Control And Modeling Of Clogging During Artificial Groundwater Recharge In Xiong’an New Area

Artificial groundwater recharge can effectively cope with groundwater overdrawing and the negative environmental effects caused by it,but the clogging problem in the recharge process seriously restricts its popularization and application.Supported by the national key research and development project "Xiongan New Area Groundwater artificial recharge,regulation and storage(2018YFC0406503)",this study designed well irrigation and river channel infiltration schemes according to the hydrogeological conditions and groundwater artificial recharge conditions of the study area,carried out the corresponding groundwater artificial recharge in-situ test,and analyzed the blocking control effect;A simulation model of surface clogging process applicable to different formation causes was constructed,and the evolution process of clogging in situ test was simulated and analyzed.The main research results are as follows:(1)Developed a control technology for well recharge and clogging.This technology is aimed at the problem that the traditional tubewell recharge blockage is difficult to control because it often occurs in the filter,filter material layer and the adjacent water-bearing medium.Three approaches are adopted to implement the prevention and treatment of the blockage:(1)Adding a porous filter device at the inlet of the recharge well,so that the main location of the blockage in the recharge well is advanced to above the surface so as to facilitate the blockage treatment;(2)Add an inner pipe that can realize the function of lifting back into the recharge well pipe,which can be handled by periodic lifting when blockage occurs in the downhole part;(3)Fill and filter medium between the recharge well pipe(outer pipe)and the return well pipe(inner pipe)to further reduce the clogging risk of the filter,filter material layer and adjacent water-bearing medium during the recharge process.(2)A control technology of river infiltration recharge and blockage is developed.Aiming at the problem that the natural permeability of vadular zone and riverbed is weak and surface water cannot recharge groundwater efficiently,the blockage control method of high level infiltration is proposed according to the gravity settlement principle of suspended matter in surface water.That is,the high permeability sand column above the surface is set in the riverbed and low floodplain and the sand column penetrates the low permeability clay layer below the surface,so as to open up the channel of surface water conversion to groundwater.This method can realize the purpose of efficient infiltration in wet season and maintenance of sand column surface in dry season.(3)The in-situ test of groundwater artificial recharge was carried out to verify the effectiveness of the clogging control technology.(1)A 30-day in-situ well irrigation test showed that: Compared with the conventional recharge well,the application of the clogging control technology has a good prevention and control effect on the blockage caused by the precipitation of suspended particulate matter,iron oxide or hydroxide in the recharge water and flocculation.The stability time of high rate recharge can be extended by 29 times,and the stable recharge rate can be increased by 77%.(2)A 52-day water infiltration and recharge test of Nanjuma River showed that: compared with natural river,the application of high level infiltration device with blockage control technology can increase the conversion intensity of river water and groundwater per unit area by one order of magnitude,and increase the recharge efficiency by 170%,and the effect is more obvious with the increase of recharge time.(4)A simulation model of surface clogging applicable to multiple mechanisms was constructed.Based on two blocking mechanisms,intermediate block and filter cake filtration,and combined with the series model of blocking resistance,this model can quantitatively simulate the change of pressure drop in the artificial recharge process of groundwater.Based on the laboratory experimental data,it is shown that the model can simulate the clogging process of the medium surface in the artificial groundwater recharge process well,and predict the replacement time of the intermediate block and the filter cake filtering clogging mechanism.The constructed surface clogging model is used to simulate the in-situ test data of groundwater artificial recharge well and river channel.It is proved that the model has good applicability to simulate the actual constant flow recharge process and artificial recharge and clogging evolution process under the condition of non-constant head,and has certain application potential.