristics of disease spectrum of homogeneous earth dam.(4)The reliability and accuracy of the forward simulation program are verified by comparing the three-dimensional slice map under ground penetrating radar scanning and Matlab program forward.Through the simulation results and the analysis of the physical experiment detection results,the understanding of the characteristics of the various disease profiles in the homogeneous earth dam is deepened,and relevant experience and theoretical knowledge are accumulated,which has improved the correctness and reliability of the map interpretation of on-site radar detection.