In-situ water-preserved mining method for high-salt high-pressure-bearing bottom plate aquifer

Abstract

The invention discloses an in-situ water-preserved mining method for a high-salt high-pressure-bearing bottom plate aquifer, and relates to the technical field of coal mining. The method comprises the steps that the damage depth of a bottom plate, the height of a confined water guide rising zone and the thickness of a minimum safe water-resisting layer are calculated according to geological and mining technical parameters; adjusting according to a preset water-preserved mining condition to enable the working face to meet the water-preserved mining condition; calculating to obtain the grouting thickness of the corrosion-resistant material; corrosion-resistant acrylate grouting liquid is injected from the upper edge of the confined water guide rising zone according to the grouting thickness of the corrosion-resistant material; monitoring the water pressure of a bottom plate aquifer and the height of a confined water guiding and rising zone, and when a preset risk condition is exceeded, determining that the working face has a water-preserved mining failure risk, and performing risk early warning; and when risk early warning occurs, secondary grouting is carried out according to the grouting thickness of the corrosion-resistant material. A chemical corrosion resistant acrylate grouting liquid is injected into the upper edge of a confined water guiding and rising zone, and gradual corrosion damage and bottom plate water inrush of a rock stratum under the action of high-salinity and high-confined water are prevented.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to an in-situ water-retaining mining method for aquifers with high salinity and high pressure. Background Technology

[0002] In my country, approximately 60% of coal seams have highly confined aquifers such as Ordovician limestone and Taiyuan limestone in their floor strata, resulting in substantial coal reserves. During coal mining, tunnel excavation above these high-confined aquifers faces the threat of floor water inrush. These aquifers experience high water pressure; for example, some Ordovician floor aquifers can reach pressures exceeding 6.5 MPa, with salinity reaching up to 40 g / L. The hydrochemical environment is complex, rich in H+, Ca2+, Mg2+, K+, OH-, SO42-, and HCO3- ions. Under the influence of high water pressure, high salinity, and complex hydrochemical environment, the floor strata undergo physicochemical processes such as dissolution, corrosion, and ion exchange, leading to deterioration of porosity, pore structure, mineral composition, and mechanical strength. With the cumulative effects of mining and long-term physicochemical processes, the floor gradually corrodes and loses its water-impermeability, resulting in the loss of floor water resources. Meanwhile, the lost high-salinity water enters the mined-out area, forming high-salinity mine water, which increases the difficulty and cost of mine water treatment.

[0003] Currently, research on water-retaining mining of aquifers with high confined foundations mainly focuses on feasibility evaluation and monitoring and early warning. Existing technologies include: 1) a method for determining water-retaining mining based on the dynamic water storage and release characteristics of confined aquifers and the overall water-blocking performance of the effective barrier strata in the mining floor; 2) analysis and early warning based on early warning indicators to achieve early warning for in-situ water-retaining coal mining; and 3) regional grouting modification to improve the strength and reduce permeability of the floor strata, thereby achieving the goal of water-retaining mining of aquifers with high confined foundations.

[0004] The aforementioned existing technologies have given relatively little consideration to the corrosive damage of chemical ions in the aquifer to the underlying rock strata and grouting bodies. Particularly for high-salt, high-pressure aquifers with high salt content and complex hydrochemical ion composition, the combined effects of long-term physicochemical action between water and rock, and the wedge effect of high-pressure water, can lead to cumulative damage to the underlying rock strata and grouting bodies, resulting in corrosion and loss of water-tightness. This presents a new challenge for in-situ water-retaining mining of high-salt, high-pressure aquifers. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ water-retaining mining method for aquifers with high salinity and high pressure, which aims to solve or improve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A method for in-situ water-retaining extraction of aquifers with high salinity and high pressure at the bottom, comprising: Obtain geological and mining technology parameters of the mine; The depth of floor failure during working face mining is calculated based on geological and mining technical parameters. Height of the pressurized water guide belt and minimum safe waterproof layer thickness ; Based on the preset water-conserving extraction conditions Adjustments were made to ensure the working face met the conditions for water-retaining mining. Based on the salinity of the pressurized water in the base plate and the minimum safe waterproof layer thickness The thickness of the corrosion-resistant material grout was calculated. ; Based on the grouting thickness of the corrosion-resistant material Inject corrosion-resistant acrylate grout from the upper edge of the pressurized water guide strip; The water pressure of the bottom aquifer and the height of the confined water riser are monitored. When the preset risk conditions are exceeded, it is determined that there is a risk of failure in water-retaining mining at the working face, and a risk warning is issued. When a risk warning is issued, the thickness of the grouting material should be considered. Secondary grouting is then performed.

[0007] Furthermore, geological and mining technical parameters include the overall stratigraphic column, density of the floor strata, uniaxial compressive strength of the rock, coal-water spacing, water pressure of the floor aquifer, salinity of the floor confined water, permeability coefficient of the floor strata, mining height, mining speed, and working face length.

[0008] Furthermore, the depth of damage to the base plate The expression is: ; In the formula, denoted as: Depth of floor failure; K as: Empirical coefficient for geological conditions; M as: Mining height; v as: Mining rate; L as: Working face length; It represents the uniaxial compressive strength of the rock.

[0009] Furthermore, the height of the pressurized water guide belt The expression is: ; In the formula, The height of the pressurized water guide belt; The driving coefficient is 0.3-1.2. The water pressure of the aquifer at the bottom slab; The distance between the coal and water is denoted as k; k is the permeability coefficient of the bottom rock strata. It represents the uniaxial compressive strength of the rock.

[0010] Furthermore, the minimum safe waterproof layer thickness The expression is: ; In the formula, Minimum safe waterproof layer thickness; The density of the base strata; L represents the uniaxial compressive strength of the rock; L represents the length of the working face. This refers to the water pressure of the aquifer at the bottom of the slab.

[0011] Furthermore, based on the pre-set water-conserving extraction conditions Adjustments were made to ensure the working face met the conditions for water-retaining mining, including: Water-conserving mining conditions are ,like If necessary, the mining technical parameters of the working face will be adjusted, and the mining process will be changed or the grouting modification method will be used until the water-retaining mining conditions are met.

[0012] Furthermore, the thickness of the grouting for corrosive materials The expression is: ; In the formula, C represents the salinity of the pressurized water in the bottom plate.

[0013] Furthermore, based on the grouting thickness of the corrosion-resistant material... The grouting conditions include injecting corrosion-resistant acrylate grout from the upper edge of the pressurized water guide strip: The grouting area is the intersection of the extended line of the bottom plate boundary angle λ and the upper edge of the pressurized water guide zone; the grouting timing is at least 50m before the working face is mined.

[0014] Furthermore, the risk conditions are: a water pressure drop in the bottom aquifer greater than 10% or a rise in the height of the confined water guide zone during the working face's advance. .

[0015] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention discloses an in-situ water-retaining mining method for aquifers with high salinity and high pressure. The method proposes to inject chemically resistant acrylate grout into the safety aquifer at the upper edge of the pressure water conduction zone, which can prevent the rock strata in the safety aquifer from gradually corroding and being damaged by high salinity and high pressure water and prevent water inrush from the bottom plate.

[0016] A method for determining key parameters such as the thickness, layer, range, and timing of acrylate grouting corrosion-resistant material injection was proposed. Furthermore, a method for real-time online monitoring and early warning of water-retaining mining effect through multi-mode monitoring during the working face mining process was proposed. The early warning threshold and the timing of secondary grouting of corrosion-resistant material were clarified, which can ensure in-situ water-retaining mining of high-salt and high-pressure bottom aquifers throughout the entire working face mining process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 This is a comprehensive stratigraphic columnar section in this embodiment; Figure 3 This is a schematic diagram of grouting and water retention of alkali-resistant materials in this embodiment; Figure 4 This is a schematic diagram of the water pressure change curve of the pressurized water in the bottom plate in this embodiment. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide an in-situ water-retaining mining method for aquifers with high salinity and high pressure, which aims to solve or improve at least one of the above-mentioned technical problems.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the present invention provides an in-situ water-retaining extraction method for aquifers with high salinity and high pressure at the bottom, comprising: Step 1: Obtain the geological features, hydrogeological features, and mining technical parameters of the mine through on-site investigation; The geological features include: the overall columnar stratigraphic structure, the density of the floor strata, the uniaxial compressive strength of the rock, and the coal seam depth; the hydrogeological features include: the coal-water spacing, the water pressure of the floor aquifer, the salinity of the floor confined water, and the permeability coefficient of the floor strata; the mining technical parameters include: mining height, mining rate, and working face length. Step 2: Based on the uniaxial compressive strength of the rock, mining height, mining speed, working face length, and the comprehensive stratigraphic column, calculate the depth of floor failure during working face mining. ,include: Depth of damage to the base plate The expression is: ; In the formula, denoted as: Depth of floor failure; K is an empirical coefficient for geological conditions, ranging from 1.2 to 2.8; M is the mining height; v is the mining rate; L is the working face length. It represents the uniaxial compressive strength of the rock.

[0023] Step 3: Calculate the height of the confined water conduction zone in the working face based on the depth of bottom failure, uniaxial compressive strength of the rock, water pressure of the bottom aquifer, coal-water distance, and permeability coefficient of the bottom strata. ,include: Height of pressurized water guide belt The expression is: ; In the formula, The height of the pressurized water guide belt; The driving coefficient is 0.3-1.2. The water pressure of the aquifer at the bottom slab; The distance between the coal and water is denoted as k; k is the permeability coefficient of the bottom rock strata. It represents the uniaxial compressive strength of the rock.

[0024] Step 4: Based on the uniaxial compressive strength of the rock, the density of the bottom strata, the water pressure of the bottom aquifer, and the length of the working face, calculate the minimum safe thickness of the aquitard layer to achieve water-retaining mining. ,include: Minimum safe waterproof layer thickness The expression is: ; In the formula, Minimum safe waterproof layer thickness; The density of the base strata; L represents the uniaxial compressive strength of the rock; L represents the length of the working face. This refers to the water pressure of the aquifer at the bottom of the slab.

[0025] Step 5: Adjust the coal-water spacing according to the preset water-conserving mining conditions, including: Water-conserving mining conditions are ,like If necessary, the mining technical parameters of the working face will be adjusted, and the mining process and grouting modification will be changed until the water-retaining mining conditions are met.

[0026] The above steps, without considering the corrosive damage to rock strength and permeability caused by the high-salt confined water on the bottom plate, are used to preliminarily determine whether the working face can achieve water-retaining mining conditions.

[0027] Step 6, based on the salinity of the pressurized water in the base plate and the minimum safe waterproof layer thickness. The thickness of the corrosion-resistant material grout was calculated. ,include: Grouting thickness of corrosive materials The expression is: ; In the formula, C represents the salinity of the pressurized water in the bottom plate.

[0028] Step 7: Inject grout from the upper edge of the confined water guide zone through surface grouting or underground roadway grouting. Thick, corrosion-resistant acrylate grout; When injecting corrosion-resistant acrylate grout in the above steps, the grouting range is the intersection of the extended line of the bottom plate boundary angle λ and the upper edge of the pressurized water guide zone; the grouting time is at least 50m before the working face is mined back.

[0029] Step 8: Monitor the water pressure of the bottom aquifer and the height of the confined water guide zone. If the preset risk conditions are exceeded, it is determined that there is a risk of water-conserving mining at the working face, and a risk warning is issued. The risk conditions are: a water pressure drop in the bottom aquifer greater than 10% or a rise in the height of the confined water guide zone during the working face's advance. .

[0030] Step 9: When a risk warning occurs, adjust the grouting thickness based on the corrosion-resistant material. Secondary grouting is carried out, with the thickness of the secondary grouting being greater than or equal to that of the primary grouting, to ensure in-situ water-retaining mining of the high-salt, high-pressure aquifer. Specific Implementation S1: Mine Geological and Mining Technical Conditions Survey: Through geological exploration, obtain the stratigraphic and hydrogeological characteristics of the target mine. This includes the lithology and thickness of the roof and floor strata of the coal seam, such as... Figure 2 As shown in Table 1, the strength, integrity, and water-bearing capacity of the top and bottom strata of the coal seam are as follows. The confined aquifer in the bottom strata with the threat of water inrush is L2 limestone, and the water pressure of the L2 limestone aquifer is 4.85-5.35 MPa. The mineralization degree of the confined water in the bottom strata is 26 g / L. The working face has a mining height of 6 m, a mining rate of 1.2 m / d, and a dip length of 190 m. Table 1

[0032] S2: Calculation of Floor Failure Depth: Based on the uniaxial compressive strength and thickness of the floor strata, the equivalent floor rock strength is 60.36 MPa, the mining height is 6 m, the mining rate is 1.2 m / d, and the working face length is 190 m. K is taken as 1.7, and the floor failure depth of the working face is calculated. =6.38m; S3: Calculation of the height of the confined water riser zone: Based on the above calculations, the failure depth of the bottom plate is 7.09m, the rock strength of the bottom plate is 40.13MPa, the coal-water spacing is 73.1m, the confined water pressure is taken as 5.1MPa, and the permeability coefficient of the bottom plate rock strata is taken as 5cm / s. Taking 1.2, the height of the confined water guide strip on the bottom plate is calculated. =8.46m; S4: Calculation of Safe Water-Retaining Layer Thickness: Based on the geological and mining technical conditions such as the strength of the bottom rock, water pressure, and working face length in the above calculations, and taking the density of the bottom rock as 2.3 g / cm3, the minimum safe water-retaining layer thickness that can achieve water-retaining mining is calculated. =2.21m.

[0033] S5: Preliminary assessment of the feasibility of water-retaining mining: Based on the above calculations of the depth of damage to the mining floor, the height of the confined water riser zone, and the thickness of the safety aquitard, and without considering the corrosive damage to rock strength and permeability caused by the high-salt confined water on the floor, this working face meets the conditions for achieving water-retaining mining. No adjustment of the working face mining parameters or grouting modification is required.

[0034] S6: Determination of grouting thickness for corrosion-resistant materials: Based on the mineralization degree of 26 g / L obtained from the chemical testing of the pressurized water in the base plate, the grouting thickness for corrosion-resistant materials was calculated. =1.27m; S7: Determination of Key Parameters for Corrosion-Resistant Material Grouting: Corrosion-resistant acrylate grouting solution with a thickness of 1.27m is injected upwards from the upper edge of the pressurized water guide zone, either through surface grouting or underground roadway grouting. The grouting range is the intersection of the extended line of the 65° boundary angle of the floor slab and the upper edge of the guide zone. Grouting is carried out 70m into the advanced working face. A schematic diagram of grouting water retention is shown below. Figure 3 As shown.

[0035] S8: Evaluation of Water-Conserving Mining Effect: During the mining process, a multi-dimensional monitoring method was comprehensively adopted, including parallel electrical resistivity tomography, audio-frequency electrical resistivity tomography, channel wave seismic analysis, and transient electromagnetic methods. Real-time online monitoring was conducted on the water pressure of the bottom aquifer, the distribution and location of the lifting zone, etc., and the fluctuation of the bottom confined water pressure change curve was monitored as follows: Figure 4 As shown, the water pressure drop remained within 2%, less than 10%; the height of the guide belt after the working face was pushed forward was maintained at... The results show that the method of the present invention effectively realizes in-situ water-retaining mining of aquifers in high-salt and high-pressure base strata.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0037] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for in-situ water-retaining extraction of aquifers with high salinity and high pressure at the bottom, characterized in that, include: Obtain geological and mining technology parameters of the mine; The depth of floor failure during working face mining is calculated based on geological and mining technical parameters. Height of the pressurized water guide belt and minimum safe waterproof layer thickness ; Based on the preset water-conserving extraction conditions Adjustments were made to ensure the working face met the conditions for water-retaining mining. Based on the salinity of the pressurized water in the base plate and the minimum safe waterproof layer thickness The thickness of the corrosion-resistant material grout was calculated. ; Based on the grouting thickness of the corrosion-resistant material Inject corrosion-resistant acrylate grout from the upper edge of the pressurized water guide strip; The water pressure of the bottom aquifer and the height of the confined water riser are monitored. When the preset risk conditions are exceeded, it is determined that there is a risk of failure in water-retaining mining at the working face, and a risk warning is issued. When a risk warning is issued, the thickness of the grouting material should be considered. Secondary grouting is then performed.

2. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 1, characterized in that, The geological and mining technical parameters include the comprehensive columnar strata, the density of the bottom strata, the uniaxial compressive strength of the rock, the coal-water spacing, the water pressure of the bottom aquifer, the salinity of the confined water in the bottom, the permeability coefficient of the bottom strata, the mining height, the mining speed, and the working face length.

3. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 2, characterized in that, The depth of damage to the base plate The expression is: ； In the formula, denoted as: Depth of floor failure; K as: Empirical coefficient for geological conditions; M as: Mining height; v as: Mining rate; L as: Working face length; It represents the uniaxial compressive strength of the rock.

4. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 2, characterized in that, The height of the pressurized water guide belt The expression is: ； In the formula, The height of the pressurized water guide belt; The driving coefficient is 0.3-1.

2. The water pressure of the aquifer at the bottom slab; The distance between the coal and water is denoted as k; k is the permeability coefficient of the bottom rock strata. It represents the uniaxial compressive strength of the rock.

5. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure at the bottom plate according to claim 2, characterized in that, Minimum safety waterproof layer thickness The expression is: ； In the formula, Minimum safe waterproof layer thickness; The density of the base strata; L represents the uniaxial compressive strength of the rock; L represents the length of the working face. This refers to the water pressure of the aquifer at the bottom of the slab.

6. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 2, characterized in that, The water-conserving mining conditions are set according to the preset conditions. Adjustments were made to ensure the working face met the conditions for water-retaining mining, including: Water-conserving mining conditions are ,like If necessary, the mining technical parameters of the working face will be adjusted, and the mining process will be changed or the grouting modification method will be used until the water-retaining mining conditions are met.

7. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure at the bottom plate according to claim 2, characterized in that, The thickness of the corrosive material grouting The expression is: ； In the formula, C represents the salinity of the pressurized water in the bottom plate.

8. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 1, characterized in that, The thickness of the grouting material according to the corrosion-resistant material The grouting conditions include injecting corrosion-resistant acrylate grout from the upper edge of the pressurized water guide strip: The grouting area is the intersection of the extended line of the bottom plate boundary angle λ and the upper edge of the pressurized water guide zone; the grouting timing is at least 50m before the working face is mined.

9. The method for in-situ water-retaining mining of aquifers with high salinity and high pressure as described in claim 1, characterized in that, The aforementioned risk conditions are: a water pressure drop in the bottom aquifer exceeding 10% or a rise in the height of the pressurized water guide zone during the working face's advance. .

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