Three Dimensional Model Test Of Ground Penetrating Radar And Forward Modeling Of Non Grid Method

For precision and adaptability requirements higher tunnel lining GPR nondestructive detection,you must first master the lining disease radar profile image features,to establish a typical model curve,so as image reconstruction and interpretation of GPR forward simulation technology has practical significance.At present,GPR simulation in finite element method and finite difference time domain method,the mesh directly affect the calculation accuracy and calculation,and Simulation in the pretreatment process is more complicated.This paper will introduce meshless method of tunnel lining of GPR forward simulation.This method is simple and adaptable,get rid of the grid limit,just before the processing field into discrete nodes will be calculated,and by moving least squares method(MSL)fitting function.Only the correct selection of base function and weight function;reasonably determine the effects of the radius and node density can be obtained with high precision,smooth and continuous results.The main research contents and results are as follows:1.studied the radar 3-D physical model of hollow bottom tunnel lining.Through the physical model making of tunnel lining cavity,the results will be processed to generate three-dimensional images of radar detection.From the image analysis,image detection accuracy of 1600 MHZ antenna is higher than that of 900 MHZ antenna;shows the real situation from the empty model in three-dimensional diagram,including the cavity size and shape.The diamond section in this test hole,from the 3D map that is increasing with depth gradually increase in the level of rectangular section.Through the experiment,explore the 3D detection method and validation of the 3D detection is more precise and reliable function of image interpretation.2.the meshless method based on the theory of sliding least squares method of selection of the negative exponential weight function and the Two-Dimensional Quadratic basis functions,in the integral by Gauss integral.On the processing of the boundary,the first kind of boundary condition is treated by the penalty function,and the reflection of the model boundary wave is suppressed by the improved SARMA absorbing boundary condition.3.using the element free Galerkin method to write the MATLAB forward program,the tunnel lining cavity in the different shapes of holes for numerical simulation and image processing.The analysis of the image,the shape of the diamond shaped hole is "parabola" shape,the double rectangular cavity shape as the intersection of the double parabolic shape,which provides a reference for the actual project image interpretation.The results of physical model test are compared with MATLAB numerical simulation results,and the shape of the 2D profile is "parabola" shape,which verifies the feasibility of the non grid method for the forward modeling of tunnel lining diseases.