A design method for extra-thick coal seam collapse and filling water conservation mining under extremely thick soil layer

Abstract

The present invention discloses a design method for collapse and filling water conservation mining of extra-thick coal seams under a thick soil layer. First, the hydrological and mining geological data of the mine are collected to understand the spatial stratum relationship, thickness and lithological characteristics of the aquifer, the thick soil layer and the extra-thick coal seam; 3DEC three-dimensional discrete element software is used to simulate and calculate the maximum thickness mining height M of the upper layer of the extra-thick coal seam when the height H of the water-conducting fracture zone develops to the overlying thick soil layer. max ; Then, further simulation research is conducted on the development height of water-conducting fracture zones and the stability of extremely thick soil layers in stratified filling mining under extra-thick coal seams, and the ultimate filling rate of stratified goaf areas under extra-thick coal seams is determined#imgabs0#, ultimately achieving stratified thickness limit and filling coordinated water-preserving mining in extra-thick coal seams.

Description

Technical Field

[0001] The present invention relates to the fields of layered caving and water-retaining coal mining technology and filling and water-retaining coal mining technology for extra-thick coal seams under extremely thick soil layers, and specifically to a design method for caving and filling and water-retaining mining of extra-thick coal seams under extremely thick soil layers. Background Art

[0002] The mining of extra-thick coal seams under aquifers mainly adopts layered and limited thickness mining, which makes it difficult to recover the remaining layered coal resources and causes a large amount of coal resources to be wasted.

[0003] The existing published patent documents CN107939401B, CN106014410A, and CN103306720A are relatively complex and only consider the mining of coal seams at the working face without considering the water-isolating effect of the thick soil layer. They cannot solve the engineering problems encountered in the mining of extra-thick coal seams under the above-mentioned aquifers.

[0004] Therefore, in order to develop coal resources and protect water resources in extra-thick coal seams in areas covered by extremely thick soil layers, it is urgent to invent a design method for collapse and filling water-preserving mining of extra-thick coal seams under extremely thick soil layers, so as to make full use of the water-impermeable properties of the extremely thick soil layers and realize the efficient recovery of coal resources and the protection of water resources.

[0005] The latest research results show that soft rocks such as mudstone or weakly cemented soil layers have the characteristics of self-repairing of cracks and easy closure of mining cracks by compaction, and are good water-proof rock layers. In the process of coal resource mining, if the role of soft rock water-proof rock layers such as mudstone or weakly cemented soil layers can be fully utilized, it will be beneficial to improve the coal recovery rate. On the other hand, backfill mining has the characteristics of controlling rock movement, inhibiting the development of water-conducting fracture zones, and reducing the degree of mining disturbance. It is currently an effective means to achieve water-saving coal mining in mines. At the same time, it can dispose of mine solid waste and avoid ground emissions and environmental pollution. Summary of the invention

[0006] Purpose of the invention: In response to the above-mentioned technical problems, the present invention proposes a design method for the collapse and filling of extra-thick coal seams under extremely thick soil layers, which can achieve the maximum mining thickness of extra-thick coal seams, improve the recovery rate of coal resources, and at the same time realize the disposal of mine solid waste and protection of water resources, enriching the technical purpose of the existing water-saving coal mining technology system.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical means:

[0008] A method for designing the collapse and filling water conservation mining of an extremely thick coal seam under a very thick soil layer comprises the following steps:

[0009] a. Collect mine hydrology and mining geological data, and understand the spatial stratigraphic relationship, thickness and lithology characteristics of aquifers, thick soil layers and extra-thick coal seams;

[0010] b. According to the engineering geological conditions and the physical and mechanical parameters of the coal and rock mass, 3DEC three-dimensional discrete element software is used to simulate and calculate the maximum limit thickness mining height M of the upper layer of the extra-thick coal seam when the height H of the water-conducting fracture zone develops to the bottom of the overlying thick soil layer. max ;

[0011] c. Use comprehensive mechanized layered caving mining method to mine the upper layer of the extra-thick coal seam, with the mining height being the maximum limit thickness mining height M. max , and at the same time, laying artificial false roof in the goaf;

[0012] d. 3DEC three-dimensional discrete element software is used to simulate the development height h of the water-conducting fracture zone under the extra-thick coal seam when different goaf filling rates are used. According to the fitting results of the simulation data, the limit filling rate φ of the goaf under the extra-thick coal seam when the water-conducting fracture zone develops to the bottom of the aquifer is determined. 极 ;

[0013] e. Use comprehensive mechanized solid filling coal mining method to mine the layered coal seams under the extra-thick coal seams, and the filling rate of the goaf area is φ;

[0014] f. Repeat steps a to e to complete the layered thickness limiting and filling coordinated water-preserving coal mining in the extra-thick coal seams of the entire mine area.

[0015] The thickness S of the thick soil layer satisfies the following conditions:

[0016] 50m≤S

[0017] The filling rate φ of the stratified goaf area under the extra-thick coal seam is greater than or equal to the limit filling rate φ of the stratified goaf area under the extra-thick coal seam 极 , while considering the safety factor, the following conditions are met:

[0018] 0≤φ 极 ≤φ≤90%.

[0019] Beneficial effects:

[0020] The present invention discloses a design method for caving and filling water-preserving mining of extra-thick coal seams under extremely thick soil layers. The method fully utilizes the water-isolating properties of extremely thick soil layers, such as self-repairing and easy closure of cracks, and gives full play to the advantages of caving and filling coal mining technology, avoiding the cumbersome processes of existing methods, having significant economic and social benefits, and having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of a design method for extra-thick coal seam collapse and filling water-retaining mining under a huge thick soil layer according to the present invention;

[0022] Figure 2 This is a location map of a certain mine with a huge thick soil layer;

[0023] Figure 3The fitting result of the relationship between the height of the water-conducting fracture zone and the mining height of the upper layer;

[0024] Figure 4 The fitting result of the relationship between the height of the water-conducting fracture zone and the filling rate of the lower layer goaf;

[0025] Figure 5 It is a schematic diagram of a design for collapse and filling water-retaining mining of a very thick coal seam under a very thick soil layer according to the present invention;

[0026] Among them: 1-aquifer, 2-extremely thick soil layer, 3-extra thick coal seam; 4-upper layer of extra thick coal seam, 5-false roof, 6-lower layer of extra thick coal seam. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] The main mining area of ​​a coal mine is an extra-thick coal seam 3 with a thickness of 11m. The average thickness of the bedrock overlying the coal seam is 60m. The upper part of the bedrock layer is a very thick soil layer 2 composed of loess and laterite, with an average thickness of 60m. The upper part of the very thick soil layer is a Quaternary loose aquifer 1 with an average thickness of 15m and strong water-richness.

[0029] To ensure safe mining and water resource protection, the mine adopted a limited thickness upper layer mining method, with the mining coal seam thickness of 5.0m, resulting in a large amount of coal resource waste.

[0030] The ultra-thick coal seam 3 is mined by adopting an ultra-thick coal seam layered thickness limiting and filling coordinated water conservation mining design method of the present invention, and the specific steps are as follows:

[0031] a. Through the collection of mine hydrogeological data, it is found that the thickness of the main extra-thick coal seam 3 is 11m, the distance between the aquifer 1 and the extra-thick coal seam 3 is an average of 140m, the average thickness of the super-thick soil layer 2 is 60m, which is loess and red soil with certain self-repairing ability, and the thickness of the bedrock layer is 60m;

[0032] b. According to the engineering geological conditions and the physical and mechanical parameters of the coal and rock mass, see Table 1, the 3DEC discrete element software was used to establish a numerical simulation model with a length × width × height of 300m × 200m × 160m; the horizontal displacement was constrained on all sides, and the vertical displacement was constrained at the bottom; the constitutive relationship adopted the Moore-Coulomb model. The height development of the water-conducting fracture zone during the mining of the upper layer 4 of the extra-thick coal seam was simulated when the mining height of the extra-thick coal seam 3 was 3m, 4m, 5m and 6m respectively.

[0033] Table 1 Physical and mechanical parameters of coal and rock mass

[0034]

[0035]

[0036] The simulation results show that the corresponding water-conducting fracture zone development heights at different mining heights are H 3m =23.1m, H 4m =39.6m, H 5m =54.3m, H 6m =66.8m, based on which the curve fitting formula is obtained, such as Figure 3 As shown in the figure, the fitting result is shown in formula (1). Substituting the height of the water-conducting fracture zone H = 60m into the formula, the maximum limit mining height M of the upper layer 4 of the extra-thick coal seam is calculated when the height of the water-conducting fracture zone H develops to the overlying thick soil layer 2. max =5.3m.

[0037] M=0.000155H 2.37 +2.74 (1)

[0038] c. Adopt comprehensive mechanized layered limited thickness mining method to mine 4 layers of coal seams on the extra-thick coal seam with a mining height of 5.3m, and lay artificial false roof 5 in the goaf;

[0039] d. 3DEC three-dimensional discrete element software was used to simulate the development height h of the water-conducting fracture zone in the ultra-thick coal seam under the 6-layer filling mining when the goaf had different filling rates. The simulation results showed that the height of the water-conducting fracture zone was 129.6m, 112.8m, 95.1m and 86.3m respectively when the filling rates were 60%, 70%, 80% and 90%. Based on this, the curve fitting formula was obtained, as shown in Figure 4 As shown in the figure, the fitting result is shown in formula (2). Substituting the height of the water-conducting fracture zone H = 120m into the formula, the limit filling rate of the goaf area of ​​layer 6 under the extra-thick coal seam when the height of the water-conducting fracture zone H develops to the bottom of the aquifer 1 is calculated.

[0040]

[0041] e. Adopt comprehensive mechanized solid filling coal mining method to mine the 6 coal seams under the extra-thick coal seam. To ensure the water conservation effect, the filling rate of the goaf needs to be greater than And take a certain safety factor, the final design is 70%;

[0042] f. Repeat steps a to e to complete the design method for collapse and filling water-preserving mining of extra-thick coal seams under extremely thick soil layers in the entire mining area.

Claims

1. A design method for extra-thick coal seam collapse and filling water conservation mining under a very thick soil layer, characterized in that: The following steps are involved: a. Collect mine hydrology and mining geological data to understand the spatial stratigraphic relationship, thickness and lithological characteristics of aquifers (1), thick soil layers (2) and extra-thick coal seams (3); b. According to the engineering geological conditions and the physical and mechanical parameters of the coal and rock mass, 3DEC three-dimensional discrete element software is used to simulate and calculate the height of the water-conducting fracture zone. H When the overlying thick soil layer (2) is developed to the bottom, the upper layer of the extra-thick coal seam (4) has the maximum limit of thickness and height ; c. Use comprehensive mechanized layered caving mining method to mine the upper layer (4) of the extra-thick coal seam, with the mining height being the maximum thickness limit. , and at the same time laying an artificial false roof in the goaf (5); d. Using 3DEC three-dimensional discrete element software to simulate the development height of water-conducting fracture zones in layered (6) filling mining under extra-thick coal seams at different goaf filling rates h According to the simulation data fitting results, the limit filling rate of the goaf area of ​​the lower layer (6) of the extra-thick coal seam when the water-conducting fracture zone develops to the bottom of the aquifer (1) is determined. φ 极 ; e. Use comprehensive mechanized solid filling coal mining method to mine the lower layer (6) of the extra-thick coal seam, and the filling rate of the goaf is φ ; f. Repeat steps a to e to complete the layered thickness limiting and filling coordinated water conservation mining of the extra-thick coal seam in the entire mine area; The thick soil layer (2) has a thickness of S The following conditions must be met: 50 m ≤ S ； The thick soil layer (2) has self-repairing ability, and cracks are easy to close; The filling rate of the goaf area in the lower layer of the extra-thick coal seam (6) φ The value is greater than or equal to the limit filling rate of the goaf area in the lower layer of the extra-thick coal seam (6) φ 极 , while considering the safety factor, the following conditions are met: 0≤ φ 极 ≤ φ ≤90% 。

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