Precise control method and equipment for initial caving pressure relief of working face and medium

Abstract

The invention relates to the technical field of coal mine roof control, and discloses a precise control method and device for initial roof caving pressure relief of a working face and a medium. The method comprises the steps that directional fracturing is conducted on a roof behind a coal mine working face open-off cut, and the roof containing a weakening ring is obtained; step pitch parameters are determined according to the top plate containing the weakening ring, and the initial fracture step pitch of the top plate containing the weakening ring is calculated based on the step pitch parameters; and the fracturing drilling depth of directional fracturing is monitored in real time, and the primary fracture step pitch is regulated and controlled in real time according to the fracturing drilling depth. According to the method, the boundary conditions of the roof can be changed, the limit span is reduced, and accurate control over the initial fracture step pitch of the roof is achieved in combination with an empirical formula and drilling parameter regulation and control.

Description

Technical Field

[0001] This invention relates to the field of coal mine roof control technology, specifically to a method, equipment, and medium for precise control of initial roof caving and pressure relief in a working face. Background Technology

[0002] In the initial mining stage of longwall mining in coal mines, the roof strata, supported by the solid coal face on all four sides, form a plate structure with fixed supports on all four sides. Under the influence of mining, this structure is prone to OX-type fractures. This fracture mode leads to the overall failure of the roof, and the load of the overlying strata is rapidly transferred to the coal face and surrounding rock of the roadway in front of the working face, causing safety hazards such as coal face spalling, strong dynamic pressure impact in the roadway, and failure of the support system. Traditional passive support methods are difficult to effectively control the roof collapse process, posing a risk of large-scale roof collapse and seriously affecting mine safety. Therefore, how to actively control the roof fracture process and achieve precise pressure relief has become an urgent problem to be solved. Summary of the Invention

[0003] The technical problem to be solved by this invention is how to automatically control the fracture process of the top plate and achieve precise pressure relief.

[0004] The present invention solves the above-mentioned technical problems through the following technical means: This invention provides a method for precise control of the initial caving and pressure relief of a working face, characterized by comprising: Directional fracturing is performed on the roof behind the cut-out of the coal mine working face to obtain a roof containing a weakened zone; The step distance parameter is determined based on the top plate containing the weakening ring, and the initial fracture step distance of the top plate containing the weakening ring is calculated based on the step distance parameter. The fracturing borehole depth of directional fracturing is monitored in real time, and the initial fracture step distance is adjusted in real time according to the fracturing borehole depth.

[0005] The present invention also provides a processing device, characterized in that it includes at least one processor and at least one memory communicatively connected to the processor, wherein: the memory stores program instructions executable by the processor, and the processor can execute the above-mentioned method for precise control of initial top release and pressure relief of the working face by calling the program instructions.

[0006] The present invention also provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, the computer instructions causing the computer to execute the above-described method for precise control of the initial caving and depressurization of the working face.

[0007] The advantages of this invention are: This invention utilizes hydraulic fracturing technology to construct a weakening zone behind the cut, which can alter the roof boundary conditions, reduce its ultimate span, and, combined with empirical formulas and drilling parameter adjustments, achieve precise control over the initial fracture step distance of the roof. Attached Figure Description

[0008] Figure 1 This is a flowchart illustrating a method for precise control of the initial jacking and depressurization of the working face in one embodiment of the present invention. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Reference Figure 1 The diagram shown is a flowchart illustrating a precise control method for initial caving and pressure relief of a working face according to an embodiment of the present invention. In this embodiment, the precise control method for initial caving and pressure relief of a working face includes: S1. Directional fracturing is performed on the roof behind the cut in the coal mine working face to obtain a roof containing a weakened zone.

[0011] In this embodiment of the invention, directional fracturing involves drilling a row of roof-cutting boreholes in the roof behind the working face cut-out, using hydraulic fracturing technology to create a high-strength directional fracture, significantly reducing the overall bearing capacity and effective tensile strength of the roof. Directional fracturing is then simultaneously implemented in both roadways along the mining direction to form a continuous pressure relief boundary, ultimately constructing an approximately one-sided "U"-shaped weakening ring in the roof, resulting in a roof containing the weakening ring.

[0012] Specifically, the directional fracturing process includes, but is not limited to, the following steps: The first step is to use an anchor drilling rig to drill holes vertically into the top slab. The second step is to install the small-diameter high-pressure fracturing packer assembly. The fracturing rod is connected to the packer assembly and pushed to the target fracturing layer. It is then locked with a locking device, which is secured with anchor chains, etc. The fracturing rod is then connected to the adapter and the high-pressure pipeline in sequence. The high-pressure pipeline is connected to the emulsification pump through the adapter. Two tees are connected near the fracturing orifice of the high-pressure hose, one for connecting to the hydraulic fracturing pressure gauge and the other for connecting to the pressure relief ball valve. The third step is to slowly open the shut-off valve after testing and debugging all the equipment, and then perform high-pressure hydraulic fracturing on the target fracturing area. The fourth step is to slowly adjust the pressure adjustment knob of the high-pressure pump to zero when the pressure monitored by the hydraulic fracturing pressure gauge is less than 5 MPa, or when water comes out of the top plate (adjacent borehole) for more than 5 to 7 minutes, or when the fracturing time exceeds 20 minutes. Then, turn off the high-pressure pump switch and the water injection stage ends. Fifth step: After water injection is completed, slowly open the ball valve to release pressure and drain water. After the water in the hole has drained and there is no pressure, the sealing device will retract. Step 6: After one stage of fracturing is completed, slowly loosen the locking device top screw, and use the fracturing rod to retract the high-pressure fracturing packer assembly to the next fracturing area of ​​the borehole to be fractured. Repeat steps 3 to 5 to carry out the retracted segmented fracturing operation.

[0013] Step 7: Remove the fracturing rod and withdraw the sealing device; Step 8: Record the pressure data and borehole data; single-hole water injection is now complete.

[0014] S2. Determine the step distance parameters based on the top plate containing the weakening ring, and calculate the initial fracture step distance of the top plate containing the weakening ring based on the step distance parameters.

[0015] In this embodiment of the invention, by forming a weakening circle, the original four-sided fixed boundary condition of the roof is transformed into a mechanical model with one side being simply supported by the goaf and the other three sides being weakened by fractures, which approximates the roof condition of a three-sided goaf or an isolated working face.

[0016] In detail, the step distance parameters include the thickness of the top strata, lithological parameters, and tensile strength. The initial fracture step distance can be calculated using the following empirical formula:

[0017] in, Indicates the initial break step distance. This represents a preset coefficient between the thickness of the top strata and the step distance. This indicates the thickness of the top strata.

[0018] in, The value typically ranges from 3.0 to 4.5. When the roof thickness is large or the lithology is relatively weak, Take 3.0~4.0; when the top plate thickness is moderate and the lithology is relatively hard, Take 4.0~4.5.

[0019] For example, the overlying rock structure and related parameters of the working face use a mudstone or sandy mudstone layer with a height of 11 meters as the immediate roof, and a combination of silty fine sandstone with a height of 6 meters and medium-fine sandstone with a height of 6.6 meters as the basic roof. Based on empirical values ​​of lithology in the Huainan mining area, the tensile strength of the fine sandstone and medium sandstone is taken as... Rock density .

[0020] The maximum span of the slats can be calculated using the following formula: (1) in, This represents the thickness of the basic top rock layer; Poisson's ratio of the rock strata; The tensile strength of the basic top rock layer; This refers to the self-weight of the rock strata and the load on it.

[0021] Before fracturing, the top plate of the cut hole is constrained around the perimeter, forming a solid coal support boundary condition on four sides, which can be calculated using the following step formula: (2) in, The length of the working surface; This represents the limit span of the plate.

[0022] In the roof and working face where a weakened zone is formed, the step distance formula for a three-sided mined-out or fault-bounded isolated working face can be expressed as: (3) in, The length of the working surface; This represents the limit span of the plate.

[0023] Before fracturing, the roof is a solid rock stratum, and its boundary conditions can be regarded as solid coal support on four sides.

[0024] The limit span of the plate is calculated according to formula (1): .

[0025] Judgment conditions: The step size can be calculated using the following formula. :

[0026] thus, .

[0027] After fracturing, a weak surface was artificially created at the cut location, significantly reducing the effective tensile strength of the rock mass. Based on engineering experience, the effective strength of the rock mass after fracturing can be reduced to one-third to one-half of its intact state. Here, we take... The mechanical nature of the roof conditions is similar to that of a three-sided mining or isolated working face.

[0028] The limit span of the plate is determined according to formula (1): .

[0029] Judgment conditions: The step size can be calculated using the following formula. :

[0030] thus, .

[0031] The calculation result is close to the actual data. Therefore, it can be concluded that the initial fracture step after hydraulic fracturing and depressurization is half that before fracturing.

[0032] S3. Monitor the fracturing borehole depth of directional fracturing in real time, and adjust the initial fracture step distance in real time according to the fracturing borehole depth.

[0033] In this embodiment of the invention, the fracturing borehole depth of directional fracturing can be used to adjust the spatial range of fracture development by changing the vertical position and extension length of the fracturing section in the top plate. This can also control the weakening range of the weakening zone. Therefore, the initial fracture step distance can be adjusted in real time by adjusting the fracturing borehole depth to achieve precise control of the step distance.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for precise control of initial roof caving and pressure relief at a working face, characterized in that, include: Directional fracturing is performed on the roof behind the cut-out of the coal mine working face to obtain a roof containing a weakened zone; The step distance parameter is determined based on the top plate containing the weakening ring, and the initial fracture step distance of the top plate containing the weakening ring is calculated based on the step distance parameter. The fracturing borehole depth of directional fracturing is monitored in real time, and the initial fracture step distance is adjusted in real time according to the fracturing borehole depth.

2. The method for precise control of initial roof caving and pressure relief at the working face as described in claim 1, characterized in that, The calculation of the initial fracture step distance of the top plate containing the weakening ring based on the step distance parameter includes: The initial fracture step distance is calculated using the following empirical formula: in, Indicates the initial break step distance. This represents a preset coefficient between the thickness of the top strata and the step distance. This indicates the thickness of the top strata.

3. A processing device, characterized in that, It includes at least one processor and at least one memory communicatively connected to the processor, wherein: the memory stores program instructions executable by the processor, and the processor can execute the method as described in any one of claims 1 to 2 by invoking the program instructions.

4. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that cause the computer to perform the method as described in any one of claims 1 to 2.

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