Study On The Change Law Of Permeability Of Quaternary Aquifer

Open-pit mining destroys the integrity of underground aquifer and water barrier,and the groundwater level changes from stable state to unstable state,resulting in the flow tendency tending to the mine pit,resulting in the phenomenon of water gushing in the mine pit,and affecting the stability of the slope and the normal production operation of the mine.The drainage well pumping method is usually used to reduce the slope water level in open-pit mines,but it is found that the drainage well capacity decreases obviously with the passage of time in the application process.In order to explore the reasons for the capacity decline of drainage Wells in use,the permeability coefficient measurement experiment,expulsion experiment and filtration experiment were designed from two perspectives of seepage filtration and ion effect of sample soil to reveal the variation rule of seepage process on the permeability of sample soil under the influence of various factors.Based on the design of filter layer,d₁₀,which determines the effective pore size of soil,was determined.Based on this,the size limits of movable particles in the seepage process in the sample soil were divided.Through Varying-head infiltration test device to determine the permeability coefficient of soil under different concentration samples,the results show that the permeability coefficient of the sample soil is related to the seepage solution.With the increase of the concentration of seepage solution,the permeability of the sample soil increases first and then decreases.The peak value of the permeability coefficient is distributed around 0.05mol/L of the solution,which is about 10%higher than the permeability under the condition of water solution.Expulsion experiment,when the soil using aqueous solution to expel salt solution,there is an obvious change of permeability,embodied in:sample soil permeability has been destroyed,the value decreased significantly,and with the increase of salt solution concentration,sample soil permeability declines.After the permeability coefficient is stable,the relationship between the percentage of residual permeability coefficient and the concentration of salt solution shows a negative exponential function e.Combined with victory in the open-pit mine hydrogeological conditions and observation level change,on the basis of the theory of drainage precipitation,the influence of the desiccating Wells on groundwater level is evaluated,the study found that drainage Wells layout density,quantity is larger,but the length of service is usually only 1?3 years,and discarded after cannot reuse,the practical value is low.Therefore,on the basis of the expulsion experiment,two ideas of constructing the water-retaining layer to block the water gushing in the slope and restore the original groundwater level are put forward through pumping experiment and stratified inner drainage.