Study On The Hydrogeochemical Process Of Simulated Abandoned-coal-mine

Taking the Zhang Shuanglou mine in Xuzhou mining area as an example,the simulation-monitoring system about hydrological and geochemical processes of closed pit in coal mine is established.This processes simulates the open and closed groundwater system after the coal mine is closed,and the simulation and monitoring of hydrogeochemical field process and groundwater dynamic field evolution process was achieved.The main results and conclusions are as follows:?1?The simulated abandoned-coal-mine includes closed and open systems,belonging to groundwater flow field and water chemistry field multi-field coupling simulation system.?2?The rock samples are coal gangue taken from Zhang Shuanglou coal mine?sample capacity of 4 to 5 tons?,and experimental flow simulates Zhang Shuanglou coal mine according to a certain percentage.Water flow of closed system is 17-19ml/min and open system is 16-18ml/min.Set the filling time for a month,water flow of the closed system being 20.11ml/min and open system being 16.77ml/min,while the actual time to full up is about two months.It is predicted that Zhang Shuanglou coal mine will be filled up after about 160 days.?3?Stratified head?flow field?monitoring of the simulation system displays that the water level in the initial stage is 10-24mm,and the hydraulic attenuation of the lower part of the simulation system is 14mm.Thus 1/3 of the depth will be stagnant.?4?The simulation system from March 14,2017 to April 24,2017 PH value of 7.35-8.45 or so,the dissolved oxygen content of 1.74-7.73mg/L,the conductivity range of 1.41-2.58ms/cm,oxidation and reduction potential 119.5m V-263.2m V.It is predicted that the water environment in the mined-out area of Zhang Shuanglou mine is weakly alkaline and weakly oxidized.Late to weak to restore the environment evolution.?5?The concentration of sulfate ion in the filtrate varied greatly,and the concentration of sulfate ion in the 0.5m horizon increased from 113.4mg/L to 600mg/L in the background value.At the same time,Ca ion decreased from the background value of 176.5mg/L to 20mg/L,while K ion increased from the background value of 1.6mg/L to 9.5mg/L,Na ion increased from 50.29mg/L to 500mg/L.And p H is always weakly alkaline,thus inferring the sulfate ion source clastic rock?especially the filler?in the gypsum,calcium is adsorbed,K,Na replacement,release.It is presumed that there are a lot of sulfate ions in the initial solution of Zhang Shuanglou Mine.?6?The content of Fe²⁺in the majority of the strata of the system increases from the background value to the detection limit of 0.2mg/L.The content of Fe³⁺ions increases from the background value to the detection limit of 0.3mg/L?the background value<0.01mg/L?.It is speculated that the iron ions will increase slowly in the early stage of the pit.?7?The Ba and Mg²⁺ions in the filtrate element were further reduced and the background value was further reduced.Barium elements from 0.138mg/L down to 0.015mg/L or so,a decrease of 89%;magnesium ions from 32.1mg/L down to 15mg/L or so,a decrease of 53%.It is deduced that the barium and magnesium ions in the initial aqueous solution of Zhang Shuanglou mine have a decreasing trend,and there may be precipitation or adsorption of barium and magnesium.?8?Trace elements molybdenum,manganese and nickel exist outside the"drinking water health standards"?GB5749-2006?phenomenon.Molybdenum maximum value of 0.105mg/L,exceeding the standard provisions of 0.07mg/L up to 50%;Manganese maximum concentration of0.12mg/L or so,exceeding the standard requirements of 0.1mg/L up to 20%;Nickel maximum concentration of 0.035 mg/L,exceeding the standard of 0.02mg/L up to 75%.Arsenic,copper,lead dissolution phenomenon,the end of the experiment should be strengthened observation.It is presumed that there may be groundwater pollution problems in the process of pit closure in Zhang Shuanglou Mine.Arsenic,copper,lead dissolution phenomenon,the end of the experiment should be strengthened observation.?9?Dissolution of dolomite,kaolinite,calcite,gypsum,CO₂?g?,precipitation of dolomite,illite and exchange of Ca²⁺/Na⁺,Ca²⁺/K⁺,Na⁺/K⁺happened in the selected flow path.It is presumed that there may be groundwater pollution problems in the process of pit closure in Zhang Shuanglou coal mine.From the above simulation results we can predict that closed pit in Zhang Shuanglou coal mine will be filled up after about 160 days,1/3 of the depth will be stagnant water;the water environment will be weak alkaline and weak oxidizing;there will be a lot of sulfate ions at an early stage,and iron ions will increase slowly,and barium ions and magnesium ions will be in a downward trend;trace elements molybdenum,manganese and nickel exist outside the Water hygiene standards?GB5749-2006?,and arsenic,copper have dissolved,may causing groundwater pollution problems.