A key layer lower effective disposal space identification and grading method and system

Abstract

The application discloses a kind of key layer lower part effective disposal space identification and grading method and system, it is related to coal mine overburden control and solid waste disposal technical field, the method carries out field measurement investigation, obtains the relevant parameters of target working face;According to stope basic information, establish shallow depth fully mechanized caving overburden physical similar model, by simulating the initial breakage and periodic breakage of key layer under different advancing distance conditions, key layer lower part mining space development and evolution and goaf compaction process, identify the candidate area of key layer lower part mining space;Establish the discriminant criterion of can be constructed-can be maintained-can be used, respectively judge whether candidate area has the condition of forming cementation combined load carrier by grouting, whether effective space can be maintained within a certain advancing distance or time after forming load carrier, and whether the space after maintenance can be effectively entered by second stage slurry and used for solid waste disposal;According to the judgment result, key layer lower space is divided into priority reinforcement area, coordinated use area and rapid failure area.

Description

Technical Field

[0001] This invention relates to the field of coal mine overburden control and solid waste disposal technology, and in particular to a method and system for identifying and classifying effective disposal spaces under key strata. Background Technology

[0002] After shallow-buried fully mechanized longwall mining, the overlying strata undergo collapse, fracturing, delamination, fissure expansion, and compaction evolution under the mining action. Mining spaces with significant temporal and spatial differences will form in the lower part of the key strata. These spaces have the potential to form a support structure and implement solid waste disposal within a certain stage. However, existing technologies mostly focus on the fracturing patterns of the overlying strata, the distribution of fissures and delamination, or the grouting process itself. They lack a systematic identification and classification method that considers the spatial development characteristics, maintenance capacity, and subsequent utilization capacity of the space under the key strata. This makes it difficult to accurately determine in actual engineering which areas are suitable for constructing cemented composite support structures, which areas can maintain effective space during the working face advancement, and which areas can meet the requirements for the second stage of slurry entry and solid waste disposal. Consequently, it affects the pertinence and effectiveness of subsequent parameter design and zoning control.

[0003] Therefore, there is an urgent need for a method and system for effective spatial identification and classification of the lower critical layer that can solve the above problems. Summary of the Invention

[0004] This solution addresses the problems and needs raised above by proposing a method and system for effective spatial identification and classification of the lower critical layer. The above technical objectives are achieved by adopting the following technical features, and several other technical effects are also brought about.

[0005] One object of the present invention is to provide a method for identifying and classifying effective disposal spaces in the lower part of a critical layer, which includes the following steps: S10: Acquisition of basic information in the mining area: Conduct on-site measurement and survey to obtain the burial depth, mining height, coal seam thickness, working face width, and advance speed of the shallow-buried fully mechanized longwall face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters, and compaction evolution parameters of the target working face; S20: Identification of candidate spaces under key strata: Based on the acquired basic information of the mining area, a physical similarity model of the overburden in shallow-buried deep fully mechanized mining is established. The deformation and fracture characteristics of the overburden structure during the advancement of the working face are simulated and analyzed. Based on the location of the key strata and its fracture control range, candidate areas that may form mining spaces under the key strata are determined. S30: Establish judgment criteria: Construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension is used to determine whether the area has the conditions for forming a cemented composite support structure through the first stage of grouting; the sustainability judgment dimension is used to determine whether the effective space can be maintained after the support structure is formed within a set advancement distance or time; the usability judgment dimension is used to determine whether the maintained space can be effectively entered by the second stage grout and used for solid waste disposal. Among these, the grouting and filling for constructing post-mining space is the first stage, and the grouting operation for filling and disposing of post-mining space is the second stage. S40: Spatial grading: Based on the judgment results of constructible discriminant dimension, sustainable discriminant dimension and usable discriminant dimension, the lower space of the critical layer is divided into: priority reinforcement zone, collaborative utilization zone and rapid failure zone.

[0006] Furthermore, the method for identifying and classifying the effective disposal space below the key layer according to the present invention may also have the following technical features: In one example of the present invention, step S20 specifically includes the following steps: by simulating the initial and periodic fractures of the key layer, the development and evolution of the mining space under the key layer, and the compaction of the goaf under different advance distances, the spatial characteristics of the void development location, void size, void connectivity, void evolution trend with advance, compaction start location, and compaction rate in the lower part of the key layer are analyzed, and candidate areas of the mining space under the key layer are identified accordingly.

[0007] In one example of the present invention, in step 30, the criteria for constructability discrimination include: the effective porosity of the delamination voids in the candidate region should not be less than 15% to ensure that the first-stage grout has sufficient filling space; the void structure should be able to meet the flow and diffusion of grout between layers; the integrity coefficient of the key layer after mining should exceed 0.5 to ensure that the surrounding rock allows the formation of a continuous bearing structure; and a comprehensive discrimination is made based on the void development location, void scale, void connectivity, void evolution trend, surrounding rock constraint conditions, and compaction state of the candidate region. The comprehensive criteria are as follows: the candidate area should be located above the top of the collapse zone to the middle and lower part of the fracture zone, with a continuous lateral development length of ≥ 20 m, and be in an insufficiently compacted stage within 15 to 25 m behind the working face. Only if the above-mentioned dimensions, connectivity and surrounding rock conditions are met can it be determined to be constructible.

[0008] In one example of the present invention, in step S30, the criteria for maintaining sustainability include: during the overburden migration stage, the location of the bearing body must be before the failure of the critical layer, and the overburden subsidence rate must be less than 3 mm / d; the layer where the bearing body is located must avoid the rapid failure zone, and the remaining fragmentation coefficient must be greater than 1.3; in terms of the mechanical properties of the filling body, the 3d strength must reach more than 4.13 MPa, and the elastic modulus must be compatible with the overlying surrounding rock.

[0009] In one example of the present invention, the mechanical properties are determined by strength discrimination, specifically including the following: first, the tensile strength, compressive strength and shear strength of the key layer are tested by core drilling, and then a strength test is performed on the quick-setting material support or the combined support formed by the quick-setting material and the slightly damaged key layer; wherein, the key layer after slight damage is obtained by Hopkinson test; when the 3d strength of the filling body reaches 4.13 MPa, the compaction rate can be lower than the formation and functioning speed of the support body.

[0010] In one example of the present invention, in step S30, the availability determination specifically includes the following steps: by establishing a void ratio calculation model, the remaining effective void ratio at different advancement stages is obtained, and the remaining effective void ratio is compared with a preset minimum disposal threshold. When the remaining effective void ratio reaches a preset percentage and the connectivity and accessibility meet the requirements of subsequent slurry filling, the candidate space is determined to be available.

[0011] In one example of the present invention, the effective porosity Based on the porosity of the caving zone Porosity of fracture zone and porosity of the delamination region The calculated expression is:

[0012]

[0013]

[0014]

[0015] In the formula, , This is the distance from a point within the goaf to the middle of the working face. , The initial and compaction expansion coefficients; , for , Directional dilatation coefficient attenuation rate; , The strike and dip length of the goaf; The compaction and bulging coefficient at the top of the caving zone; The distance from any point in the overlying strata to the coal seam; ρ is the average density of the overlying rock strata; g is the gravitational acceleration; b is the grain size correlation coefficient; The height of the landslide zone; , The heights of the i-th and i+1-th rock layers; , The subsidence amounts of the i-th and i+1-th rock layers; This represents the difference in subsidence between adjacent rock layers. and are respectively For variables and The partial derivatives; This is the distance from the rock stratum fracture line to the working face; This represents the center-to-center distance of each rock layer.

[0016] In one example of the present invention, in step S40, the priority reinforcement zone is configured as a region that simultaneously satisfies constructability, maintainability, and usability, delaying the failure of the critical layer and maintaining effective space during the advancement of the working face; the cooperative utilization zone is configured as a region that satisfies constructability or usability, but has limited maintainability and needs to be implemented in coordination with the process window; the rapid failure zone is configured as a region that has gaps for a short time, but compacts too quickly or lacks usability and is not suitable as a control target.

[0017] Another objective of this invention is to provide an effective disposal space identification and hierarchical system for the lower part of a critical layer, comprising: The basic information acquisition module for the mining area is configured to conduct on-site measurement and surveys to obtain the burial depth, mining height, coal seam thickness, working face width, and advance speed of the shallow fully mechanized longwall mining face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters, and compaction evolution parameters of the target working face; The candidate space identification module under the key layer is configured to establish a physical similarity model of the overburden in shallow and deep fully mechanized mining based on the acquired basic information of the mining area, simulate and analyze the deformation and fracture characteristics of the overburden structure during the advancement of the working face, and determine the candidate areas in the lower part of the key layer that may form mining space according to the location of the key layer and its fracture control range. A judgment criterion module is established and configured to construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension is used to determine whether the area has the conditions for forming a cemented composite support structure through the first-stage grouting. The sustainability judgment dimension is used to determine whether the effective space can be maintained after the support structure is formed within a set advancement distance or time. The usability judgment dimension is used to determine whether the maintained space can be effectively entered by the second-stage grout and used for solid waste disposal. The grouting and filling for constructing the post-mining space is the first stage, and the grouting operation for filling and disposing of the post-mining space is the second stage. The spatial grading module is configured to divide the lower space of the critical layer into three zones based on the judgment results of constructible, sustainable, and usable discriminant dimensions: a priority reinforcement zone, a collaborative utilization zone, and a rapid failure zone.

[0018] In one example of the present invention, the candidate space identification module for the lower part of the key layer includes: The simulation unit is configured to simulate the initial and periodic failure of the key layer under different advance distances, the development and evolution of the mining space under the key layer, and the compaction of the goaf. The analysis unit is configured to analyze the spatial characteristics of void development location, void size, void connectivity, void evolution trend as it advances, compaction initiation location, and compaction rate in the lower part of the key stratum, and thereby identify candidate regions of the mining space in the lower part of the key stratum.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention focuses on the mining space beneath key strata and constructs a complete technical path of "candidate space identification - constructability judgment - maintainability judgment - usability judgment - spatial classification." It can identify effective spaces with disposal potential beneath key strata during face advancement, clarify the possibility of different spatial sections forming cemented composite support structures, maintaining effective space, and realizing subsequent solid waste disposal and utilization. These spaces are divided into priority reinforcement zones, synergistic utilization zones, and rapid failure zones, providing a basis for determining subsequent control priorities, selecting control methods, designing parameters, and implementing zoned management. This method helps improve the accuracy of identifying disposal spaces beneath key strata and the targeting of engineering control, avoiding blind construction and ineffective grouting, significantly improving the targeting and economy of underground solid waste disposal, and having beneficial effects on improving underground solid waste disposal efficiency, enhancing overburden control effects, and mitigating mining damage. Simultaneously, this method can delay key strata fracture, enhance overburden bearing capacity, effectively mitigate mining damage, and reduce mine pressure manifestation, possessing significant engineering application value for achieving green coal mining and solid waste resource utilization.

[0020] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0022] Figure 1 This is a flowchart of a method for identifying and classifying effective disposal spaces in the lower part of a key layer according to an embodiment of the present invention; Figure 2 This is a schematic diagram of spatial hierarchy according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0025] According to a first aspect of the present invention, a method for identifying and classifying effective disposal spaces in the lower part of a critical layer is provided, such as... Figure 1 and Figure 2 As shown, it includes the following steps: S10: Acquisition of basic information in the mining area: Conduct on-site measurement and survey to obtain key parameters such as the burial depth, mining height, coal seam thickness, working face width, and advance speed of the shallow-buried fully mechanized longwall face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters, and compaction evolution parameters of the target working face; S20: Identification of candidate spaces under key strata: Based on the acquired basic information of the mining area, a physical similarity model of the overburden in shallow-buried deep fully mechanized mining is established. The deformation and fracture characteristics of the overburden structure during the advancement of the working face are simulated and analyzed. Based on the location of the key strata and its fracture control range, candidate areas that may form mining spaces under the key strata are determined. S30: Establish Judgment Criteria: Construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension is used to determine whether the area meets the conditions for forming a cemented composite support structure through the first-stage grouting. The sustainability judgment dimension is used to determine whether, after the support structure is formed, it can maintain effective space within a set advancement distance or time. The usability judgment dimension is used to determine whether the maintained space can be effectively entered by the second-stage grout and used for solid waste disposal. The grouting and filling used to construct the post-mining space constitutes the first stage, and the first-stage grouting is injected at the following location: Figure 2 The priority reinforcement zone is shown; the grouting operation used to fill and treat the post-mining space is the second stage, and it is carried out after the completion of the first stage of grouting and the formation of the post-mining space. Figure 2 The injection is performed after the "cooperative utilization zone" shown, and the injection location is the "cooperative utilization zone".

[0026] S40: Spatial grading: Based on the judgment results of constructible discriminant dimension, sustainable discriminant dimension and usable discriminant dimension, the lower space of the critical layer is divided into: priority reinforcement zone, collaborative utilization zone and rapid failure zone.

[0027] This identification and classification method obtains relevant parameters of the target working face through field surveys and measurements. Based on basic information from the mining area, a physical similarity model of the overburden rock in shallow-buried, deep-laid caving mining operation is established. By simulating the initial and periodic failure of the key stratum under different advance distances, the development and evolution of the mining space below the key stratum, and the compaction process of the goaf, candidate areas for mining space below the key stratum are identified. Furthermore, a "constructible-sustainable-usable" discrimination rule is established. Finally, based on the judgment results, the space below the key stratum is divided into a priority reinforcement zone, a collaborative utilization zone, and a rapid failure zone, thereby achieving the identification and classification of effective disposal space below the key stratum. Therefore, conducting research on the identification and classification of effective disposal space below the key stratum is of great significance for achieving accurate determination of disposal space below the key stratum, improving the rationality of subsequent control parameter design, and enhancing the effectiveness of engineering implementation.

[0028] This identification and classification method focuses on the mining space below the critical stratum and constructs a complete technical path of "candidate space identification - constructability judgment - sustainability judgment - usability judgment - spatial classification". It can identify effective spaces with disposal potential below the critical stratum during working face advancement, clarify the possibility of different spatial sections forming cemented composite carriers, maintaining effective space, and realizing subsequent solid waste disposal and utilization, and divide them into priority reinforcement zones, synergistic utilization zones, and rapid failure zones. This provides a basis for determining subsequent control priorities, selecting control methods, designing parameters, and implementing zoned control. This method helps improve the accuracy of identifying disposal spaces below the critical stratum and the targeting of engineering control, reducing blind construction and ineffective disposal. It has significant engineering application value for improving the efficiency of underground solid waste disposal, enhancing overburden control, and mitigating mining damage.

[0029] In one example of the present invention, step S20 specifically includes the following steps: by simulating the initial and periodic fractures of the key layer under different advance distances, the development and evolution of the mining space under the key layer, and the compaction of the goaf, the spatial characteristics such as the location of void development, void size, void connectivity, void evolution trend with advancement, compaction start position, and compaction rate of the void under the key layer are analyzed. The criteria for identification are good "three-zone" development characteristics and void connectivity, compaction start position lagging behind the working face by more than 10m, and slow compaction rate. Based on this, candidate areas of the mining space under the key layer are identified.

[0030] In one example of the present invention, in step 30, the criteria for constructability discrimination include: the effective porosity of the delamination voids in the candidate region should not be less than 15% to ensure that the first-stage grout has sufficient filling space; the void structure should be able to meet the flow and diffusion of grout between layers; the integrity coefficient of the key layer after mining should exceed 0.5 to ensure that the surrounding rock allows the formation of a continuous bearing structure; and a comprehensive discrimination is made based on the void development location, void scale, void connectivity, void evolution trend, surrounding rock constraint conditions, and compaction state of the candidate region. The comprehensive criteria are as follows: the candidate area should be located above the top of the caving zone to the middle and lower part of the fracture zone (generally ≤ 5 m from the bottom of the key layer), with a continuous lateral development length ≥ 20 m, and be in an insufficiently compacted stage within 15 to 25 m behind the working face (compaction degree ≤ 40%). Only if the above-mentioned dimensions, connectivity and surrounding rock conditions are met can it be determined to be constructible.

[0031] In one example of the present invention, in step S30, the criteria for maintaining sustainability include: during the overburden migration stage, the location of the bearing body must be before the failure of the critical layer, and the overburden subsidence rate must be less than 3 mm / d; the layer where the bearing body is located must avoid the rapid failure zone, and the remaining fragmentation coefficient must be greater than 1.3; in terms of the mechanical properties of the filling body, the 3d strength must reach more than 4.13 MPa, and the elastic modulus must be compatible with the overlying surrounding rock.

[0032] Mechanical properties: The 3-day uniaxial compressive strength of the filling body shall not be less than 4.13 MPa (to ensure that the solidification rate exceeds the compaction rate); the 28-day strength shall reach 6 to 8 MPa; and the elastic modulus shall be compatible with the overlying surrounding rock (1.5 to 3 GPa) to ensure that the bearing body does not undergo brittle failure under cyclic pressure loads and can effectively support the top plate to maintain effective space.

[0033] In one example of the present invention, the mechanical properties are determined by strength discrimination, specifically including the following: first, the tensile strength, compressive strength and shear strength of the key layer are tested by core drilling, and then the strength test is carried out on the quick-setting material support or the combined support formed by the quick-setting material and the slightly damaged key layer; wherein, the key layer after slight damage can be obtained by Hopkinson test; when the 3d strength of the filling body reaches 4.13MPa, the compaction rate can be lower than the formation and functioning speed of the support body.

[0034] In one example of the present invention, in step S30, the availability determination specifically includes the following steps: by establishing a void ratio calculation model, the remaining effective void ratio at different advancement stages is obtained, and the remaining effective void ratio is compared with a preset minimum disposal threshold. When the remaining effective void ratio reaches a preset percentage and the connectivity and accessibility meet the requirements of subsequent slurry filling, the candidate space is determined to be available.

[0035] In one example of the present invention, the effective porosity Based on the porosity of the caving zone Porosity of fracture zone and porosity of the delamination region The calculated expression is:

[0036]

[0037]

[0038]

[0039] In the formula, , This is the distance from a point within the goaf to the middle of the working face. , The initial and compaction expansion coefficients; , for , Directional dilatation coefficient attenuation rate; , The strike and dip length of the goaf; The compaction and bulging coefficient at the top of the caving zone; The distance from any point in the overlying strata to the coal seam; ρ is the average density of the overlying rock strata; g is the gravitational acceleration; b is the grain size correlation coefficient; The height of the landslide zone; , The heights of the i-th and i+1-th rock layers; , The subsidence amounts of the i-th and i+1-th rock layers; This represents the difference in subsidence between adjacent rock layers. and are respectively For variables and The partial derivatives; This is the distance from the rock stratum fracture line to the working face; This represents the center-to-center distance of each rock layer.

[0040] In one example of the present invention, in step S40, the priority reinforcement zone is configured as a region that simultaneously satisfies constructability, maintainability, and availability, delaying the failure of the critical layer and maintaining effective space during the advancement of the working face; the cooperative utilization zone is configured as a region that satisfies constructability or availability but has limited maintainability and needs to be implemented in coordination with the process window; the rapid failure zone is configured as a region that has gaps for a short time but is compacted too quickly or lacks availability and is not suitable as a primary control target.

[0041] According to a second aspect of the present invention, a key layer lower effective disposal space identification and hierarchical system includes: The basic information acquisition module for the mining area is configured to conduct on-site measurement and surveys to obtain key parameters such as the burial depth, mining height, coal seam thickness, working face width, and advance speed of the shallow-buried fully mechanized longwall face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters, and compaction evolution parameters of the target working face; The candidate space identification module under the key layer is configured to establish a physical similarity model of the overburden in shallow and deep fully mechanized mining based on the acquired basic information of the mining area, simulate and analyze the deformation and fracture characteristics of the overburden structure during the advancement of the working face, and determine the candidate areas in the lower part of the key layer that may form mining space according to the location of the key layer and its fracture control range. A judgment criterion module is established and configured to construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension determines whether the area meets the conditions for forming a cemented composite support structure through the first-stage grouting. The sustainability judgment dimension determines whether, after the support structure is formed, it can maintain effective space within a set advancement distance or time. The usability judgment dimension determines whether the maintained space can be effectively entered by the second-stage grout and used for solid waste disposal. The grouting and filling for constructing post-mining space constitutes the first stage, and the first-stage grouting is injected at the designated location. Figure 2 The priority reinforcement zone is shown; the grouting operation used to fill and treat the post-mining space is the second stage, and it is carried out after the completion of the first stage of grouting and the formation of the post-mining space. Figure 2 The injection is performed after the "cooperative utilization zone" shown, and the injection location is the "cooperative utilization zone".

[0042] The spatial grading module is configured to divide the lower space of the critical layer into three zones based on the judgment results of constructible, sustainable, and usable discriminant dimensions: a priority reinforcement zone, a collaborative utilization zone, and a rapid failure zone.

[0043] This identification and grading system focuses on the mining space beneath key strata, constructing a complete technical path of "candidate space identification - constructability judgment - sustainability judgment - usability judgment - spatial grading." It can identify effective spaces with disposal potential beneath key strata during face advancement, clarifying the possibility of different spatial sections forming cemented composite carriers, maintaining effective space, and achieving subsequent solid waste disposal and utilization. These spaces are then divided into priority reinforcement zones, synergistic utilization zones, and rapid failure zones, providing a basis for determining subsequent control priorities, selecting control methods, designing parameters, and implementing zoned management. This method helps improve the accuracy of identifying disposal spaces beneath key strata and the targeting of engineering control, reducing blind construction and ineffective disposal. It has significant engineering application value for improving the efficiency of underground solid waste disposal, enhancing overburden control, and mitigating mining damage.

[0044] In one example of the present invention, the candidate space identification module for the lower part of the key layer includes: The simulation unit is configured to simulate the initial and periodic failure of the key layer under different advance distances, the development and evolution of the mining space under the key layer, and the compaction of the goaf. The analysis unit is configured to analyze the spatial characteristics of the lower part of the key layer, such as the location of void development, void size, void connectivity, void evolution trend as it advances, compaction initiation location, and compaction rate, and to identify candidate areas of the mining space in the lower part of the key layer accordingly.

[0045] It should be noted that the critical layer lower effective disposal space identification and classification system of the present invention can also perform any of the processing as described in the critical layer lower effective disposal space identification and classification method previously described, and the specific details are not repeated here.

[0046] The foregoing description, with reference to preferred embodiments, details an exemplary implementation of the method and system for effective disposal space identification and classification in the lower part of a key layer proposed by the present invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed by the present invention without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A method for effective spatial identification and hierarchical classification of the lower part of a critical layer, characterized in that, Includes the following steps: S10: Acquisition of basic information in the mining area: Conduct on-site measurement and survey to obtain the burial depth, mining height, coal seam thickness, working face width and advance speed of the shallow fully mechanized longwall face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters and compaction evolution parameters of the target working face; S20: Identification of candidate spaces under key strata: Based on the acquired basic information of the mining area, a physical similarity model of the overburden in shallow-buried deep fully mechanized mining is established. The deformation and fracture characteristics of the overburden structure during the advancement of the working face are simulated and analyzed. Based on the location of the key strata and its fracture control range, candidate areas that may form mining spaces under the key strata are determined. S30: Establish judgment criteria: Construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension is used to determine whether the area has the conditions for forming a cemented composite support structure through the first stage of grouting; the sustainability judgment dimension is used to determine whether the effective space can be maintained after the support structure is formed within a set advancement distance or time; the usability judgment dimension is used to determine whether the maintained space can be effectively entered by the second stage grout and used for solid waste disposal. Among these, the grouting and filling for constructing post-mining space is the first stage, and the grouting operation for filling and disposing of post-mining space is the second stage. S40: Spatial grading: Based on the judgment results of constructible discriminant dimension, sustainable discriminant dimension and usable discriminant dimension, the lower space of the critical layer is divided into: priority reinforcement zone, collaborative utilization zone and rapid failure zone.

2. The method for identifying and classifying the effective disposal space in the lower part of the key layer according to claim 1, characterized in that, Step S20 specifically includes the following steps: by simulating the initial and periodic fractures of the key stratum, the development and evolution of the mining space under the key stratum, and the compaction of the goaf under different advance distances, the spatial characteristics of the void development location, void size, void connectivity, void evolution trend with advance, compaction start location, and compaction rate under the key stratum are analyzed, and candidate areas of the mining space under the key stratum are identified accordingly.

3. The method for identifying and classifying the effective disposal space in the lower part of the key layer according to claim 1, characterized in that, In step 30, the criteria for constructability discrimination include: the effective porosity of the delamination voids in the candidate region should not be less than 15% to ensure that the first-stage grout has sufficient filling space; the void structure should be able to meet the flow and diffusion of grout between layers; the integrity coefficient of the key layer after mining should exceed 0.5 to ensure that the surrounding rock allows the formation of a continuous bearing structure; and a comprehensive discrimination is made based on the void development location, void scale, void connectivity, void evolution trend, surrounding rock constraint conditions, and compaction state of the candidate region. The comprehensive criteria are as follows: the candidate area should be located above the top of the collapse zone to the middle and lower part of the fracture zone, with a continuous lateral development length of ≥ 20 m, and be in an insufficiently compacted stage within 15 to 25 m behind the working face. Only if the above-mentioned dimensions, connectivity and surrounding rock conditions are met can it be determined to be constructible.

4. The method for identifying and classifying the effective disposal space in the lower part of the critical layer according to claim 1, characterized in that, In step S30, the criteria for maintaining sustainability include: during the overburden migration stage, the location of the bearing body must be before the failure of the critical layer, and the overburden subsidence rate must be below 3 mm / d; the layer where the bearing body is located must avoid the rapid failure zone, and the remaining fragmentation coefficient must be greater than 1.3; in terms of the mechanical properties of the filling body, the 3d strength must reach above 4.13 MPa, and the elastic modulus must be compatible with the overlying surrounding rock.

5. The method for identifying and classifying the effective disposal space in the lower part of the key layer according to claim 4, characterized in that, The mechanical properties are determined by strength discrimination, specifically including the following: first, the tensile strength, compressive strength and shear strength of the key layer are tested by core drilling; then, the strength test is carried out on the quick-setting material support or the combined support formed by the quick-setting material and the slightly damaged key layer; wherein, the key layer after slight damage is obtained by Hopkinson test; when the 3d strength of the filling body reaches 4.13MPa, the compaction rate can be lower than the formation and functioning speed of the support body.

6. The method for identifying and classifying the effective disposal space in the lower part of the critical layer according to claim 1, characterized in that, In step S30, the availability determination specifically includes the following steps: by establishing a void ratio calculation model, the remaining effective void ratio at different advancement stages is obtained, and the remaining effective void ratio is compared with a preset minimum disposal threshold. When the remaining effective void ratio reaches a preset percentage and the connectivity and accessibility meet the requirements for subsequent slurry filling, the candidate space is determined to be available.

7. The method for identifying and classifying the effective disposal space in the lower part of the key layer according to claim 6, characterized in that, The effective porosity Based on the porosity of the caving zone Porosity of fracture zone and porosity of the delamination region The calculated expression is: In the formula, , This is the distance from a point within the goaf to the middle of the working face. , The initial and compaction expansion coefficients; , for , Directional dilatation coefficient attenuation rate; , The strike and dip length of the goaf; The compaction and bulging coefficient at the top of the caving zone; The distance from any point in the overlying strata to the coal seam; ρ is the average density of the overlying rock strata; g is the gravitational acceleration; b is the grain size correlation coefficient; The height of the landslide zone; , The heights of the i-th and i+1-th rock layers; , The subsidence amounts of the i-th and i+1-th rock layers; This represents the difference in subsidence between adjacent rock layers. and are respectively For variables and The partial derivatives; This is the distance from the rock stratum fracture line to the working face; This represents the center-to-center distance of each rock layer.

8. The method for identifying and classifying the effective disposal space in the lower part of the critical layer according to claim 1, characterized in that, In step S40, the priority reinforcement zone is configured to simultaneously satisfy constructability, maintainability, and usability, delaying the failure of the critical layer and maintaining effective space during the advancement of the working face; the collaborative utilization zone is configured to satisfy constructability or usability, but with limited maintainability and needs to be implemented in coordination with the process window. The rapid failure zone is defined as an area that, although it has voids for a short time, is compacted too quickly or is not usable and is not suitable for regulation.

9. A system for identifying and classifying effective disposal spaces in the lower part of a critical layer, characterized in that, include: The basic information acquisition module for the mining area is configured to conduct on-site measurement and surveys to obtain the burial depth, mining height, coal seam thickness, working face width, and advance speed of the shallow fully mechanized longwall mining face; select typical areas with similar mining conditions in the mining area that have been mined but have not applied grouting and filling technology to obtain the key layer location, thickness, lithology, fracture step distance, overburden movement and mine pressure manifestation characteristics, mining space void distribution parameters, and compaction evolution parameters of the target working face; The candidate space identification module under the key layer is configured to establish a physical similarity model of the overburden in shallow and deep fully mechanized mining based on the acquired basic information of the mining area, simulate and analyze the deformation and fracture characteristics of the overburden structure during the advancement of the working face, and determine the candidate areas in the lower part of the key layer that may form mining space according to the location of the key layer and its fracture control range. A judgment criterion module is established and configured to construct three judgment dimensions: constructability, sustainability, and usability. The constructability judgment dimension is used to determine whether the area has the conditions for forming a cemented composite support structure through the first-stage grouting. The sustainability judgment dimension is used to determine whether the effective space can be maintained after the support structure is formed within a set advancement distance or time. The usability judgment dimension is used to determine whether the maintained space can be effectively entered by the second-stage grout and used for solid waste disposal. The grouting and filling for constructing the post-mining space is the first stage, and the grouting operation for filling and disposing of the post-mining space is the second stage. The spatial grading module is configured to divide the lower space of the critical layer into three zones based on the judgment results of constructible, sustainable, and usable discriminant dimensions: a priority reinforcement zone, a collaborative utilization zone, and a rapid failure zone.

10. The key layer lower effective disposal space identification and hierarchical system according to claim 9, characterized in that, The key layer lower candidate space identification module includes: The simulation unit is configured to simulate the initial and periodic failure of the key layer under different advance distances, the development and evolution of the mining space under the key layer, and the compaction of the goaf. The analysis unit is configured to analyze the spatial characteristics of void development location, void size, void connectivity, void evolution trend as it advances, compaction initiation location, and compaction rate in the lower part of the key stratum, and thereby identify candidate regions of the mining space in the lower part of the key stratum.

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