LU505020B1

LU505020B1 - A model for constructing the landscape of subsidence wetlands caused by high-water-level coal mining

Info

Publication number: LU505020B1
Application number: LU505020A
Authority: LU
Inventors: Junfeng Qu
Original assignee: Xuzhou Inst Of Ecological Civilization Construction; Univ China Mining
Priority date: 2023-08-29
Filing date: 2023-08-29
Publication date: 2024-02-29

Abstract

This invention provides a model for constructing the landscape of subsidence wetlands caused by high-water-level coal mining. It pertains to the field of ecological landscape technology and includes the following steps: functional zoning, construction of small scattered waterlogged areas, building pollution-resistant and impermeable embankments, creating impermeable layers in the expanded lake area, establishing slope protection, maintaining water balance in the water system, and configuring vegetation and landscapes. By constructing secondary wetland landscapes in both small scattered waterlogged areas and large contiguous waterlogged areas in high-water-level coal mining areas at a regional scale, the goal is to address the fragmented landscape issue of subsidence wetlands in high-water-level coal mining regions. This aims to enhance the ecosystem's service value, as well as improve the living environment in the surrounding areas.

Description

DESCRIPTION LU505020

A MODEL FOR CONSTRUCTING THE LANDSCAPE OF

SUBSIDENCE WETLANDS CAUSED BY HIGH-WATER-LEVEL COAL

MINING

TECHNICAL FIELD

This invention pertains to the field of ecological landscape technology, specifically focusing on the landscape construction model for high water table coal mining subsidence wetlands.

BACKGROUND

In the high water table plain mining areas in the eastern part of our country, due to the high underground water table, extensive surface subsidence and water accumulation occur after extensive coal mining. This results in the formation of large-scale coal mining subsidence wetlands, creating a unique combined water and land ecological environment in mining regions.

As mining areas are surrounded by mining production and residential zones, the secondary wetlands formed by the water accumulation in high water table coal mining areas gradually acquire service functions in addition to the mentioned functions, and after landscape construction, they can become places for residents' leisure and recreation. Due to the long timescales and complexity of coal mining, as well as the variability in geological conditions and structures, water accumulation areas in high water table coal mining areas present two types: scattered water accumulation areas and large continuous water accumulation areas, with complex and irregular terrain and landforms.

Common methods in existing technologies mainly involve backfilling and reclamation for agricultural or construction purposes, or converting individual water accumulation areas into deeper aquaculture waters. The current approaches for management are single and relatively extensive, but lack the regional-scale functional zoning of high water table coal mining areas and the landscape construction of water accumulation wetlands.

SUMMARY LU505020

Addressing the shortcomings of existing technologies, this invention introduces a landscape construction model for high water table coal mining subsidence wetlands. It resolves the limitations of current methods that offer singular approaches for the reuse of coal mining subsidence wetlands formed after coal extraction. Furthermore, it addresses the absence of regional-scale functional zoning of high water table coal mining areas and the lack of landscape construction for water accumulation wetlands.

In order to achieve the above purpose, this invention provides a high-water-level coal mining subsidence wetland landscape construction model comprising the following steps:

S1. Functional zoning: Based on the conditions of perennial waterlogged areas caused by subsidence in high-water-level coal mining, seasonal water collection areas, and a large number of sloping farmlands, divide the coal mining area into small scattered waterlogged areas and large contiguous waterlogged areas.

S2. Construction of large and small scattered waterlogged areas: For small scattered waterlogged areas near farmlands, utilize backfill reclamation to convert them into farmland, forming large contiguous farmland areas with the surrounding lands. In the case of large waterlogged areas where the water depth 1s less than 1.5m, priority should be given to restoring them as farmland. For small scattered waterlogged areas far from farmlands, employ deep excavation to create breeding ponds, and use the method of constructing large contiguous waterlogged areas to expand the lakes into wetland landscapes.

S3. Construction of pollution-resistant and impermeable embankments: Construct pollution-resistant and impermeable embankments in the small scattered waterlogged areas that have been deepened for fish ponds or slightly elevated for farmland. This prevents pollution of fish ponds and farmland from the surrounding coal mining area's wastewater, and mitigates potential flooding damage to the fields due to high water levels.

S4. Construction of impermeable layers in expanded lake areas: For the construction of artificial wetlands in large waterlogged areas, apply geosynthetic membrane impermeable treatments.

SS. Establishment of slope protection: Implement slope protection measures where needed.

S6. Water system balance and maintenance: Based on the actual conditions of waterloggéd/505020 wetlands in high-water-level coal mining areas, analyze available water sources, potential water losses, and whether there are nearby rivers or large reservoirs that can serve as beneficial supplements for regulating wetland water levels.

S7. Vegetation and landscape configuration: Select plant species with ecological adaptability and aesthetic appeal. Considering both landscape and ecological effects, establish a wetland plant configuration pattern.

Preferably, in S3, constructing pollution-proof and impermeable embankments is achieved by accumulating fill material and forming clay barriers, which are then heightened and thickened, effectively separating fish ponds, farmland, and sewage.

Preferably, the geosynthetic membrane impermeable treatment comprises the steps are as follows: draining accumulated water from the lake, removing silt and organic soil layers, laying the upper and lower support layers, compacting the base, incorporating artificial impermeable materials to create a composite impermeable base, and finally covering with an upper protective layer before comprehensive compaction.

Preferably, the upper support layer is constructed by layering loess, fine sand, and gravel, compacted in layers. The lower support layer consists of layered crushed stone, medium sand, and fine sand, compacted to achieve a relative density of 90% or more. Its thickness ranges from 300mm to 500mm.

Preferably, in S5, the preferred approach involves using disposable erosion-resistant vegetation measures made from dehydrated plant fibers and hemp rope. Alternatively, it may incorporate aquatic plants, semi-aquatic plants, and terrestrial plants as the primary components of the embankment, along with the addition of landscape plants.

Preferably, the water sources include atmospheric precipitation, mine water, and surrounding compliant industrial wastewater, with water source losses attributed to evaporation or underground runoff leakage.

Preferably, the wetland plant configuration patterns include aquatic plant configuration, lake island plant configuration, or embankment plant configuration.

This invention introduces a landscape construction model for high water table coal mining subsidence wetlands, offering several beneficial effects:

The present invention constructs the landscape of secondary wetlands in high water tabt&}505020 coal mining subsidence areas, integrating small scattered water accumulation areas and large continuous water accumulation areas at a regional scale. This aims to address the fragmented landscape issue in secondary wetlands formed by water accumulation in high water table coal mining subsidence areas. By doing so, it enhances the ecological system's service value and improves the surrounding living environment.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a flow chart of the present invention;

Fig. 2 1s a schematic diagram of the construction of the pollution impervious dike in the present invention;

Fig. 3 is a flow chart of the construction process of the impervious layer in the enlarged lake area of the present invention;

Fig. 4 is a schematic diagram of the vegetation revetment belt in the present invention;

Fig. 5 is a screening layout diagram of bank slopes and aquatic plants in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the technical scheme in the embodiment of the invention will be clearly and completely described with reference to the attached drawings. Obviously, the described embodiment is only a part of the embodiment of the invention, but not the whole embodiment.

Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative labor belong to the scope of protection of the present invention.

As shown in Figures 1-5, the embodiment of the present invention provides a model for the construction of high water table coal mining subsidence wetland landscapes. The steps for wetland landscape construction are as follows:

S1: Combining subsidence land management with ecological restoration, the invention establishes a new integrated approach encompassing "basic farmland reorganization, coal mining subsidence land reclamation, ecological environment restoration, and wetland landscape development." Considering various factors such as the shape of subsidence water accumulation areas, soil types, stratigraphic structures, settlement stability, and water depth, these areas at&/505020 divided into scattered water accumulation areas and continuous water accumulation areas.

S2: For the scattered water accumulation areas, reclamation is conducted based on planning requirements and actual conditions. Backfill reclamation is used for developing agricultural land as part of a wetland park for "farm tourism," while excavation is carried out to create fishing ponds for leisure fishing within the park. Due to the presence of sporadic water bodies within the large continuous water accumulation areas in high water table coal mining subsidence zones, separated by non-water barriers, maintaining normal wetland functions becomes challenging.

Therefore, it's necessary to expand and deepen water bodies in a way that accommodates subsidence deformations, expanding and deepening water surfaces. Current ponds planned to be part of extensive continuous water areas undergo dredging, excavation, and treatment to form complete lakes, including the Southeast Lake, West Lake, and Northeast Lake.

S3: Before the remediation: The water system in the northern Jiuli Lake wetland coal mining subsidence area was disorderly, with water accumulation in subsidence pits connected to the wastewater discharge channels of a paper mill and mine water discharge. The surface water bodies were severely polluted, and ponds and agricultural irrigation water sources were mostly contaminated. Consequently, there were significant risks to the quality of agricultural products.

After remediation, the use of clay barriers for impermeability and the elevation of embankments successfully separated irrigation water sources from sewage, gradually controlling and improving the quality of irrigation water. Additionally, measures were taken to prevent new pollution from backfilling waste. This was achieved by analyzing the mineral composition, chemical components, acidity, and alkalinity of the waste before backfilling. Dividing and filling waste in relatively small sections (50m x 100m) effectively controlled pollution sources through containment.

S4: Construction of the impermeable layer for expanding the Jiuli Lake wetland. Firstly, water was drained and sediment was cleared to prepare for construction. The lake bed was leveled, and the natural soil of the base was compacted, shaping the lake. The lower support layer was then built on the base soil, with layers of 300mm crushed stone, 100mm medium-coarse sand, and 50mm fine sand. The crushed stone layer served to drain groundwater and prevent the impermeable layer from being lifted when the lake water was drained. The impermeable layer was constructed by placing a 100g non-woven fabric as an isolation layer ¢#505020 top of the fine sand layer, followed by a 2mm thick high-density polyethylene (HDPE) impermeable membrane and another 100g non-woven fabric as an isolation layer. The upper protective layer was built on the isolation layer, consisting of 500mm compacted clay, 250mm fine sand, and 250mm natural sand and gravel. Layered compaction was performed to complete the construction of the entire impermeable layer.

SS: Establishing shoreline protection for the Jiuli Lake wetland. As shown in Figure 4, considering that the Jiuli area's coal mining subsidence falls within a stable subsidence zone, a one-time vegetation shoreline protection approach can be adopted. With the expanded water area after lake expansion (3.5 km2 main lake area), which experiences significant wind and waves, and considering residual deformations, wave erosion, and wetland landscape requirements, a wooden pile revetment is installed at the base of the slope. The wooden piles are locally sourced from the cleared wood within the demonstration area. The inner side of the wooden piles is layered with crushed stone cages for filtration, and a geotextile fabric is placed between the inner side of the crushed stone cages and the slope, ensuring the integrity of the natural aquatic-terrestrial ecosystem while preventing slope erosion and soil loss. Additionally, considering water level dynamics, a biodegradable erosion-resistant cover is placed at the bottom of the slope.

S6: Ensuring water balance and maintenance for the Jiuli Lake wetland. The planning for the Jiuli Lake wetland follows a surface flow artificial wetland model. The region receives an average annual precipitation of 845.2mm and has an average annual evaporation of 1082. 9mm.

Due to the uneven distribution of precipitation and evaporation throughout the year, the available water supply in the Jiuli Lake wetland varies across different months. During periods of high water consumption, particularly outside the flood season, dynamic regulation should be performed in conjunction with the main drainage channels between the coal mining area and small watersheds. Additionally, groundwater extraction and external water supply can be used for supplementation. In flood years, the main drainage system can be employed to drain excess water, ensuring relative water balance in the wetland.

S7: Vegetation and Landscape Configuration of Jiuli Lake Wetland. The coal mining subsidence in the Jiuli area is characterized by complex geological and mining conditions,

including multiple coal seams, repeated mining activities, and a long period of subsidené&/505020 stabilization. Analyzing the extent of surface deformation and destruction, various zones such as subsidence cracks, subsidence water accumulation areas, and seasonal water accumulation areas are identified. Considering the local native species and introduced species, a combination of both is chosen. Plants that exhibit strong adaptability, resistance to adverse conditions, and require less intensive management are selected to reduce maintenance costs and establish an eco-friendly garden, enhancing the stability of the ecosystem.

A survey of plant species composition within the study area and herbaceous layer is conducted using Im x 1m quadrats. Parameters such as cover, abundance, frequency, and estimated biomass of shrubs and herbaceous vegetation are measured, along with the assessment of plant growth both within and outside the sample plots. A similar approach is used to investigate plant species composition, cover, and abundance in the coal mining subsidence areas, along with assessing plant growth both within and outside the study plots.

The conclusion indicates that within the collapsed area, herbaceous plants are mainly dominated by Poaceae species. Dominant species include reed (10%), white grass (70%), knotgrass (2%), and dogtooth grass (5%), among others. Other species present include cattail, purslane, pigweed, cleavers, bluegrass, dandelion, black-eyed Susan, barnyard grass, barnyard millet, wheat, quackgrass, foxtail, ryegrass, panic grass, snake venom grass, and buckwheat. The herbaceous plants in the surveyed area are categorized into three layers: the first layer dominated by reed, the second layer by white grass and dogtail grass, and the third layer by dogtooth grass.

Therefore, the aquatic plant arrangement in Jiuli Lake wetland is tailored to different water qualities and depths, including emergent plants like reed and cattail, floating plants like lotus and water lily, and submerged plants like various types of aquatic grasses. Groundcover plants like caltrop and daisy are also present.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

CLAIMS LU505020

1. A high-water-level coal mining subsidence wetland landscape construction model comprises the following steps:

sl. functional zoning: based on the conditions of perennial waterlogged areas caused by subsidence in high-water-level coal mining, seasonal water collection areas, and a large number of sloping farmlands, divide the coal mining area into small scattered waterlogged areas and large contiguous waterlogged areas;

s2. construction of large and small scattered waterlogged areas: for small scattered waterlogged areas near farmlands, utilize backfill reclamation to convert them into farmland, forming large contiguous farmland areas with the surrounding lands; in the case of large waterlogged areas where the water depth is less than 1.5m, priority should be given to restoring them as farmland; for small scattered waterlogged areas far from farmlands, employ deep excavation to create breeding ponds, and use the method of constructing large contiguous waterlogged areas to expand the lakes into wetland landscapes;

s3. construction of pollution-resistant and impermeable embankments: construct pollution-resistant and impermeable embankments in the small scattered waterlogged areas that have been deepened for fish ponds or slightly elevated for farmland; this prevents pollution of fish ponds and farmland from the surrounding coal mining area's wastewater, and mitigates potential flooding damage to the fields due to high water levels;

s4. construction of impermeable layers in expanded lake areas: for the construction of artificial wetlands in large waterlogged areas, apply geosynthetic membrane impermeable treatments;

s5. establishment of slope protection: implement slope protection measures where needed;

s6. water system balance and maintenance: based on the actual conditions of waterlogged wetlands in high-water-level coal mining areas, analyze available water sources, potential water losses, and whether there are nearby rivers or large reservoirs that can serve as beneficial supplements for regulating wetland water levels;

s7. vegetation and landscape configuration: select plant species with ecological adaptabilit##505020 and aesthetic appeal; considering both landscape and ecological effects, establish a wetland plant configuration pattern.

2. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 1, wherein in s3, the construction of pollution-resistant and impermeable embankments is achieved by the accumulation of fill materials and the formation of clay-lined barriers; these barriers are raised and reinforced to create a separation between the fish ponds, farmland, and polluted water.

3. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 2, the steps for the geosynthetic membrane impermeable treatment are as follows: firstly, drain the accumulated water within the lake, remove silt and organic soil layers; then, lay the upper and lower support layers and compact the base; -afterward, combine artificial impermeable materials to create a composite impermeable base; finally, lay the upper protective layer and conduct overall compaction by rolling.

4. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 2, the upper support layer is constructed by layering loess, fine sand, and gravel, and then compacting each layer individually; the lower support layer is composed of layered crushed stone, medium sand, and fine sand, compacted to achieve a relative density of 90% or higher.

5. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 4, the measures used in s5 are either disposable erosion control measures made from dehydrated plant fibers and hemp rope, or plant-based erosion control measures that utilize aquatic plants, semi-aquatic plants, and terrestrial plants as the main components of the embankment, along with additional landscape plants.

6. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 1, the available water sources include atmospheric precipitation, mine water,

and surrounding compliant industrial wastewater. Water source losses refer to evaporation bH#505020 underground runoff leakage.

7. The high-water-level coal mining subsidence wetland landscape construction model, as claimed in claim 1, the wetland plant configuration pattern is one of the following: aquatic plant configuration, lake island plant configuration, or embankment plant configuration.