Numerical Simulation Study of Underground Pipelines Survey Based on FDTD
Ground penetrating radar,as a non-destructive testing method,is widely used in underground pipeline detection.It can quickly detect the location,burial depth,and diameter of underground pipelines,bringing great convenience to engineering construction.However,the wavelength of high-frequency radar waves and strong medium absorption make the detection profile more complex,and the detection effect of ground penetrating radar on underground pipelines also varies depending on the pipeline material and antenna frequency.In order to improve the effectiveness of detection and the accuracy of interpretation,the gprMax open-source code based on finite difference time-domain is used for numerical simulation of underground pipeline detection.Under the working condition of antenna frequency of 400 MHz and buried depth of 0.9 m in a circular tube,simulations are conducted on different pipeline materials.The results show that the reflected electric field intensity of the metal circular tube is twice that of the PVC circular tube.When the material of the pipeline differs greatly from the dielectric constant of the surrounding medium,the reflected wave energy is strong and the radar profile structure is clearer.Simulations are conducted on antenna frequencies of 400,900,and 1500 MHz,and the results show that the resolution of the radar image improves with increasing antenna frequency.Finally,simulations are conducted on the working conditions with air and water as the media inside the tube.At an antenna frequency of 400 MHz,the radar image of water as the medium inside the tube shows three obvious hyperbolas,and the radar image value of air as the medium inside the tube shows one obvious hyperbola,indicating that the energy attenuation of electromagnetic waves in water is less than that in air.
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