Permeability Test Of Loose Medium In Groundwater Reservoir And Numerical Simulation Of Seepage Field

The underground water reservoir is a water conservancy project that utilizes the permeability of porous media as a water storage medium,and has the advantages of low construction cost,low risk,and small negative effect of running environment.The law of groundwater movement in loose water storage medium involves the cross-disciplinary problems of water conservancy,geotechnical and geological,which restricts the construction and operation of underground reservoirs.In this paper,the motion process of groundwater in heterogeneous saturated aquifers is studied experimentally and verified by numerical analysis methods.Combined with the groundwater reservoir,the variation law of groundwater level under different parameters of underground dam is analyzed.The effects of rainfall infiltration,recharge and pumping on groundwater recharge are studied.The basic research conclusions are as follows:(1)The variation of water head and fl,ow velocity in heterogeneous saturated aquifers is revealed.Based on the combination of two-dimensional sand tank test and numerical calculation,the infiltration flow of groundwater in heterogeneous saturated aquifer is clarified,and the change of water head and flow velocity around the abrupt change of natu,ral aquifer medium is studied.Combined with the flow velocity distribution obtained by experiments and numerical calculations,the heterogeneous influence function was determined by statistical software SPSS.The results show that the head of the seepage field around the low-permeability mirror has a variation range of±0.005m under heterogeneous conditions.The maximum flow rate is 1.1 to 1.23 times the average flow rate under homogeneous conditions.(2)The effects of depth,width and permeability coefficient of different underground dams on the seepage field of groundwater reservoirs were studied.The depth of the underground dam has a great influence on the drop height of the groundwater level in front of the dam,and the two have a quadratic function relationship,the width of the underground dam has little effect on the drop height of the groundwater level before the dam;the permeability coefficient of the olocal dam is less than or equal to 1×10-8 m/s,the impact on the groundwater level will be significantly reduced.The three parameters of the underground dam are analyzed by the sensitivity based on orthogonal experiment.The depth of the underground dam and the permeability coefficient have significant influence on the sensitivity of the groundwater level in front of the dam.The width and permeability coefficient have significant influence on the maximum flow velocity;Depth has a great influence on the single flow of seepage.(3)The seepage model of groundwater reservoir considering rainfall infiltration is established.Based on Fredlund&Xing unsaturated soil theory,the unsteady seepage field of groundwater reservoir under different rainfall conditions is calculated.Combined with the anti-seepage measures of single and multi-channel underground dams,the water level growth form under different rainfall intensities is calculated;the upstream water level in front of the underground dam of the single-bank is increased by 71.1%,and the water level changes in the reservoir are mainly concentrated in 1#and 6#storage space;different rainfall patterns have a certain influence on the time when the pore pressure of the upper and lower surface layers reaches the maximum value and the peak value of the surface water content.(4)By establishing a complete recharge well model of confined aquifer,combined with the well flow equation of the complete pumping aquifer and the groundwater level change under the recirculation of ADINA-T,the single well is recharged and pumped.Under the action of the seepage field change,the displacement and settlement under the action of pumping are analyzed.The results show that when the rcharge pumping ratio reaches 1/2-1/5,the recharge has a significant slowdown to the ground subsidence.(5)Through the calculation and analysis of the anti-seepage effect and the recharge effect of the groundwater reservoir,combined with the idea of constructing the underground reservoir in the outwash fan of the northern Qinling Mountains,the variation of the seepage flow of the groundwater reservoir under different anti-seepage measures is analyzed.By setting up a suspended anti-seepage underground dam with a depth of 110 m and double-row anti-seepage curtains,the seepage flow can be reduced by 68.70%,which provides advise for the construction of underground reservoirs and the construction of underground dams for outwash fan of the northern Qinling Mountains.