A unified topological characterization method for evolution of overburden rock fracture field under different geological conditions

Abstract

The present application belongs to the field of coal mining strata damage and movement control and mining area ecological protection. Specifically relates to a unified topological model and method for representing the evolution of overburden rock fracture field under different geological conditions. The core of the present application is to establish a unified topological model for describing the spatial distribution of overburden rock fracture field under different geological conditions. The topological parameters in the model can be quantitatively calculated according to the overburden structure and mechanical parameters, breaking through the bottleneck that most parameters in traditional rock movement prediction model are empirical values. According to the overburden strata supporting pressure and mechanical parameters of different layers monitored by optical fiber arranged in mine hydrological hole, the inflection point layer and concave-convex nature of overburden rock fracture field are determined, and the evolution form of overburden rock fracture field under different geological conditions is obtained. The unified topological model is used to represent the distribution of overburden rock fracture field, and whether there is a separation zone and its layer in the overburden rock fracture field is determined, which scientifically guides the accurate grouting in the separation zone to control the surface subsidence and protect the mining area ecology.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of coal mining strata damage and movement control and ecological protection of mining area. Specifically relates to a method for characterizing the evolution of overburden fissure field under different geological conditions. The core of the application is to establish a unified topological characterization method to describe the spatial distribution of overburden fissure field under different geological conditions. The topological parameters in the model can be quantitatively calculated according to the overburden structure and mechanical parameters, breaking the bottleneck that most parameters in traditional strata movement prediction models are empirically valued. According to the overburden fissure field and the mechanical parameters of each rock layer, the inflection point layer and the concave-convex nature of the overburden fissure field are determined, and it is found that there are three evolution patterns of overburden fissure field under different geological conditions. The overburden fissure field does not have an inflection point, the overburden of shallow mining has no key layer, and the strata movement pattern can be grouted in the goaf; the overburden fissure field has a pair of inflection points, the overburden of conventional depth has a key layer, and the strata movement pattern can be grouted in the separation zone below the inflection point of the key layer; the overburden fissure field has two pairs of inflection points, the overburden of deep mining has a key layer, and the strata movement pattern can be grouted in the separation zone below the convex inflection point of the first key layer. In the three cases, accurate grouting can control the surface subsidence and protect the ecological environment of the mining area. BACKGROUND

[0002] Safety, efficiency and green are the three major themes of today's coal mining. In the process of coal mining, as the ore is removed, the stress balance of the rock mass above the goaf is destroyed, causing displacement and deformation of the surrounding rock, and then causing surface subsidence. This subsidence not only affects the stability of the surface, but also can cause damage to ground buildings. Especially in mining areas with high water level, ground subsidence can also cause large areas of farmland to become water accumulation basins, causing serious impact on the local ecological environment and landform structure. Surface subsidence has a high probability of triggering geological disasters such as mudslides and landslides. Coal mine surface subsidence not only directly damages land resources and agricultural production, but also threatens the safety of buildings, and has a profound impact on local social stability and economic development. Therefore, the harm of coal mine surface subsidence is quite large, and effective control measures need to be taken to alleviate its impact.

[0003] Therefore, it is necessary to understand a unified topological characterization method of overburden fissure field evolution under different geological conditions, understand the development law of overburden fissure field under different overburden conditions, and establish a unified topological model to characterize and describe. Through the characterization equation, it is determined whether there is a separation zone in the overburden fissure field and its layer, and scientific guidance is provided for accurate grouting in the separation zone to control surface subsidence and protect the ecological environment of the mining area. SUMMARY

[0004] The purpose of the application is to control the strata damage and movement of coal mining and control the damage of surface and buildings caused by surface subsidence, and protect the ecological environment of the mining area.

[0005] The application provides a unified topological characterization method for evolution of a coal mining overburden rock crack field under different geological conditions.

[0006] The application provides a unified topological characterization method for evolution of a coal mining overburden rock crack field under different geological conditions.

[0007] (1) arranging an optical fiber in a mine hydrological observation hole to monitor variation of a mining support pressure at different layers during coal mining;

[0008] (2) determining a turning point of the coal mining overburden rock crack field from a shallow layer to a deep layer;

[0009] (3) determining, according to the turning point of the overburden rock damage form, that there are three evolution forms of the coal mining overburden rock crack field under different geological conditions, and that the evolution forms of the coal mining overburden rock crack field under different geological conditions can be characterized by a topological model;

[0010] x 2 =az 3 +bz 2 +cz+d+(Az 2 +Bz+C)(z-H PKS )+(Dz 2 +Ez+F)(z-H <ks>< / ks> ) (1)

[0011] Among them H PKS main key layer; H KS> sub key layer;

[0012] (4) when the maximum mining support pressure σ max of each overburden rock layer is greater than the uniaxial compressive strength σ c of the rock layer, the coal mining overburden rock crack field has no turning point, and each parameter calculation formula for shallow mining is obtained;

[0013] c Ⅰ =-(3a Ⅰ H coal 2 +2b Ⅰ H coal ); Among them Htopsoil is the overburden depth; H coal is the coal seam depth; x coal is the positive horizontal coordinate of the coal seam movement boundary point; x topsoil is the positive horizontal coordinate of the upper boundary point of the soft rock layer above the bedrock; x surface is the positive horizontal coordinate of the surface subsidence boundary point; x coal , x topsoil , x surface may be calculated by

[0014] D is the coal seam excavation width; M is the coal seam thickness; is the coal seam friction angle; is the average internal friction angle of the soft rock layer above the main key stratum; is the overburden friction angle;

[0015] (5) Shallow mining and no key stratum in the overburden strata, grouting can be performed in the goaf;

[0016] (6) When the maximum mining-induced support pressure σ max and the uniaxial compressive strength σ c of the adjacent two rock strata change from σ max > σ c to σ max < σ c , the boundary between the two rock strata is the inflection point of the overburden fracture field, and if the judgment continues layer by layer, the deep rock strata all satisfy σ max < σ c , at this time the overburden fracture field only has one pair of inflection points, the overburden movement has one pair of inflection points, and it is a conventional mining, and the parameter calculation formula is as follows;

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

[0018] d Ⅱ = x coal 2 -a Ⅱ H coal 3 -b Ⅱ H coal 2 -c Ⅱ H coal ;

[0019] wherein H PKS is the main key stratum depth; x PKS is the positive horizontal coordinate of the main key stratum movement boundary point; xPKS The coal seam can be mined by θ is the failure surface angle between the main key stratum and the coal seam;

[0020] (7) When the coal seam is mined conventionally and the overlying strata have key strata, grouting can be performed in the separation zone below the key stratum at the inflection point;

[0021] (8) When the maximum mining-induced support pressure σ max and the uniaxial compressive strength σ c of the shallow strata is σ max > σ c and the uniaxial compressive strength σ max < σ c , and the uniaxial compressive strength σ max < σ c of the deep strata is σ max > σ c , the overlying strata crack field has two pairs of inflection points, the turning point of the shallow strata is the convex inflection point of the crack field, and the turning point of the deep strata is the concave inflection point of the crack field, and the parameters are calculated according to the formula for deep mining;

[0022]

[0023] c Ⅲ =-(3a Ⅲ H <ks>< / ks> 2 +2b Ⅲ H <ks>< / ks> );

[0024]

[0025] wherein x excavation is the positive coordinate of the excavation boundary; x excavation =D / 2; H excavation is the buried 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 obtained by is the average internal friction angle of the deep strata;

[0026] (9) When the coal seam is mined deeply and the overlying strata have key strata, grouting can be performed in the separation zone below the convex inflection point of the first key stratum in the shallow part;

[0027] (10) Grouting can control the surface subsidence and protect the ecology of the mining area.

[0028] The optical fiber arrangement is located near the middle region of the width of the coal mining face, and the optical fiber is fixed with the strata and cannot slide relative to the strata.

[0029] The crack field form of the overburden strata under different geological conditions can be obtained, and the grouting position can be accurately found, and the strata movement and the ecological protection of the mining area can be realized.

[0030] The crack field development law under different overburden strata conditions can better understand the movement law of the strata, and it is of great significance to control the surface subsidence. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Strata movement form of overburden strata without key layer under shallow mining

[0032] Figure 2 Strata movement form of overburden strata with key layer under conventional depth

[0033] Figure 3 Strata movement form of overburden strata under deep mining

[0034] Figure 4 Flow chart for inflection point discrimination

[0035] Wherein σ max is the maximum mining abutment pressure of the strata, σ c is the uniaxial compressive strength of the strata.

[0036] In the figure: 1. internal friction angle φ; 2. topsoil layer; 3. weak strata; 4. coal seam; 5. shallow water level; 6. main key layer; 7. aquifer; 8. basic roof; 9. separation zone; 10. tension-shear failure 11. inflection point; 12. sub-key layer; 13. compression-shear failure DETAILED DESCRIPTION

[0037] The application will be further described below in combination with the drawings and examples.

[0038] (1) In the process of laying optical fiber in the mine hydrological observation hole to monitor the change law of the mining abutment pressure of different layers, the coal seam mining process is monitored;

[0039] (2) The inflection point of the crack field of the overburden strata under mining is discriminated layer by layer from shallow to deep;

[0040] (3) According to the inflection point discrimination of the overburden strata damage form, it is known that there are three evolution forms of the crack field of the overburden strata under different geological conditions, but the evolution form of the crack field of the overburden strata under different geological conditions can be characterized by a topological model:

[0041]

[0042] Wherein H PKS main key layer; H <ks>< / ks> sub-key layer;

[0043] (4) When the maximum mining support pressure σ of the overlying rock strata max Greater than the uniaxial compressive strength σ of the rock stratum c When there is no inflection point in the overlying rock fracture field during mining, the calculation formulas for various parameters are used for shallow mining.

[0044] c Ⅰ =-(3a) Ⅰ H coal 2 +2b Ⅰ H coal ); Where H topsoil The depth of the topsoil burial; H coal For coal seam burial depth; x coal x is the positive x-coordinate of the boundary point of coal seam movement; topsoil x represents the positive x-coordinate of the settlement boundary point on the bedrock surface; surface x is the positive x-coordinate of the surface subsidence boundary point; coal x topsoil x surface can be

[0045] D is the width of the coal seam excavation; M is the thickness of the coal seam. The angle of friction of the coal seam; This represents the average friction angle between the main key layer of the soft soil and the topsoil. Topsoil friction angle;

[0046] (5) If shallow mining is carried out and there are no key layers in the overlying rock strata, grouting can be performed in the goaf.

[0047] (6) When the maximum mining support pressure σ of two adjacent rock strata max and uniaxial compressive strength σ c From σ max >σ c Transform into σ max <σ c The boundary between these two rock layers is a convex inflection point of the overlying fracture field. If we continue to examine each layer, the deeper rock layers all satisfy σ. max <σ c At this time, there is only one pair of convex inflection points in the overburden fracture field, and there is one pair of inflection points in the overburden movement. This is the calculation formula for each parameter in conventional mining.

[0048] c Ⅱ =-(3a) Ⅱ H coal 2 +2b Ⅱ H coal );

[0049] d Ⅱ = x coal 2 - a Ⅱ H coal 3 - b Ⅱ H coal 2 - c Ⅱ H coal ;

[0050] where H PKS is the main key stratum buried depth; x PKS is the positive horizontal coordinate of the main key stratum moving boundary point; x PKS may be obtained by θ is the failure surface angle between the main key stratum and the coal seam;

[0051] (7) When the conventional mining and the overburden strata exist key stratum, grouting can be carried out in the parting area under the inflection point of the key stratum;

[0052] (8) When the maximum mining support pressure σ max of the shallow adjacent two strata and the uniaxial compressive strength σ c σ max > σ c changes to σ max < σ c , and the deep strata σ max < σ c changes to σ max > σ c , at this time, the overburden strata crack field exists two pairs of inflection points, the turning point of the shallow strata is the convex inflection point of the crack field, and the turning point of the deep strata is the concave inflection point of the crack field, and the parameters calculation formula for deep mining is obtained;

[0053]

[0054] c Ⅲ = -(3a Ⅲ H <ks>< / ks> 2 + 2b Ⅲ H <ks>< / ks> );

[0055]

[0056] where x excavation is the positive horizontal coordinate of the coal seam excavation boundary; x excavation = D / 2; H excavation is the lower boundary buried depth of the coal seam; x <ks>< / ks> is the positive horizontal coordinate of the inflection point; x <ks>< / ks> may be obtained by The average friction angle between the top of the key stratum and the coal seam;

[0057] (9) When the overburden strata have key strata, grouting can be performed in the separation zone under the shallow inflection point of the first key stratum;

[0058] (10) Grouting can control strata movement and protect the ecological environment of the mining area.

[0059] (11) Effective control of strata movement and prediction of surface subsidence can reduce the damage to the surface and buildings, thereby effectively protecting the ecological environment and the topography, and promoting the social stability and economic development of the local area.

Claims

1. A unified topological characterization method of overburden fracture field evolution under different geological conditions, comprising: (a) arranging optical fibers in mine hydrological observation holes to monitor the variation of abutment pressure at different layers during coal mining; (b) determining the inflection point of the overburden fracture field of each rock layer from shallow to deep; When the maximum mining support pressure of each rock stratum overlying is greater than the uniaxial compressive strength of the rock stratum , the fracture field of the overlying rock stratum of mining has no inflection point; When the maximum mining abutment pressure of two adjacent rock strata and uniaxial compressive strength By Changes to The two rock strata boundary is the inflection point of the overburden fracture field. If the layer-by-layer judgment continues, the deep rock strata all meet At this time, the overburden fracture field only exists a pair of inflection points; When the maximum mining abutment pressure of the two adjacent rock strata in the shallow part and the uniaxial compressive strength by becomes , and the deep rock stratum becomes from , at this time the overburden rock fracture field has two pairs of inflection points, the turning point of the shallow rock stratum is the convex inflection point of the fracture field, and the turning point of the deep rock stratum is the concave inflection point of the fracture field; (c) determining the existence of three evolution patterns of overburden fracture field under different geological conditions according to the inflection point of the overburden fracture field: when shallow mining and no key layer exists in the overburden, the overburden fracture field has no inflection point; when non-deep mining and a key layer exists in the overburden, the overburden fracture field has a pair of inflection points; wherein ; ; ; ; ; ; ; ; ; ; The above parameters are explained as follows: ; ; ; ; is the buried depth of the surface soil; is the buried depth of the coal seam; is the positive horizontal coordinate of the movement boundary point of the coal seam; is the positive horizontal coordinate of the settlement boundary point of the upper interface of the bedrock; is the positive horizontal coordinate of the settlement boundary point of the surface; , , can be obtained from ; ; ; D is the excavation width of the coal seam; M is the thickness of the 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 stratum; is the friction angle of the surface soil; ; ; ; ; is the buried depth of the main key stratum; is the positive horizontal coordinate of the moving boundary point of the main key stratum; may be ; is the failure surface angle of the rock stratum between the main key stratum and the coal seam; ; ; ; ; is the positive coordinate of the excavation boundary; ; is the depth of the sub-key stratum; is the depth of the lower boundary of the coal seam; is the positive horizontal coordinate of the inflection point; may be calculated by ; is the average internal friction angle of the deep stratum.

2. The unified topological characterization method for the evolution of fracture fields in coal-bearing overburden under different geological conditions as described in claim 1, wherein the maximum mining-induced bearing pressure of each stratum... The magnitude is related to the lithology of the overlying strata, the mining depth, and the mining method, and the value ranges from 1 to 5 times the initial geostress. when deep mining and a key layer exists in the overburden, the overburden fracture field has two pairs of inflection points; 4. The unified topological characterization method of overburden rock fracture field evolution of coal mining in different geological conditions according to claim 1, wherein the range of internal friction angle of the shallow topsoil layer is 30°-40°. ~ , the deep bedrock mainly contains two types of mudstone and sandstone, the range of internal friction angle of the mudstone is 30°-40°. ~ , the range of internal friction angle of the sandstone is 30°-40°. ~ . but the evolution patterns of overburden fracture field under different geological conditions are characterized by a unified topological model. 3.The unified topological characterization method of overburden fracture field evolution under different geological conditions according to claim 1, wherein the range of shallow mining is 150m-300m, the range of conventional mining is 300m-700m, and the range of deep mining is greater than 700m. 5.The unified topological characterization method of overburden fracture field evolution under different geological conditions according to claim 1, wherein the optical fibers are arranged near the middle area of the coal mining face, and the optical fibers are fixed between the rock layers and cannot slide relative to the rock layers. 6.The unified topological characterization method of overburden fracture field evolution under different geological conditions according to claim 1, wherein the grouting position in the separation zone can be determined in the separation zone under the key layer of the shallow convex inflection point according to the overburden fracture field pattern under different geological conditions, so as to control the movement of rock layers and protect the ecology of the mining area. 7.The method of claim 1, wherein the uniaxial compressive strength of each stratum is 0.5-0.7 times the uniaxial compressive strength of the rock mass, which is the uniaxial compressive strength of the rock block tested in the laboratory. 0.5-0.7 times the uniaxial compressive strength of the rock mass, which is the uniaxial compressive strength of the rock block tested in the laboratory.

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