I. Land reclamation technology
After 10 years of research, the reclamation method has developed from a simple process of "one digging, two leveling and three transformation" to a reclamation technical system combining various forms, ways and methods, such as foundation pond reclamation, drainage reclamation, gangue fly ash reclamation, ecological engineering reclamation and biological reclamation. Among them, the planning technology and biotechnology of reclamation are the most studied, and the more mature ones are mud pump reclamation technology and coal gangue filling compaction technology.
1. Technical Problems of Reclamation Planning
Reclaimed land planning is the key to the success or failure of land reclamation in mining areas, and it is also an important special planning in the overall land use planning. In the investigation and evaluation of regional reclamation conditions before reclamation planning, mathematical quantitative analysis methods such as fuzzy comprehensive evaluation and grey cluster analysis are introduced. According to the mining plan, it is one of the key technologies to predict the land destruction form, landform change law and landscape ecological pattern after mining, and the mining subsidence theory and environmental system engineering theory become the technical support in this respect. The determination of reclamation land use direction, the optimization of reclamation land structure and the selection of reclamation engineering measures are the core contents of reclamation planning. Advanced planning methods such as analytic hierarchy process, linear programming and grey decision theory have been successfully applied to practice.
2. Recycling of biotechnology
Reclamation biotechnology includes ecological engineering reclamation technology, soil improvement biotechnology and rapid vegetation restoration technology. At present, the development is mainly based on field testing, and a standard with universal knowledge and popularization and application has not yet been formed.
3. Technical problems of reclamation project
Among all kinds of deep excavation methods, mud pump reclamation is an effective method widely used in eastern plain mining areas, so the research on it is also in-depth.
4. The resource technology of coal gangue filling has become a research hotspot.
Among them, coal gangue filling method, filling thickness, compaction technology, covering soil thickness, planting varieties and soil improvement constitute the technical system in this direction.
Second, the basic theoretical research of land reclamation
The basic theoretical research of land reclamation is mainly reflected in macro and micro levels. Macroscopically, the theoretical research of reclamation decision-making is systematic, and the characteristics, contents, objectives and criteria of reclamation decision-making are clarified, which is of great guiding significance for establishing quantitative model of reclamation decision-making factors, decision-making language model, land use structure optimization model and comprehensive effect measurement index system of reclamation scheme optimization. The concept, connotation, boundary and main system of land reclamation are discussed. Microscopically, the damage mechanism of mining to cultivated land and the principle of soil profile reconstruction have been studied, and the principle of "layered stripping and staggered backfill" and the quantitative model (PI model) for evaluating the productivity of reclaimed soil have been put forward. In addition, on the basis of applying system engineering theory and ecological engineering theory to guide reclamation practice, and introducing the viewpoint of landscape ecology, six principles of landscape ecological reconstruction in mining areas are put forward, thus combining land reclamation with ecological reconstruction and expanding the connotation of land reclamation.
Third, the problems of land reclamation in China
Land reclamation in China still faces many problems. In the reclamation work and research, the quantity of reclamation is emphasized, while the quality of reclamation is neglected; Attach importance to reclamation projects and neglect reclamation management; Pay attention to the technical ways and modes of land reclamation, but ignore the basic research such as the evolution law, technical standards and theoretical system of land destruction and reclamation; Emphasis on local research and neglect of overall research are more prominent.
The theoretical research of reclamation lags behind the practice of reclamation. For a long time, many scholars believe that land reclamation is only a pure engineering problem with no scientific research value, which leads to a low starting point and low reclamation benefit in China.
The research on agricultural reclamation is not enough. The new Land Management Law stipulates that reclaimed land should be used in agriculture first, but the benefits of agricultural reclamation in mining areas are not very obvious at present. On the one hand, agriculture is a weak industry with low comparative benefits. On the other hand, the poor physical and chemical properties of reclaimed soil, coupled with the large investment in soil improvement, make the initial input-output of reclamation low.
Fourthly, the development trend of land reclamation.
1. Development prospect of land reclamation
(1) Agricultural reclamation will become the main utilization direction of reclaimed land, and the research on improving the benefits of agricultural reclamation will become the focus of reclamation research.
(2) Under the impetus of high-tech reclamation, the industrialization of reclamation will stand out.
(3) Continuously improve the reclamation technology system and formulate technical specifications and standards.
(4) Constantly improve the system of policies and regulations to form a benign reclamation mechanism.
(5) The traditional land reclamation field will be further expanded.
(6) Gradually establish the discipline system and theoretical framework of land reclamation.
2. Development trend of land reclamation technology
(1) underground mining and reclamation technology. According to reclamation engineering measures, underground mining reclamation technology can be divided into two categories: filling reclamation and non-filling reclamation.
Filling reclamation is to fill the subsidence area with solid waste such as gangue and fly ash. Its use is mainly used for building land and homestead, planting trees and crops and comprehensive mode. Its technical key is to prevent secondary pollution.
The key technology of reclamation without filler is surface subsidence prediction and damage degree analysis. According to the local natural ecological environment, combined with the classified transformation and comprehensive treatment of collapse, the purpose of ecological agriculture utilization can be achieved.
(2) Open-pit reclamation technology. The technology is divided into three stages: in the first stage, the stripped material is discharged according to the requirements of land reclamation, that is, the rock stratum and fertile soil layer with small particle size and low gravel degree are placed in the upper part and the rest are placed in the lower part; The second stage is to rectify the dump according to the reclamation elevation; The third stage is to restore the soil according to the specific use after reclamation. The key technology is to consider the mining method, technology and reclamation in a unified way to form a unified mining-dumping-reclamation process.
(3) Ecological agriculture reclamation technology. The principle of this technology is as follows: ① According to local conditions, that is, according to the actual situation, determine the purpose and utilization structure of reclaimed land; ② Optimize the structure of reclaimed land, that is, rationally allocate the structure of agriculture, forestry, animal husbandry and fishery in the reclaimed area according to the principle of ecosystem, so as to promote the development of agricultural system and ecological villages.
(4) Rapid microbial reclamation technology of gangue without complex soil. The characteristics of this technology are: there is no need to cover the surface soil of solid waste sites such as coal gangue and open pit mine, and a stable active soil microbial community is established after a plant growth cycle (6 months). The key technology is to popularize effective microbial agents, control the pH value of microbial soil and promote the formation of soil.
(5) Recovery technology of mud pump. This technology was designed by Professor Hu of China University of Mining and Technology. Its key technology is to simulate the scouring principle of natural water flow, transform electromechanical power into hydraulic power for digging, transporting and filling soil, cut and crush soil with high-pressure water gun, make it wet and disintegrate, form mixed liquid of soil and clods, and then send it to the land to be reclaimed by mud pump through conveying pipe.
The advantage of this method is that it can make the bulk density, porosity, water content and infiltration, organic matter content and nutrient content of the reclaimed soil suitable, thus improving the productivity of the land.