Gob underground space model-based gangue filling target area prediction method and system

Abstract

This application discloses a method and system for predicting target areas for gangue filling based on an underground space model of a goaf. The method includes: acquiring mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry; registering various types of data to a unified spatial coordinate system and dividing them into three-dimensional units, determining the underground space state, the volume that can be contained, and the effective spatial scale, establishing spatial connection relationships, and forming an underground space model of the goaf; mapping candidate borehole trajectories and final borehole positions to the model, calculating slurry flow rate, the proportion of particles that can pass through, and the amount of particles retained in time intervals, and updating the effective spatial scale accordingly; determining the reachable range of the solid phase based on the cumulative solid volume received by each three-dimensional unit, screening candidate boreholes in combination with inlet pressure, liquid phase escape, and borehole construction constraints, determining the target area for gangue filling, and outputting the borehole trajectory and final borehole coordinates.

Description

Technical Field

[0001] This application relates to the field of coal mine goaf backfilling technology, specifically to a method and system for predicting target areas for backfilling based on an underground space model of the goaf. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining. Crushing and slurrying the gangue, then transporting it through surface boreholes to underground goaf areas for backfilling, can reduce gangue accumulation on the surface and, to some extent, control residual deformation and surface subsidence in the goaf. Before implementing gangue backfilling, it is necessary to determine a reasonable borehole termination location and backfilling range based on the goaf's geological conditions, internal spatial distribution, and slurry transport conditions.

[0003] Current goaf backfilling designs typically rely on mining engineering data, geophysical survey results, or limited verification borehole data to determine the goaf boundaries, caving zone extent, and remaining space, and then combine this with experience to determine the location of grouting holes. However, goaf areas usually contain loose caving bodies, residual cavities, inter-layer separation, coal pillars, and fracture channels simultaneously, and the accommodateable volume and connectivity conditions vary significantly between different areas. Single survey data is insufficient to accurately reflect the actual state of the underground space, and the results revealed by local boreholes cannot directly represent the entire goaf.

[0004] Furthermore, the migration of gangue slurry in underground spaces is not only affected by spatial connectivity but also by slurry concentration, rheological properties, particle size distribution, and channel clearance. Larger particles, when trapped in narrow channels, further reduce the slurry flow space, altering subsequent flow rate, pressure, and the reach of the solid phase. Existing methods typically treat underground channels as fixed, interconnected spaces, failing to reflect the dynamic blockage process caused by particle retention. They also fail to comprehensively consider inlet pressure, liquid escape, protection of aquifer areas, and drilling conditions, potentially leading to discrepancies between predicted filling range and actual solid phase reach, unreasonable borehole layout, or difficulty in pre-identifying grouting risks. Summary of the Invention

[0005] In view of this, this disclosure proposes a method and system for predicting target areas for gangue filling based on an underground space model of goaf areas.

[0006] According to one aspect of this disclosure, a method for predicting target areas for gangue filling based on an underground space model of a goaf is provided, including:

[0007] Acquire mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry;

[0008] The mining engineering data, the multi-source detection data, and the borehole verification data are registered to a spatial coordinate system and divided into three-dimensional units. The underground space status, accommodating volume, and effective spatial scale of the three-dimensional units are determined. Spatial connection relationships are established based on the connection status, blocking conditions, and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf.

[0009] The candidate borehole trajectory and final borehole location are mapped to the underground space model of the goaf. Based on the particle size distribution data, the slurry parameters and the spatial connectivity, the slurry flow rate, the proportion of passable particles and the particle retention are calculated time-by-time. The effective spatial scale is updated according to the particle retention, and the calculation is repeated based on the updated effective spatial scale until the calculation termination condition is met.

[0010] The solid phase reachable range is determined based on the cumulative solid volume received by the three-dimensional unit. Candidate boreholes are screened based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The solid phase reachable range of the screened candidate boreholes is determined as the gangue filling target area, and the borehole trajectory and final borehole coordinates are output.

[0011] In one possible implementation, the multi-source detection data includes 3D seismic data, transient electromagnetic data, and micromotion detection data; the predetermined goaf boundary is determined based on the mining engineering data; the fault boundary, interlayer separation range, and spatial extension direction are determined based on the 3D seismic data; the water-bearing anomaly range is determined based on the transient electromagnetic data, and the protected water-bearing area is identified from it; the degree of compaction is determined based on the micromotion detection data, and the accommodateable volume is corrected based on the degree of compaction; the underground space state, effective spatial scale, and accommodateable volume of the 3D unit traversed by the borehole are locally corrected based on the borehole verification data.

[0012] In one possible implementation, the underground space state includes intact rock strata units, coal pillar units, loose caving bodies units, residual cavities units, interlayer separation units, and uncertain units; the intact rock strata units and the coal pillar units are designated as blocking units, the loose caving bodies units, the residual cavities units, and the interlayer separation units are incorporated into the establishment of the spatial connection relationship, and the uncertain units are updated after obtaining supplementary borehole verification data.

[0013] In one possible implementation, the effective spatial scale is determined as follows: for cavities or fractures directly observed by downhole television, the effective spatial scale is measured based on scale-marked images; for drilling fluid leakage sections, the effective spatial scale is back-calculated based on the thickness of the leakage section, the leakage per unit time, and flow tests on similar rock samples with fractures; for areas not penetrated by boreholes, spatial interpolation is performed based on the results of 3D seismic interpretation and the effective spatial scale of adjacent boreholes, and the lower limit of the interpolation interval is taken.

[0014] In one possible implementation, the spatial connection relationship is established according to the following conditions: adjacent three-dimensional units have a common surface or are connected through an identified fracture, there is no blocking unit at the common surface or connection position, and the directional difference between adjacent three-dimensional units with spatial extension direction does not exceed the allowable directional difference; the allowable directional difference is determined by the directional difference between the three-dimensional seismic interpretation direction of the borehole verification position and the downhole television observation direction.

[0015] In one possible implementation, by setting up fracture specimens with different openings and injecting test slurry with the same particle size distribution as the gangue slurry to be predicted, the specimen opening when the orifice pressure begins to rise continuously under continuous injection conditions and the maximum particle size that stably passes through at the specimen opening are recorded, and a particle passing correction coefficient is determined based on the ratio of the two; the critical particle size is determined based on the effective spatial scale and the particle passing correction coefficient, and the proportion of particles that can pass through is obtained from the cumulative sieving curve corresponding to the particle size distribution data.

[0016] In one possible implementation, the slurry parameters include mass concentration, solid density, liquid density, plastic viscosity, and yield stress. The solid volume fraction is determined based on the mass concentration, solid density, and liquid density. Viscous flow resistance and yield pressure difference are determined based on the plastic viscosity, yield stress, and the connection length, connection width, and effective spatial scale corresponding to the spatial connection relationship. The slurry flow rate is solved by combining the viscous flow resistance, the yield pressure difference, the pressure difference between adjacent three-dimensional elements, and the flow conservation relationship of the three-dimensional elements. The proportion of non-passing particles is determined based on the proportion of passable particles, and the particle retention is determined based on the slurry flow rate, the solid volume fraction, the calculation time step, and the proportion of non-passing particles. The equivalent deposition area is determined based on the connection width and the deposition zone length calibrated by the fracture flow test. The effective spatial scale is reduced according to the particle retention and the equivalent deposition area. The calculation time step is determined based on the minimum remaining accommodative volume in the three-dimensional elements involved in the calculation and the inlet slurry flow rate.

[0017] In one possible implementation, the calculation termination condition includes any of the following conditions: the inlet pressure reaches the allowable inlet pressure, all connectable spaces corresponding to the candidate borehole have no remaining accommodating volume, or the cumulative injection volume reaches the planned injection volume for a single borehole; the allowable inlet pressure is the minimum value among the allowable outlet pressure of the filling pump, the allowable pressure of the surface pipeline, the allowable pressure of the borehole casing, and the formation fracturing pressure corrected by a safety factor, wherein the safety factor is determined based on the dispersion of the formation fracturing pressure obtained from the stepped injection test and the error of the pressure sensor, and the inlet pressure not exceeding the allowable inlet pressure is used as the inlet pressure constraint.

[0018] In one possible implementation, the solid phase reachable range is formed by 3D units where the cumulative received solid volume exceeds the solid volume tolerance, and the liquid phase migration range is formed by spatial connections where there is liquid flow and the solid flow is lower than the solid flow tolerance, along with their subsequent 3D units. The solid volume tolerance and the solid flow tolerance are determined by successively reducing the corresponding tolerances until the total volume change of the solid phase reachable range falls within the volume error range of the goaf underground space model after further reduction. The volume error range is determined based on geophysical boundary position error, grid size, and borehole verification error.

[0019] According to another aspect of this disclosure, a target area prediction system for gangue filling based on a goaf underground space model is provided, comprising:

[0020] The data acquisition module is used to acquire mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry;

[0021] The model building module is used to register the mining engineering data, the multi-source detection data and the borehole verification data to the spatial coordinate system and divide them into three-dimensional units. It determines the underground space status, accommodating volume and effective spatial scale of the three-dimensional units, and establishes spatial connection relationships based on the connection status, blocking conditions and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf.

[0022] The migration calculation module is used to map the candidate borehole trajectory and the final borehole position to the underground space model of the goaf. Based on the particle size distribution data, the slurry parameters and the spatial connectivity, it calculates the slurry flow rate, the proportion of passable particles and the particle retention amount in time intervals. It updates the effective spatial scale according to the particle retention amount and repeats the calculation based on the updated effective spatial scale until the calculation termination condition is met.

[0023] The target area determination module is used to determine the reachable range of the solid phase based on the cumulative solid volume received by the three-dimensional unit. It screens candidate boreholes based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The reachable range of the solid phase of the screened candidate boreholes is determined as the target area for gangue filling, and the borehole trajectory and final borehole coordinates are output.

[0024] This application unifies the registration of mining engineering data, multi-source detection data, and borehole verification data to the same spatial coordinate system. It uses three-dimensional units to characterize different underground spatial states, accommodating volumes, and effective spatial dimensions within the goaf. Spatial connections are established based on the connection and obstruction conditions of adjacent units, allowing the spatial structure within the goaf suitable for slurry transport to be calculated using a unified model. Based on this, and considering the particle size distribution and slurry parameters of the gangue slurry, the slurry flow rate, particle throughput ratio, and particle retention are calculated time-by-time. The effective spatial dimensions are updated using the particle retention results, reflecting the actual process of gradual narrowing of local channels and changes in the solid phase transport range during slurry injection. The solid phase reachable range determined in this way can accurately correspond to the actual gangue filling area. Furthermore, by combining inlet pressure, liquid phase escape, and borehole construction conditions to screen candidate boreholes, the risks of improper borehole location selection, excessive injection pressure, and slurry entering protected areas can be reduced, providing a reliable basis for determining the gangue filling target area, borehole trajectory, and final borehole location.

[0025] Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0026] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this disclosure together with the specification and serve to explain the principles of this disclosure.

[0027] Figure 1 A flowchart is shown below illustrating a method for predicting target areas for gangue filling based on an underground space model of a goaf, according to an embodiment of this disclosure.

[0028] Figure 2 A flowchart illustrating the formation of a goaf underground space model according to an embodiment of the present disclosure is shown.

[0029] Figure 3 A flowchart illustrating the determination of the reachable range of the solid phase according to an embodiment of the present disclosure is shown.

[0030] Figure 4 A flowchart illustrating the process of screening candidate boreholes and determining the target area for gangue filling according to an embodiment of the present disclosure is shown.

[0031] Figure 5 This diagram illustrates the structure of a target area prediction system for gangue filling based on an underground space model of a goaf, according to an embodiment of the present disclosure.

[0032] Figure 6 A schematic diagram of the structure of an electronic device according to an embodiment of the present disclosure is shown. Detailed Implementation

[0033] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise. The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0034] This embodiment is applicable to scenarios where coal gangue slurry is injected into old goaf areas using surface vertical wells or directional drilling, and the target area for gangue filling is predicted before formal borehole layout and grouting. The study area should have mining engineering data, 3D seismic data, transient electromagnetic data, and micromotion detection data, as well as at least one type of borehole verification data, including drilling fluid loss records, downhole television results, or existing verification borehole data. During implementation, particle size distribution data, mass concentration, solid density, liquid density, plastic viscosity, and yield stress of the gangue slurry are also obtained. All data use the same mining area engineering coordinate system, and the computing equipment can be an engineering server configured with a multi-core processor and at least 64GB of memory.

[0035] The implementation process of the method described in this application will be described in detail below with reference to specific embodiments. It should be noted that this embodiment is only used to explain this application and is not intended to limit the scope of protection of this application. Conventional adjustments or substitutions of each step by those skilled in the art without departing from the concept of this application should be included in the scope of protection of this application.

[0036] Figure 1 A flowchart illustrating a method for predicting target areas for gangue filling based on a goaf underground space model, according to an embodiment of this disclosure, is shown. Figure 1 As shown, the method may include:

[0037] In step S11, mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry are obtained.

[0038] In one embodiment, the data processing program reads mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry. Mining engineering data includes working face boundaries, roadway boundaries, coal pillar boundaries, coal seam roof elevation, coal seam floor elevation, mining thickness, mining time, prohibited drilling areas, and known aquifer boundaries; 3D seismic data includes reflection interfaces, fault locations, attribute anomaly ranges, and interpreted spatial extension directions; transient electromagnetic data includes 3D resistivity or apparent resistivity data; micromotion detection data includes 3D shear wave velocity data; and borehole verification data includes borehole coordinates, borehole inclination, azimuth, depth, drilling speed, drilling fluid leakage start and end depths, leakage per unit time, and downhole television results.

[0039] During spatial registration, all types of data are first converted to the same mining area engineering coordinate system. Then, the goaf and its overlying area are used as the modeling boundary to divide the space into three-dimensional units. A three-dimensional unit refers to the smallest computational volume divided according to fixed length, width, and height within a unified spatial coordinate system. Each three-dimensional unit has a unique spatial index.

[0040] The length, width, and height of the 3D unit are determined based on the modeling area scale, the spatial resolution of multi-source detection data, the spatial distribution of borehole verification data, and the minimum spatial variation scale of the underground space to be identified. Specifically, the grid size along the strike and dip of the working face is limited to the ability to stably identify fracture boundaries, residual cavity boundaries, and other planar spatial variations. The grid size along the elevation direction is limited to the ability to stably identify vertical variations in coal seam thickness, interlayer separation, and borehole leakage sections. The grid size should not be significantly smaller than the effective spatial resolution of the corresponding detection data to prevent false details exceeding the resolution of the original data through spatial interpolation. For areas with fractures, residual cavities, interlayer separation, or rapidly changing effective spatial scales, the grid size can be reduced within the range that meets the corresponding data resolution requirements. After the initial grid is determined, the grid size is gradually reduced, and effective spatial scale interpolation, slurry transport, and particle retention calculations are repeatedly performed. When the change in the total volume of the solid phase obtained after further reducing the grid size falls within the volume error range of the underground space model of the goaf, and the solid connection state of the main spatial relationships remains unchanged, the grid size before further reduction is adopted; otherwise, the grid size continues to be reduced. In this way, the appropriate grid size is determined for goafs of different sizes and geological complexities based on their actual data resolution and the convergence of calculation results.

[0041] For example, the area to be predicted is 600m long along the strike of the working face, 300m wide along the dip direction, and 60m thick along the elevation direction. A 5m grid is used along the strike and dip directions, and a 2m grid is used along the elevation direction, forming 120×60×30 three-dimensional elements. Three-dimensional seismic data, transient electromagnetic data, and micromotion detection data are interpolated to the center of the three-dimensional elements according to their respective sampling locations. The borehole trajectory is calculated segment by segment based on the borehole opening coordinates, borehole inclination, azimuth, and depth, and a correspondence is established with the three-dimensional elements traversed.

[0042] Among them, 3D seismic data is used to determine fault boundaries, interlayer separation ranges, and spatial extension directions; transient electromagnetic data is used to determine the range of water-bearing anomalies and, in conjunction with known aquifer boundaries, to determine protected aquifer areas; micromotion data is used to determine the degree of compaction and, based on the degree of compaction, to correct the containment volume. Borehole verification data is used to prioritize the correction of the 3D elements actually traversed by the borehole, with the correction range limited to the 3D elements containing the borehole trajectory and adjacent 3D elements matching the borehole observation resolution, avoiding the direct extension of local measured results to the entire working face.

[0043] In step S12, the mining engineering data, the multi-source detection data, and the borehole verification data are registered to the spatial coordinate system and divided into three-dimensional units. The underground space status, accommodating volume, and effective spatial scale of the three-dimensional units are determined. Spatial connection relationships are established based on the connection status, blocking conditions, and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf.

[0044] Specifically, Figure 2 A flowchart illustrating the formation of an underground space model in a goaf area according to an embodiment of this disclosure is shown. Figure 2 As shown, in step S1201, the underground space status and the volume that can be contained are determined.

[0045] In one embodiment, each three-dimensional unit represents the underground space state. The underground space state includes intact rock strata units, coal pillar units, loose caving body units, residual cavity units, interlayer separation units, and indeterminate units. Intact rock strata units represent spaces where both exploration and mining data indicate continuous rock mass; coal pillar units represent retained coal seams as indicated by mining data; loose caving body units represent spaces composed of blocky rock masses and their interstices after roof collapse; residual cavity units represent continuous spaces not occupied by collapsed rock blocks; interlayer separation units represent thin-layered spaces formed after the separation of adjacent rock strata interfaces; and indeterminate units represent areas whose spatial state cannot be uniquely determined by existing data.

[0046] In this study, intact rock strata units and coal pillar units are designated as blocking units and do not participate in slurry reception or the establishment of spatial connectivity. Loose caving units, residual cavity units, and interlayer separation units are included in subsequent spatial connectivity calculations. Uncertain units retain all original data and will be updated after supplementary borehole verification data is obtained.

[0047] For loose, collapsed mass units, the initial porosity is calculated based on the fragmentation coefficient of the corresponding roof rock:

[0048]

[0049] in, Indicates the first The initial porosity of each three-dimensional unit This represents the fragmentation coefficient of the corresponding rock. The fragmentation coefficient is obtained through indoor fragmentation and deposition tests on similar roof rocks. During the test, the solid volume of the rock sample before fragmentation and the total volume after natural deposition are measured respectively. The ratio of the total volume of natural deposition to the solid volume is used as the fragmentation coefficient. The initial accommodative volume of a three-dimensional element is obtained by multiplying the geometric volume of the three-dimensional element by the initial porosity.

[0050] For example, if a three-dimensional unit has dimensions of 5m × 5m × 2m and a geometric volume of 50m³, corresponding to a rock fragmentation coefficient of 1.25, then the initial porosity is 0.20, and the initial accommodative volume is 10m³. The accommodative volume of residual void units is determined based on the boundaries of downhole television and 3D seismic interpretation, as well as the borehole penetration height; the accommodative volume of interlayer separation units is determined by the product of the interlayer separation degree and the planar area of ​​the three-dimensional unit.

[0051] When micro-motion detection data indicates that the compaction degree of a loose, collapsed body unit is higher than that of the adjacent verification area, the initial acceptable volume is corrected by using the correspondence between the unit volume leakage and the velocity anomaly amplitude in the verification area. To establish this correspondence, the verification borehole data are grouped according to the velocity anomaly amplitude interval, the median of the unit volume leakage in each group is calculated, and then the medians of adjacent groups are linearly interpolated. For example, if the velocity anomaly amplitude in the verification area increases by 20%, the median of the unit volume leakage decreases by 15%, then the initial acceptable volume of the three-dimensional unit within the same velocity anomaly amplitude range is multiplied by 0.85.

[0052] In step S1202, the effective spatial scale is determined. The effective spatial scale refers to the minimum clearance size that controls the passage of slurry particles between adjacent three-dimensional units, and the unit is m or mm. For cavities or fractures directly observed by downhole television, the effective spatial scale is measured based on the scaled images; for drilling fluid loss sections, the effective spatial scale is calculated back based on the thickness of the loss section, the loss per unit time, and the flow test of similar rock samples with fractures; for areas not penetrated by boreholes, spatial interpolation is performed based on the three-dimensional seismic interpretation results and the effective spatial scale of adjacent boreholes, and the lower limit of the interpolation interval is taken.

[0053] Specifically, the fracture flow test used rock samples with the same or similar lithology as the roof of the study area to prepare fracture specimens. Specimen openings of 2mm, 3mm, 4mm, 5mm, and 6mm were set, and the flow rate per unit time was recorded under the same pressure differential and fluid viscosity conditions. The thickness of a certain leakage section in the field borehole was 1.5m, and the leakage rate per unit time under a pressure differential of 0.4MPa was 1.8m³ / h. After converting the field leakage rate to the test pressure differential and fluid viscosity, the equivalent opening was obtained by comparing with the test curve, which was 4.6mm. Therefore, the effective spatial scale at this location was taken as 4.6mm.

[0054] For adjacent areas not penetrated by boreholes, inverse distance-weighted interpolation is used to determine the effective spatial scale. The interpolation weight refers to the normalized proportion of the inverse distance between adjacent borehole verification locations. For example, if the distances between three adjacent verification locations and the target location are 20m, 30m, and 50m, the corresponding effective spatial scales are 4.2mm, 5.0mm, and 5.6mm, respectively. After normalization using the inverse distance, the interpolation result is approximately 4.7mm. The measurement error of each verification location is then passed to the interpolation result to form the effective spatial scale range. If the range is 4.0mm to 5.2mm, then the effective spatial scale used in subsequent calculations is 4.0mm.

[0055] The effective spatial scale between residual void units is taken as the minimum clearance at the common connection location; the effective spatial scale between loose cavitation units is taken as the equivalent opening of the channel between cavitation blocks; when an interlayer separation unit is adjacent to other three-dimensional units, the smaller value between the interlayer separation degree and the clearance at the connection location is taken. All of the above values ​​are saved in the corresponding spatial connection relationship and updated after subsequent particle retention calculations.

[0056] In step S1203, spatial connection relationships are established based on the connection status of adjacent three-dimensional units, obstruction conditions, and effective spatial scale to form an underground space model of the goaf.

[0057] In one embodiment, spatial connections are established using three-dimensional units as nodes and the points where slurry can pass between adjacent three-dimensional units as connecting edges. Each connecting edge stores the starting three-dimensional unit, the ending three-dimensional unit, the connection length, the connection width, the effective spatial scale, and the spatial extension direction. When establishing a connecting edge, the connection condition, the blocking condition, and the direction difference are checked sequentially: if adjacent three-dimensional units have a common surface or are connected through an identified fracture, the connection condition is met; if there are no intact rock strata units, coal pillar units, or known closed structures at the common surface or connection location, the blocking condition is met; if the direction difference between adjacent three-dimensional units with a spatial extension direction does not exceed the allowable direction difference, the direction condition is met.

[0058] The permissible directional difference is the 95th percentile value of the directional difference between the 3D seismic interpretation direction and the downhole television observation direction at the borehole verification location. Specifically, the directional differences of at least 10 valid verification locations are collected and arranged in ascending order, and the 95th percentile value is determined using the nearest rank method. As an example, if the directional differences of 20 valid verification locations are arranged in ascending order and the 19th value is 18°, then the permissible directional difference is 18°. A connection edge is established when the directional difference between adjacent 3D elements is 12°, and no connection edge is established when the directional difference is 23°. If there are fewer than 10 verification locations, a temporary permissible directional difference is first determined based on the 3D seismic lateral resolution and the distance between adjacent 3D elements. Once 10 additional verification locations are obtained, the permissible directional difference is updated in the above manner.

[0059] Spatial connectivity is stored separately for liquid phase connectivity and solid phase connectivity. When there is clearance at the connection point, the liquid phase connectivity is set to continuous; the solid phase connectivity is determined based on the proportion of passable particles and the actual solid phase flow rate, as detailed below. This process forms a goaf underground space model, which includes a set of three-dimensional elements, the underground space state and accommodating volume of each element, and the spatial connectivity between the elements.

[0060] In step S13, the candidate borehole trajectory and final borehole position are mapped to the underground space model of the goaf. Based on the particle size distribution data, the slurry parameters and the spatial connection relationship, the slurry flow rate, the proportion of permissible particles and the particle retention amount are calculated for each time period.

[0061] For each candidate borehole, the data processing program maps the borehole coordinates, borehole trajectory, and final borehole coordinates to the underground space model of the goaf. It sets the 3D element containing the final borehole location as the entrance 3D element and extracts the spatial connections to this entrance 3D element. The candidate borehole trajectory and final borehole location are generated from the workable surface area, the allowable descent location, the goaf boundary, and the coal pillar boundary. Each candidate borehole is independently calculated using the same particle size distribution data and slurry parameters. Its output includes the pressure of each 3D element, the slurry flow rate of each spatial connection, and the updated effective spatial scale.

[0062] Specifically, Figure 3 A flowchart illustrating the determination of the reachable range of the solid phase according to embodiments of this disclosure is shown. Figure 3 As shown, in step S1301, the particle passage conditions are determined.

[0063] To reflect the impact of fracture wall roughness on particle passage, test slurry with the same particle size distribution as the gangue slurry to be predicted was injected into fracture specimens with different apertures, and the orifice pressure and discharge particle size were continuously recorded. For example, when the orifice pressure increased for three consecutive sampling cycles and the increase exceeded the repeatability error of the pressure sensor, and no particles of the corresponding size appeared at the specimen outlet, the specimen aperture at this point was taken as the critical test aperture. The particle passage correction factor was determined by the ratio of the critical test aperture to the maximum stable particle size.

[0064] For example, when the specimen opening is 5mm, particles with a maximum diameter of 2mm can pass through stably, while particles with a diameter exceeding 2mm are retained at the inlet. Therefore, the particle passage correction factor is 2.5. Within the calculation period, the first The third three-dimensional unit and the first The critical particle size between the three-dimensional units is:

[0065]

[0066] in, Indicates the critical particle size, in m or mm; Indicates the first The effective spatial scale for each computation period is the same as the critical particle size. This indicates the correction factor for particle passage. Based on the critical particle size, the cumulative sieving curve corresponding to the particle size distribution data is retrieved to obtain the proportion of particles that can pass through.

[0067]

[0068] in, This indicates the particle ratio; This represents the cumulative sieving function. The input is the particle size, and the output is the volume fraction of particles whose size does not exceed the input value. For example, when the effective space size is 5 mm and the particle passing correction factor is 2.5, the critical particle size is 2 mm. If the cumulative sieving curve shows that the volume fraction of particles with a size not exceeding 2 mm is 0.82, then the proportion of particles that pass through is 0.82, and the proportion of particles that do not pass through is 0.18.

[0069] The cumulative sieving function is established based on the particle size distribution data of the gangue slurry to be predicted. Specifically, the gangue particles are sieved to obtain the particle size of each sieve opening and the corresponding cumulative passing volume fraction. A cumulative sieving curve is formed with particle size as the independent variable and cumulative passing volume fraction as the dependent variable, and the function relationship corresponding to the cumulative sieving curve is used as the cumulative sieving function. When the critical particle size is located between two adjacent sieve opening sizes, linear interpolation is performed based on the cumulative passing volume fractions corresponding to the two adjacent sieve opening sizes to obtain the proportion of particles that can pass through the critical particle size.

[0070] In step S1302, the slurry flow rate is calculated based on the slurry parameters. Specifically, the slurry parameters include mass concentration, solid density, liquid density, plastic viscosity, and yield stress. The mass concentration is converted to solid volume fraction:

[0071]

[0072] in, Indicates the volume fraction of solids; Indicates mass concentration; This indicates the density of a solid, expressed in kg / m³. This indicates the liquid density, expressed in kg / m³. For example, if the mass concentration is 0.75, the solid density is 2400 kg / m³, and the liquid density is 1000 kg / m³, then the solid volume fraction is 0.556.

[0073] The plastic viscosity and yield stress were measured using a rotational rheometer, and the apparent viscosity was determined using the Bingham fluid model.

[0074]

[0075] in, This represents apparent viscosity, expressed in Pa·s. This indicates plastic viscosity, expressed in Pa·s. This represents the yield stress, with units of Pa. This represents the reference shear rate, measured in seconds (s). For example, the plastic viscosity is 0.45 Pa·s, the yield stress is 18 Pa, and the reference shear rate is 60 s⁻¹. The apparent viscosity is 0.75 Pa·s.

[0076] Optionally, the reference shear rate is calibrated based on fracture flow tests. Specifically, using the same slurry as the gangue slurry to be predicted, flow tests are conducted under different specimen openings and pressure difference combinations within the effective spatial scale and pressure difference range of the covering project, and the stable slurry flow rate is recorded. The reference shear rate is adjusted for each test condition to match the slurry flow rate calculated based on the Bingham fluid model with the measured stable flow rate, thus obtaining the correspondence between specimen opening, pressure difference, and reference shear rate. In actual calculations, the reference shear rate is selected or interpolated from the correspondence based on the effective spatial scale and pressure difference of the current spatial connection relationship.

[0077] For the connection edge represented by the equivalent slit, the viscous flow resistance is calculated based on the connection length, connection width, and effective spatial dimensions:

[0078]

[0079] in, This represents the resistance to viscous flow, with units of Pa·s / m³. This indicates the connection length, in meters (m). This indicates the connection width, in meters (m). This represents the effective spatial dimension, in meters (m). The yield pressure difference is calculated based on the yield stress, connection length, and effective spatial dimension.

[0080]

[0081] in, This represents the yield pressure difference, expressed in Pa. This represents the yield stress, with units of Pa. and All are lengths, in meters (m).

[0082] A flow conservation equation is established for all three-dimensional elements, and the inlet slurry flow rate is applied to the inlet three-dimensional element. In this embodiment, all pressures represent relative pressures. For end three-dimensional elements with remaining usable volume and no subsequent connecting edges, their relative pressure is set to 0. End three-dimensional elements with no remaining usable volume are removed from the pressure boundary set. Then, the pressure of each three-dimensional element is solved. When the pressure difference between adjacent three-dimensional elements does not exceed the yield pressure difference, the slurry flow rate of that connecting edge is taken as 0; when it exceeds the yield pressure difference, it is calculated according to the following formula:

[0083]

[0084] in, This indicates the flow rate of the slurry, with units of m³ / s; and These represent the pressures of adjacent three-dimensional elements, in Pa; This represents the yield pressure difference, expressed in Pa. This represents the resistance to viscous flow, with units of Pa·s / m³. This represents a sign function. As an example, the viscous flow resistance of a certain connecting edge is... Given a pressure difference of 0.08 MPa (Pa·s / m³) and a pressure difference of 0.68 MPa between adjacent three-dimensional elements, the slurry flow rate is 0.004 m³ / s. The slurry flow rate at each connecting edge is then used as input for calculating particle retention.

[0085] In one embodiment, when solving the flow conservation equation, the pressure of the three-dimensional element at the current calculation time step is used as the unknown. First, it is determined whether the pressure difference between each connecting edge exceeds the yield pressure difference based on the pressure of the previous round. Then, the connecting edges in the flow state are written into the sparse coefficient matrix, and the pressure increment is solved using the conjugate gradient method. After the pressure is updated, the state of the connecting edges is re-evaluated until both the state of the connecting edges and the pressure of the three-dimensional element reach the iteration termination condition. The input of the conjugate gradient method is the sparse coefficient matrix and the inlet boundary, and the output is the pressure of each three-dimensional element. Subsequently, the slurry flow rate of each connecting edge is calculated based on the pressure of each three-dimensional element.

[0086] The iteration termination tolerance is determined through repeated calculations. First, it's taken as one ten-thousandth of the inlet pressure, then the tolerance is halved. If the maximum relative change in slurry flow rate at each connection edge after halving does not exceed one-thousandth, then the previous tolerance is adopted. For example, a local network includes 125 three-dimensional elements and 310 connection edges, with an inlet pressure of 2.0 MPa. Using a 20 Pa termination tolerance, the total outlet flow rate is 0.0316 m³ / s after 46 iterations. After reducing the termination tolerance to 10 Pa, the total outlet flow rate is 0.03158 m³ / s, with the maximum relative change less than one-thousandth. Therefore, a 20 Pa termination tolerance is used in subsequent calculations.

[0087] In step S1303, the calculation time step and particle retention are determined. Specifically, the calculation time step is determined based on the minimum remaining containment volume in the three-dimensional element involved in the calculation and the inlet slurry flow rate:

[0088]

[0089] in, This indicates the calculation time step, in seconds (s). This represents the minimum remaining capacity, in m³. Indicates the inlet slurry flow rate, in m³ / s; This represents the proportion of the allowable injection volume to the minimum remaining accommodateable volume in a single computational time step. It is determined through time-step convergence experiments. First, a value of 0.02 is used for one calculation, then 0.01 is used for the next calculation. If the difference in the total solid volume obtained from the two calculations is less than the volume error range of the underground space model of the goaf, and the time difference corresponding to the spatial connection relationship where the first effective spatial scale decreases to 0 does not exceed the calculation time step used in the subsequent calculation, then 0.02 is used. For example, the minimum remaining accommodative volume is 10 m³, and the inlet slurry flow rate is 0.05 m³ / s. When the value is 0.02, the upper limit of the calculation time step is 4s, but it is actually taken as 2s.

[0090] The particle retention rate of each connection edge within a calculation time step is determined by the solid volume fraction, slurry flow rate, calculation time step size, and proportion of unpassed particles:

[0091]

[0092] in, This indicates the amount of particles retained, in m³. Indicates the volume fraction of solids; This indicates the flow rate of the slurry, with units of m³ / s; This indicates the calculation time step, in seconds (s). This indicates that the effective spatial scale can be determined by the particle ratio. The equivalent depositional area is determined by multiplying the connection width by the depositional zone length calibrated by fracture flow tests. When the connection width can be determined from probe data or borehole verification data, the actual determined connection width is used. When the connection width is discretized and approximated by the common surface of adjacent 3D units, the corresponding connection width is determined according to the current mesh size. During the verification process of progressively decreasing mesh size, the connection width and equivalent depositional area are updated synchronously to ensure that the reduction in effective spatial scale calculated from particle retention is consistent with the current mesh division. Then, the effective spatial scale is reduced based on particle retention and equivalent depositional area:

[0093]

[0094] in, and These represent the effective spatial scale before and after the update, respectively, in meters; This indicates the amount of particles retained, in m³. This represents the equivalent depositional area, expressed in m². The length of the depositional zone is determined by the ratio of the actual depositional zone length to the connection length in a fracture flow test. For example, if the connection width is 2m and the connection length is 5m, and the test shows that the depositional zone length accounts for 60% of the connection length, then the equivalent depositional area is 6m².

[0095] In practical applications, with a slurry flow rate of 0.004 m³ / s, a solids volume fraction of 0.556, a calculation time step of 2 s, and a passable particle ratio of 0.82, the particle retention is approximately 0.00080 m³. When the equivalent deposition area is 6 m², the effective spatial scale decreases by 0.000133 m, or 0.133 mm. In the next calculation time step, the system recalculates the critical particle size, passable particle ratio, viscous flow resistance, yield pressure difference, and slurry flow rate using the updated effective spatial scale. When particle retention occurs in multiple consecutive calculation time steps, the effective spatial scale gradually decreases, and the slurry flow rate at the corresponding connection edge decreases as the viscous flow resistance increases.

[0096] In step S1304, the calculation termination conditions and allowable inlet pressure are determined. Specifically, the calculation termination conditions include any of the following: the inlet pressure reaches the allowable inlet pressure; there is no remaining accommodating volume in all connectable spaces corresponding to the candidate borehole; the cumulative injected volume reaches the planned injection volume for a single borehole. The allowable inlet pressure is the minimum value among the allowable outlet pressure of the filling pump, the allowable pressure of the surface pipeline, the allowable pressure of the borehole casing, and the formation fracturing initiation pressure corrected for a safety factor:

[0097]

[0098] in, Indicates the allowable inlet pressure, in MPa; This indicates the allowable outlet pressure of the filling pump, in MPa. This indicates the allowable pressure of the ground pipeline, in MPa. This indicates the allowable pressure of the borehole casing, in MPa. This represents the formation fracturing initiation pressure, expressed in MPa. This represents the safety factor.

[0099] The safety factor is determined based on the dispersion of the formation fracturing pressure obtained from the stepped injection tests and the pressure sensor error. For example, the formation fracturing pressures obtained from three stepped injection tests were 8.4 MPa, 8.7 MPa, and 8.5 MPa, respectively, with a maximum pressure sensor error of 0.1 MPa. A safety factor is chosen that ensures the formation fracturing pressure, after safety factor correction, is lower than the minimum value after subtracting the sensor error from the three test results; for example, 1.25. If the allowable outlet pressure of the filling pump is 9.0 MPa, the allowable pressure of the surface pipeline is 8.0 MPa, the allowable pressure of the borehole casing is 8.5 MPa, and the formation fracturing pressure after safety factor correction is 6.72 MPa, then the allowable inlet pressure is 6.72 MPa.

[0100] In step S14, the solid phase reachable range is determined based on the cumulative solid volume received by the three-dimensional unit. Candidate boreholes are screened based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The solid phase reachable range of the screened candidate boreholes is determined as the gangue filling target area, and the borehole trajectory and final borehole coordinates are output.

[0101] Specifically, Figure 4 A flowchart illustrating the process of screening candidate boreholes and determining the target area for gangue filling according to an embodiment of this disclosure is shown. Figure 4 As shown, in step S1401, the reachable range of the solid phase and the migration range of the liquid phase are determined.

[0102] Specifically, after each calculation time step, the solid and liquid volumes received by each 3D element are accumulated. The solid volume flowing into a 3D element is determined based on the slurry flow rate, solid volume fraction, permissible particle ratio, and calculation time step, and the solid volume flowing out of that 3D element is deducted. For example, if the slurry flow rates of two inflowing connecting edges are 0.003 m³ / s and 0.002 m³ / s, the permissible particle ratios are 0.80 and 0.90 respectively, the solid volume fraction is 0.556, the calculation time step is 2 s, and there is no solid outflow in that time step, then the newly added solid volume of that 3D element is 0.00467 m³. After the accumulated solid volume received by a 3D element reaches its capacity, the subsequent flow rate is allocated to other spatial connections that still have remaining capacity.

[0103] The solid volume tolerance is defined as the solid phase reachable range by 3D units where the cumulative received solid volume exceeds the solid volume tolerance; the liquid phase migration range is defined as the spatial connection relationship where there is liquid flow and the solid flow is lower than the solid flow tolerance, and its subsequent 3D units. The solid volume tolerance and solid flow tolerance are determined by successively reducing the corresponding tolerances until the total volume change of the solid phase reachable range falls within the volume error range of the goaf underground space model after further reduction.

[0104] The volumetric error range of the underground space model in the goaf is determined based on the geophysical boundary position error, grid size, and borehole verification error. Specifically, the boundary discretization error corresponding to the grid size is determined based on the spatial size of the three-dimensional unit containing the underground space boundary. The boundary is shifted inward and outward by one grid discretization range towards the adjacent three-dimensional unit, forming the inner and outer disturbance ranges of the boundary position together with the geophysical boundary position error and the borehole verification error. When the grid size is adjusted, the corresponding grid discretization error is redefined. Specifically, the underground space boundary is shifted inward and outward according to the aforementioned errors, forming a lower boundary model and an upper boundary model. The difference between the total achievable solid volume obtained from the two models is used as the volumetric error range. For example, if the total achievable solid volume of the lower boundary model is 40500 m³ and that of the upper boundary model is 43200 m³, then the volumetric error range is 2700 m³.

[0105] When the solid volume tolerance decreases from 0.02 m³ to 0.01 m³, the total volume of the solid phase changes to 900 m³. Further decreasing to 0.005 m³ results in a change of 300 m³, both less than 2700 m³. Therefore, 0.01 m³ is adopted as the solid volume tolerance. The solid flow tolerance is determined using the same convergence method. For example, when decreasing from 0.00002 m³ / s to 0.00001 m³ / s, the total volume of the solid phase changes to 620 m³. Further decreasing to 0.000005 m³ / s results in a change of 210 m³, both falling within the 2700 m³ volume error range. Therefore, 0.00001 m³ / s is adopted as the solid flow tolerance.

[0106] In step S1402, inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints are determined. The inlet pressure constraint is defined as the inlet pressure not exceeding the allowable inlet pressure. For spatial connections crossing the predetermined goaf boundary and spatial connections ending in a protected aquifer, the product of the liquid phase flow rate and the calculation time step is accumulated step by step to obtain the liquid volume flowing out of the predetermined goaf boundary or into the protected aquifer; the liquid phase escape ratio is determined based on this liquid volume and the inlet injection liquid volume.

[0107]

[0108] in, Indicates the proportion of liquid phase that escapes; The volume of liquid flowing out of the predetermined goaf boundary or into the protected aquifer is expressed in m³. This indicates the volume of liquid injected into the inlet, in m³.

[0109] The permissible liquid phase escape ratio was determined through a stepwise injection test using clean water or low-concentration slurry. During the test, the water level and tracer response of the corresponding hydrological observation well in the protected aquifer were simultaneously observed. A water level response was determined to have occurred when the water level change exceeded the sum of the maximum natural water level fluctuation and the water level gauge measurement error within the same observation period before the test; a tracer response was determined to have occurred when the tracer concentration exceeded the sum of the maximum background concentration and the detection limit. The ratio of the maximum volume of liquid that did not show a water level response or tracer response to the corresponding inlet injection volume was taken as the permissible liquid phase escape ratio.

[0110] For example, in the stepped injection test, 100 m³, 150 m³, and 200 m³ of clean water were injected respectively. No water level response or tracer response was observed in the first two stages, but a tracer response was observed in the third stage. According to the underground space model, the volume of liquid escaping from the second stage is 15 m³, so the allowable liquid phase escaping ratio is 0.10. Calculations for candidate boreholes show that when the inlet injection volume is 180 m³ and the escaping volume is 12 m³, the liquid phase escaping ratio is 0.067, satisfying the liquid phase escaping constraint. When the escaping volume is 25 m³, the liquid phase escaping ratio is 0.139, which does not satisfy the liquid phase escaping constraint.

[0111] Drilling constraints include avoiding prohibited drilling areas on the borehole trajectory, and ensuring the final borehole location is within a loose caving unit, a residual cavity unit, or an interlayer separation unit. Prohibited drilling areas are defined by extending a check distance outward from known aquifer boundaries, fault water-conducting regions, and coal pillar boundaries. This check distance is determined by adding the design distance for water control, borehole trajectory measurement error, and geophysical boundary interpretation error. For example, if the design distance for water control is 20m, the borehole trajectory measurement error is 2m, and the geophysical boundary interpretation error is 5m, then the check distance is 27m, and the prohibited drilling area is generated accordingly.

[0112] In step S1403, candidate boreholes are screened and the target area for gangue filling is output. The total achievable solid volume, maximum inlet pressure, liquid phase escape ratio, and borehole trajectory verification results calculated by the aforementioned steps for each candidate borehole are obtained. Candidate boreholes that do not meet the inlet pressure constraint, liquid phase escape constraint, or borehole construction constraint are first eliminated, and then the candidate borehole with the largest achievable solid volume is selected from the remaining candidate boreholes.

[0113] In one example, candidate borehole A has a total achievable solid volume of 42,000 m³, a maximum inlet pressure of 6.3 MPa, and a liquid phase escape ratio of 0.067. The borehole trajectory meets the drilling constraints. Candidate borehole B has a total achievable solid volume of 48,000 m³, a maximum inlet pressure of 6.4 MPa, and a liquid phase escape ratio of 0.139. Candidate borehole C has a total achievable solid volume of 39,000 m³, but its borehole trajectory enters a prohibited drilling zone. The allowable inlet pressure is 6.72 MPa, and the allowable liquid phase escape ratio is 0.10. Therefore, candidate boreholes B and C are excluded, and candidate borehole A is retained.

[0114] Candidate borehole A consists of three-dimensional units that are continuously connected within the solid phase reachable range, forming the gangue filling target area. The output includes the three-dimensional boundary of the gangue filling target area, the total solid phase reachable volume, the liquid phase migration range, the borehole coordinates of candidate borehole A, the borehole trajectory, the final borehole coordinates, the inlet pressure change data over time, and the spatial connection relationship of particle retention.

[0115] In some embodiments, the underground space model of the goaf is corrected and re-predicted based on the construction verification borehole. Specifically, after the construction verification borehole, the drilling speed, drilling fluid leakage section, and downhole television results are mapped to the underground space model of the goaf. When the downhole television detects a cavity, the corresponding 3D unit is updated to a residual cavity unit, and the effective spatial scale and containment volume are corrected according to the cavity height and the cavity's planar extension range. When there is leakage in the drilling fluid leakage section and no cavity is detected by the downhole television, the corresponding location is determined as a fracture connection location, and the effective spatial scale is corrected according to the leakage per unit time and the fracture flow test correspondence table. When the predicted residual cavity unit does not show any changes in drilling speed, drilling fluid leakage, or visible voids, the corresponding 3D unit is updated to an uncertain unit.

[0116] For example, in a verification borehole, a drilling fluid loss of 2.1 m³ / h occurred between 286m and 288m, but no continuous cavities were observed on downhole television. According to the correspondence table of fracture flow tests under the same pressure difference and viscosity conditions, 2.1 m³ / h corresponds to an equivalent aperture of 5.1 mm. Therefore, fracture connection positions are established between the corresponding three-dimensional elements, and the effective spatial scale is corrected to 5.1 mm. In another predicted residual cavity element, the drilling rate in the section shows no significant change, there is no drilling fluid loss, and no cavities are observed on downhole television. In this case, the three-dimensional element is updated to an uncertain element.

[0117] After the correction is completed, the spatial connection relationship of the affected area is re-established, the slurry flow rate, the proportion of permissible particles and the amount of particle retention are calculated for each time period, the effective spatial scale is updated, the range of solid phase accessibility is determined again and candidate boreholes are screened, and finally the corrected gangue filling target area, borehole trajectory and final borehole coordinates are adopted.

[0118] Through the above implementation process, the underground space status, containment volume, and effective spatial scale are determined by mining engineering data, multi-source detection data, and borehole verification data, respectively. The particle size distribution of the gangue slurry further restricts the solid phase passage conditions; the particle retention amount updates the effective spatial scale as the grouting process progresses, so that whether the space behind the narrow connection position continues to receive solids is determined by the time-period calculation results. The reachable range of the solid phase, the migration range of the liquid phase, as well as the inlet pressure, liquid phase escape, and borehole construction conditions jointly participate in the candidate borehole screening, and the output results directly correspond to the gangue filling target area, borehole trajectory, and final borehole coordinates.

[0119] Figure 5 This diagram illustrates a block diagram of a target area prediction system for gangue filling based on a goaf underground space model, according to an embodiment of the present disclosure. Figure 5 As shown, the system includes:

[0120] The data acquisition module 501 is used to acquire mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry;

[0121] The model building module 502 is used to register the mining engineering data, the multi-source detection data and the borehole verification data to the spatial coordinate system and divide them into three-dimensional units, determine the underground space status, accommodating volume and effective spatial scale of the three-dimensional units, and establish spatial connection relationships based on the connection status, blocking conditions and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf.

[0122] The transport calculation module 503 is used to map the candidate borehole trajectory and the final borehole position to the underground space model of the goaf area, and calculate the slurry flow rate, the proportion of passable particles and the particle retention amount in time period according to the particle size distribution data, the slurry parameters and the spatial connection relationship; update the effective spatial scale according to the particle retention amount, and repeat the calculation based on the updated effective spatial scale until the calculation termination condition is met.

[0123] The target area determination module 504 is used to determine the reachable range of the solid phase based on the cumulative solid volume received by the three-dimensional unit. It screens candidate boreholes based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The reachable range of the solid phase of the screened candidate boreholes is determined as the target area for gangue filling, and the borehole trajectory and final borehole coordinates are output.

[0124] In some embodiments, the system provided in this disclosure may have functions or include modules that can be used to execute the methods described in the above method embodiments. The specific implementation of these methods can be referred to the description in the above method embodiments, and for the sake of brevity, they will not be repeated here.

[0125] Figure 6 A block diagram of an electronic device according to an embodiment of the present disclosure is shown. (Refer to...) Figure 6Electronic devices can be provided as servers or terminal devices. (See reference...) Figure 6 The electronic device includes a processing component 601, which further includes one or more processors, and memory resources represented by memory 602 for storing instructions, such as application programs, that can be executed by the processing component 601. The application programs stored in memory 602 may include one or more modules, each corresponding to a set of instructions. Furthermore, the processing component 601 is configured to execute instructions to perform the methods described above.

[0126] The electronic device may also include a power supply component 603 configured to perform power management of the electronic device, a wired or wireless network interface 604 configured to connect the electronic device to a network, and an input / output interface 605 (I / O interface). The electronic device can operate on an operating system stored in memory 602.

[0127] In an exemplary embodiment, a non-volatile computer-readable storage medium is also provided, such as a memory 602 including computer program instructions that can be executed by a processing component 601 of an electronic device to perform the above-described method.

[0128] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for predicting target areas for gangue filling based on an underground space model of a goaf, characterized in that, include: Acquire mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry; The mining engineering data, the multi-source detection data, and the borehole verification data are registered to a spatial coordinate system and divided into three-dimensional units. The underground space status, accommodating volume, and effective spatial scale of the three-dimensional units are determined. Spatial connection relationships are established based on the connection status, blocking conditions, and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf. The candidate borehole trajectory and final borehole location are mapped to the underground space model of the goaf area. Based on the particle size distribution data, the slurry parameters and the spatial connection relationship, the slurry flow rate, the proportion of permissible particles and the particle retention amount are calculated for each time period. The effective spatial scale is updated according to the particle retention amount, and the calculation is repeated based on the updated effective spatial scale until the calculation termination condition is met. The solid phase reachable range is determined based on the cumulative solid volume received by the three-dimensional unit. Candidate boreholes are screened based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The solid phase reachable range of the screened candidate boreholes is determined as the gangue filling target area, and the borehole trajectory and final borehole coordinates are output.

2. The method according to claim 1, characterized in that, The multi-source detection data includes 3D seismic data, transient electromagnetic data, and micromotion detection data; the predetermined goaf boundary is determined based on the mining engineering data; the fault boundary, interlayer separation range, and spatial extension direction are determined based on the 3D seismic data; the water-bearing anomaly range is determined based on the transient electromagnetic data, and the protected water-bearing area is identified from it; the degree of compaction is determined based on the micromotion detection data, and the accommodateable volume is corrected based on the degree of compaction; the underground space state, effective spatial scale, and accommodateable volume of the 3D unit traversed by the borehole are locally corrected based on the borehole verification data.

3. The method according to claim 2, characterized in that, The underground space state includes intact rock strata units, coal pillar units, loose caving bodies units, residual cavities units, interlayer separation units, and uncertain units; the intact rock strata units and the coal pillar units are set as blocking units, the loose caving bodies units, the residual cavities units, and the interlayer separation units are included in the establishment of the spatial connection relationship, and the uncertain units are updated after obtaining supplementary borehole verification data.

4. The method according to claim 3, characterized in that, The effective spatial scale is determined as follows: for cavities or fractures directly observed by downhole television, the effective spatial scale is measured based on images with scale markings; for drilling fluid leakage sections, the effective spatial scale is calculated back based on the thickness of the leakage section, the leakage per unit time, and flow tests on similar rock samples; for areas not penetrated by boreholes, spatial interpolation is performed based on the results of 3D seismic interpretation and the effective spatial scale of adjacent boreholes, and the lower limit of the interpolation interval is taken.

5. The method according to claim 4, characterized in that, The spatial connection relationship is established according to the following conditions: adjacent three-dimensional units have a common surface or are connected through an identified fracture, there is no blocking unit at the common surface or connection position, and the directional difference between adjacent three-dimensional units with spatial extension direction does not exceed the allowable directional difference; the allowable directional difference is determined by the directional difference between the three-dimensional seismic interpretation direction of the borehole verification position and the downhole television observation direction.

6. The method according to claim 5, characterized in that, By setting up fracture specimens with different openings and injecting test slurry with the same particle size distribution as the gangue slurry to be predicted, the specimen opening when the orifice pressure begins to rise continuously under continuous injection conditions and the maximum particle size that stably passes through at the specimen opening are recorded. The particle passing correction coefficient is determined based on the ratio of the two. The critical particle size is determined based on the effective spatial scale and the particle passing correction coefficient, and the proportion of particles that can pass through is obtained from the cumulative sieving curve corresponding to the particle size distribution data.

7. The method according to claim 6, characterized in that, The slurry parameters include mass concentration, solid density, liquid density, plastic viscosity, and yield stress. The solid volume fraction is determined based on the mass concentration, solid density, and liquid density. Viscous flow resistance and yield pressure difference are determined based on the plastic viscosity, yield stress, and the connection length, connection width, and effective spatial scale corresponding to the spatial connection relationship. The slurry flow rate is calculated by combining the viscous flow resistance, yield pressure difference, pressure difference between adjacent three-dimensional elements, and the flow conservation relationship of the three-dimensional elements. The proportion of non-passing particles is determined based on the proportion of passable particles, and the particle retention is determined based on the slurry flow rate, solid volume fraction, calculation time step, and the proportion of non-passing particles. The equivalent deposition area is determined based on the connection width and the deposition zone length calibrated by the fracture flow test. The effective spatial scale is reduced according to the particle retention and the equivalent deposition area. The calculation time step is determined based on the minimum remaining accommodative volume and the inlet slurry flow rate in the three-dimensional unit involved in the calculation.

8. The method according to claim 7, characterized in that, The calculation termination conditions include any of the following: the inlet pressure reaches the allowable inlet pressure, all connectable spaces corresponding to the candidate borehole have no remaining volume, or the cumulative injection volume reaches the planned injection volume for a single borehole; the allowable inlet pressure is the minimum value among the allowable outlet pressure of the filling pump, the allowable pressure of the surface pipeline, the allowable pressure of the borehole casing, and the formation fracturing pressure corrected by a safety factor. The safety factor is determined based on the dispersion of the formation fracturing pressure obtained from the stepped injection test and the error of the pressure sensor, and the inlet pressure not exceeding the allowable inlet pressure is used as the inlet pressure constraint.

9. The method according to claim 8, characterized in that, The solid volume of the three-dimensional units that have received a cumulative solid volume exceeding the solid volume tolerance are formed into a solid phase reachable range. The spatial connection relationship with liquid flow and solid flow that is lower than the solid flow tolerance, and its subsequent three-dimensional units are formed into a liquid phase migration range. The solid volume tolerance and the solid flow tolerance are determined by successively reducing the corresponding tolerances until the total volume change of the solid phase reachable range falls within the volume error range of the goaf underground space model after further reduction. The volume error range is determined based on the geophysical boundary position error, grid size, and borehole verification error.

10. A target area prediction system for gangue backfilling based on an underground space model of a goaf, characterized in that, include: The data acquisition module is used to acquire mining engineering data, multi-source detection data, borehole verification data, and particle size distribution data and slurry parameters of gangue slurry; The model building module is used to register the mining engineering data, the multi-source detection data and the borehole verification data to the spatial coordinate system and divide them into three-dimensional units. It determines the underground space status, accommodating volume and effective spatial scale of the three-dimensional units, and establishes spatial connection relationships based on the connection status, blocking conditions and effective spatial scale of adjacent three-dimensional units to form an underground space model of the goaf. The migration calculation module is used to map the candidate borehole trajectory and the final borehole position to the underground space model of the goaf area, and calculate the slurry flow rate, the proportion of passable particles and the particle retention amount on a time-by-time basis according to the particle size distribution data, the slurry parameters and the spatial connection relationship. The effective spatial scale is updated according to the particle retention amount, and the calculation is repeated based on the updated effective spatial scale until the calculation termination condition is met. The target area determination module is used to determine the reachable range of the solid phase based on the cumulative solid volume received by the three-dimensional unit. It screens candidate boreholes based on inlet pressure constraints, liquid phase escape constraints, and borehole construction constraints. The reachable range of the solid phase of the screened candidate boreholes is determined as the target area for gangue filling, and the borehole trajectory and final borehole coordinates are output.

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