Unsteady seepage analysis for a groundwater reservoir under different rainfall conditions

Rainfall infiltration is one of the main sources of water for the underground reservoir.The influence of rainfall on the groundwater reservoir water level and the water storage capacity of the groundwater reservoir are investigated in this study with a single reservoir of single channel anti seepage underground dam and a reservoir group of multi channel anti seepage underground dam.A two dimensional finite element model was established to estimate the unsteady seepage field of the groundwater reservoir under different rainfall intensities and different rainfall patterns,with the Seep/W module in GeoStudio finite element software.Rainfall intensity was chosen by taking into account annual average rainfall and annual maximum rainfall for a period of 1 year.Rainfall types include average type,forward type,center type and post peak type,with a total rainfall of 100 mm.The simulation results show that the upstream water level of the single base underground dam increased by 71.1% and the downstream water level increased by 11.7% under different rainfall intensities.The water level changes are mainly occurred in the #1 and #6 water storage spaces under multiple water storage spaces in an actual underground reservoir group,and the maximum water level changes are 8.8 m and 12.5 m under average rainfall and maximum rainfall,respectively.The water level in the middle storage space has only a minor change.The single reservoir has little changes of an overall water level.The installation of the reservoir group has a great influence on the water level for each water storage space,which might be beneficial to the water intake.Under different rainfall patterns,the pressures of the upper and lower surface pores of the single reservoir and the reservoir group reached their maximum.The peaks of the surface water content could be affected,and the maximum water content lasts the longest time with forwardtype rainfall.The research results provide a reference for the groundwater reservoir to store water under different rainfall conditions.

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