Method for regulating and controlling curvature and bearing pressure of moving hyperbolic curve of coal mine mining overburden strata to restrain disasters

Abstract

The invention belongs to the field of mine disaster control, and particularly relates to cooperative regulation and control of coal mine mining overburden moving hyperbolic curvature and bearing pressure so as to achieve the purpose of disaster reduction and suppression. The method is characterized in that the curvature of the vertex position of a hyperbolic-like curve of an overlying rock stratum is changed by cutting the top at the theoretically determined position of a main key layer, and the curvature of the vertex position of the hyperbolic-like curve is reduced after the top is cut; meanwhile, the mining bearing pressure peak value and the influence range are reduced, the bearing pressure optimization effect is obvious, and mine disaster control is achieved. After top cutting, the fracture block of the main key layer rotates to extrude the lower overhanging rock stratum, and the overhanging part of the lower rock stratum also has chain type fracture. According to the quantitative relation between the vertex curvature of the rock stratum moving hyperbolic curve and the boundary mining-induced bearing pressure of the coal seam goaf, the accurate roof cutting position of the main key layer is determined, and the technology can be more accurately guided to be applied on site.

Description

Technical Field

[0001] The patent of this invention relates to the field of mine disaster control, especially the field of support pressure control in goaf areas, and specifically to a method for regulating and suppressing disasters by controlling the hyperbolic curvature and support pressure of overburden movement during coal mining. Background Art

[0002] As the difficulty of coal mining in my country continues to increase, deep coal mining is not only a strategic choice for my country's energy security, but also an inevitable trend. However, with the increase in mining depth, the rock mass will face a complex stress environment of "three highs and one disturbance", the tunnel surrounding rock will be severely damaged, the mine pressure will be severe, the plastic zone and the broken zone will increase, and the surrounding rock deformation will be large. Therefore, it is very necessary to conduct research on the stress conditions and stability of deep tunnels.

[0003] Roof cutting and pressure relief technology is one of the new mining methods. By changing the overall mechanical structure of the roof, this technology has brought coal mining to a new level and significantly improved the overall mining efficiency. At the same time, it has reduced the collection costs for related companies and avoided environmental pollution and waste of resources.

[0004] We call the rock layer that controls the partial overburden of the mining site or the entire rock mass on the surface the key layer. The former is called the sub-key layer, and the latter is called the main key layer. Among them, based on the key layer theory and the damage and movement morphology of rock strata at different levels, Zuo Jianping et al. established a hyperbolic model of the overall movement of the mining-induced overburden. This model unifies the "funnel-shaped" subsidence of the surface and the "inverted funnel-shaped" fracture of the roof into a whole. The vertex of the hyperbola is approximately located at the main key layer, that is, the main key layer is the narrowest damaged rock layer in the overburden. The hyperbolic model reveals the internal movement law and mechanical mechanism of the overburden, and points out that the main key layer is at the inflection point, which is the key layer controlling the fracture and movement of the rock strata. It plays a major controlling role in the activities of the overburden strata in the mining site, so it is very necessary to study the key layer.

[0005] Therefore, it is necessary to link the hyperbolic model of overburden movement with the support pressure, and study how to change the curvature of the hyperbolic model by cutting the top of the main key layer, thereby changing the mining support pressure at the boundary of the coal seam goaf. The core is to control the peak value of the mining support pressure within the range of the uniaxial compressive strength of the coal body by cutting the top of the main key layer. If the support pressure is higher than the uniaxial compressive strength of the coal body, the precise cutting position of the main key layer is re-determined based on the established quantitative relationship between the vertex curvature of the hyperbolic model of rock layer movement and the support pressure at the boundary of the coal seam goaf. Finally, after cutting the top at the precise position, the curvature of the vertex position of the hyperbolic model of the overburden layer is reduced, and the peak value and influence range of the mining support pressure are also reduced, thereby achieving the control of mine disasters. Summary of the invention

[0006] The present invention mainly cuts the top at the main key layer position determined by theory, so that the curvature of the hyperbola vertex position of the overlying rock layer after cutting is reduced, and the peak value and influence range of the mining support pressure are also reduced. The purpose is to provide a technical method that can effectively reduce the peak value and influence range of the support pressure, reduce the area of ​​the stress concentration area, and realize the control of mine disasters.

[0007] The present invention proposes a method for controlling the curvature of the hyperbola of overburden movement and the support pressure to prevent disasters in coal mines. This technology links the hyperbola model of overburden movement with the support pressure at the boundary of the coal seam goaf, and controls the support pressure by changing the curvature of the vertex position of the overburden stratum hyperbola. On the basis of traditional top cutting and pressure relief, the position of top cutting can be found quickly according to the established quantitative relationship between the vertex curvature of the hyperbola of stratum movement and the mining support pressure at the boundary of the coal seam goaf. By top cutting the main key layer, the fractured blocks of the main key layer rotate and squeeze the lower overhanging rock layer, and the overhanging part of the lower rock layer will also undergo chain fractures, and the peak value and influence range of the mining support pressure will also be reduced. This invention can be applied to support pressure control, mine disaster control and other aspects.

[0008] To achieve the above objectives, a method for controlling the hyperbolic curvature and support pressure of overburden movement in coal mining is designed:

[0009] (1) First, according to the key layer theory, the main key layer in the overburden must meet the two conditions of strength and stiffness:

[0010]

[0011] in,

[0012] Where E, h, and γ are the elastic modulus, thickness, and bulk density of the rock formation, respectively; q is the load on the rock formation; [σ t ] is the tensile strength of the rock layer; L is the periodic fracture step of the rock layer. From this, the key rock layer in the overlying rock layer can be determined, and the uppermost key rock layer is called the main key layer;

[0013] (2) Based on the hyperbolic model of rock strata movement, the curvature of the hyperbolic boundary and vertex position formed by the natural breaking of the roof is obtained;

[0014] (3) The peak value of the mining support pressure P at the boundary of the coal seam goaf measured on site max , the borehole pressure sensor is used for measurement, a borehole is arranged in the coal seam, a pressure sensor is installed, and the change of the support pressure is monitored in real time through the pressure sensor;

[0015] (4) The uniaxial compressive strength σ of the coal body measured by indoor test c, apply uniaxial pressure on the specimen to determine the bearing capacity of the material under compressive load. By cutting the top of the main key layer, fracturing cycles are carried out until the peak value of the mining support pressure is controlled to be less than the uniaxial compressive strength of the coal body;

[0016] (5) By removing the pressure from the top of the main key layer, the peak pressure of the mining support can be controlled to less than [σ c ], according to the quantitative relationship between the vertex curvature of the hyperbola of rock movement and the mining support pressure at the boundary of the coal seam goaf, the precise cutting position of the main key layer can be determined:

[0017]

[0018] Among them, k 1 is the curvature of the hyperbola vertex after truncating k 2 is the curvature of the hyperbola vertex before truncating a, b are the real and imaginary axes of the hyperbola before truncating; r 1 is the radius of the tunnel and mining space; C is the cohesion of the rock mass; is the internal friction angle of the rock mass.

[0019] There must be a main key layer in the overlying rock layer, which is determined according to the key layer theory.

[0020] The main key layer top cutting generally adopts hydraulic fracturing top cutting technology, which can add sand to the water in advance, open a groove under high pressure, generate stress concentration at the groove end, and facilitate directional fracturing, and the general depth is 0.5m to 1.0m.

[0021] The water pressure of the hydraulic fracturing top cutting of the main key layer is positively correlated with the burial depth. No sand is added to the water during fracturing. At the general conventional mining depth, the water pressure ranges from 30MPa to 70MPa, and the water pressure for deep mining must be greater than 70MPa.

[0022] The on-site measurement of the peak value of the mining support pressure requires real-time monitoring using a borehole stress gauge to observe whether it has dropped to the expected value. If it is higher than the expected value, in the next fracturing cycle, it is necessary to reduce the curvature of the hyperbola vertex, readjust the fracturing position, and increase the hyperbola vertex spacing.

[0023] The main key layer fracturing can be carried out by drilling wells on the ground, using horizontal well staged fracturing, or drilling holes into the top plate for fracturing. The specific method to be used determines the optimal drilling method based on the location of the main key layer.

[0024] Compared with the traditional mining support pressure control technology, the present invention has the following advantages:

[0025] First, according to the quantitative relationship between the vertex curvature of the stratum movement hyperbola and the mining support pressure at the boundary of the coal seam goaf, the present invention can quickly find the cutting top position, and the preliminary preparation work can be completed quickly, saving manpower and time.

[0026] Secondly, the present invention achieves the purpose of reducing the peak value of the supporting pressure and the impact range by changing the curvature of the hyperbola vertex position of the overlying rock strata, thereby improving the safety of the coal mine and achieving the purpose of reducing and suppressing disasters.

[0027] Third, the top cutting technology has been put into actual engineering use. We use hydraulic fracturing to weaken the top cutting technology, which is relatively mature, safer and more efficient, and reduces the stress of the surrounding rock of the tunnel. The construction process is mature, can achieve twice the result with half the effort, save resources, and is highly economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of disaster prevention and control of overburden movement hyperbolic curvature and support pressure in coal mining

[0029] Figure 2 Image of the change of support pressure before and after the top cutting of the main key layer

[0030] Figure 3 Flow chart of disaster prevention and control of hyperbolic curvature and support pressure of overburden movement in coal mining

[0031] The marks in the figure are: 1. The quasi-hyperbolic movement shape after roof cutting; 2. The quasi-hyperbolic movement shape before roof cutting; 3. Topsoil layer; 4. Main key layer; 5. Basic roof; 6. Direct roof; 7. Fracturing cracks at the top of the main key layer; 8. Chain fractures at the external hanging rock layer; 9. Coal seam; 10. Tunnel; 11. Coal pillar; 12. Coal pillar; 13. Support pressure image before roof cutting; 14. Support pressure image after roof cutting. DETAILED DESCRIPTION

[0032] The present invention reduces the curvature of the hyperbola vertex position of the overlying rock layer by cutting the top at the theoretically determined main key layer position, and also reduces the peak value and influence range of the mining support pressure, thereby achieving mine disaster control, minimizing the occurrence of tunnel surrounding rock damage, and improving the overall mining efficiency. The present invention is further described below in conjunction with the accompanying drawings, including the following structure, principle and specific implementation steps:

[0033] As attached Figure 1 As shown, a method for controlling the curvature and support pressure of a hyperbola-like curve of overburden movement caused by coal mining involves cutting the top at a determined position of the main key layer to generate a fracturing crack 7, and at the same time, a chain fracture will occur in the sub-key layer and the rock layer controlled by it 8. By cutting the top at the theoretically determined main key layer position, the hyperbola-like curve of overburden movement caused by mining will change from form 2 to form 1, the curvature of the vertex position will be significantly reduced, and the distance between the vertices of the hyperbola-like curve will be increased.

[0034] The changes of surrounding rock support pressure in goaf before and after roof cutting are as follows: Figure 2 Before the top is cut, the distribution of the supporting pressure of the surrounding rock caused by mining is shown in 13. In the process from the side of the goaf to the deep rock mass, the supporting pressure shows the following trend: it increases from 0 to P max1 , then decreases, when the distance reaches d 2 The abutment pressure tends to the constant value of γH. The change of abutment pressure after top cutting is shown in 14. In the process from the side of the goaf to the deep rock mass, the abutment pressure shows the following trend: it increases from 0 to P max2 , then decreases, when the distance reaches d 1 When the abutment pressure approaches the constant value of γH, it can be concluded that the peak value of the abutment pressure decreases before and after the top cutting, and the surrounding rock stress recovers to the original rock stress earlier, indicating that the top cutting can reduce the peak value and influence range of the abutment pressure.

[0035] The specific implementation methods and principles are as follows:

[0036] (1) First, according to the key layer theory, the main key layer in the overlying rock layer is determined. The top key layer is determined as the main key layer, which must meet the following two conditions: strength and stiffness:

[0037]

[0038] in,

[0039] Where E, h, and γ are the elastic modulus, thickness, and bulk density of the rock formation, respectively; q is the load on the rock formation; [σ t ] is the tensile strength of the rock layer; L is the periodic fracture step of the rock layer. The key rock layer in the overlying rock layer can be determined, and the uppermost key rock layer is called the main key layer.

[0040] (2) Based on the hyperbolic model of rock strata movement, the curvature of the hyperbolic boundary and vertex position formed by the natural breaking of the roof is obtained;

[0041] (3) The peak value of the mining support pressure P at the boundary of the coal seam goaf measured on site max When monitoring the changes in the supporting pressure during mining, 5 measuring stations were selected on the working face, and borehole stress gauges were installed on the measuring stations to monitor the changes in the peak supporting pressure after top cutting.

[0042] (4) The uniaxial compressive strength σ of the coal body measured by indoor test c Indoor experiments were conducted to determine the uniaxial compressive strength of coal. Uniaxial pressure was applied to the sample, and the stress-strain relationship of the material under different loads was recorded to determine its uniaxial compressive strength.

[0043] (5) By removing the pressure from the top of the main key layer, the peak pressure of the mining support can be controlled to less than [σ c ], according to the quantitative relationship between the vertex curvature of the hyperbola of rock movement and the mining support pressure at the boundary of the coal seam goaf, the precise cutting position of the main key layer can be determined:

[0044]

[0045] Among them, k 1 is the curvature of the hyperbola vertex after truncating k 2 is the curvature of the hyperbola vertex before truncating a, b are the real and imaginary axes of the hyperbola before truncating; r 1 is the radius of the tunnel and mining space; C is the cohesion of the rock mass; is the internal friction angle of the rock mass.

[0046] (6) By cutting off the top at the theoretically determined main key layer position, the fractured blocks of the main key layer rotate and squeeze the lower overhanging rock layer, and the overhanging part of the lower rock layer will also undergo chain fracture. After cutting off the top, the curvature of the hyperbolic vertex position of the overlying rock layer is reduced, and the peak value and impact range of the mining support pressure are also reduced, thereby achieving the control of mine disasters.

[0047] (7) The present invention proves that by cutting the top at the determined position of the main key layer, the hyperbolic curvature of the overburden movement in the coal mine and the support pressure are coordinated and regulated. By cutting the top to relieve pressure, the curvature of the vertex position of the hyperbolic overburden is changed, so that the peak value and the influence range of the mining support pressure are also reduced, thereby achieving mine disaster control.

Claims

1. A method for controlling and suppressing disasters caused by overburden movement in coal mining by regulating the hyperbolic curvature and support pressure, which mainly includes the following contents: (a) Determine the key layer in the overlying rock layer according to the key layer theory, and determine the topmost key layer as the main key layer; (b) Based on the hyperbolic model of rock strata movement, the curvature of the hyperbolic boundary and vertex position formed by the natural breaking of the roof is obtained; (c) Peak value of the mining support pressure P at the boundary of the coal seam goaf measured on site max The uniaxial compressive strength of coal measured by indoor test σ c ; (d) By removing the pressure from the top of the main key layer, the peak pressure of the mining support can be controlled to less than [σ c ], according to the quantitative relationship between the vertex curvature of the hyperbola of rock movement and the mining support pressure at the boundary of the coal seam goaf, the precise cutting position of the main key layer can be determined: (e) By cutting off the top at the theoretically determined main key layer position, the fractured blocks of the main key layer rotate and squeeze the lower overhanging rock layer, and the overhanging part of the lower rock layer will also undergo chain fracture. After cutting off the top, the curvature of the hyperbolic vertex position of the overlying rock layer is reduced, and the peak value and impact range of the mining support pressure are also reduced, thereby achieving the control of mine disasters.

2. According to the method of claim 1 for controlling and suppressing disasters by regulating the hyperbolic curvature and support pressure of overburden movement caused by coal mining, there must be a main key layer in the overburden, which is determined according to the key layer theory.

3. According to the method of claim 1, which is a method for controlling the hyperbolic curvature and support pressure of overburden movement in coal mining, the main key layer is generally cut by hydraulic fracturing. Sand can be added to the water in advance, and a groove can be opened under high pressure. Stress concentration is generated at the end of the groove, which is easy to directional fracturing. The general depth is 0.5m to 1.0m.

4. According to claim 1, a method for controlling and suppressing disasters by regulating the hyperbolic curvature of overburden movement and support pressure during coal mining, wherein the water pressure of hydraulic fracturing and cutting top of the main key layer is positively correlated with the burial depth, and no sand is added to the water during fracturing. At the general conventional mining depth, the water pressure ranges from 30MPa to 70MPa, and the water pressure for deep mining must be greater than 70MPa.

5. According to the method of controlling and suppressing disasters by hyperbolic curvature and supporting pressure of overburden movement in coal mining as described in claim 1, after the main key layer is cut off, the sub-key layer below the main key layer and the rock strata controlled by it will undergo chain fractures, thus avoiding fracturing of multiple key layers. The length of the chain fracture blocks in the sub-key layer is less than the periodic pressure step, generally 8m to 15m, and the chain fracture angle is greater than the natural fracture angle, generally ranging from 75° to 90°.

6. According to the method for controlling and suppressing disasters caused by the hyperbolic curvature and support pressure of overburden movement in coal mining as described in claim 1, after the main key layer is fracturing, a borehole stress gauge is used on site to monitor the mining support pressure in real time to see whether it has been reduced to the expected value. If it is higher than the expected value, in the next fracturing cycle, it is necessary to reduce the curvature of the hyperbolic vertex, readjust the fracturing position, and increase the spacing between the hyperbolic vertices.

7. According to the method of controlling the hyperbolic curvature and support pressure of overburden movement in coal mining as described in claim 1, the main key layer fracturing can be done by ground drilling, horizontal well staged fracturing, or underground drilling and fracturing on the roof. The specific method to be used determines the optimal drilling method based on the location of the main key layer.

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