A method for determining a mining mode and parameters for in-situ protection of a roof aquifer
By establishing a water-retaining mining method based on the ratio of hypothetical mining height to coal seam thickness and a calculation model for the compaction coefficient based on the compaction effect, the problems of insufficient parameter quantification and failure to consider the compaction effect of the filling body in the existing technology are solved, thus realizing in-situ protection and efficient mining of the roof aquifer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH
- Filing Date
- 2026-06-02
- Publication Date
- 2026-07-31
AI Technical Summary
Existing water-conserving mining technologies suffer from problems such as insufficient quantification of parameters, poor coordination between mining and filling operations, limited applicability, and insufficient consideration of the compaction effect of the filling body, resulting in unstable in-situ protection of the roof aquifer.
By establishing a judgment logic for water-retaining mining methods based on the ratio of hypothetical mining height to coal seam thickness, and combining it with a calculation model for the bridging coefficient that takes into account the compaction effect, the system determines the key technical parameters corresponding to different water-retaining mining methods, including technical paths such as high-level filling of the collapse zone and grouting modification, to achieve in-situ protection of the aquifer.
It has enabled the systematic and quantitative determination of water-conserving mining parameters, improved the reliability and safety of mining, expanded the scope of application, and improved the mining efficiency of large mines through parallel operations.
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Figure CN122328117B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal mining technology, specifically to a mining mode and parameter determination method for in-situ protection of roof aquifers. Background Technology
[0002] Currently, a series of water-conserving mining methods have been proposed. For example, the patent application with publication number CN114086955A proposes to determine the scope of influence of mining-induced fractures before freezing and grouting to repair the water-retaining layer.
[0003] Another type of method, such as patent applications with publication numbers CN117248907A and CN117662153A, reduces the disturbance to the aquifer during mining by coupling coal seam filling columns with grouting modification of loose layers or aquitards. This method adds modification measures to traditional filling column mining. However, filling column mining requires filling aggregate before the next mining cycle and waiting for the filling column to reach a certain strength. Furthermore, the filling column width is relatively large, the filling efficiency is low, and the mining-filling operation is out of sync, affecting mining efficiency. More importantly, this type of method does not provide a sufficient quantitative description of the aquitard modification range and filling parameters, nor does it clarify whether water-conducting fractures will still develop to the modified layer after using filling columns, leading to problems such as aquitard modification failure and unstable water retention.
[0004] Another type of method uses delamination grouting to reduce settlement as its core, indirectly achieving water retention. For example, the publication number is... The patent application, applicable to mines where a key stratum exists in the overburden and the aquifer is located above the key stratum, suffers from problems such as limited grouting space, difficulty in determining the grouting stratum, and limited applicability. Another example is the publication number... The patent proposes a method for filling high-level gangue in the caving zone of a longwall working face, which solves the problem of temporal and spatial interference between filling and mining operations in the caving zone of a longwall working face. However, this method mainly aims at parallel mining and filling, without considering key factors such as the adaptability of water-retaining mining, the compaction characteristics of the filling body, and the filling rate.
[0005] In summary, existing water-conserving mining technologies still suffer from problems such as insufficient parameter quantification, poor coordination between mining and filling operations, limited applicability, and insufficient consideration of the compaction effect of the filling body. There is an urgent need to establish a complete technical system that integrates geological condition assessment, selection of water-conserving mining modes, and calculation of key parameters, so as to achieve in-situ protection of the roof aquifer without damaging it, while also taking into account high-yield and high-efficiency mining in large mines. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for determining the technical parameters of in-situ water-retaining mining of roof aquifers. By establishing a judgment logic for water-retaining mining methods based on the ratio of hypothetical mining height to coal seam thickness, and combining a calculation model of the bridging coefficient considering the compaction effect, the key technical parameters corresponding to different water-retaining mining methods are systematically determined, thereby achieving efficient water-retaining mining under the premise of in-situ protection of aquifers.
[0007] To achieve the above objectives, this invention provides a method for determining the mining mode and parameters for in-situ protection of the roof aquifer, comprising the following steps: Step To obtain the geological and hydrogeological parameters of the target working face and the mining technical parameters.
[0008] step The weighted equivalent strength of the overlying strata is calculated based on the geological and hydrogeological parameters. To determine the intensity type and to identify different hypothetical mining heights. Slit extraction ratio under certain conditions .
[0009] Step S3: Calculate the development height of the water-conducting fracture zone. Determine the equivalent filling rate coefficient of high-level backfilling in the collapse zone. Minimum thickness required for rock strata modification Based on this, and considering the development height of the water-conducting fracture zone and the distance between the coal seam and the aquifer, and combined with the constraint that the distance between the coal seam and the aquifer is greater than or equal to the sum of the products of the development height of the water-conducting fracture zone, the surplus coefficient, and the hypothetical mining height, the maximum value of the ratio of the hypothetical mining height to the coal seam thickness that satisfies the water-conserving mining requirements is calculated. Based on the maximum ratio, the equivalent filling rate coefficient, and the minimum thickness required for strata modification, the appropriate water-conserving mining mode is determined. These water-conserving mining modes include: high-level backfilling water-conserving mining mode in the caving zone; high-level backfilling and grouting modification combined water-conserving mining mode in the caving zone; and height-limited mining and high-level backfilling and grouting modification combined water-conserving mining mode in the caving zone.
[0010] Step S4: Determine the water-retaining mining technical parameters based on the judgment result of step S3: When it is determined that the high-level backfilling water-retaining coal mining mode in the caving zone is adopted, the maximum value of the ratio and the crushing expansion coefficient considering the compaction effect are used. Determine the minimum filling height When it is determined that a combined water-conserving mining mode of high-level backfilling and grouting modification in the collapse zone is adopted, the backfilling height shall be determined. Modified thickness The modification range is defined, with the filling height determined based on the principle of complete filling, and the modification thickness based on the development height of the water-conducting fracture zone after filling. Confirmed; When it is determined that a water-conserving mining mode combining height-restricted mining, high-level backfilling in the caving zone, and grouting modification is adopted, the maximum height-restricted mining height is calculated based on the aforementioned water-conserving mining requirements. and determine the filling height. Modified thickness and the scope of modification.
[0011] Further, steps The geological and hydrogeological parameters mentioned include coal seam thickness. Coal seam burial depth Aquifer water content, distance between coal seam and aquifer Uniaxial compressive strength of each rock stratum between the coal seam and the aquifer and thickness Working face length , advance distance Further, steps The formula for calculating the weighted equivalent strength of the overburden, as described above, is: ;in, The weighted equivalent strength of the overburden is expressed in units of... ; The uniaxial compressive strength of each rock stratum is given in units of 1. ; The thickness of each rock layer is given in units of 1. ; The distance between the coal seam and the aquifer, in units of 1. ; This represents the total number of rock strata.
[0012] like The strength type is weak rock layer; if The strength type is medium-hard rock strata; if The strength type is hard rock strata.
[0013] Further, steps The fracture-to-extraction ratio under different hypothetical mining heights described in the article The following is determined: If the strength type is weak rock layer: when hour, ;when hour, ;when hour, ;when hour, .
[0014] If the strength type is medium-hard rock layer: when hour, ;when hour, ;when hour, ;when hour, .
[0015] If the strength type is hard rock layer: when hour, ;when hour, ;when hour, ;when hour, .
[0016] Equivalent fullness coefficient Values: For weak rock layers, take Medium-hard rock strata Hard rock strata Minimum thickness required for rock strata modification Set as .
[0017] Furthermore, the water-conducting fracture zone is highly developed. Compared with the cracking ratio and hypothetical mining height The following conditions must be met: The constraints for water-conserving extraction requirements are as follows: ;in, This is the distance between the coal seam and the aquifer, in meters (m). When the aquifer has a strong water-bearing capacity, the abundance coefficient is used. When the aquifer has a moderate water-bearing capacity, When the aquifer's water-bearing capacity is weak, Further, steps The determination logic for the water-conserving extraction mode described in the text is as follows: when At that time, it was determined that the high-level backfilling and water-conserving coal mining mode in the collapse zone should be adopted.
[0018] when ,and At that time, it was determined that a high-level filling and grouting modification combined water-retaining coal mining mode should be adopted in the collapse zone.
[0019] when ,and At that time, it was determined that a water-conserving coal mining mode combining height-restricted mining, high-level backfilling of the caving area, and grouting modification should be adopted.
[0020] Further, steps When it is determined that a high-level backfilling water-conserving coal mining mode is adopted in the collapse zone, the minimum backfilling height is... The calculation formula is: ;in, Minimum filling height, in units of ; Coal seam thickness, in units of ; This represents a hypothetical mining height, in units of... ; The equivalent fullness coefficient; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of .
[0021] Furthermore, the coefficient of swell considering compaction effect The specific solution expression is as follows: ;in, The elastic modulus of the direct top, in units of , To directly top the initial expansion coefficient, the initial volume is... The direct top rock sample was crushed, and the volume of the crushed material was measured using the standard sand volume replacement method. ,but ; The average unit weight of the overlying strata is given in units. ; The depth of the coal seam is expressed in units of 1. .
[0022] Furthermore, in step S4, when it is determined that a high-level backfilling and grouting modification synergistic water-retaining coal mining mode is adopted in the collapse zone, the formula for calculating the backfilling height is: (5); among which, The filling height is expressed in units of 1. ; Coal seam thickness, in units of ; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of .
[0023] The modified thickness Distance between coal seam and aquifer Subtract the height of the water-conducting fracture zone after filling The remaining thickness after that is: After filling, the water-conducting fracture zone developed to a high degree. According to the strike of the working face and the angle of rock strata movement and the angle of rock strata movement in the direction of dip Calculate the modification range: the outer extension on both sides of the direction is The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of direction, the extension of tendency and The maximum value is taken as the extensional modification range of the working surface; the modified area is determined by the length of the working surface. and propulsion distance It was determined that horizontal multi-branch directional drilling would be used for grouting modification.
[0024] Furthermore, in step S4, when it is determined that a water-conserving coal mining mode combining height-limited mining, high-level backfilling in the caving zone, and grouting modification is adopted, the maximum height-limited mining height is... The calculation formula is: (6); among which, The maximum maximum mining height is expressed in units of... ; The distance between the coal seam and the aquifer, in units of 1. ; Minimum thickness required for rock strata modification, in units of ; The ratio of cracked to extracted material; This is the equivalent fullness coefficient.
[0025] The formula for calculating the filling height is: (7); among which, The filling height is expressed in units of 1. ; The maximum maximum mining height is expressed in units of... ; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of .
[0026] The modified thickness The minimum thickness required for rock strata modification, i.e.: .
[0027] The height of the water-conducting fracture zone after filling is: .
[0028] Based on the working face strike and rock strata movement angle and the angle of rock strata movement in the direction of dip Calculate the modification range, with the outer extension on both sides of the direction being... The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of the direction of orientation and the extension of the direction of dip, and... The maximum value is taken as the range of extensional modification of the working surface.
[0029] Further, steps The middle and high-level filling layers were determined to be the basic top and bottom layers. Filling was carried out through the main borehole, inclined borehole, and horizontal directional borehole constructed on the ground. The mass ratio of the filling material was gangue. ,cement ,water The horizontal borehole spacing is The grouting modification can be adjusted according to the grout spread; the grouting modification operation is completed before the working face is mined, and horizontal multi-branch directional drilling is used for grouting modification. The minimum injectable particle size of the grouting modification material is [missing information]. The horizontal directional drilling spacing is It can be further adjusted according to the slurry diffusion range.
[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention obtains the geological and hydrogeological parameters and mining technical parameters of the target working face, calculates the weighted equivalent strength of the overburden to determine the strength type and the crack-mining ratio, calculates the development height of the water-conducting fracture zone, sets the equivalent filling rate coefficient of the high-level filling in the collapse zone and the minimum thickness required for strata modification, calculates the maximum value of the ratio of the hypothetical mining height to the coal seam thickness that meets the requirements of water-conserving mining, and determines the water-conserving mining mode to be adopted based on the maximum value of the ratio, the equivalent filling rate coefficient and the minimum thickness required for strata modification, and then determines the corresponding water-conserving mining parameters based on the determination results. Thus, a complete technical chain is established from the acquisition of geological parameters, determination of strength type, determination of crack-mining ratio, back calculation of ratio, determination of mode to determination of parameters, realizing the systematic and quantitative determination of water-conserving mining parameters.
[0031] (2) This invention introduces a coefficient of swell that takes into account the compaction effect. The fragmentation coefficient is calculated based on the elastic modulus of the immediate roof and the initial fragmentation coefficient, which fully considers the compaction characteristics of the filling body under the action of overburden pressure, making the calculation of the filling height more accurate and reasonable, and improving the reliability and safety of water-conserving mining.
[0032] (3) In view of different geological conditions and water-retaining mining requirements, this invention systematically establishes three technical paths: high-level filling water-retaining mining mode in the collapse area, high-level filling and grouting modification combined water-retaining mining mode in the collapse area, and high-limited mining and high-level filling and grouting modification combined water-retaining mining mode in the collapse area. It also gives quantitative determination methods for key parameters such as filling height, modification thickness, modification range, and maximum limited mining height, thus expanding the applicable scope of water-retaining mining technology.
[0033] (4) This invention determines the high-level filling layer as the basic top and bottom, and combines the main hole, sloping hole and horizontal directional drilling of the ground construction for filling. The grouting modification operation is completed before the working face is mined, realizing the parallel operation of mining, filling and injection. This is conducive to overcoming the problem of the imbalance of mining and filling operations in traditional filling column mining and improving the mining efficiency of large mines. Attached Figure Description
[0034] Figure 1 This is a flowchart of the method of the present invention.
[0035] Figure 2 This is a schematic diagram of the plan view for high-level backfilling and water-retaining mining in the collapse area, as shown in the embodiment.
[0036] Figure 3 This is a schematic cross-sectional view of the high-level backfilling and water-retaining mining direction in the collapse area, as shown in the embodiment.
[0037] Figure 4 This is a schematic diagram of the grouting modification in the embodiment.
[0038] Figure 5 This is a schematic cross-section of the strike of the coal seam where high-level backfilling and grouting modification are combined to retain water in the collapse zone, as shown in the example.
[0039] Figure 6 This is a schematic diagram illustrating the synergistic water-retaining coal mining effect of high-level backfilling and grouting modification in the collapse zone in Example 2.
[0040] Attached reference numerals: 1. Ground grouting station; 2. Vertical directional borehole; 3. Inclined borehole; 4. Horizontal directional borehole; 5. High-level filling body; 6. Collapse zone. Detailed Implementation
[0041] 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0042] Unless otherwise specifically stated, the relative arrangement, expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0043] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist, for example... and / or , can represent existence alone , coexisting and Existing alone These are the three cases. Additionally, the character " / " in this article generally indicates that the objects before and after it have an "or" relationship.
[0044] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0045] In this invention, Indicates the thickness of the coal seam. Indicates the hypothetical mining height. Indicates the maximum maximum mining height. Indicates the distance between the coal seam and the aquifer. Indicates the development height of the water-conducting fracture zone. This indicates the height of the water-conducting fracture zone after filling. Indicates the minimum filling height. This indicates the filling height in the high-level filling and grouting modification synergistic water-retaining coal mining mode in the collapse zone. Indicates the direct top thickness. Indicates the modified thickness. Indicates the minimum thickness required for rock strata modification. Indicates the weighted equivalent strength of the overburden. This represents the equivalent fullness coefficient. Indicates the fracture-to-mining ratio. This indicates the average unit weight of the overlying strata. This represents the coefficient of swell considering compaction effects. This indicates the initial expansion coefficient directly at the top. This indicates the direct elastic modulus. Indicates the radius of influence of the aquifer. Indicates the angle of movement of the rock strata. Indicates the angle of rock strata movement in the direction of dip. Indicates the length of the working face. Indicates the distance traveled.
[0046] like Figure 1 The present invention provides a mining mode and parameter determination method for in-situ protection of aquifers on the roof, comprising the following steps: Step To obtain the geological and hydrogeological parameters and mining technical parameters of the target working face, including coal seam thickness. Coal seam burial depth Aquifer water content, distance between coal seam and aquifer Compressive strength of each rock stratum between coal seam and aquifer and thickness and working face length , advance distance .
[0047] step Based on the compressive strength of each rock layer between the coal seam and the aquifer and thickness Calculate the weighted equivalent strength of overburden To determine the type of overburden strength and to identify different hypothetical mining heights. Slit extraction ratio under certain conditions .
[0048] The formula for calculating the weighted equivalent strength of overburden is: ;in, The overburden weighted equivalent strength is expressed in MPa. This represents the compressive strength of each rock stratum between the coal seam and the aquifer, expressed in MPa. The thickness of each rock layer is given in meters (m). This is the distance between the coal seam and the aquifer, in meters (m). This represents the total number of rock strata.
[0049] when At that time, it was a weak rock layer; when At that time, it was a medium-hard rock layer; when At that time, it was a hard rock layer.
[0050] Slit extraction ratio under different hypothetical mining height conditions When the following conditions are met: For weak rock strata: , ; , ; , ; , .
[0051] When the rock strata are medium to hard: , ; , ; , ; , .
[0052] When the rock strata are hard: , ; , ; , ; , .
[0053] Equivalent fullness coefficient The value is taken as follows: for weak rock layers Medium-hard rock strata Hard rock strata Minimum thickness required for rock strata modification Set as .
[0054] step Calculate the development height of the water-conducting fracture zone Determine the equivalent filling rate coefficient of high-level backfilling in the collapse zone. Minimum thickness required for rock strata modification Based on this, and considering the development height of the water-conducting fracture zone... Distance between coal seam and aquifer By combining the constraint that the distance between the coal seam and the aquifer must be greater than or equal to the sum of the products of the development height of the water-conducting fracture zone, the surplus coefficient, and the hypothetical mining height, the ratio of the hypothetical mining height to the coal seam thickness that satisfies the water-conserving mining requirement can be calculated. The maximum value of the ratio; the water-retaining mining mode to be adopted is determined based on the maximum value of the ratio, the equivalent filling rate coefficient and the minimum thickness required for the rock layer modification.
[0055] High development level of water-conducting fracture zone Compared with the cracking ratio and hypothetical mining height The following conditions must be met: The constraints for water-conserving extraction requirements are as follows: ;in, The abundance coefficient indicates that the aquifer has strong water-bearing capacity. When the aquifer has a moderate water-bearing capacity When the aquifer's water-bearing capacity is weak .
[0056] At different hypothetical mining heights Under the conditions, the comprehensive formulas (1) to (2) and The verification was performed, and the ratio of the hypothetical mining height to the coal seam thickness that meets the requirements for water-retaining mining was obtained by back-calculation. The maximum value is used as the basis for subsequent pattern determination.
[0057] step The logic for determining the water-conserving extraction mode is as follows: when At that time, it was determined that the high-level backfilling and water-conserving coal mining mode in the collapse zone should be adopted.
[0058] when At that time, it was determined that a high-level filling and grouting modification combined water-retaining coal mining mode should be adopted in the collapse zone.
[0059] when At that time, it was determined that a water-conserving coal mining mode combining height-restricted mining, high-level backfilling of the caving area, and grouting modification should be adopted.
[0060] step According to the steps The determination results determine the technical parameters for water-retaining mining: when the high-level backfilling water-retaining coal mining mode in the caving zone is adopted, the maximum value of the ratio and the swell coefficient considering the compaction effect are used. Determine the minimum filling height The calculation formula is as follows: .
[0061] The coefficient of swell considering compaction effect The specific solution expression is as follows: ;in, The elastic modulus of the direct top is expressed in MPa. To directly top the initial expansion coefficient, the initial volume is... The direct top rock sample was crushed, and the volume of the crushed material was measured using the standard sand volume replacement method. ,but: ; The average unit weight of the overlying strata is given in units. ; This represents the coal seam burial depth, expressed in meters (m).
[0062] When it is determined that a high-level backfilling and grouting modification combined water-retaining mining mode is adopted in the collapse zone, the formula for calculating the backfilling height is: .
[0063] Modified thickness Distance between coal seam and aquifer Subtract the height of the water-conducting fracture zone after filling The remaining thickness after that is: .
[0064] The height of the water-conducting fracture zone after filling is: .
[0065] Based on the working face strike and rock strata movement angle and the angle of rock strata movement in the direction of dip Calculate the modification range, with the outer extension on both sides of the direction being... The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of the direction of orientation and the extension of the direction of dip, and... The maximum value is taken as the extensional modification range of the working surface; the modified area is determined by the length of the working surface. and propulsion distance It was determined that horizontal multi-branch directional drilling would be used for grouting modification.
[0066] When a water-conserving coal mining mode combining height-restricted mining, high-level backfilling in the caving zone, and grouting modification is adopted, the formula for calculating the maximum height restriction is as follows: .
[0067] The formula for calculating the filling height is: .
[0068] Modified thickness The minimum thickness required for rock strata modification, i.e.: .
[0069] The height of the water-conducting fracture zone after filling is: .
[0070] The method for determining the modification range is consistent with the method for determining the modification range in the high-level filling and grouting modification combined water-retaining coal mining mode in the collapse zone.
[0071] In all the above models, the high-level filling layer is defined as the basic top and bottom layers. Filling is carried out through main boreholes, inclined boreholes, and horizontal directional boreholes constructed on the ground. The mass ratio of the filling material is gangue. ,cement ,water The horizontal borehole spacing is The grouting modification can be adjusted according to the grout spread; the grouting modification operation is completed before the working face is mined, and horizontal multi-branch directional drilling is used for grouting modification. The minimum injectable particle size of the grouting modification material is [missing information]. The horizontal directional drilling spacing is It can be further adjusted according to the slurry diffusion range.
[0072] Example 1
[0073] like Figure 2 and Figure 3 As shown below, a specific embodiment will be used to describe in detail the method for determining the technical parameters of in-situ water-retaining mining of roof aquifers according to the present invention. This embodiment provides a parameter determination process for achieving in-situ protection of roof aquifers by using only the high-level backfilling water-retaining coal mining method in the collapse zone. This embodiment demonstrates the high-level backfilling water-retaining coal mining mode in the collapse zone.
[0074] step Through data collection, on-site sampling, and laboratory testing, geological and hydrogeological parameters and mining technical parameters of the target working face, including coal seam thickness, were obtained. Coal seam burial depth Aquifer water content, distance between coal seam and aquifer Uniaxial compressive strength of each rock stratum between the coal seam and the aquifer and thickness and working face length and propulsion distance In this embodiment, the aquifer has a moderate water-bearing capacity, and the working face length is [missing information]. The advance distance is Other geological and hydrogeological parameters are shown in Table 1.
[0075] Table 1
[0076]
[0077] step Based on the uniaxial compressive strength of each rock stratum between the coal seam and the aquifer and thickness Calculate the weighted equivalent strength of overburden The distance between the coal seam and the aquifer is: Substituting into equation (1), we get: Therefore, the overlying strata are classified as medium-hard rock. Based on the fracture-to-extraction ratio corresponding to different hypothetical mining heights under medium-hard rock conditions... The results of the fracture-to-mining ratio are shown in Table 2.
[0078] Table 2
[0079]
[0080] step The development of water-conducting fracture zones highly satisfies The constraints for water-conserving extraction are as follows: In this embodiment, the aquifer has a moderate water-bearing capacity, therefore The equivalent fullness coefficient corresponding to medium-hard rock strata Minimum thickness required for rock strata modification .
[0081] Substituting the above parameters, we obtain the water-conserving extraction constraints: In medium-hard rock strata, Within the interval, Then we have: .
[0082] Coal seam thickness in this embodiment Therefore, the maximum value of the hypothetical mining height to coal seam thickness ratio that satisfies the requirements for water-retaining mining is: And because And satisfy Therefore, it was determined that the water-conserving mining mode of high-level backfilling in the collapse zone could be used to achieve water-conserving mining.
[0083] step Based on the compressive strength and thickness of each rock layer between the coal seam and the aquifer, the position of the rock layer above the coal seam is determined. Thick sandy mudstone forms the immediate top. A thick layer of fine-grained sandstone forms the base, and the bottom of this base is designated as the high-level filling layer. Vertical directional boreholes 2, inclined boreholes 3, and horizontal directional boreholes 4 are sequentially constructed from ground grouting station 1. A perforated pipe is installed in horizontal directional borehole 4 as both the high-level grouting feed and transport port. The spacing between the horizontal boreholes is... A total of One hole.
[0084] In this embodiment, the direct top elastic modulus is known. Directly top the initial fragmentation coefficient average bulk density of overlying strata Coal seam burial depth Before substituting the above parameters into equation (4), it is necessary to... and The dimensions of the product are unified. The dimensions are , with Measurement Before adding, you should follow Unit conversion: .
[0085] Therefore, equation (4) can be written as: ; Obtain the coefficient of fragmentation .
[0086] Minimum filling height The calculation formula is equation (3), substituting into... , , , , ,get: In engineering applications, considering construction errors and safety margins, the minimum filling height is designed to be no less than [amount missing]. .
[0087] During the mining of the working face, high-level backfilling is carried out before the basic roof is broken. The backfilling material is prepared by the ground grouting station 1 and then transported to the horizontal directional borehole 4 through the vertical directional borehole 2 and the inclined borehole 3. It is injected into the backfilling space at the bottom of the basic roof and forms a high-level backfilling body 5 above the collapse zone 6. As the working face advances, a periodically recurring high-level backfilling space is formed under the support of the unbroken basic roof, and the high-level backfilling is completed periodically until the mining of the working face is completed.
[0088] Example 2
[0089] This embodiment provides a parameter determination process for achieving in-situ protection of the roof aquifer using a method that combines height-restricted mining, high-level backfilling in the caving zone, and grouting modification for water-retaining coal mining. This embodiment demonstrates a water-retaining coal mining mode that combines height-restricted mining, high-level backfilling in the caving zone, and grouting modification for water-retaining coal mining.
[0090] step Through data collection, on-site sampling, and laboratory testing, geological and hydrogeological parameters and mining technical parameters of the target working face, including coal seam thickness, were obtained. Coal seam burial depth Aquifer water content, distance between coal seam and aquifer Uniaxial compressive strength of each rock stratum between the coal seam and the aquifer and thickness and working face length and propulsion distance In this embodiment, the aquifer has weak water-bearing capacity, and the working face length is... The advance distance is Other geological and hydrogeological parameters are shown in Table 3.
[0091] Table 3
[0092]
[0093] step According to the compressive strength of each rock layer between the coal seam and the aquifer in Table 3 and thickness Calculate the weighted equivalent strength of the overburden according to formula (1). Based on this, the type of overburden strength is determined, and then combined with different hypothetical mining heights. Determine the corresponding fracture-to-mining ratio within the specified range. The results can be summarized in Table 4.
[0094] Table 4
[0095]
[0096] step Based on the development height of the water-conducting fracture zone and water-conserving extraction constraints Verification was performed. In this embodiment, the aquifer's water-bearing capacity is weak, and the water abundance coefficient is... ; combination Based on the determined overburden strength type, take the corresponding... Value, minimum thickness required for rock strata modification .
[0097] Under the condition of not adopting height restriction mining and fully mining thick coal seams, it can be based on Table 4. Calculate the development height of the water-conducting fracture zone. Then calculate the development height of the water-conducting fracture zone after filling. And determine: .
[0098] The modified thickness requirement under the collaborative mode cannot be met, so a water-retaining coal mining mode that combines height-limited mining with high-level backfilling and grouting modification in the caving zone is required.
[0099] The maximum mining height is calculated according to formula (6): .
[0100] In engineering design, the corresponding intervals in Table 4 can be used as a reference. Value, based on the principle of conservatism Iterative verification is performed. In this embodiment, the final selection is... This serves as a limit on the mining height to meet the constraints of water-conserving mining.
[0101] step Based on the determination, a water-conserving coal mining mode combining height-limited mining, high-level backfilling in the caving zone, and grouting modification was adopted to determine the backfilling height, modification thickness, and modification range.
[0102] Based on Table 3 and the characteristics of the overburden structure, the high-level infill layer is located at the bottom of the basic top, and the thickness of the immediate top is taken as... .
[0103] In this embodiment, the direct top elastic modulus is taken. Directly top the initial fragmentation coefficient average bulk density of overlying strata Coal seam burial depth Similarly, The dimensions are In relation to Unit conversion is required before superposition: .
[0104] Substituting the above results into equation (4), we get: Therefore, in this embodiment, the coefficient of fragmentation is taken as... .
[0105] Under the height-restricted mining and collaborative mining model, the filling height is determined according to formula (7): .
[0106] Substitution , , ,get: .
[0107] To ensure sufficient thickness of the modified strata, the modification thickness in this embodiment is taken as the minimum thickness required for rock strata modification: .
[0108] The height of the water-conducting fracture zone after filling is: .
[0109] Based on the working face strike and rock strata movement angle and the angle of rock strata movement in the direction of dip Calculate the modification range, with the outer extension on both sides of the direction being... The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of the direction of orientation and the extension of the direction of dip, and... The maximum value is taken as the extensional modification range of the working surface. The modified area is determined by the length of the working surface. and propulsion distance It was determined that horizontal multi-branch directional drilling would be used to perform grouting modification within the aforementioned range.
[0110] During construction, high-level filling utilizes a high-level grouting system combining a ground grouting station with vertically directional boreholes, inclined boreholes, and horizontally directional boreholes. The width of the high-level filling is approximately equal to the length of the working face, and the spacing between horizontal boreholes is [missing information]. The grouting modification can be optimized according to the grouting expansion range. Ultrafine cement-based materials are used for grouting modification, with a minimum injectable particle size of [missing information]. Fiber-reinforced materials can be added as needed to improve the integrity and toughness of the modified rock strata. Through the synergistic effect of height-limited mining, high-level backfilling, and grouting modification and reinforcement, the water-blocking performance of the rock strata above the water-conducting fracture zone is reconstructed, achieving in-situ protection of the roof aquifer and ensuring safe and efficient mining of the working face.
[0111] Those skilled in the art can adjust the specific parameters in the above embodiments or make equivalent substitutions without departing from the spirit and essence of the present invention, and such substitutions and modifications should all fall within the protection scope of the present invention.
Claims
1. A method for determining the mining mode and parameters for in-situ protection of aquifers on the roof, characterized in that, Includes the following steps: Step S1: Obtain the geological and hydrogeological parameters and mining technical parameters of the target working face; Step S2: Calculate the weighted equivalent strength of the overlying rock based on the geological and hydrogeological parameters to determine the strength type and the fracture-to-mining ratio under different hypothetical mining height conditions; Step S3: Calculate the development height of the water-conducting fracture zone, determine the equivalent filling rate coefficient of high-level backfilling in the collapse zone and the minimum thickness required for strata modification. Based on this, and considering the development height of the water-conducting fracture zone and the distance between the coal seam and the aquifer, and combined with the constraint that the distance between the coal seam and the aquifer is greater than or equal to the sum of the products of the development height of the water-conducting fracture zone, the surplus coefficient, and the hypothetical mining height, the maximum value of the ratio of the hypothetical mining height to the coal seam thickness that satisfies the water-conserving mining requirements is calculated. Based on the maximum value of the ratio, the equivalent filling rate coefficient, and the minimum thickness required for strata modification, determine the appropriate water-conserving mining mode. The water-conserving mining modes include the high-level backfilling water-conserving coal mining mode in the collapse zone, the high-level backfilling and grouting modification combined water-conserving coal mining mode in the collapse zone, and the height-limited mining and high-level backfilling and grouting modification combined water-conserving coal mining mode in the collapse zone. Step S4: Determine the water-retaining mining technical parameters based on the judgment results of Step S3: When it is determined that the high-level backfilling water-retaining coal mining mode in the caving zone is adopted, determine the minimum backfilling height using the maximum value of the ratio and the crushing expansion coefficient considering the compaction effect; when it is determined that the high-level backfilling and grouting modification combined water-retaining coal mining mode in the caving zone is adopted, determine the backfilling height, modification thickness, and modification range, wherein the backfilling height is determined based on the principle of complete backfilling, and the modification thickness is determined based on the development height of the water-conducting fracture zone after backfilling; when it is determined that the high-limited mining and the high-level backfilling and grouting modification combined water-retaining coal mining mode in the caving zone are adopted, calculate the maximum high-limited mining height based on the water-retaining mining requirements, and determine the backfilling height, modification thickness, and modification range. The geological and hydrogeological parameters mentioned in step S1 include coal seam thickness, coal seam burial depth, aquifer water-bearing capacity, distance between the coal seam and the aquifer, and compressive strength and thickness of each rock stratum between the coal seam and the aquifer; the calculation formula for the weighted equivalent strength of the overburden in step S2 is: ； in, The weighted equivalent strength of the overburden is expressed in units of... ; The uniaxial compressive strength of each rock stratum between the coal seam and the aquifer, in units of... ; To correspond to the thickness of each rock layer, the unit is... ; The distance between the coal seam and the aquifer, in units of 1. ; This represents the total number of rock strata. The intensity type is determined as follows: If It is a weak rock layer; if It is a medium-hard rock layer; if It is a hard rock layer.
2. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 1, characterized in that, The fracture-to-mining ratio under different hypothetical mining height conditions described in step S2 The following is confirmed: If the strength type is weak rock strata: hypothetical mining height hour, ; hour, ; hour, ; hour, ; If the strength type is medium-hard rock layer: hour, ; hour, ; hour, ; hour, ; If the strength type is hard rock layer: hour, ; hour, ; hour, ; hour, ; The equivalent fullness coefficient The value is taken as follows: for weak rock layers ; medium-hard rock strata Hard rock strata Minimum thickness required for rock strata modification for .
3. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 2, characterized in that, High development level of water-conducting fracture zone Compared with the cracking ratio and hypothetical mining height Between The relationship between the coal seam and the aquifer, and the constraint of water-conserving mining requirements, is the distance between the coal seam and the aquifer. Greater than or equal to the sum of the products of the development height of the water-conducting fracture zone, the surplus coefficient, and the hypothetical mining height, i.e. ,in When the aquifer has a strong water-bearing capacity, the abundance coefficient is used. When the aquifer has a moderate water-bearing capacity, When the aquifer's water-bearing capacity is weak, .
4. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 3, characterized in that, The determination logic for the water-conserving mining mode in step S3 is as follows: when At that time, it was determined that the high-level backfilling and water-conserving coal mining mode in the collapse zone should be adopted; when ,and At that time, it was determined that a high-level filling and grouting modification combined water-retaining coal mining mode should be adopted in the collapse zone; when ,and At that time, it was determined that a water-conserving coal mining mode combining height-restricted mining, high-level backfilling of the caving zone, and grouting modification should be adopted. in, Coal seam thickness, in units of .
5. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 4, characterized in that, In step S4, when it is determined that the high-level backfilling water-retaining coal mining mode in the collapse zone is adopted, the formula for calculating the minimum backfilling height is: ； in, Minimum filling height, in units of ; Coal seam thickness, in units of ; This represents a hypothetical mining height, in units of... ; The equivalent fullness coefficient; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of .
6. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 5, characterized in that, The specific expression for solving the fragmentation coefficient considering the compaction effect is as follows: ； in, The elastic modulus of the direct top, in units of ; To directly top the initial expansion coefficient, the initial volume is... The direct top rock sample was crushed, and the volume of the crushed material was measured using the standard sand volume replacement method. ,but ; The average unit weight of the overlying strata is given in units. ; The depth of the coal seam is expressed in units of 1. .
7. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 6, characterized in that, In step S4, when it is determined that a high-level backfilling and grouting modification synergistic water-retaining mining mode is adopted in the collapse zone, the formula for calculating the backfilling height is: （5）； in, The filling height is expressed in units of 1. ; Coal seam thickness, in units of ; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of The modified thickness Distance between coal seam and aquifer Subtract the height of the water-conducting fracture zone after filling The remaining thickness after that, i.e. After filling, the water-conducting fracture zone developed to a high degree. According to the strike of the working face and the angle of rock strata movement and the angle of rock strata movement in the direction of dip Calculate the modification range, with the outer extension on both sides of the direction being... The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of the direction of orientation and the extension of the direction of inclination. The maximum value is taken as the range of extensional modification of the working surface.
8. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 7, characterized in that, In step S4, when it is determined that a water-retaining coal mining mode combining height-limited mining, high-level backfilling in the caving zone, and grouting modification is adopted, the formula for calculating the maximum height-limited mining height is: （6）； in, The maximum maximum mining height is expressed in units of... ; The distance between the coal seam and the aquifer, in units of 1. ; Minimum thickness required for rock strata modification, in units of ; The ratio of cracked to extracted material; The equivalent filling rate coefficient is used; the formula for calculating the filling height is: （7）； in, The filling height is expressed in units of 1. ; The maximum maximum mining height is expressed in units of... ; The coefficient of swell is used to account for the compaction effect; The thickness is the direct top thickness, in units of The modified thickness The minimum thickness required for rock stratum modification, i.e. After filling, the water-conducting fracture zone developed to a high degree. According to the strike of the working face and the angle of rock strata movement and the angle of rock strata movement in the direction of dip Calculate the modification range, with the outer extension on both sides of the direction being... The lateral extension of the inclined direction is The radius of influence of the aquifer was obtained through pumping or injection interference tests. Take the extension of the direction of orientation and the extension of the direction of inclination. The maximum value is taken as the range of extensional modification of the working surface.
9. The method for determining the mining mode and parameters for in-situ protection of the roof aquifer according to claim 8, characterized in that, In step S4, the high-level filling layer is determined to be the basic top and bottom. Filling is carried out through the main borehole, inclined borehole, and horizontal directional borehole constructed on the ground. The mass ratio of the filling material is gangue. ,cement ,water The horizontal borehole spacing is The grouting modification can be adjusted according to the grout spread; the grouting modification operation is completed before the working face is mined, and horizontal multi-branch directional drilling is used for grouting modification. The minimum injectable particle size of the grouting modification material is [missing information]. The horizontal directional drilling spacing is It can be further adjusted according to the slurry diffusion range.