Study On Soil Quality Improvement And Fertilization Of Open-Pit Mine Dumping Based On Fly Ash Improvement Test

As an important coal and electric power production base in China,the coal and power base in eastern Inner Mongolia plays a significant role in ensuring energy security in eastern Inner Mongolia and even the whole northeastern region.The ecological environment in this area is fragile,and coal mining has aggravated soil erosion and grassland desertification,resulting in poor soil quality in the mining area and difficult reclamation.Meanwhile,fly ash discharge from surrounding power plants occupies a large amount of land resources and causes land pollution.Based on the above situation,this paper explores the feasibility of using ultrasonic modified fly ash combined with straw powder to improve the soil of open-pit coal mine dump as well as the determination of its relevant parameters.A feasible plan for soil improvement is provided in the paper so as to improve the soil reclamation of open-pit coal mine dump and achieve comprehensive utilization of fly ash.Aiming at problems of the fly ash,such as high pH value,excessive salt content and excessive heavy metals,this paper designs three factors and three levels of orthogonal experiments of ultrasonic frequency,ultrasonic time and ultrasonic temperature,and uses ultrasonic wave to modify the fly ash.Through response surface analysis,the effects of different modification conditions on various parameters of fly ash were obtained,the modified evaluation function of modified fly ash was proposed,and the optimal modification conditions of fly ash were obtained.Corn stalk powder was used as soil fertilization material for open-pit coal mine.Considering the allelopathic effect of corn stalk usage,different concentrations of corn stalk extract were designed.Corn,alfalfa and soybean were selected for hydroponic experiment.The germination of corn,alfalfa and soybean seedlings and the growth of their seedlings were affected by the corn stalk extract.The concentration of corn stalk extract could promote seed germination and seedling growth in the range of 0-20%.It will inhibit the growth of seedlings when the concentration exceeds 30%,and the optimum promotion point is close to 20%.Modified fly ash,straw powder and soil of open-pit coal mine dump were mixed to improve the soil physicochemical properties of the dump.Through laboratory planting experiments,the effects of different soil ratios were obtained for plant germination rate,germination potential,seedling root length,seedling length,plant fresh weight,dry weight,plant chlorophyll and other indicators.It was determined that the application of fly ash did not cause serious secondary pollution of heavy metal to the plant,and the best ratio of dumping soil improvement is 70% open-pit coal mine dumping soil + 20% modified fly ash + 10% straw powder.A seasonal mining and dump technology is proposed to adjust the mining sequence of the mining area as well as provide time and space preparation for the reclamation of the mining area.Based on the construction method of combing fly ash and straw powder to improving the soil of open-pit coal mine dump,this paper puts forward operation methods like mixed dumping,single heap with multiple mixed,multiple heap with multiple mixed,and stratified ploughing.Through the comprehensive comparison,it is determined that the single heap with the multiple mixed or the multiple heap with multiple mixed and the stratified ploughing are adopted to realize the soil improvement construction in open-pit coal mine dump.This paper puts forward a method of storage and allocation of water resources for seasonal mining and dump of open-pit coal mine as a safeguard project,which provides water resources guarantee for soil reclamation of open-pit coal mines after fly ash improvement,and realizes the integration of mining,dumping,reform and rehabilitation of the open-pit coal mine.