| The karst area in southwest China covers 451 counties in 8 provinces,including Guizhou,Yunnan,Guangxi,Hunan,Hubei,Chongqing,Sichuan and Guangdong.The total area of karst is 5.197×105Km~2.Karst area is a kind of fragile geological environment,and its vulnerability is mainly manifested in the dissolution of the soluble rocks in the karst aquifer.For example,pollutants are easy to enter the groundwater through the water holes and pipes in karst areas,causing groundwater pollution.Alternatively,the material of the soluble rock itself is taken away by the water because of the dissolution,and it is difficult to form soil and leads to soil loss.Therefore,it is very important to determine the spatial distribution of groundwater in the karst aquifer and accurately describe the structure of the karst aquifer to manage water resources,water environment and geological disaster prevention and control.In this paper,the numerical model of hydraulic tomography and resistivity tomography was established respectively to explore the possibility of describing karst pipelines by hydraulic tomography and resistivity tomography,and the influence of prior parameter selection on the description accuracy was studied.Secondly,based on the results of numerical simulation test,the indoor sand box model of heterogeneous karst aquifer is constructed,and its imaging is carried out by using hydraulic tomography and resistivity tomography respectively,which verifies the effectiveness of the two methods in karst highly heterogeneous aquifer.Finally,hydraulic tomography and resistivity tomography are fused to explore whether the fusion of the two methods can further describe the inversion accuracy of karst heterogeneous aquifer.The research contents are as follows:(1)Construction of hydraulic tomographic scanning numerical model.To verify the effectiveness of its characterization of karst highly heterogeneous aquifer and explore the influence of the number of stimulus sources,pumping rate and the selection of initial inversion value on the results of hydraulic tomography.(2)The numerical model of resistivity tomography scanning was constructed.To verify its effectiveness in characterizing highly heterogeneous karst aquifers and explore the influence of electrical stimulation intensity and boundary conditions on resistivity tomography.(3)The indoor sand box test of the heterogeneous karst aquifer was carried out.The response values of water head and electric potential were obtained by pumping and electric stimulation respectively.Then,the model of karst heterogeneous aquifer in the sand box was imaged by using hydraulic tomography and resistivity tomography,and the reliability of the inversion results was verified.(4)Tomographic scanning imaging based on homologous data fusion was studied.The data of permeability coefficient and conductivity obtained in the sand box test were logarithmically transformed respectively and the linear fitting relationship between the two data was obtained.Using the linear fitting relationship,the conductivity was converted to the permeability coefficient,which was used as the prior information of the hydraulic tomographic scan of the sand box to carry out the fusion imaging of the hydraulic tomographic scan.The permeability coefficient is converted into electrical conductivity and used as the prior information of the inversion of the sand box resistivity tomography for the fusion imaging of resistivity tomography. |
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