Calculation And Analysis Of Spatial Variation Of Hydraulic Conductivity In A Contaminated Site

Soil pore in the contaminated site is the space of storage,migration and transformation of pollutant in groundwater,and hydraulic conductivity is the key index to characterize the permeability of aquifer,which directly controls the flow of groundwater and then affects the pollutant migration process.Influenced by the sedimentary environment,the hydraulic conductivity often show different degrees of spatial variability,and the complex spatial variability of aquifer medium leads to the complexity of groundwater flow and solute transport.Therefore,calculation and identification of spatial variability of hydraulic conductivity are the precondition of studying contaminated sites and making reasonable remediation strategies.Pumping test is a common method to obtain hydraulic conductivity of aquifer.However,it is difficult to obtain a large number of hydraulic conductivity by pumping test for the limit of monitoring well quantity and the cost of treating the extracted polluted groundwater at site investigation stage.According to the correlation of stratigraphic lithology and permeability,this paper establishes a method for calculating the hydraulic conductivity by combining pumping test method and lithology analysis method.Kriging interpolation is used to obtain the spatial distribution of hydraulic conductivity.The calculation results of the scatter hydraulic conductivity indicated that the permeability coefficient in the study area is 0.09⁰.49m/d.The kriging interpolation results showed that the spatial distribution of hydraulic conductivity is uneven,the permeability coefficient is relatively high in the northeast-southwest location,and the hydraulic conductivity is relatively low in the corner of northwest and southeast.The spatial variability of the hydraulic conductivity was analyzed by variogram function.The results showed that the upper and lower layers were fitted well with Gaussian model and the middle layer was fitted well with an exponential function model.The coefficient of basal effect C₀/C?0?of the middle was the smallest,and the upper layer and the lower layer are relatively large;The ranges of the upper layer from54.45 m to 71.10 m,the middle layer from 128.92m to 174.33 m,and the lower layer from 85.77m to 190.52 m.A numerical simulation model of groundwater flow was established to compare the groundwater flow processes under the conditions of mean value and interpolated value of hydraulic conductivity.The simulation results show that the former situation have the greater water level change than the latter.The groundwater flow field simulated using the parameters calculated by the established method is closer to the actual situation.The overall trend of groundwater flow has not been influenced dramatically for the limited spatial variability of this site.