Study On Some Problems Of Hydrogeology In Unconsolidated Aquifer

The experimental study of hydrogeological parameters and study of groundwater dynamic both are important contents of hydrogeology research.Recently,there are three main problems in the experimental study of hydrogeological parameters.(1)Theoretically,the influence of the factors such as well loss can be avoided when 2 or more observation wells are used,and the results are more ideal;but in actual work,due to the restrictions of site and funds,it is difficult to build observation well,just do the observation in the pumping well.But because of the well loss,there is a deviation in the result of parameter calculation.(2)In addition,the theory of pumping test is mainly for the fully penetrating well.For the partial penetrating well,it is usually to convert it to fully penetrating well,and then to calculate the parameters.At present,there is no widely accepted method for parameter calculation of pumping test in partial penetrating wells.(3)With the development of unsteady flow theory,although the “influence radius" and "effective diameter" concept is gradually weakened;it is often necessary to analyze these parameters in the remediation of groundwater pollution,the calculation of mine water inflow and the pumping of wells.To solve the above problems,in this paper,the large unconsolidated aquifer aquifer in Beijing plain and the middle reaches of Gansu River Basin in Heihe are taken as the research objects respectively,and the Packer stratified packer technology is adopted,(1)For the fully penetrating well,the hydrogeological parameters obtained by using the pumping test data of different time periods are analyzed and compared in the case of with observation well and without observation well;it is proposed that when there is no observation well,the parameters of unsteady flow should be calculated by using the observation data between 5 minutes and 120 minutes after the pump is stopped(2)For the partial penetrating well,the hydrogeological parameters obtained by using the pumping test data of different time periods are analyzed and compared in the case of with observation well and without observation well;and also compared with the parameters results of fully penetrating well,the results shows that the water conductivity obtained by pumping test of the partial penetrating well represents the water conductivity coefficient of the whole aquifer in the location of the filter pipe section;the practical significance of the hydrogeological parameters which are obtained by pumping test in the partial penetrating well is clarified.(3)Based on the steady and non-steady flow theoretical formula,Newton iterative method,by using the observational data of drawdown in stable section in the fully penetrating well pumping test,the rapid calculation formula of “influence radius" and "effective diameter" are derived respectively.Groundwater dynamics is an essential basis for water resources assessing and detecting,as well as the important content of hydrogeology research.Utilized the middle reaches of Heihe long series of underground water level monitoring data,combined with the hydrogeological conditions for the comprehensive study of regional groundwater dynamic;also analyse the water level data and runoff data of Heihe with wavelet transform,we got two points of understanding:(1)There are five main types of groundwater dynamics in the middle reaches of Heihe: Unbalance area of groundwater in the Shandanhe Basin,the self balance area of groundwater in the Zhangye Basin,unbalance area of groundwater in the multi-river bBasin in the front of the Yumu Mountain,unbalance area of groundwater in the Yanchi Basin and the self balance area of groundwater in the lower end erosion and accumulation plain of the middle reaches of Heihe.(2)In the middle of Heihe River Basin,within the range of 1.7km on both sides of the main stream,the groundwater with depth in 10 m under the surface is interacting faster with the river runoff;out of the range 4.7km on both sides of the river,groundwater is interacting slower with the river runoff;in the middle of Heihe basin,on both sides of the revier,the interacting of groundwater with depeth more than 30 m under the surface is lagging behind.