Experimental Study On The Factors Influencing The Evolution Of Characteristic Components Of Karst Water

It is the key to analyze the groundwater evolution process of karst water system and clarify the interaction mechanism between karst water system and external environment.Therefore,with the aid of the simulation device of water rock interaction in different occurrence environments of karst water system,the indoor corrosion simulation device of carbonate rock under closed conditions and the high-pressure continuous flow liquid-phase corrosion reactor,the corrosion simulation experiments under different occurrence environments and pressures are carried out,and the change rule and control factors of the characteristic components of the underground water in karst water system are analyzed from the macroscopic and microscopic aspects In this paper,the characteristics of carbonate corrosion are analyzed.The results show that under the influence of CO₂ content in aqueous solution,the carbonate rocks have the strongest dissolution in the open environment of the supply area,forming the solution pores and gaps with high connectivity.The average value of total dissolution rate of carbonate rocks is 1.43 times of that in the semi open environment,2.70 times of that in the closed environment.The microstructure of carbonate rocks after dissolution in the semi closed and semi closed environment is between isolated micropores and complete pores Full connectivity between solution gaps.In addition,with the change of depth,the amount of dissolution decreased gradually,and the change of shallow part was more obvious.In different environments,dissolution of carbonate rocks is also controlled by lithology and p H value of aqueous solution.The dissolution increases with the increase of calcite(or Cao)content and decreases with the increase of dolomite(or Mg O)content;the dissolution of carbonate increases with the decrease of solution p H and decreases with the change of occurrence environment.When p H decreased from 6 to5.5,the total dissolution rate of open environment increased about 4.16 times,1.06times of semi closed environment and 2.32 times of closed environment.Carbonate rocks mainly consume CO₂ dissolved in water under closed condition.Karst is hindered to a certain extent,so the development speed is slow.The dissolution of carbonate rock is gradually weakened along the runoff direction,the particle structure of the rock is gradually becoming loose from the relatively dense state,the local fragmentation is gradually obvious,and the dissolution pores and gaps are gradually reduced.The amount of dissolution of rocks in different depths decreases gradually along the direction of runoff,and the change of shallow part is obvious.Under different pressure conditions,the dissolution of carbonate rock increases with the increase of pressure,and the total dissolution rate increases about 1.2 times under the pressure of 1MPa compared with 0.5MPa.The change curve of each characteristic component changes significantly with the change of pressure.After dissolution,the pores and fissures of the rock increase,the edge angles and lines of the fracture section of the crystal wall of the micrite containing dolomite begin to be fuzzy and smooth gradually,and the surface dissolution pores increase and deepen;the internal pore structure of the rock changes,resulting in secondary pores,forming"slash like"dissolution zone,"honeycomb like"dissolution pore,reducing its permeability and weakening the connection of the structural plane.