Coal seam roof and floor aquifer advanced area treatment grouting drilling layout method

Abstract

The application discloses a coal seam roof and floor aquifer advanced area treatment grouting borehole layout method, which comprises the following steps: determining a grouting reconstruction horizon in an advanced area in a coal seam roof and / or a coal seam floor; obtaining a first grouting slurry diffusion radius in an aquifer through theoretical calculation, obtaining a second grouting slurry diffusion radius in the aquifer through numerical simulation calculation, and taking the smaller one of the first diffusion radius and the second diffusion radius as the grouting slurry diffusion radius; determining a grouting borehole layout shape, wherein the grouting borehole layout shape comprises a fan shape, a feather shape and a comb shape; determining grouting borehole trajectory design parameters; performing directional advanced drilling construction according to the grouting borehole trajectory design parameters, obtaining drilling parameters in real time by using a while-drilling measurement device in the construction process, and adjusting the drilling trajectory in real time according to the grouting borehole trajectory design parameters until the grouting borehole layout operation is completed. The grouting reconstruction horizon selected by the method is more accurate and reasonable, and the problems of unscientific, inaccurate and low design efficiency of the grouting borehole layout in the advanced area are solved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine roof and floor water hazard prevention technology, specifically relating to a method for grouting borehole layout for advanced treatment of aquifers in the roof and floor of coal seams. Background Technology

[0002] The Carboniferous-Permian coalfields in central and eastern China and the Jurassic coalfields in western my country are the main coal-producing areas. However, the mining of Carboniferous-Permian coal resources has long been threatened by water inrushes from the underlying Ordovician limestone aquifers, while the development of Jurassic coalfields has long been threatened by water hazards from the roof sandstone aquifers. The safe and efficient development of coal resources has been severely constrained, especially during the process of extending mining to deeper layers. Under the complex geomechanical environment of high ground stress, high water pressure, and strong disturbance, the threat of water hazards from the floor limestone and roof sandstone is even more severe. To address the aforementioned water hazard threats from the floor limestone and roof sandstone of the coal seams, surface horizontal borehole directional drilling technology has begun to be applied in aquifer grouting and modification projects. By constructing horizontally directional branch boreholes along the bedding planes and pre-grouting to modify the target aquifer in the subsequent mining area, the thickness of the aquitard is increased, reducing the risk of water inrushes. Although the use of ground horizontal borehole directional drilling technology for advanced regional treatment and grouting modification of aquifers has released a large amount of coal resources threatened by water hazards, the existing advanced grouting borehole trajectory design has the following main defects: it relies on manual design, and the determination of the advanced regional grouting modification layer and the design of the grouting modification borehole spacing mainly depend on engineering practice experience, which is difficult to quantify scientifically. This results in low efficiency and unsatisfactory effect of advanced regional treatment and grouting modification of aquifers in the top and bottom of coal seams, and may even lead to modification failure.

[0003] Therefore, designing a reasonable method for the layout of grouting boreholes for the advanced treatment of aquifers in the top and bottom of coal seams is an urgent problem to be solved in the current intelligent prevention and control of water hazards in coal mines. Summary of the Invention

[0004] To address the deficiencies and shortcomings of existing technologies, this invention provides a method for laying out grouting boreholes for advanced treatment of aquifers in the roof and floor of coal seams, thereby solving the technical problems of low efficiency and unsatisfactory results in grouting modification of advanced aquifers in the roof and floor of coal seams in existing technologies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for grouting borehole layout for advanced treatment of aquifers in the roof and floor of coal seams, the method comprising the following steps:

[0007] Step 1: Collect borehole data and geophysical exploration data to determine the advanced grouting and modification layers in the coal seam roof and / or coal seam floor.

[0008] Step 2: Based on the borehole data and geophysical exploration data collected in Step 1, determine the mechanical properties of the grouting modification layer in the advanced area, obtain the first diffusion radius of the grout in the aquifer through theoretical calculation, obtain the second diffusion radius of the grout in the aquifer through numerical simulation calculation, and take the smaller of the first diffusion radius and the second diffusion radius as the diffusion radius of the grout.

[0009] Step 3: Based on the mechanical properties of the determined advanced grouting modification layer, determine the hole layout shape of the grouting boreholes. The hole layout shapes of the grouting boreholes include fan-shaped, feather-shaped, and comb-shaped.

[0010] Step 4: Based on the advanced grouting modification layer determined in Step 1, the grout diffusion radius determined in Step 2, and the hole layout shape of the grouting boreholes determined in Step 3, determine the grouting borehole trajectory design parameters.

[0011] Step 5: Conduct directional advance drilling according to the determined grouting borehole trajectory design parameters. During the construction process, use the drilling measurement and control device to obtain drilling parameters in real time, and adjust the drilling trajectory in real time according to the grouting borehole trajectory design parameters until the grouting borehole layout operation is completed.

[0012] The present invention also has the following technical features:

[0013] Specifically, step 1 includes:

[0014] When the advanced grouting modification layer is located within the coal seam floor, based on the "lower three zones" theory, the depth values ​​of the three mining-induced water-conducting failure zones of the coal seam floor are obtained through theoretical calculations, physical similarity simulation tests, and numerical simulation calculations. The maximum value among the three mining-induced water-conducting failure zone depth values ​​of the coal seam floor is taken as the standard value, and the aquifer with the smallest difference between the depth value and the standard value is taken as the grouting modification layer of the floor.

[0015] When the advanced grouting modification layer is located within the coal seam roof, based on the "upper three zones" theory, the development height values ​​of the three coal seam roof water-conducting fracture zones are obtained through theoretical calculations, physical similarity simulation experiments, and numerical simulation calculations. The maximum value among the three coal seam roof water-conducting fracture zone development height values ​​is taken as the standard value, and the aquifer with the smallest difference between the height value and the standard value is taken as the roof grouting modification layer.

[0016] Furthermore, the first diffusion radius of the grout within the aquifer is determined by the following formula:

[0017]

[0018] In the formula: r1 is the first diffusion radius, in meters; K is the aquifer permeability coefficient, in meters per second; z is the grouting pressure head, in meters; t is the grouting time, in seconds. λ represents the porosity of the rock mass at the grouting layer; λ is the ratio of the grout viscosity to the water viscosity; r0 is the radius of the grouting borehole, in meters.

[0019] Furthermore, step 3, which involves determining the hole layout shape for grouting based on the characteristics of the determined grouting modification layer, specifically includes:

[0020] When the drilling success rate of grouting-modified formation is greater than or equal to 85%, the hole layout of the grouting boreholes is comb-shaped.

[0021] When the borehole formation completion rate of grouting modification drilling is greater than or equal to 60% and less than 85%, the borehole layout shape of the grouting borehole is feather-shaped.

[0022] When the borehole formation completion rate of grouting modification drilling is less than 60%, the borehole layout of grouting drilling is fan-shaped.

[0023] Furthermore, the drilling trajectory design parameters described in step 4 include the opening position, the final hole position, the branch hole opening position, the drilling spacing, the drilling depth, the drilling inclination angle, the drilling azimuth angle, the drilling skew point position, the drilling stabilization point position, and the drilling bending strength.

[0024] Compared with the prior art, the beneficial technical effects of this invention are:

[0025] (1) When designing grouting boreholes, the method of the present invention first integrates theoretical calculations, physical similarity simulation calculations and numerical simulation calculations to obtain the depth of the water-conducting failure zone of the coal seam floor and the height of the water-conducting fracture zone of the coal seam roof, respectively. Then, based on the calculation results, the grouting modification layer in the coal seam roof and / or coal seam floor is determined. Since the calculated values ​​are closer to the actual values, the selection of the grouting modification layer is more accurate and reasonable. The design parameters of the grouting borehole trajectory are determined by combining the determined grouting modification layer, the diffusion radius of the grouting slurry, and the hole shape of the grouting borehole. This solves the problems of unscientific and inaccurate layout of grouting boreholes in the advanced area and low design efficiency.

[0026] (2) The method of the present invention has the advantages of high drilling design efficiency, small error and fast drilling design adjustment. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method of the present invention;

[0028] Figure 2 This is a physical similarity model for coal seam mining in Example 1;

[0029] Figure 3 The results are from the physical similarity simulation of coal seam mining in Example 1;

[0030] Figure 4 This is a three-dimensional numerical calculation model for coal seam mining in Example 1;

[0031] Figure 5 The results of a three-dimensional numerical simulation of coal seam mining;

[0032] Figure 6 This is a schematic diagram showing the calculation results of the second diffusion radius of the grout in Example 1;

[0033] Figure 7 The diagram shows the hole layout for grouting drilling, where (a) is fan-shaped, (b) is feather-shaped, and (c) is comb-shaped.

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0035] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention. The present invention will be further described in detail below with reference to the embodiments.

[0036] Example 1

[0037] Following the above technical solutions, such as Figure 1 As shown in the figure, this embodiment discloses a method for grouting borehole layout for advanced treatment of aquifers in the roof and floor of coal seams. The method includes the following steps:

[0038] Step 1: Collect borehole data and geophysical exploration data to determine the advanced grouting and modification layers in the coal seam roof and / or coal seam floor.

[0039] Drilling data includes borehole columnar sections that display lithology, rock color, structure, and mineral composition at different depths from the surface to underground. Mechanical properties obtainable from drilling data include: formation porosity, formation permeability, working face slope length, mining depth, average unit weight of the base rock strata, compressive strength of the base rock mass, and internal friction angle of the base rock mass.

[0040] Geophysical data is acquired by deploying seismic sources and receivers on the Earth's surface. It involves recording the propagation and reflection of seismic waves underground to infer the structure and properties of subsurface rock strata. The obtained data primarily includes seismic wavefield data, velocity information, geological structural information, and subsurface interface data. This data can determine the location, strike, dip, and displacement of subsurface faults, and also reflect the bending and deformation of subsurface strata. Analysis can reveal the interfaces between different strata, the thickness of each stratum, lithology, and the top and bottom plate boundaries.

[0041] Based on the obtained data, the advanced grouting modification layers in the coal seam roof and / or coal seam floor can be determined, specifically including:

[0042] When the advanced grouting modification layer is located within the coal seam floor, based on the "lower three zones" theory, the depth values ​​of the three mining-induced water-conducting failure zones of the coal seam floor are obtained through theoretical calculations, physical similarity simulation tests, and numerical simulation calculations. The maximum value among the three mining-induced water-conducting failure zone depth values ​​of the coal seam floor is taken as the standard value, and the aquifer with the smallest difference between the depth value and the standard value is taken as the grouting modification layer of the floor.

[0043] The calculation of the depth of the water-conducting failure zone in the coal seam floor caused by mining specifically includes:

[0044] Based on the formulas of plastic mechanics theory, a theoretical value for the depth of the water-conducting failure zone in the coal seam floor caused by mining is obtained:

[0045]

[0046] In the formula: H is the mining depth, in meters; The internal friction angle of the base rock mass is expressed in degrees (°).

[0047] When the advanced grouting modification layer is located within the coal seam roof, based on the "upper three zones" theory, the development height values ​​of the three coal seam roof water-conducting fracture zones are obtained through theoretical calculations, physical similarity simulation experiments, and numerical simulation calculations. The maximum value among the three coal seam roof water-conducting fracture zone development height values ​​is taken as the standard value, and the aquifer with the smallest difference between the height value and the standard value is taken as the roof grouting modification layer.

[0048] The theoretical calculated value of the development height of the water-conducting fracture zone in the roof of the coal seam is obtained by using the calculation formula in the "Coal Mine Water Control Handbook" (Table 1).

[0049] Table 1

[0050]

[0051] In Table 1, H1 is the theoretical value (m) of the development height of the water-conducting fracture zone in the roof of the coal seam; M is the mining thickness (m).

[0052] Using the formulas in the table above, the theoretical value of the development height of a water-conducting fracture zone in the roof of a coal seam can be calculated.

[0053] Physical similarity experiments can more intuitively demonstrate the development characteristics of the floor failure zone and the roof water-conducting fracture zone during coal seam mining, such as... Figure 2As shown, an existing physical similarity model for coal seam mining is used to simulate the depth of the floor failure zone and the development height of the water-conducting fracture zone during coal seam mining. Specifically, based on basic similarity theory, similar materials such as river sand, fly ash, gypsum, and calcium carbonate are selected and mixed according to a preset ratio. After stirring with water, the mixture is placed into a model frame to build a physical similarity model with geometric, stress, and bulk density similarity. The model dimensions are: length × width × height = 3000mm × 1000mm × 200mm. After the physical similarity model is built, the development process of the floor water-conducting failure zone and the roof water-conducting fracture zone during coal seam mining is simulated. By measuring the fracture height generated on the surface of the physical model, the depth value of the floor water-conducting failure zone and the height value of the roof water-conducting fracture zone after coal seam mining are obtained. Through similarity ratio conversion, the depth value of the floor water-conducting failure zone and the development height value of the roof water-conducting fracture zone are obtained. The simulation results are shown below. Figure 3 As shown.

[0054] Numerical simulation is another effective means of obtaining the development characteristics of the floor failure zone and the roof water-conducting fracture zone during coal seam mining, such as... Figure 4 As shown, using existing numerical simulation software, a three-dimensional numerical simulation model was established based on actual working conditions and engineering geological conditions. The depth of the floor failure zone and the height of the water-conducting fracture zone during coal seam mining were numerically simulated to obtain the depth of the floor water-conducting failure zone and the height of the roof water-conducting fracture zone during coal seam mining. The numerical simulation results are as follows: Figure 5 As shown.

[0055] Based on the above theoretical calculations, physical similarity experiments, and numerical simulations, the depth values ​​of the mining-induced water-conducting fracture zones in the floor of the three coal seams and the development height values ​​of the water-conducting fracture zones in the roof of the three coal seams were obtained. The maximum value among the three depth values ​​of the mining-induced water-conducting fracture zones in the floor of the three coal seams was taken as the standard value, and the aquifer with the smallest difference between the depth value and the standard value was taken as the grouting modification layer in the floor. Using the maximum value as the standard value is to select the grouting modification layer above the water-conducting fracture zone as much as possible, so as to avoid the water-conducting fracture zone developing to the grouting modification layer after the coal seam is mined, causing fractures in the grouting modification layer and thus affecting the grouting modification effect.

[0056] Step 2: Based on the determined mechanical properties of the grouting modification layer, the first diffusion radius of the grout in the aquifer is obtained through theoretical calculation, and the second diffusion radius of the grout in the aquifer is obtained through numerical simulation calculation. The smaller of the first and second diffusion radii is taken as the diffusion radius of the grout.

[0057] Specifically, in theoretical calculations, the grout enters the underground aquifer through the grouting hole. Since the aquifer can be considered a porous medium, the grout enters the aquifer via permeation. The first diffusion radius can be determined using the permeation grouting theory and the following formula:

[0058]

[0059] In the formula: r1 is the first diffusion radius, in meters; K is the aquifer permeability coefficient, in meters per second; z is the grouting pressure head, in meters; t is the grouting time, in seconds. λ represents the porosity of the rock mass at the grouting layer; λ is the ratio of the grout viscosity to the water viscosity; r0 is the radius of the grouting borehole in meters. Wherein, K = 4.051 × 10⁻⁶. -5 m / s; z = 250 m; λ=97.2; r0=0.076m, and the grouting time t is taken as 1h, 60h and 120h respectively.

[0060] In this embodiment, calculations show that the first diffusion radius is 1.11m, 6.64m, and 9.08m when the grouting time is 1h, 60h, and 120h, respectively.

[0061] The second diffusion radius was determined by numerical simulation using the fluid dynamics module in COMSOL Multiphysics finite element software.

[0062] Specifically, this includes: setting numerical simulation calculation parameters and conditions based on actual grouting operation conditions to simulate the diffusion process of grout in an aquifer. Grouting in an aquifer is essentially a process of grout displacing groundwater. The flow of grout and groundwater in the aquifer is a two-phase flow. The volume fraction is used to characterize the diffusion radius of the grout in the aquifer in the numerical simulation results. The grout diffusion pattern is a circular diffusion centered on the grouting hole. Figure 6 The red portion represents the slurry concentration, with a volume fraction close to 100%, while the blue portion represents groundwater, with a slurry volume fraction close to 0, meaning the groundwater volume fraction is close to 100%.

[0063] In numerical software, monitoring points are set up to monitor the mixing zone of grout and groundwater at different time periods. The distance of the monitored mixing zone from the grouting hole is the diffusion radius of the grout.

[0064] like Figure 6 As shown, when t = 60h, the length of the slurry mixing zone from the grouting hole was 6.78m, which means the slurry diffusion radius r was 6.78m.

[0065] Therefore, after grouting for 1 hour, 60 hours, and 120 hours, the second diffusion radii calculated by numerical simulation were 1.16 m, 6.78 m, and 9.23 m, respectively.

[0066] The smaller of the first diffusion radius and the second diffusion radius is taken as the diffusion radius of the grout.

[0067] In summary, the final determined diffusion radius of the grout is 1.11m for 1 hour of grouting, 6.64m for 60 hours of grouting, and 9.08m for 120 hours of grouting.

[0068] Step 3: Based on the determined characteristics of the grouting modification layer, determine the hole layout shape for the grouting boreholes. The hole layout shapes include fan-shaped, feather-shaped, and comb-shaped. The hole layout shapes for the grouting boreholes are as follows: Figure 7 As shown.

[0069] The characteristics of fan-shaped boreholes are low construction difficulty, high drilling efficiency, and flexible drilling and grouting coordinated construction, but they also have the disadvantage of concentrated and repetitive workload.

[0070] Feather drilling is characterized by uniform hole distribution, fewer grouting blind zones, and less repetitive work, but it presents moderate construction challenges, moderate drilling efficiency, and is not flexible enough in drilling and grouting coordination.

[0071] Comb-shaped drilling is characterized by uniform hole distribution, virtually no grouting blind spots, and no repetitive work, but it is also more difficult to construct, particularly in coordinating drilling and grouting. Based on the characteristics of the grouting-modified strata and the specific conditions of the on-site drilling, a suitable hole layout is selected for construction, including:

[0072] When the drilling success rate of grouting-modified formation is greater than or equal to 85%, the hole layout of the grouting boreholes is comb-shaped.

[0073] When the borehole formation completion rate of grouting modification drilling is greater than or equal to 60% and less than 85%, the borehole layout shape of the grouting borehole is feather-shaped.

[0074] When the borehole formation completion rate of grouting modification is less than 60%, the borehole layout of grouting boreholes is fan-shaped to ensure drilling efficiency under formation conditions with low completion rates.

[0075] Step 4: Based on the grout diffusion radius determined in Step 2 and the borehole layout shape determined in Step 3, determine the grouting borehole trajectory design parameters.

[0076] The drilling trajectory design parameters include the opening position, the final hole position, the branch hole opening position, the drilling spacing, the drilling depth, the drilling inclination angle, the drilling azimuth angle, the drilling skew point position, the drilling stabilization point position, and the drilling bending strength.

[0077] Step 5: Conduct directional advance drilling according to the determined grouting borehole trajectory design parameters. During the construction process, use the drilling measurement while drilling device to obtain drilling parameters in real time, and adjust the drilling trajectory in real time according to the grouting borehole trajectory design parameters. That is, adjust the trajectory of the borehole in a timely manner according to the design parameters, correct the actual construction borehole trajectory, and make the borehole drill as close to the design trajectory as possible until the grouting borehole layout operation is completed.

[0078] The method of this invention integrates theoretical calculations, physical similarity simulation calculations, and numerical simulation calculations when designing grouting boreholes. It obtains the depth of the water-conducting failure zone of the coal seam floor and the height of the water-conducting fracture zone of the coal seam roof, respectively. Then, it determines the grouting modification layer based on the calculation results. Since the calculated values ​​are closer to the actual values, the selection of the grouting modification layer is more accurate and reasonable.

[0079] In the above description, unless otherwise explicitly specified and limited, terms such as "setup" and "connection" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections, etc. Those skilled in the art can understand the specific meaning of the above terms in this technical solution according to the specific circumstances.

[0080] The specific technical features described in the above embodiments can be combined in any suitable manner without contradiction, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method for arranging grouting boreholes for advanced treatment of aquifers in the roof and floor of coal seams, characterized in that, The method includes the following steps: Step 1: Collect borehole data and geophysical exploration data to determine the advanced grouting and modification layers in the coal seam roof and / or coal seam floor. Step 2: Based on the borehole data and geophysical exploration data collected in Step 1, determine the mechanical properties of the grouting modification layer in the advanced area, obtain the first diffusion radius of the grout in the aquifer through theoretical calculation, obtain the second diffusion radius of the grout in the aquifer through numerical simulation calculation, and take the smaller of the first diffusion radius and the second diffusion radius as the diffusion radius of the grout. Step 3: Based on the mechanical properties of the determined advanced grouting modification layer, determine the hole layout shape of the grouting boreholes. The hole layout shapes of the grouting boreholes include fan-shaped, feather-shaped, and comb-shaped. Step 4: Based on the advanced grouting modification layer determined in Step 1, the grout diffusion radius determined in Step 2, and the hole layout shape of the grouting boreholes determined in Step 3, determine the grouting borehole trajectory design parameters. Step 5: Conduct directional advance drilling according to the determined grouting borehole trajectory design parameters. During the construction process, use the drilling measurement and control device to obtain drilling parameters in real time, and adjust the drilling trajectory in real time according to the grouting borehole trajectory design parameters until the grouting borehole layout operation is completed. Step 1 specifically includes: when the advanced grouting modification layer is located within the coal seam floor, based on the "lower three zones" theory, the depth values ​​of the three mining-induced water-conducting failure zones of the coal seam floor are obtained through theoretical calculations, physical similarity simulation tests, and numerical simulation calculations. The maximum value among the three mining-induced water-conducting failure zone depth values ​​of the coal seam floor is taken as the standard value, and the aquifer with the smallest difference between the depth value and the standard value is taken as the grouting modification layer of the floor. When the advanced grouting modification layer is located within the coal seam roof, based on the "upper three zones" theory, the development height values ​​of the three coal seam roof water-conducting fracture zones are obtained by theoretical calculation, physical similarity simulation test and numerical simulation calculation using the coal seam roof water-conducting fracture zone theoretical calculation, physical similarity simulation test and numerical simulation calculation. The maximum value among the three coal seam roof water-conducting fracture zone development height values ​​is taken as the standard value, and the aquifer with the smallest difference between the height value and the standard value is taken as the roof grouting modification layer. The first diffusion radius mentioned in step 2 is determined by the following formula: In the formula: r 1 represents the first diffusion radius, in meters (m). K The aquifer permeability coefficient is expressed in m / s. z This refers to the grouting pressure head, measured in meters (m). t Grouting time, in seconds; The porosity of the rock mass in the grouting layer; This is the ratio of the viscosity of the grout to the viscosity of water; The radius of the grouting borehole is in meters (m). Step 3, which involves determining the borehole layout shape based on the mechanical properties of the advanced grouting modification layer, specifically includes: When the drilling success rate of grouting-modified formation is greater than or equal to 85%, the hole layout of the grouting boreholes is comb-shaped. When the borehole formation completion rate of grouting modification drilling is greater than or equal to 60% and less than 85%, the borehole layout shape of the grouting borehole is feather-shaped. When the borehole formation completion rate of grouting modification drilling is less than 60%, the borehole layout of grouting drilling is fan-shaped.

2. The method for grouting borehole layout for advanced treatment of aquifers in the roof and floor of coal seams as described in claim 1, characterized in that, The drilling trajectory design parameters described in step 4 include the opening position, the final hole position, the branch hole opening position, the drilling spacing, the drilling depth, the drilling inclination angle, the drilling azimuth angle, the drilling skew point position, the drilling stabilization point position, and the drilling bending strength.

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