Research On Electromagnetic Field Forward Modeling Of Geological Radar In Loess Layer

In this paper,the finite difference time domain method is used to simulate the electromagnetic wave forward modeling of GPR(ground penetrating radar).By Yee grid division method will the study area is divided into a certain number of spatial mesh,and using the finite difference method approximate the Maxwell's equations,and then complete the time discretization,the simulated calculation of the region boundary using the fully matched layer(PML)absorbing boundary.Thus achieving the simulation of wave field through the solution of Maxwell's equations,and the forward simulation study is carried out on geoelectric model of loess.In order to establish a reasonable loess geoelectric model,the paper using the data sampled from seven typical loess profile field in northern Shaanxi,Luochuan,Baoji area,summarized the Loess of dielectric properties and resistivity properties,and distinguished the difference between the electric characteristics of loess layer and the clay layer.Preliminary discussion on the relationship and influence factors of electrical parameters in northern shaanxi.Taking the loess section of the Chang-10 wells which has the most accurate data acquisition as an example,through the detailed analysis,the fine electrical characterization and description of the long 10 well loess section are described.The loess electrical characteristics of theoretical basis,radar profile interpretation,and the electric modeling basis are provided for Radar?s probing of detection of layered loess in loess tableland area.And the different electrical,clay layer thickness,clay layer depth of GPR loess geoelectric forward models are designed based on it,realized the forward simulation of two-dimensional electromagnetic wave,and obtain the corresponding electromagnetic wave field characteristic.Through achieving the forward simulation of two-dimensional electromagnetic wave on different geoelectric model of loess,obtaining the electromagnetic wave field characteristics in the loess layer and the clay layer,and the influence of frequency of antenna,clay layer depth,surface resistivity,differences in clay and loess layer resistivity,differences in dielectric constant on the GPR?s resolution of clay layer.By achieving forward modeling and interpreting the geological radar profile of Chang-10 loess model,combining electromagnetic wave theory of GPR,discussed the feasibility of detecting the clay layer by GPR.