Unified topology model and method for evolution characterization of coal mining overlying strata fracture field under different geological conditions

Abstract

The invention belongs to the field of coal mining rock stratum damage movement control and mining area ecological protection. The invention particularly relates to a coal mining overlying strata fracture field evolution representation unified topology model and method under different geological conditions. The core of the method is to establish a unified topological model for describing the spatial distribution of the coal mining overlying strata fracture field under different geological conditions, topological parameters in the model can be quantitatively calculated according to an overlying strata structure and mechanical parameters, and the bottleneck that most parameters in a traditional strata movement prediction model are empirical values is broken through. The method comprises the following steps of: judging inflection point horizon and concavity and convexity of a mining overlying strata fracture field according to mining bearing pressure of different horizon monitored by arranging optical fibers in a mine hydrological hole and mechanical parameters of each rock stratum, obtaining an evolution form of the mining overlying strata fracture field under different geological conditions, and representing distribution of the mining overlying strata fracture field by adopting a unified topology model. And whether the overlying strata crack field has a separation layer area and the position thereof is determined, and accurate grouting in the separation layer area is scientifically guided to control surface subsidence and protect the ecology of a mining area.

Description

Technical Field

[0001] The patent of this invention belongs to the field of coal mining rock destruction and movement control and mining area ecological protection. Specifically, it relates to a unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions. The core of this invention is to establish a unified topological model that describes the spatial distribution of overburden fracture field under different geological conditions. The topological parameters in this model can be quantitatively calculated according to the structure and mechanical parameters of the overburden strata, breaking through the bottleneck that most parameters in the traditional strata movement prediction model are empirical values. According to the different strata mining support pressures and mechanical parameters of each stratum monitored by optical fiber arranged in the mine hydrological holes, the inflection point stratum and the concavity of the overburden fracture field are determined, and it is known that there are three evolutionary forms of overburden fracture field under different geological conditions. If there is no inflection point in the overburden fissure field, and there is no key layer of overburden movement in shallow mining, grouting can be done in the goaf; if there is a pair of inflection points in the overburden fissure field, the overburden has a conventional burial depth and there is a key layer of overburden movement, grouting can be done in the delamination area below the key layer where the inflection point is located; if there are two pairs of inflection points in the overburden fissure field, and there is a deep mining overburden movement, grouting can be done in the delamination area under the shallow convex inflection point of the first key layer. In these three cases, precise grouting can be used to control surface subsidence and protect the mining area ecology. Background Art

[0002] Safety, efficiency and greenness are the three major themes of coal mining today. In the process of coal mining, as the ore is removed, the stress balance of the rock mass above the goaf is destroyed, resulting in displacement and deformation of the surrounding rock, which in turn leads to surface subsidence. This subsidence not only affects the stability of the surface, but may also cause damage to ground buildings and facilities. Especially in mining areas with high groundwater levels, ground collapse may also cause large tracts of farmland to become waterlogged basins, causing serious impacts on the local ecological environment and landform structure. There is a high probability that surface subsidence will cause geological disasters such as mudslides and landslides. Surface subsidence in coal mines not only causes direct damage to land resources and agricultural production, but also poses a threat to the safety of buildings, and has a profound impact on local social stability and economic development. Therefore, the harm of surface subsidence in coal mines is considerable, and effective governance measures need to be taken to mitigate its impact.

[0003] Therefore, it is necessary to understand a unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions, understand the development law of overburden fracture field under different overburden conditions, and establish a unified topological model to characterize and describe it. Through the characterization equation, it is determined whether there is a delamination zone and its position in the overburden fracture field, and scientifically guide the precise grouting in the delamination zone to control surface subsidence and protect the mining area ecology. Summary of the invention

[0004] The purpose of the present invention is to control the destruction and movement of rock strata during coal mining and the damage to the surface and buildings caused by surface subsidence, so as to protect the ecology of the mining area.

[0005] The present invention proposes a unified topological model and method for characterizing the evolution of overburden fracture fields under different geological conditions. According to the mining support pressures of different layers monitored by optical fiber in the mine hydrological holes and the mechanical parameters of each rock layer, the inflection point layer and the concavity and convexity of the overburden fracture field are determined, and the evolutionary morphology of the overburden fracture field under different geological conditions is obtained. A unified topological model is used to characterize the distribution of the overburden fracture field under mining, and it is determined whether there is a delamination zone and its layer in the overburden fracture field, so as to provide scientific guidance for precise grouting in the delamination zone to control surface subsidence and protect the mining area ecology.

[0006] To achieve the above objectives, a unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions was designed:

[0007] (1) Arrange optical fiber in the mine hydrological observation hole to monitor the change law of the supporting pressure at different layers during coal mining;

[0008] (2) Identify the turning points of the mining-induced overburden fracture field layer by layer from shallow to deep;

[0009] (3) According to the inflection point of the overburden failure morphology, it is known that there are three evolutionary forms of overburden fracture field under different geological conditions. However, the evolutionary forms of overburden fracture field under different geological conditions can be uniformly characterized by a topological model:

[0010]

[0011] in H PKS Main key layer; H <ks>< / ks> Sub-critical layer;

[0012] (4) When the maximum mining bearing pressure of the overlying rock layers σ max Greater than the uniaxial compressive strength of the rock formation σ c When there is no inflection point in the overburden fracture field, it is the calculation formula for various parameters of shallow mining;

[0013] c Ⅰ =-(3a Ⅰ H coal 2 +2b Ⅰ H coal );d Ⅰ =x surface 2 ;

[0014] Among them, H topsoil H is the topsoil burial depth; coal is the coal seam burial depth; x coalis the positive horizontal coordinate of the boundary point of coal seam movement; topsoil is the positive horizontal coordinate of the settlement boundary point on the bedrock interface; surface is the positive horizontal coordinate of the surface settlement boundary point; x coal , x topsoil , x surface can be D is the width of coal seam excavation; M is the thickness of coal seam; is the friction angle of the coal seam; is the average internal friction angle of the soft rock layer above the main key layer; Topsoil friction angle;

[0015] (5) In case of shallow mining and no critical layer in the overlying rock formation, grouting can be performed in the goaf;

[0016] (6) When the maximum mining bearing pressure σ of two adjacent rock layers max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c The boundary between the two rock layers is the convex inflection point of the overburden fracture field. If we continue to judge layer by layer, the deep rock layers all meet σ max <σ c At this time, there is only a pair of convex inflection points in the overburden fracture field and a pair of inflection points in the overburden movement, which is the calculation formula for various parameters of conventional mining;

[0017] c Ⅱ =-(3a Ⅱ H coal 2 +2b Ⅱ H coal );d Ⅱ =x coal 2 -a Ⅱ H coal 3 -b Ⅱ H coal 2 -c Ⅱ H coal ;

[0018] Among them, H PKS is the burial depth of the main key layer; PKS x is the positive horizontal coordinate of the moving boundary point of the main key layer; PKS can be θ is the failure plane angle of the rock layer between the main key layer and the coal seam;

[0019] (7) In case of conventional mining and the presence of a key layer in the overlying rock formation, grouting can be performed in the delamination zone below the key layer where the inflection point is located;

[0020] (8) When the maximum mining bearing pressure of two adjacent shallow rock layers σ max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c , and the deep rock layer is composed of σ max <σ c becomes σ max >σ c At this time, there are two pairs of inflection points in the overburden fracture field. The inflection point of the shallow rock formation is the convex inflection point of the fracture field, and the inflection point of the deep rock formation is the concave inflection point of the fracture field. This is the calculation formula for each parameter of deep mining;

[0021] c Ⅲ =-(3a Ⅲ H <ks>< / ks> 2 +2b Ⅲ H <ks>< / ks> );d Ⅲ =x excavation 2 -a Ⅲ H excavation 3 -b Ⅲ H excavation 2 -c Ⅲ H excavation ;

[0022] where x excavation is the positive coordinate of the excavation boundary; x excavation =D / 2; H excavation is the depth of the lower boundary of the coal seam; x <ks>< / ks> is the positive horizontal coordinate of the inflection point; x <ks>< / ks> can be is the average internal friction angle of the deep rock layer at the concave inflection point;

[0023] (9) In deep mining where there is a key layer in the overlying rock layer, grouting can be performed in the separation zone below the shallow convex inflection point of the first key layer;

[0024] (10) Grouting can control surface subsidence and protect the ecology of mining areas.

[0025] The optical fiber arrangement should be located near the middle area of ​​the width of the coal mining working face, and the optical fiber and the rock layer should be fixed without relative slippage.

[0026] According to the morphology of the overburden fissure field under different geological conditions, the grouting position can be accurately found to control the movement of rock strata and protect the ecology of the mining area.

[0027] The above-mentioned understanding of the development law of the fracture field under different overburden conditions can better clarify the movement law inside the rock layer, which is of great significance for controlling surface subsidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Movement pattern of overburden without key layer in shallow mining

[0029] Figure 2 Conventional burial depth and the presence of key layers of overburden movement

[0030] Figure 3 Movement patterns of overburden in deep mining

[0031] Figure 4 Inflection point determination flow chart

[0032] where σ max is the maximum mining bearing pressure of the rock formation, σ c is the uniaxial compressive strength of the rock formation.

[0033] In the figure: 1. internal friction angle φ; 2. topsoil layer; 3. weak rock layer; 4. coal seam; 5. shallow water level; 6. main key layer; 7. aquifer; 8. basic top; 9. separation zone; 10. tensile shear failure 11. Inflection point; 12. Subcritical layer; 13. Compression shear failure DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0035] (1) Arrange optical fiber in the mine hydrological observation hole to monitor the change law of the supporting pressure at different layers during coal mining;

[0036] (2) Identify the turning points of the mining-induced overburden fracture field layer by layer from shallow to deep;

[0037] (3) According to the inflection point of the overburden failure morphology, it is known that there are three evolutionary forms of overburden fracture field under different geological conditions. However, the evolutionary forms of overburden fracture field under different geological conditions can be uniformly characterized by a topological model:

[0038]

[0039] in

[0040] H PKSMain key layer; H <ks>< / ks> Sub-critical layer;

[0041] (4) When the maximum mining bearing pressure of the overlying rock layers σ max Greater than the uniaxial compressive strength of the rock formation σ c When there is no inflection point in the overburden fracture field, it is the calculation formula for various parameters of shallow mining;

[0042]

[0043] c Ⅰ =-(3a Ⅰ H coal 2 +2b Ⅰ H coal );d Ⅰ =x surface 2 ;

[0044] Among them, H topsoil H is the topsoil burial depth; coal is the coal seam burial depth; x coal is the positive horizontal coordinate of the boundary point of coal seam movement; topsoil is the positive horizontal coordinate of the settlement boundary point on the bedrock interface; surface is the positive horizontal coordinate of the surface settlement boundary point; x coal , x topsoil , x surface can be D is the width of coal seam excavation; M is the thickness of coal seam; is the friction angle of the coal seam; is the average friction angle between the main key layer of the soft stratum and the topsoil; Topsoil friction angle;

[0045] (5) In case of shallow mining and no critical layer in the overlying rock formation, grouting can be performed in the goaf;

[0046] (6) When the maximum mining bearing pressure σ of two adjacent rock layers max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c The boundary between the two rock layers is the convex inflection point of the overburden fracture field. If we continue to judge layer by layer, the deep rock layers all meet σ max <σ c At this time, there is only a pair of convex inflection points in the overburden fracture field and a pair of inflection points in the overburden movement, which is the calculation formula for various parameters of conventional mining;

[0047] c Ⅱ =-(3aⅡ H coal 2 +2b Ⅱ H coal );

[0048] d Ⅱ =x coal 2 -a Ⅱ H coal 3 -b Ⅱ H coal 2 -c Ⅱ H coal ;

[0049] Among them, H PKS is the burial depth of the main key layer; PKS x is the positive horizontal coordinate of the moving boundary point of the main key layer; PKS can be θ is the failure plane angle of the rock layer between the main key layer and the coal seam;

[0050] (7) In case of conventional mining and the presence of a key layer in the overlying rock formation, grouting can be performed in the delamination zone below the key layer where the inflection point is located;

[0051] (8) When the maximum mining bearing pressure of two adjacent shallow rock layers σ max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c , and the deep rock layer is composed of σ max <σ c becomes σ max >σ c At this time, there are two pairs of inflection points in the overburden fracture field. The inflection point of the shallow rock formation is the convex inflection point of the fracture field, and the inflection point of the deep rock formation is the concave inflection point of the fracture field. This is the calculation formula for each parameter of deep mining;

[0052]

[0053] c Ⅲ =-(3a Ⅲ H <ks>< / ks> 2 +2b Ⅲ H <ks>< / ks> );d Ⅲ =x excavation 2 -a Ⅲ H excavation 3 -b Ⅲ H excavation2 -c Ⅲ H excavation ;

[0054] where x excavation x is the positive horizontal coordinate of the coal seam excavation boundary; excavation =D / 2; H excavation is the depth of the lower boundary of the coal seam; x KS > is the positive horizontal coordinate of the inflection point; x <ks>< / ks> can be is the average friction angle between the roof of the down-bending key layer and the coal seam;

[0055] (9) In deep mining where there is a key layer in the overlying rock layer, grouting can be performed in the separation zone below the shallow convex inflection point of the first key layer;

[0056] (10) Grouting can control rock movement and protect the mining area ecology.

[0057] (11) Effectively control rock movement and predict surface subsidence, thereby reducing damage to the surface and buildings, and effectively protecting the ecological environment and landform structure, which is beneficial to local social stability and economic development.

Claims

1. A unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions, comprising: (a) Optical fiber is arranged in the mine hydrological observation hole to monitor the change law of mining support pressure at different layers during coal mining. (b) Determine the turning point of the mining-induced overburden fracture field layer by layer from shallow to deep: When the maximum mining bearing pressure of the overlying rock layers σ max Greater than the uniaxial compressive strength of the rock formation σ c When , there is no turning point in the mining-induced overburden fracture field; When the maximum mining bearing pressure of two adjacent rock formations σ max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c The boundary between the two rock layers is the convex inflection point of the overburden fracture field. If we continue to judge layer by layer, the deep rock layers all meet σ max <σ c , at this time, there is only a pair of convex inflection points in the overburden fracture field; When the maximum mining bearing pressure of two adjacent shallow rock layers σ max and uniaxial compressive strength σ c By σ max >σ c becomes σ max <σ c , and the deep rock layer is composed of σ max <σ c becomes σ max >σ c At this time, there are two pairs of inflection points in the overburden fracture field. The inflection point of the shallow rock layer is the convex inflection point of the fracture field, and the inflection point of the deep rock layer is the concave inflection point of the fracture field. (c) According to the inflection point of the overburden failure morphology, it is known that there are three evolutionary forms of overburden fracture field under different geological conditions: When mining is shallow and there is no key layer in the overburden, there is no inflection point in the overburden fracture field caused by mining; When non-deep mining occurs and there is a key layer in the overburden, there is a pair of inflection points in the mining-induced overburden fracture field; When deep mining occurs and there is a key layer in the overburden, there are two pairs of inflection points in the overburden fracture field caused by mining. However, the evolution of the fracture field in the overburden under different geological conditions can be uniformly characterized by a topological model: in 2. According to the unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions under coal mining according to claim 1, the maximum mining bearing pressure σ of each rock layer is max The size is related to the lithology of the overlying rock strata, mining depth, mining method and other factors, and the value range is generally 1 to 5 times the initial geostress.

3. According to claim 1, a unified topological model and method for characterizing the evolution of overburden fracture fields in coal mining under different geological conditions, wherein the range of shallow mining is 150m to 300m, the range of conventional mining is 300m to 700m, and the range of deep mining is greater than 700m.

4. According to claim 1, a unified topological model and method for characterizing the evolution of overburden fracture fields under different geological conditions for coal mining, wherein the internal friction angle of the shallow topsoil layer ranges from 10° to 40°, and the deep bedrock mainly includes mudstone and sandstone. The internal friction angle of mudstone ranges from 20° to 30°, and the internal friction angle of sandstone ranges from 30° to 45°.

5. According to the unified topological model and method for characterizing the evolution of overburden fracture fields under different geological conditions in coal mining as described in claim 1, the optical fiber arrangement should be located near the middle area of ​​the width of the coal mining working face, and the optical fiber and the rock layer should be fixed without relative slippage.

6. According to the unified topological model and method for characterizing the evolution of overburden fracture fields under different geological conditions in coal mining as described in claim 1, wherein the grouting position of the delamination zone can be determined in the delamination zone below the key layer of the shallow convex inflection point according to the morphology of the overburden fracture field under different geological conditions, so as to control the movement of rock strata and protect the ecology of the mining area.

7. The unified topological model and method for characterizing the evolution of overburden fracture field under different geological conditions in coal mining according to claim 1, wherein the uniaxial compressive strength σ of each rock layer is c It is the uniaxial compressive strength of the rock mass, which is about 0.5 to 0.7 times the uniaxial compressive strength of the rock block tested in the laboratory.

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