Optimal selection method for grouting target region of reconstructed water-resisting layer of mining-induced fracture stratum

Abstract

The invention relates to the technical field of coal mining, and discloses a mining-induced fissure stratum reconstructed water-resisting layer grouting target region optimization method, which comprises the following steps: drawing a rock stratum-fissure-slurry running height space relation comprehensive chart through overlying strata structure analysis, mining-induced fissure development characteristic analysis, working face / goaf slurry running height calculation and the like; and a working face overlying strata fissure zone tension area is determined, and then a vertical groutable rock stratum and a plane grouting range are preferably selected, so that final determination of a reconstructed water-resisting layer grouting target area is realized. According to the method, through accurate selection of the grouting target area, underground and ground grout leakage can be prevented while the grout diffusion radius can be increased, and the grouting effect and the quality of the reconstructed water-resisting layer are guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of coal mining, and in particular to a method for optimizing target areas for grouting of reconstructed impermeable layers in mining-induced fractured strata. Background Art

[0002] Reconstructed aquiclude refers to the process of artificially reconstructing an aquiclude in underground space in geological engineering to prevent groundwater infiltration and pollution. Aquicludes are rock layers that cannot penetrate or release water, or rock layers that can penetrate and release very little water, usually composed of clay, shale, clay rock, etc.

[0003] Grouting is one of the common methods to achieve the reconstruction of aquiclude. It mainly forms aquiclude by injecting cement slurry or other waterproof materials into the ground to fill the rock gaps. This method can effectively prevent groundwater infiltration and is suitable for various geological conditions.

[0004] In the prior art, there are technologies related to the use of grouting to recreate aquicludes, such as CN116481975A (publication date: 20230725), which discloses a three-dimensional visualization simulation system for mining fissure grouting and high-pressure water inrush and its use method. The top and bottom plates are pressurized by air bags and water is filled into the top and bottom plate rock layers to simulate the top and bottom plate pressure-bearing aquifers. The mining field simulation device adjusts the size of different working faces and mining steps. The reserved grouting pipe simulates the mining overburden fissure grouting process, and the dynamic changes of aquifer water pressure, grouting pressure, grouting volume, grouting rate and water inrush volume during the water inrush process are monitored by metering pumps, flow sensors, pressure sensors and overburden monitoring points. This technical solution realizes the multi-factor real-time monitoring of the evolution of mining overburden fissures, water inrush seepage field and slurry migration field, which can provide a basis for studying the water-slurry-rock combination, and evaluating the effectiveness of the top and bottom plate grouting to recreate the aquiclude and the law of water inrush volume, and further guide the grouting engineering for water hazard prevention and control of the top and bottom plates in the mining area.

[0005] After searching, it was found that there is no technology that can ensure the effect of reconstructing the waterproof layer by selecting the grouting target area. Therefore, this application intends to effectively construct the waterproof layer through the accurate selection of the grouting target area, so that the reconstructed waterproof layer can effectively prevent groundwater infiltration and pollution, and ensure the safety and stability of the underground space. Summary of the invention

[0006] The purpose of the present application is to provide a method for optimizing grouting target areas for recreating a water-proof layer in a mining-induced fractured stratum, so as to ensure the effect of recreating the water-proof layer through accurate selection of the grouting target areas.

[0007] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0008] A method for selecting target areas for grouting in reconstructed impermeable layers in mining-induced fractured strata, the method comprising:

[0009] Based on the analysis of the overburden structure, the rock formation characteristics are determined, wherein the rock formation characteristics include the lithology combination characteristics, the aquiclude characteristics and the aquifer pore structure characteristics;

[0010] Based on the analysis of the development characteristics of mining-induced fissures, a model of the fissure field in the working face is established;

[0011] Calculate the slurry run height of the working face and / or goaf;

[0012] Based on the rock formation characteristics, the model of the fracture field of the working face, and the slurry run-off height of the working face and / or the goaf, a comprehensive chart of the spatial relationship between rock formation, fracture, and slurry run-off height is drawn;

[0013] Based on the comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height, determine the vertical rock layer that can be grouted;

[0014] Determine the tension area of ​​the overburden fracture zone of the working face based on the model of the working face fracture field and the slurry running height of the working face and / or goaf;

[0015] Based on the tension area of ​​the overburden fracture zone of the working face, determining the plane grouting range;

[0016] The target area for grouting of the reconstructed aquiclude is determined based on the determined vertical groutable rock layer and the horizontal grouting range.

[0017] Furthermore, the lithology combination characteristics include the thickness, lithology, uniaxial compressive strength of different rock layers, the spatial combination relationship between rock layers, the lithology combination profiles of different working faces, and the overall compressive strength of the formation; the aquiclude characteristics include the spatial distribution characteristics of the aquifer and aquiclude; the aquiclude pore structure characteristics include the scale range, connectivity, and permeability of the pores and cracks in the rock formation;

[0018] Based on the analysis of the overburden structure, the rock formation characteristics are determined, including:

[0019] According to the geological and hydrogeological conditions of the mine, the thickness, lithology, uniaxial compressive strength of rocks and the spatial combination relationship between rock layers are determined; based on the borehole columnar data, through the well profile analysis, a three-dimensional geological model of the mining area is established, and through the slice analysis, the lithology combination profiles of different working faces are obtained. For the interbedded sandstone and mudstone strata, the overall compressive strength of the strata is calculated by the following formula:

[0020]

[0021] In the formula, w i is the lithology weight coefficient of the nth rock, where sandstone takes 0.4 and mudstone takes 0.6; M n is the rock layer thickness, UCS t is the overall compressive strength of the formation, UCSn is the uniaxial compressive strength of the nth rock;

[0022] Based on the lithological characteristics, aquifers and aquicludes are determined, and based on the three-dimensional geological model, the spatial distribution characteristics of aquifers and aquicludes are determined;

[0023] Based on the core data of mine drilling, the pore structure characteristics of the aquifer rock samples are tested to determine the scale range, connectivity and permeability coefficient of the pores and fractures in the rock formation.

[0024] Furthermore, based on the analysis of the development characteristics of mining-induced fissures, a model of the fissure field of the working face is established, including:

[0025] Drill holes are arranged on the working face that has been mined. The drilling positions are as follows: a row of drill holes is arranged on both sides of the coal wall where the working face is cut, with a spacing of 100 to 200 meters, and a drill hole is arranged at intervals of 200 to 300 meters along the direction of the working face. During the drilling process, the height and scale of the crack development in the overburden after mining are observed.

[0026] If the fissure develops to the surface, the height H of the fissure zone can be obtained by directly observing from the surface. e If the fissures have not developed to the surface, the consumption of flushing fluid in the borehole will have a sudden change from top to bottom. The initial position where the consumption is 3 to 5 times higher will be located to determine the height of the fissure zone development H. e ;

[0027] In the absence of drilling data on the surface, the fracture development height H2 of the current mine is calculated by the following formula:

[0028]

[0029] In the formula, M2 represents the current mining height, H1 represents the height of the fissure development in the adjacent mine, M1 represents the mining height of the adjacent mine, and c represents a constant. If the lithology is hard rock, c = 20-22; if the lithology is medium-hard rock, c = 25-27; if the lithology is soft rock, c = 28-30;

[0030] By using borehole peek photos or downhole TV photos, calculate the number of cracks N and the crack width per unit length; the crack width includes the first crack width d 90 , the second crack width d 50 , the third crack width d 25 ;

[0031] Based on the development height of each fracture zone, rock permeability, water-conducting fracture density, and average fracture width, a fracture field model of the entire working face is established using the linear interpolation method.

[0032] Furthermore, the slurry running height of the working face and / or goaf is calculated, including:

[0033] According to the setting time requirements and the requirements for solid waste disposal in the mining area, the type of mining grouting material is selected and the grouting material is prepared; among them, the grouting material particles D 90 Satisfaction: D 90 <0.2d 25 ; The liquid-to-solid ratio of the grouting material is 0.5-1.0; The slurry properties of the grouting material meet the following requirements: initial setting time>300min, viscosity<800mPa.s, 3-day setting strength>1.0MPa, 7-day setting strength>2.0MPa, and slurry setting shrinkage rate is less than 0.2;

[0034] The slurry rheology of the grouting material is characterized by a characterization model, and the characterization model is expressed as:

[0035]

[0036] In the formula, τ is the shear stress; τ0 is the yield stress; μ is the consistency coefficient; is the shear rate;

[0037] The running height is calculated by the following formula:

[0038]

[0039] In the formula, Δp is the grouting pressure difference, I is the grouting height, b is the crack width, and d is taken 90 , s is the intermediate variable (a function of the pulp running height I), t gel is the slurry coagulation time.

[0040] Furthermore, based on the rock formation characteristics, the model of the fracture field of the working face, and the slurry run height of the working face and / or the goaf, a comprehensive chart of the spatial relationship between rock formation, fracture, and slurry run height is drawn, including:

[0041] According to the set scale, the position of each rock layer and the height of the fracture zone H e , and slurry running height I are plotted on the same graph to form a comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height.

[0042] Further, based on the comprehensive chart of the spatial relationship between rock formation, fracture and slurry running height, the vertical rock formation that can be grouted is determined, including:

[0043] When water inrush occurs under natural conditions, select the natural grouting layer for grouting. The pore diameter D of the natural grouting layer is 90 Satisfaction:d 50 >5D 90 ;

[0044] If the grouting layer satisfies the first condition and the second condition at the same time, the grouting layer is determined to be a comprehensive grouting layer; wherein, the first condition is that the grouting layer is located above the grouting height, and the second condition is that the grouting layer is located within the fracture zone, or is located inside a naturally groutable layer.

[0045] Further, based on the model of the working face fracture field and the slurry running height of the working face and / or goaf, the tension area of ​​the overburden fracture zone of the working face is determined, including:

[0046] According to the characteristics of crack development and stress state, three areas formed in the horizontal direction of the mining working face are determined, namely the coal wall support area, stress recovery area, and re-compaction area;

[0047] Under the action of stress recovery, the crack width and crack permeability of the cracks in the re-compacted area are reduced;

[0048] The rock layers at both ends of the stress recovery zone are unevenly broken, cracks develop inside the rock mass, and the permeability increases to exceed the first threshold;

[0049] The rock layer in the coal wall support area is bent, internal cracks develop, and the permeability increases to below the first threshold;

[0050] The overburden fracture zone tension area is determined within the stress recovery area and the coal wall support area.

[0051] Further, based on the tension area of ​​the overburden fracture zone of the working face, the plane grouting range is determined, including:

[0052] When the post-mining drilling density exceeds the second threshold, the plane grouting range is directly determined based on the drilling detection situation;

[0053] When the post-mining drilling density is lower than the second threshold, the plane grouting range is determined according to the tension area of ​​the overburden fracture zone of the working face.

[0054] Furthermore, according to the determined vertical groutable rock layer and the plane grouting range, the grouting target area of ​​the reconstructed aquiclude is determined, including:

[0055] The intersection of the vertical groutable rock layer position and the plane grouting range is determined as the target area for grouting of the reconstructed aquiclude.

[0056] Further, based on the tension area of ​​the overburden fracture zone of the working face, determining the plane grouting range also includes:

[0057] If the grouting target area is located in the coal pillar support area and stress recovery area of ​​the working face opening eye, stop mining line, and the left and right coal walls of the two sides, then considering the influence of the rock formation movement angle, the plane grouting range is expanded outward, which is expressed as:

[0058] X=60~80+Ttanθ

[0059] Where X is the span of the grouting range above the coal wall, T is the distance between the grouting layer and the coal seam goaf, and θ is the rock movement angle.

[0060] The beneficial effects of this application are:

[0061] The present application determines the comprehensive spatial relationship map of strata-cracks-slurry run height and the tension area of ​​the overburden rock fracture zone at the working face through analysis of the overburden structure, analysis of the development characteristics of mining-induced fractures and calculation of the slurry run height in the goaf, and then optimizes the vertical groutable strata and the horizontal grouting range, thereby achieving the final determination of the grouting target area for the reconstructed aquiclude. This can increase the slurry diffusion radius while preventing slurry run underground and on the ground, thereby ensuring the grouting effect and the quality of the reconstructed aquiclude. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 An overall flow chart of a method for selecting target areas for grouting in a reconstructed aquiclude in a mining-induced fractured stratum provided in an embodiment of the present application;

[0063] Figure 2 A flowchart of an implementation of a method for optimizing a target area for grouting a water-blocking layer in a mining-induced fractured stratum provided in an embodiment of the present application;

[0064] Figure 3 A schematic diagram of a comprehensive diagram of the spatial relationship between rock formations, fractures and slurry height provided in an embodiment of the present application;

[0065] Figure 4 A schematic diagram for determining the plane grouting range provided in an embodiment of the present application. DETAILED DESCRIPTION

[0066] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0067] The specific implementation of the present application is further described in detail below in conjunction with the drawings and examples.

[0068] See also Figure 1, which is an overall flow chart of a method for optimizing target areas for grouting of reconstructed aquicludes in mining-induced fractured strata provided in an embodiment of the present application. An embodiment of the present application provides a method for optimizing target areas for grouting of reconstructed aquicludes in mining-induced fractured strata. The method draws a comprehensive map of the spatial relationship between strata-fractures-grouting height through steps such as overburden structure analysis, mining fracture development characteristics analysis, and working face / goaf area grouting height calculation, determines the tension area of ​​the overburden fracture zone of the working face, and then optimizes the vertical groutable rock strata and the planar grouting range, thereby achieving the final determination of the grouting target area for the reconstructed aquiclude.

[0069] For more information, see Figure 2 , is a flowchart of an implementation of a method for optimizing a target area for grouting a water-proof layer in a mining fractured stratum provided in an embodiment of the present application. The method for optimizing a target area for grouting a water-proof layer in a mining fractured stratum is specifically implemented through the following steps S100 to S800.

[0070] S100: Determine the rock formation characteristics based on the overburden structure analysis.

[0071] In this embodiment, the rock formation characteristics include lithology combination characteristics, aquiclude characteristics and aquifer pore structure characteristics.

[0072] In an exemplary embodiment, the lithology combination characteristics include the thickness, lithology, uniaxial compressive strength of different rock layers, the spatial combination relationship between rock layers, the lithology combination profiles of different working faces, and the overall compressive strength of the formation; the aquiclude characteristics include the spatial distribution characteristics of the aquifer and aquiclude; the aquiclude pore structure characteristics include the scale range, connectivity, and permeability of the pores and fractures of the rock formation. Step S100 specifically includes the following steps:

[0073] S101, lithology combination analysis: According to the geological and hydrogeological conditions of the mine, determine the thickness, lithology, uniaxial compressive strength (UCS) of different rock layers, and the spatial combination relationship between rock layers; based on the borehole columnar data, through the well profile analysis, establish a three-dimensional geological model of the mining area, and then through the slice analysis, obtain the lithology combination profile of different working faces. For sandstone and mudstone interbedded strata, the overall UCS of the stratum can be calculated according to the following formula:

[0074]

[0075] In the formula, w i is the lithology weight coefficient of the nth rock, where sandstone takes 0.4 and mudstone takes 0.6; M n is the rock layer thickness, UCS t is the overall compressive strength of the formation, UCS n is the uniaxial compressive strength of the nth rock.

[0076] S102, characteristics of aquicludes: based on lithological characteristics, determine aquifers and aquicludes; based on the three-dimensional geological model, determine the spatial distribution characteristics of aquifers and aquicludes. Aquifers are generally sand layers, loose rock layers, fractured clastic rocks, fractured weathering crust bedrock, etc., and aquicludes are generally loess layers, laterite layers, mudstones, complete siltstones, etc.

[0077] S103, Pore structure characteristics of aquifers: Based on the core data of mine drilling, the pore structure characteristics of aquifer rock samples are tested to determine the scale range, connectivity, and permeability of the pores and fractures in the rock formation.

[0078] S200, based on the analysis of the development characteristics of mining-induced fissures, a model of the working face fissure field is established.

[0079] In an exemplary embodiment, step S200 specifically includes the following steps:

[0080] S201, post-mining drilling exploration: Drill holes are arranged on the mined working face. The drilling positions are as follows: a row of drill holes are arranged on both sides of the coal wall where the working face is cut, with a spacing of 100 to 200 m (usually for a 300 m wide working face, 3 drill holes can be arranged, distributed in the middle and at both ends), and a drill hole is arranged at intervals of 200 to 300 m along the direction of the working face. During the drilling process, the height and scale of the cracks in the overburden after mining are observed.

[0081] S202, fracture height statistics: If the fracture develops to the surface, it can be directly observed from the surface and directly counted as the fracture zone development height H e If the fissures have not developed to the surface, the consumption of flushing fluid in the borehole will have a sudden change from top to bottom, and the consumption will be 3 to 5 times higher than the initial position to locate the height of the fissure zone H. e .

[0082] If there is no surface and no drilling data, it is necessary to estimate the height of the fissure development in the nearby mines. If the mining height of the adjacent mine is M1, the fissure development height of the adjacent mine is H1, and the current mine is mined at M2, then the fissure development height H2 can be approximately calculated as:

[0083]

[0084] In the formula, c represents a constant. If the lithology is hard rock, c=20-22; if the lithology is medium-hard rock, c=25-27; if the lithology is soft rock, c=28-30.

[0085] S203, fracture structure analysis: mainly through borehole peek photos or downhole TV photos, count the number of fractures per unit length N and the width d of the fractures. The fracture width statistics focus on recording three fracture widths, namely the first fracture width d 90 , the second crack width d50 , the third crack width d 25 In some embodiments, the subscripts of the three crack widths represent the development height of the crack.

[0086] S204, fracture field modeling: Based on the parameters such as the development height of the fracture zone of each borehole, the permeability coefficient of the rock formation, the development density of water-conducting fractures, the average width of the fractures, etc., a model of the fracture field of the entire working face is established based on the linear interpolation method to lay the foundation for the implementation of subsequent steps.

[0087] S300, calculating the slurry running height of the working face and / or goaf.

[0088] In an exemplary embodiment, step S300 specifically includes the following steps:

[0089] S301, grouting material selection: according to the setting time requirements, mining area solid waste disposal requirements, etc., select the type of mining grouting material and prepare the grouting material. To ensure the injectability of the slurry, the grouting material particles D 90 Crack width d 25 Need to meet: D 90 <0.2d 25 The liquid-to-solid ratio of the grouting material is usually selected to be 0.5-1.0, and the design is based on the setting time and setting strength. Under normal circumstances, the slurry performance should meet the following requirements: initial setting time>300min, viscosity<800mPa.s, 3d setting strength>1.0MPa, 7d setting strength>2.0MPa, and the slurry setting shrinkage should be less than 0.2.

[0090] S302, Rheological properties of slurry: Generally, the rheological properties of grouting materials are characterized by the Bingham model, that is: In the formula: τ—shear stress; τ0—yield stress; μ—consistency coefficient; —Shear rate.

[0091] S303, calculation of slurry run height: The flow from the grouting layer to the goaf is considered as one-dimensional flow, and its slurry run height can be calculated by the following formula:

[0092]

[0093] In the formula, Δp is the grouting pressure difference, I is the grouting height, b is the crack width, and d is taken 90 , s is the intermediate variable (a function of the pulp running height I), t gel is the slurry coagulation time.

[0094] S400, based on the rock formation characteristics, the model of the working face fracture field and the slurry run height of the working face and / or goaf, draws a comprehensive chart of the spatial relationship between rock formation-fracture-slurry run height.

[0095] In an exemplary embodiment, the positions of various rock layers, the height of fracture zone development He, and the calculation result of slurry run height I are plotted on the same map according to a certain scale to form a comprehensive map of the spatial relationship between rock layer, fracture, and slurry run height. Figure 3 , which is a schematic diagram of the comprehensive spatial relationship diagram of rock layer-crack-slurry running height provided in an embodiment of the present application.

[0096] S500, based on the comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height, determine the vertical rock layer that can be grouted.

[0097] In an exemplary embodiment, step S500 specifically includes the following steps:

[0098] S501, Determination of the natural grouting layer: If the fracture zone is small in height and the formation permeability is high, resulting in water inrush under natural conditions, the natural grouting layer can be selected for grouting. The pore diameter D of the grouting layer is required to be 90 And the second crack opening satisfies: d 50 >5D 90 .

[0099] In this embodiment, when determining whether water inrush occurs under natural conditions according to the fracture zone development height and the formation permeability, the fracture zone development height threshold and the formation permeability coefficient threshold can be set to determine. For example, if the fracture zone development height is less than the fracture zone development height threshold and the formation permeability coefficient is greater than the formation permeability coefficient threshold, it is determined that water inrush will occur under natural conditions. If the fracture zone development height is less than the fracture zone development height threshold and the formation permeability coefficient is greater than the formation permeability coefficient threshold, it is determined that water inrush will not occur under natural conditions. Then, the selection of comprehensive grouting layers can be performed by executing the following step S502. Or, when there are multiple natural grouting layers, step S502 is also executed to further select multiple natural grouting layers, so as to determine the vertical grouting rock layer. It should be noted that the fracture zone development height threshold and the formation permeability coefficient threshold are different under different geographical conditions, such as different rock properties. The numerical values ​​of the above two thresholds are not specifically limited in this embodiment.

[0100] S502, comprehensive grouting layer determination: The grouting layer needs to meet two conditions at the same time. On the one hand, the grouting layer should be located above the grouting height. On the other hand, the grouting layer should be located within the fracture zone or inside the natural grouting layer.

[0101] In this embodiment, the grouting layer that satisfies both conditions is the determined vertical groutable rock layer.

[0102] S600. Determine the tensile zone of the overlying strata fracture zone of the working face based on the model of the fracture field of the working face and the grout leakage height of the working face and / or the goaf.

[0103] In an exemplary embodiment, step S600 specifically includes:

[0104] S601. According to the characteristics of fracture development and stress state, the mined working face mainly has a coal wall support area, a stress recovery area, and a recompaction area in the lateral direction.

[0105] Among them, in the recompaction area, under the action of stress recovery, the fracture width and fracture permeability decrease.

[0106] In the stress recovery area, this part of the rock stratum is located at the junction of the coal wall and the goaf, and as a whole, it migrates and breaks towards the goaf under the action of gravity. However, due to the different bearing capacities of the coal wall and the goaf, the two ends of the rock stratum in this area break unevenly, fractures develop inside the rock mass, and the permeability increases significantly.

[0107] The state of the rock stratum in the coal wall support area is similar to that of the caving - support area. It is affected by the abutment pressure. At the same time, due to the deformation of the rock stratum in the fracture - recovery area, stress is transmitted in the horizontal direction in the fracture - support area, and this part of the rock stratum bends accordingly, fractures develop inside, and the permeability increases. And although this part of the rock stratum is relatively intact as a whole, it cannot be gradually compacted like the rock stratum in the goaf under the action of stress recovery. Therefore, although the increase in permeability of this area of the rock stratum is not significant, the fractures in this part will exist for a long time and are the main channels for groundwater seepage.

[0108] It should be noted that both the stress recovery area and the coal wall support area show an increase in permeability. Therefore, in order to distinguish the stress recovery area and the coal wall support area, when using the permeability coefficient to characterize permeability, based on the average permeability coefficient k, a first threshold a is set. This first threshold k1 is the growth rate of the set permeability coefficient k1 relative to the average permeability coefficient k, that is, a=(k1 - k) / k. The actual permeability coefficient of the rock stratum is k2. When k2>k, the corresponding growth rate is b=(k2 - k) / k. If b>a, it means that the permeability increases significantly, and this rock stratum is located in the stress recovery area. If b<a, it means that the increase in permeability is not significant, and this rock stratum is located in the coal wall support area. If k2≤k, it means that the permeability of the rock stratum has not increased, and the rock stratum is not in the stress recovery area and the coal wall support area, and is probably located in the recompaction area.

[0109] S602. Determine the tensile zone of the overlying strata fracture zone within the stress recovery area and the coal wall support area.

[0110] S700. Determine the plane grouting range based on the tensile zone of the overlying strata fracture zone of the working face.

[0111] In an exemplary embodiment, step S700 specifically includes the following steps:

[0112] S701, for the case where the borehole density detected after mining is relatively dense, the plane grouting range can be directly determined based on the borehole detection situation. Within the grouting range, the pore diameter D of the grouting layer 90 And the second crack opening satisfies: d 50 >5D 90 .

[0113] S702: When the drilling density detected after mining is not too dense, the plane grouting range is determined according to the tension area of ​​the overburden fracture zone of the working face.

[0114] In this embodiment, the distinction between relatively dense and less dense drilling density can be determined based on a second threshold, where the second threshold can be the number of drill holes or the number of drill holes per unit area. If the drilling density detected after mining is greater than the second threshold, it is determined to be a relatively dense situation and step S701 is executed. Otherwise, it is determined to be a less dense situation and step S702 is executed.

[0115] In an exemplary embodiment, see Figure 4 , which is a schematic diagram of determining the plane grouting range provided in the embodiment of the present application. According to the distribution characteristics of the mainstream water channel of a single working face, the grouting target area is located in the coal pillar support area and stress recovery area on the left and right sides of the working face cutting eye, the stop mining line, and the two sides of the coal wall, with a width of about 60 to 80m on both sides. Considering the influence of the rock formation movement angle θ, the grouting range should be expanded outward by a certain range, which is:

[0116] X=60~80+Ttanθ

[0117] Where X is the span of the grouting range above the coal wall, and T is the distance between the grouting layer and the coal seam goaf.

[0118] S800: Determine the target area for grouting the reconstructed aquiclude according to the determined vertical groutable rock layer and the plane grouting range.

[0119] In this embodiment, based on the results of step S500 and step S700, the intersection range of the vertical grouting layer and the plane grouting range is determined as the target area for grouting the reconstructed aquiclude.

[0120] The above implementation modes are only used to illustrate the present application, and are not intended to limit the present application. Ordinary technicians in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions also belong to the scope of the present application, and the scope of patent protection of the present application shall be limited by the claims.

Claims

1. A method for optimizing target areas for grouting in reconstructed impermeable layers in mining-induced fractured strata, characterized in that: The method comprises: Based on the analysis of the overburden structure, the rock formation characteristics are determined, wherein the rock formation characteristics include the lithology combination characteristics, the aquiclude characteristics and the aquifer pore structure characteristics; Based on the analysis of the development characteristics of mining-induced fissures, a model of the fissure field in the working face is established; Calculate the slurry run height of the working face and / or goaf; Based on the rock formation characteristics, the model of the fracture field of the working face, and the slurry run-off height of the working face and / or the goaf, a comprehensive chart of the spatial relationship between rock formation, fracture, and slurry run-off height is drawn; Based on the comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height, determine the vertical rock layer that can be grouted; Determine the tension area of ​​the overburden fracture zone of the working face based on the model of the working face fracture field and the slurry running height of the working face and / or goaf; Based on the tension area of ​​the overburden fracture zone of the working face, determining the plane grouting range; The target area for grouting of the reconstructed aquiclude is determined based on the determined vertical groutable rock layer and the horizontal grouting range.

2. The method for optimizing the target area of ​​grouting for recreating the water-proof layer in the mining-induced fractured stratum according to claim 1, characterized in that: The lithology combination characteristics include the thickness, lithology, uniaxial compressive strength of different rock layers, the spatial combination relationship between rock layers, the lithology combination profiles of different working faces, and the overall compressive strength of the formation; the aquiclude characteristics include the spatial distribution characteristics of aquifers and aquicludes; The pore structure characteristics of the aquifer include the scale range, connectivity and permeability of the pores and fractures in the rock formation; Based on the analysis of the overburden structure, the rock formation characteristics are determined, including: According to the geological and hydrogeological conditions of the mine, the thickness, lithology, uniaxial compressive strength of rocks and the spatial combination relationship between rock layers are determined; based on the borehole columnar data, through the well profile analysis, a three-dimensional geological model of the mining area is established, and through the slice analysis, the lithology combination profiles of different working faces are obtained. For the interbedded sandstone and mudstone strata, the overall compressive strength of the strata is calculated by the following formula: In the formula, w i is the lithology weight coefficient of the nth rock, where sandstone takes 0.4 and mudstone takes 0.6; M n is the rock layer thickness, UCS t is the overall compressive strength of the formation, UCS n is the uniaxial compressive strength of the nth rock; Based on the lithological characteristics, aquifers and aquicludes are determined, and based on the three-dimensional geological model, the spatial distribution characteristics of aquifers and aquicludes are determined; Based on the core data of mine drilling, the pore structure characteristics of the aquifer rock samples are tested to determine the scale range, connectivity and permeability coefficient of the pores and fractures in the rock formation.

3. The method for optimizing the target area of ​​grouting for recreating the aquiclude in mining-induced fractured strata according to claim 1, characterized in that: Based on the analysis of the development characteristics of mining-induced fissures, a model of the fissure field of the working face is established, including: Drill holes are arranged on the working face that has been mined. The drilling positions are as follows: a row of drill holes is arranged on both sides of the coal wall where the working face is cut, with a spacing of 100 to 200 meters, and a drill hole is arranged at intervals of 200 to 300 meters along the direction of the working face. During the drilling process, the height and scale of the crack development in the overburden after mining are observed. If the fissure develops to the surface, the height H of the fissure zone can be obtained by directly observing from the surface. e If the fissures have not developed to the surface, the consumption of flushing fluid in the borehole will have a sudden change from top to bottom. The initial position where the consumption is 3 to 5 times higher will be located to determine the height of the fissure zone development H. e ; In the absence of drilling data on the surface, the fracture development height H2 of the current mine is calculated by the following formula: In the formula, M2 represents the current mining height, H1 represents the height of the fissure development in the adjacent mine, M1 represents the mining height of the adjacent mine, and c represents a constant. If the lithology is hard rock, c = 20-22; if the lithology is medium-hard rock, c = 25-27; if the lithology is soft rock, c = 28-30; By using borehole peek photos or downhole TV photos, calculate the number of cracks N and the crack width per unit length; the crack width includes the first crack width d 90 , the second crack width d 50 , the third crack width d 25 ; Based on the development height of each fracture zone, rock permeability, water-conducting fracture density, and average fracture width, a fracture field model of the entire working face is established using the linear interpolation method.

4. The method for optimizing the target area of ​​grouting in the reconstructed impermeable layer of mining fractured strata according to claim 3, characterized in that: Calculate the slurry run height in the working face and / or goaf, including: According to the setting time requirements and the requirements for solid waste disposal in the mining area, the type of mining grouting material is selected and the grouting material is prepared; among them, the grouting material particles D 90 Satisfaction: D 90 <0.2d 25 ; The liquid-to-solid ratio of the grouting material is 0.5-1.0; The slurry properties of the grouting material meet the following requirements: initial setting time>300min, viscosity<800mPa.s, 3-day setting strength>1.0MPa, 7-day setting strength>2.0MPa, and slurry setting shrinkage rate is less than 0.2; The slurry rheology of the grouting material is characterized by a characterization model, and the characterization model is expressed as: In the formula, τ is the shear stress; τ0 is the yield stress; μ is the consistency coefficient; is the shear rate; The running height is calculated by the following formula: In the formula, Δp is the grouting pressure difference, I is the grouting height, b is the crack width, s is the intermediate variable, and t gel is the slurry coagulation time.

5. The method for optimizing the target area of ​​grouting for recreating the impermeable layer in the mining-induced fractured stratum according to claim 4, characterized in that: Based on the rock formation characteristics, the model of the working face fracture field and the slurry run height of the working face and / or goaf, a comprehensive chart of the spatial relationship between rock formation, fracture and slurry run height is drawn, including: According to the set scale, the position of each rock layer and the height of the fracture zone H e , and slurry running height I are plotted on the same graph to form a comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height.

6. The method for optimizing the target area of ​​grouting for recreating the impermeable layer in mining-induced fractured strata according to claim 5, characterized in that: Based on the comprehensive chart of the spatial relationship between rock layer, fracture and slurry running height, the vertical rock layer that can be grouted is determined, including: When water inrush occurs naturally, select the natural grouting layer for grouting. The pore diameter D of the natural grouting layer is 90 Satisfaction:d 50 >5D 90 ; If the grouting layer satisfies the first condition and the second condition at the same time, the grouting layer is determined to be a comprehensive grouting layer; wherein, the first condition is that the grouting layer is located above the grouting height, and the second condition is that the grouting layer is located within the fracture zone, or is located inside a naturally groutable layer.

7. The method for optimizing the target area of ​​grouting in the reconstructed impermeable layer of mining fractured strata according to claim 5, characterized in that: Based on the model of the working face fracture field and the slurry running height of the working face and / or goaf, the tension area of ​​the overburden fracture zone of the working face is determined, including: According to the characteristics of crack development and stress state, three areas formed in the horizontal direction of the mining working face are determined, namely the coal wall support area, stress recovery area, and re-compaction area; Under the action of stress recovery, the crack width and crack permeability of the cracks in the re-compacted area are reduced; The rock layers at both ends of the stress recovery zone are unevenly broken, cracks develop inside the rock mass, and the permeability increases to exceed the first threshold; The rock layer in the coal wall support area is bent, internal cracks develop, and the permeability increases to below the first threshold; The overburden fracture zone tension area is determined within the stress recovery area and the coal wall support area.

8. The method for selecting target areas for grouting in recreating aquiclude in mining-induced fractured strata as claimed in claim 7, characterized in that: Based on the tensile area of ​​the overburden fracture zone of the working face, the plane grouting range is determined, including: When the post-mining drilling density exceeds the second threshold, the plane grouting range is directly determined based on the drilling detection situation; When the post-mining drilling density is lower than the second threshold, the plane grouting range is determined according to the tension area of ​​the overburden fracture zone of the working face.

9. The method for optimizing the target area of ​​grouting in the reconstructed impermeable layer of mining fractured strata according to claim 8, characterized in that: According to the determined vertical groutable rock layer and plane grouting range, the grouting target area of ​​the reconstructed aquiclude is determined, including: The intersection of the vertical groutable rock layer position and the plane grouting range is determined as the target area for grouting of the reconstructed aquiclude.

10. The method for selecting target areas for grouting in recreating aquiclude in mining-induced fractured strata as claimed in claim 9, characterized in that: Based on the tensile area of ​​the overburden fracture zone of the working face, determining the plane grouting range also includes: If the grouting target area is located in the coal pillar support area and stress recovery area of ​​the working face opening eye, stop mining line, and the left and right coal walls of the two sides, then considering the influence of the rock formation movement angle, the plane grouting range is expanded outward, which is expressed as: X=60~80+Ttanθ Where X is the span of the grouting range above the coal wall, T is the distance between the grouting layer and the coal seam goaf, and θ is the rock movement angle.

Images