Principles and technical contents of mine ecological restoration

(6) According to the presence or absence of pollutants in the tailings, appropriate plant species should be selected for direct restoration without soil cover or soil cover restoration with isolation layer.

(2) Ecological restoration mode of mine cultivated land

The ecological restoration modes of mine cultivated land mainly include: mining subsidence area, open mining chassis area and dry land ecological restoration mode.

1. Ecological restoration model of paddy field in mining subsidence area

(1) The ecological restoration land in the subsidence area is given priority to agriculture, and the leading mode of ecological comprehensive restoration in the subsidence area is generally adopted as "focusing on the restoration of cultivated land and taking into account relocation land and aquaculture".

(2) In mountainous and hilly areas, the terrain is originally uneven, the collapse is not deep, does not affect the cultivation can be properly smooth, can be directly restored to paddy field;

(3) In plain areas, shallow surface collapse that is not deep can be levelled on the spot; When the middle layer collapses and there is sufficient solid waste such as coal gangue and fly ash, the topsoil is stripped first, then the waste is backfilled, and then the soil is covered to restore the paddy field.

(4) The subsidence area with large area, deep collapse, shallow diving level and rich surface water resources should be comprehensively treated, and the method of "digging deep and filling shallow" should be adopted to restore it to paddy field.

It is not difficult to restore paddy field in coal mining subsidence area. The key points to be paid attention to are the thickness control of topsoil, the elevation design of cultivated land and the auxiliary construction of water conservancy projects. For those repaired as paddy fields, measures should be taken to prevent cracks in the surface soil of paddy fields from being affected by caving collapse, resulting in destruction of the water holding capacity of the surface soil of paddy fields and water leakage.

2. Ecological restoration model of paddy field in undercropping area

The last mining platform of an open-pit mine, the chassis area or flat area, often forms a relatively large flat area. Due to the high landform position, most of the area can be naturally drained, and the area can also be restored to dry land when sufficient soil sources are available. Only when the restoration area has a water conservancy project and a guaranteed irrigation water source, it is possible to restore the irrigated land or paddy field, and it is also necessary to build farmland water conservancy, roads and other supporting facilities.

3. Ecological restoration model of mining cave-in backfill and open-mining underbed dryland

There is a large demand for topsoil when the subsidence backfill area and open mining chassis are repaired as dry land, and it is generally required that there is sufficient and stable soil source nearby. Maintenance ponds and ditches in the chassis area can generally be considered to meet the irrigation and drainage needs of drylands.

In order to prevent water accumulation, the site should be leveled in this area, and a slope of 2% to 3% should be formed in a certain direction according to the surrounding terrain. The mining platform of the stope can cut drainage ditches in the slope to collect the surface runoff and discharge the water outside the mining site.

(3) Ecological restoration model of mine wetland

The ecological restoration modes of mine wetland mainly include: coal mining subsidence water area, mining water area in open mining mountain depression, and "wet beach area" of tailings pond.

1. Wetland ecological restoration model in cave-in waterlogged area

Subsidence area is a new type of constructed wetland, which is mainly formed by surface subsidence pit of coal mining in plain area. According to statistics, in the mining area of high diving position in the east coast of China, the rate of mining subsidence water is more than 30%, and in North China it is between 20% and 30%. This area is mainly the main grain producing area or the basic farmland protection area. Due to the shallow buried groundwater level, part of the subsidence area has become a seasonal or perennial water accumulation area, and the farmland water conservancy and transportation facilities above the subsidence area have suffered damage. The central and eastern mining areas located in the Huang-Huai-hai Plain of China belong to this category. In China's eastern plain coal mining areas, such as Zaozhuang, Yanzhou, Datun, Huainan, Huaibei, Xuzhou and other mining areas, due to the high underground diving level, mining subsidence water is quite common, and some areas even appear salinization trend.

2. Ecological restoration model of wetland in waterlogged area of open stope

When the mining elevation of building stone mine and sand clay mine is lower than the local erosion base level (that is, the natural drainage elevation) or the local groundwater level, or although the mining elevation is higher than the local erosion base level, but there is depression mining, and the water inflow around the mining area is greater than the sum of the leakage and evaporation of the mining pit, the depression part will be permanently flooded after the mining is stopped. Retaining this water area as a wetland would provide water for the conservation of newly planted plants for ecological restoration and also improve the ecological environment in small areas.