Study Site Pollution Diffusion Detection Based On ?-Type Structure Detection Method

Resistivity method is an important component in the field of geophysical exploration and is commonly used in environmental pollution investigation,oil and gas search,geohydrological exploration and other fields due to its advantages of high automation and high resolution of results.Based on the heterogeneity of resistivity parameters in the stratum,ERT introduces an artificial electric field to analyze the characteristics of subsurface medium parameters by the potential distribution characteristics of the study area.If leachate leakage occurs in a landfill,the presence of various heavy metals and other chemical substances in the leachate will cause significant changes in the resistivity of the contaminated area,so ERT can be used to obtain and analyze the distribution characteristics of the stable current field for the purpose of detecting the spread of landfill pollution.Based on the above analysis,the following studies are carried out in this paper for detecting landfill leachate pollution dispersion.(1)To address the problems of limited detection depth of the ground-based highdensity electrical method,limited horizontal detection distance of the well ground resistivity CT(Computerized Tomography,CT)method,and poor convergence of the cross-hole resistivity CT method in the near-borehole region in the traditional resistivity method,by comparing the characteristics of the traditional resistivity method at different detection scales,we propose a ?-type structure detection method containing ground information constraints and subsurface information constraints to improve the detection sensitivity.(2)The forward run uses an unstructured grid with high grid quality and flexible control of grid sparsity to dissect the study area,and takes advantage of the modeling advantages of the unstructured grid to improve the model characterization criteria and computational accuracy.(3)To address the problems that the mature least squares algorithm in the inversion algorithm depends on high a priori information and has weak ability to analyze local media anomalies under the geological stratification structure,this paper proposes a serially coupled inversion method of Multiple Population Genetic Algorithm(MPGA)and least squares algorithm to obtain better layer thickness parameters by using MPGA,and then use the a priori information to construct the least squares algorithm to optimize the inversion operation and improve the resolution of local anomalies.(4)A landfill in Jiangsu province was used as the research object to construct a brine diffusion model,and the brine diffusion law was analyzed by means of numerical simulation.And use this as a guide to construct a leachate diffusion scene using brine at the site,The brine infusion data were obtained by the ?-type structure detection method,and the data were processed by the improved forward and inverse algorithm to achieve the purpose of detecting brine diffusion on site.The calculated results were compared with the professional exploration software of AGI and the numerical simulation results of brine diffusion to verify the feasibility of the detection method and the forward and inverse algorithm in detecting the contamination diffusion of the landfill from the perspective of engineering experiments and to provide some reference values for the subsequent treatment of leachate.