Study On Calculation Model Of Horizontal Seepage Well Of Deep Drawdown

Horizontal seepage wells are placed in the riverbed to obtain uninterrupted supply ofnaturally filtered groundwater through highly permeable saturated riverbed aquifers.Horizontal seepage wells have following advantages over traditional vertical wells, gallery,radial collector wells and other water intake engineering: large water yield, good water quality,the operating cost of the wells tends to be low and has little influence on environment. Owingto these benefits, in recent years, horizontal seepage wells have attracted considerableattention as groundwater supply wells, especially in arid and semiarid regions such asnorthern Shaanxi.Current calculation model for groundwater flowing to horizontal seepage wells is onlyapplicable to saturated seepage flow, not to unsaturated seepage. The river will bedisconnected to groundwater when the pumping rate is greater than the river’s recharge rate,while unsaturated zone exist at the bottom of riverbed. In this paper, based on the NationalNatural Science Fund Project (40972154)“Study on calculation model and physical modelingof non-casting-well groundwater-collecting catchment working mechanism”. Through thesand tank physical simulation experiment of horizontal seepage well pumping, further studyon horizontal seepage well of deep drawdown has been done, and modeling for groundwaterflowing to horizontal seepage well of variably saturated flow.Seepage sand tank, miniature of horizontal seepage well, surveying system,water-cycling system and other equipment are used during the physical simulation test ofhorizontal seepage well. The simulation test is on three different drawdown of vertical shaft,two rivers of different leakage capacity, and the corresponding data plan, axial pressure dropdata from experiment, water yield and pressure drop distribution data of each observationpoint in the tank. Method of particle size analysis and vertical tube is used to study thepermeability of aquifer medium, which as a reference for modeling. Figuring soil watercharacteristic curve based on data getting by method of grittiness funnel.By comparing the test results of simulation test, following conclusions can be drawn: thewater yield of seepage well increase with increase of drawdown in vertical well when other conditions are identical; the stronger of the river’s leakage capacity, the larger of the wateryield of seepage well; water yield will be still increased when unsaturated zone exist, butspecific water yield significantly reduce.In the study area as a whole sand trap, based on the actual size of a sand trap physicalsimulation test each device, three-dimensional finite difference grid as the basis, using theexchange amount between the aquifer and the well pipe as the coupling point for theestablishment of the “variably saturated of coupled seepage–pipe flow model of thesimulation test and calculate the water yield”. The simulation results show good fit of themeasured water yield of test, which indicate that the numerical model was effective andreliable. Calculating water yield of horizontal seepage well during different drawdown toconfirm the critical moment that river disconnected to groundwater.