Study On The Law Of Groundwater Seepage In Coal Mine Gangue Dump And The Effect Of Blind Ditch Drainage

The wet piles of coal gangue dumping have a high moisture content,which will further increase the water content of the gangue piles under the effect of rainfall,resulting in a decrease in the shear strength of the piles.There is a potential risk of geological disasters in it,and the engineering measures shall be taken to discharged it in a timely manner to ensure the safe operation of the waste dump.There are many factors affecting the groundwater seepage and drainage in the dumping ground.Among all the factors,it is the effect that water replenishment and groundwater drainage measures under different rainfall intensities has on the groundwater seepage and transfer of the dumping ground has the research value most in the safe operation of the dumping.The gangue dumping site of Hecaogou coal mine in Zichang city has been chosen as the research target.In order to get the characteristics of the gangue stack in the gangue dumping site and obtain engineering geological data related to the waste dump,some effective measures have been taken such as field investigation,engineering geological analysis,field test,laboratory test and numerical simulation.What’s more,the physical and mechanical indexes and permeability coefficients of coal gangue deposits in different areas and numerical simulation experiments also play important role in the process of drawing the conclusion.The conclusions are as the followings:(1)Hecaogou coal mine dump is a valley-type landfill dump,and its density of the accumulation in some areas is about 1.678g/cm~3,and the water content of the gangue(with slime)is about 13.0%.The particle gradation is good,having a high plastic deformation ability meanwhile its initial permeability coefficient keeps 1.062cm/s,and the permeability of saturation and coefficient is 2.766cm/s.(2)Groundwater seepage in the dump site cannot form a stable flow under the combined action of different rainfall intensity and blind ditch.It transfers to the bottom of the valley in the form of a transient saturation zone at the initial rainfall mainly,infiltrating downward along the impervious layer of the two wings and the axis area of the blind trench in the middle in the form of a transient saturation zone in the middle and later periods.The greater the rainfall intensity,the greater the transfer frequency and the peak pore water pressure peak of the transient saturation zone in the accumulation body during the early rainfall,and the greater the pore water pressure in the accumulation body during the middle and late periods.The Increasing rainfall intensity has a greater influence on coal gangue deposits,while the decreasing rainfall intensity has the most obvious effect on the central area of the deposit.The direct influence range of blind ditch is about 30m.(3)The evaluation method,discharge efficiency index and efficiency grade of the blind ditch drainage effect are proposed based on studying the variation of pore water pressure at the monitoring points in the accumulation body.Although the blind ditch cannot exert its proper drainage capacity most of the time under the deep burial effect,it has a high excretion efficiency when it can exert its excretion ability.