Deep floor water hammer water inrush effect model judgment method

Abstract

The invention discloses a deep floor water hammer water inrush effect model judgment method, which comprises the following steps of: in a deep coal seam floor, firstly, determining whether a confined aquifer and a potential water guide channel exist or not according to geological conditions of the deep coal seam floor; if the potential water guide channel exists, the water flow in the fracture channel is instantaneously cut off, and the water flow velocity change meets the formation condition of the water hammer pressure, determining that the fracture channel may have the water hammer water inrush effect; then key parameters are calculated through a fissure water hammer theoretical formula delta p = rhoc (v-v2) and a water wedge extension depth theoretical calculation formula x = B / K (2.32 + lnps), coal seam mining floor water inrush types are divided in combination with micro-seismic, water inrush points and other characteristics, and correspondingly, micro-seismic monitoring and local grouting, geophysical exploration and drilling and fault zone grouting and ground multi-level collaborative grouting prevention and control methods can be adopted. According to the method, a deep coal seam mining floor water inrush judgment and prevention and control system is enriched, and the method has important economic and social values for guaranteeing safe and efficient mining of a deep coal mine and meeting the development requirements of the coal industry.

Description

Technical Field

[0001] This invention relates to a method for determining the water hammer and water inrush effect model of deep bottom plates. Background Technology

[0002] There is a close connection between rock strata fracturing and floor water inrush. Direct roof collapse and movement of overlying strata after coal seam mining inevitably alter the development of rock fissures. In particular, the continuous changes in the floor failure zone provide a channel for the upwelling of confined water. Essentially, this is a mechanical phenomenon involving the coupling of stress, water flow (water pressure), and rock mass, affecting and restricting the effectiveness of deep coal mining safety and water hazard control. In the early days, my country's main coal mining areas had shallow coal seams and simple geological structures, allowing many mines to predict floor water inrush using traditional methods such as the "water inrush coefficient method" and the "lower three-zone theory." However, with increasing mining depth (generally exceeding 1000m), the geological structure becomes more complex. If a thick aquitard and a highly confined limestone aquifer exist in the floor (water pressure reaching 15MPa), the accuracy of traditional water inrush prediction methods is significantly hampered. It should be noted that under conditions of thick aquitards and high-pressure water, water inrush from the floor is not only the result of hydrostatic pressure causing damage to the aquitard, but also a process of "instantaneous closure-opening" of fractures triggered by mining stress, followed by the formation of a water hammer effect that drives the progressive uplift of fractures. Currently, the dynamic effects of water hammer on the floor and the laws governing the progressive uplift of fractures are not clearly explained, and a unified connection has not been established between the evolution of fractures caused by mining stress and the influence of water hammer on water inrush. Therefore, there are still many shortcomings and deficiencies in revealing the mechanical essence of deep floor water inrush.

[0003] To reveal the coupled outburst mechanism under the influence of water hammer effect in the mining floor, and to provide a scientific basis for early warning of water inrush risk in deep floor, formulation of targeted prevention and control technologies, and safe mining design under high-confined aquifers, this invention proposes a method for determining the water hammer effect model in deep floor, providing a reference for the theoretical understanding system and prevention and control technology evaluation of deep floor water inrush mechanism. Summary of the Invention

[0004] To address the technical problems of unclear water inrush mechanism, low judgment accuracy, and poor targeted water inrush prevention and control under the influence of water hammer effect in deep slabs, this invention aims to provide a method for judging the water hammer effect model of deep slabs under the influence of water hammer effect, which can theoretically calculate water hammer pressure and crack propagation length.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for determining the water hammer and water inrush effect model of deep bottom plate, comprising the following steps:

[0006] S1: Based on the geological conditions of the coal seam floor, determine whether there is a confined aquifer below the coal seam floor; if so, the degree of fracture development and the distribution of potential water-conducting channels (such as faults, collapse columns, etc.) can be determined through comprehensive detection methods such as physical and chemical methods.

[0007] S2: Further, if a potential water-conducting channel exists, considering the coupling effect of mining stress and water pressure, determine whether there are necessary conditions for the formation of water hammer effect in the channel of the fractured rock mass in the floor; when the water flow in the channel of the fractured rock mass in the floor is instantaneously cut off (such as sudden closure / opening of the fracture, fault slippage and blockage, etc.), and the change in water flow velocity meets the conditions for the formation of water hammer pressure, it is considered that there is a water hammer inrush effect in the channel of the fractured rock mass of the confined water.

[0008] S3: Based on the water flow velocity v, fluid density ρ, pressure wave propagation velocity c, and water flow reduction velocity v2 in the fractured rock mass, a theoretical formula for the water hammer effect in the fractured rock mass can be established to obtain the water hammer pressure Δp; combined with the fracture width B, rock mass fracture roughness coefficient K, and stable water hammer pressure ps, the theoretical propagation depth x of the water wedge fracture under the influence of water hammer can be obtained through the water wedge propagation length formula;

[0009] S4: Further, based on the actual geological conditions of the mine working face, the distribution characteristics of microseismic events, the location of water inrush points and water quality composition, water inrushes at specific working faces can be classified into three major types: water hammer-water wedge-guided water inrushes in fractured rock masses, stress erosion-fracture water inrushes in concealed faults, and water inrushes through large structural faults.

[0010] S5: For different types of water inrush, corresponding prevention and control methods shall be adopted: For water hammer-water wedge-guided water inrush in fractured rock mass, the main method can be downhole microseismic monitoring + local grouting reinforcement; for stress erosion-fracture water inrush in concealed faults, the method of pre-mining geophysical drilling + fault zone grouting can be considered; for water inrush through large structural faults, the method of multi-level coordinated grouting on the surface + dynamic drainage of confined water can be considered.

[0011] The above-mentioned method for determining the deep floor water hammer and water inrush effect model is characterized in that: the geological conditions of the deep floor must meet the following requirements: the coal seam burial depth should be ≥300m, the aquifer water pressure should be ≥8MPa, and the effective water-resistant layer thickness of the floor should be within the theoretically calculated safe thickness range.

[0012] The above-mentioned method for determining the deep bottom plate water hammer and sudden water inrush effect model is characterized in that: the theoretical calculation formula for the water hammer pressure Δp is Δp=ρc(v-v2); when the water flow is completely cut off, v2=0, and the formula simplifies to Δp=pcv; wherein, the calculation formula for the pressure wave propagation velocity c is... d is the diameter of the seepage channel in the fractured rock mass, δ is the effective thickness of the rock mass, and E w E is the fluid elastic modulus. r C is the elastic modulus of the rock mass. w The propagation speed of water hammer pressure waves in water (value taken as 1440 m / s);

[0013] The above-mentioned method for determining the deep bottom plate water hammer and water inrush effect model is characterized in that: the calculation formula for the water wedge crack propagation depth x is as follows: In the formula, B is the width of the rock mass fracture (unit: m), K is the surface roughness coefficient of the rock mass fracture (value: 0.1 to 0.3), ps is the steady water hammer pressure (unit: MPa), and the fracture stops expanding when ps drops to 0.098 MPa;

[0014] The above-mentioned method for determining the deep bottom plate water hammer and inrush effect model is characterized in that: the changes in the type and amount of inrush may have the following characteristics: (1) Water hammer-water wedge-guided water inrush in fractured rock mass: Water inrush points are scattered in the lower part of the working face goaf, and microseismic events have multiple peak values ​​and are earlier than the peak value of water inrush. (2) Hidden fault stress erosion-fracture water inrush: the water inrush point is concentrated in a certain place, and the water inrush volume shows a multi-peak characteristic of "rise-fall-rise again"; (3) Water inrush caused by large structural faults: Water inrush is in the form of explosive piping, with fast water inrush speed and strong impact force.

[0015] Compared with previous methods for determining and preventing water inrush in deep foundations, this invention has the following advantages:

[0016] 1. The deep bottom plate water hammer inrush effect model proposed in this invention takes the water hammer effect as the core inrush mechanism and reveals the essence of water inrush caused by repeated impact of water driven by water hammer and water wedge promoting fracture uplift, which can better describe the actual evolution law of water inrush disaster in deep mines.

[0017] 2. For deep mining conditions with well-developed rock fractures and significant water hammer effects, this model reflects the relationship between water flow velocity and water hammer pressure based on the theoretical formula Δp=ρc(v-v2). It clarifies the depth of water wedge crack propagation through theory and reveals the progressive-lifting process driven by water hammer pressure and water wedge action, making it more accurate in evaluating the risk level, disaster scale and evolution trend of water hammer-water wedge-lifted water inrush.

[0018] 3. This model can serve as a critical criterion for predicting different types of water inrush (such as hidden fault stress erosion-fracture water inrush, large structural fault conduction water inrush, etc.), and provide guidance for the selection of water inrush prevention and control measures and engineering implementation. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the determination process of the present invention. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, a method for determining the water hammer and water inrush effect model in deep bottom plates includes the following steps:

[0022] S1: Based on the geological conditions of the coal seam floor, determine whether there is a confined aquifer below the coal seam floor; if so, the degree of fracture development and the distribution of potential water-conducting channels (such as faults, collapse columns, etc.) can be determined through comprehensive detection methods such as theory, physics, and chemistry.

[0023] S2: Further, if a potential water-conducting channel exists, considering the coupling effect of mining stress and water pressure, determine whether there are necessary conditions for the formation of water hammer effect in the channel of the fractured rock mass in the floor; when the water flow in the channel of the fractured rock mass in the floor is instantaneously cut off (such as sudden closure / opening of the fracture, fault slippage and blockage, etc.), and the change in water flow velocity meets the conditions for the formation of water hammer pressure, it is considered that there is a water hammer inrush effect in the channel of the fractured rock mass of the confined water.

[0024] S3: Based on the water flow velocity v, fluid density ρ, pressure wave propagation velocity c, and water flow reduction velocity v2 in the fractured rock mass, a theoretical formula for the water hammer effect in the fractured rock mass can be established to obtain the water hammer pressure Δp; combined with the fracture width B, rock mass fracture roughness coefficient K, and stable water hammer pressure ps, the theoretical propagation depth x of the water wedge fracture under the influence of water hammer can be obtained through the water wedge propagation length formula;

[0025] S4: Further, based on the actual geological conditions of the mine working face, the distribution characteristics of microseismic events, the location of water inrush points and water quality composition, water inrushes at specific working faces can be classified into three major types: water hammer-water wedge-guided water inrushes in fractured rock masses, stress erosion-fracture water inrushes in concealed faults, and water inrushes through large structural faults.

[0026] S5: For different types of water inrush, corresponding prevention and control methods shall be adopted: For water hammer-water wedge-guided water inrush in fractured rock mass, the main method can be downhole microseismic monitoring + local grouting reinforcement; for stress erosion-fracture water inrush in concealed faults, the method of pre-mining geophysical drilling + fault zone grouting can be considered; for water inrush through large structural faults, the method of multi-level coordinated grouting on the surface + dynamic drainage of confined water can be considered.

[0027] The method for determining the deep floor water hammer and water inrush effect model is characterized in that: the geological conditions of the deep floor must meet the following requirements: the coal seam burial depth should be ≥300m, the aquifer water pressure should be ≥8MPa, and the effective water-resistant layer thickness of the floor should be within the theoretically calculated safe thickness range.

[0028] The method for determining the deep bottom plate water hammer and sudden water inrush effect model is characterized in that: the theoretical calculation formula for the water hammer pressure Δp is Δp=ρc(v-v2); when the water flow is completely cut off, v2=0, and the formula simplifies to Δp=pcv; wherein, the calculation formula for the pressure wave propagation velocity c is... d is the diameter of the seepage channel in the fractured rock mass, δ is the effective thickness of the rock mass, and E w E is the fluid elastic modulus. r C is the elastic modulus of the rock mass. wThe propagation speed of water hammer pressure waves in water (value taken as 1440 m / s);

[0029] The method for determining the deep bottom plate water hammer and water inrush effect model is characterized in that: the formula for calculating the water wedge crack propagation depth x is as follows: In the formula, B is the width of the rock mass fracture (m), K is the surface roughness coefficient of the rock mass fracture (value is 0.1 to 0.3), ps is the steady water hammer pressure (MPa), and the fracture stops expanding when ps drops to 0.098MPa;

[0030] In the aforementioned method for determining the conjugate inner and outer "hyperbolic" model of rock strata movement, the surface subsidence range D is calculated according to the following formula. The aforementioned surface subsidence movement value is calculated according to the following formula.

[0031] The method for determining the deep bottom plate water hammer and inrush effect model is characterized in that the changes in the type and amount of inrush may have the following features: (1) Water hammer-water wedge-guided water inrush in fractured rock mass: Water inrush points are scattered in the lower part of the working face goaf, and microseismic events have multiple peak values ​​and are earlier than the peak value of water inrush. (2) Hidden fault stress erosion-fracture water inrush: the water inrush point is concentrated in a certain place, and the water inrush volume shows a multi-peak characteristic of "rise-fall-rise again"; (3) Water inrush caused by large structural faults: Water inrush is in the form of explosive piping, with fast water inrush speed and strong impact force.

Claims

1. A method for determining the water hammer and water inrush effect model in deep bottom plates, characterized in that, Includes the following steps: S1: Based on the geological conditions of the coal seam floor, determine whether there is a confined aquifer below the coal seam floor; if so, the degree of fracture development and the distribution of potential water-conducting channels (such as faults, collapse columns, etc.) can be determined through comprehensive detection methods such as physical and chemical methods. S2: Further, if a potential water-conducting channel exists, considering the coupling effect of mining stress and water pressure, determine whether there are necessary conditions for the formation of water hammer effect in the channel of the fractured rock mass in the floor; when the water flow in the channel of the fractured rock mass in the floor is instantaneously cut off (such as sudden closure / opening of the fracture, fault slippage and blockage, etc.), and the change in water flow velocity meets the conditions for the formation of water hammer pressure, it is considered that there is a water hammer inrush effect in the channel of the fractured rock mass of the confined water. S3: Based on the water flow velocity v, fluid density ρ, pressure wave propagation velocity c, and water flow reduction velocity v2 in fractured rock mass, a theoretical formula for the water hammer effect in fractured rock mass can be established to calculate the water hammer pressure Δp; combined with the fracture width B, rock mass fracture roughness coefficient K, and stable water hammer pressure p s The theoretical propagation depth x of water wedge crack texture under the influence of water hammer is obtained by using the water wedge propagation length formula; S4: Further, based on the actual geological conditions of the mine working face, the distribution characteristics of microseismic events, the location of water inrush points and water quality composition, water inrushes at specific working faces can be classified into three major types: water hammer-water wedge-guided water inrushes in fractured rock masses, stress erosion-fracture water inrushes in concealed faults, and water inrushes through large structural faults. S5: For different types of water inrush, corresponding prevention and control methods are adopted: For water hammer-water wedge-guided water inrush in fractured rock masses, the main method can be downhole microseismic monitoring + local grouting reinforcement; for stress erosion-fracture water inrush in concealed faults, the method can be pre-mining geophysical drilling + fault zone grouting; for water inrush through large structural faults, the method can be multi-level coordinated grouting on the surface + dynamic drainage of confined water.

2. The method for determining the deep bottom plate water hammer and water inrush effect model according to claim 1, characterized in that: The geological conditions of the deep bottom plate must meet the following requirements: the coal seam burial depth should be ≥300m, the aquifer water pressure should be ≥8MPa, and the effective water-resistant layer thickness of the bottom plate should be within the theoretically calculated safe thickness range.

3. The method for determining the deep bottom plate water hammer and water inrush effect model according to claim 1, characterized in that: The theoretical formula for calculating the water hammer pressure Δp is Δp=ρc(v-v2); when the water flow is completely cut off, v2=0, and the formula simplifies to Δp=pcv; In the formula, the propagation velocity c of the pressure wave is calculated as follows: d is the diameter of the seepage channel in the fractured rock mass, δ is the effective thickness of the rock mass, and E w E is the fluid elastic modulus. r C is the elastic modulus of the rock mass. w The propagation speed of the water hammer pressure wave in water is 1440 m / s.

4. The method for determining the deep bottom plate water hammer and water inrush effect model according to claim 1, characterized in that: The theoretical formula for calculating the water wedge crack propagation depth x is as follows: In the formula, B is the width of the rock mass fracture (unit: m), K is the surface roughness coefficient of the rock mass fracture (value range: 0.1 to 0.3), and p s To stabilize the water hammer pressure (unit: MPa), and when p s When the pressure drops to 0.098 MPa, the crack stops propagating.

5. The method for determining the deep bottom plate water hammer and water inrush effect model according to claim 1, characterized in that, The changes in water inrush volume of the aforementioned water inrush type may have the following characteristics: (1) Water hammer-water wedge-guided water inrush in fractured rock mass: Water inrush points are scattered in the lower part of the working face goaf, and microseismic events have multiple peak values ​​and are earlier than the peak value of water inrush. (2) Hidden fault stress erosion-fracture water inrush: the water inrush point is concentrated in a certain place, and the water inrush volume shows a multi-peak characteristic of "rise-fall-rise again"; (3) Water inrush caused by large structural faults: Water inrush is in the form of explosive piping, with fast water inrush speed and strong impact force.

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