Non-homogeneous coal pillar grouting reinforcement method

Abstract

The embodiment of the invention provides a heterogeneous coal pillar grouting reinforcement method. The method comprises the steps that hydraulic fracturing is carried out after a grout stopping layer is constructed on a roadway coal pillar; and reverse water absorption operation is conducted through the hydraulic fracturing grouting pipe, and then cracks of the surrounding rock are blocked in the mode that shallow hole grouting is conducted firstly, then medium-deep hole grouting is conducted, and finally deep hole grouting is conducted. Thus, a large amount of grout leakage or grout leakage during grouting is prevented through the grout stop layer, then the characteristics of the coal pillar rock mass are improved through hydraulic fracturing, the influence of subsequent residual water on the grouting material can be avoided through reverse water absorption operation, the problem of hole collapse of subsequent grouting drill holes is solved, and therefore the completeness of surrounding rock is improved; the pore characteristics of the heterogeneous coal pillar are effectively improved through the hydraulic fracturing technology, the hydraulic fracturing technology and the grouting reinforcement technology are combined, the reinforcement effect is improved, and the short-circuit effect problem in the follow-up grouting process is solved.

Description

Technical Field

[0001] The invention relates to the technical field of coal pillar management and reinforcement in coal mine tunnels, and relates to but is not limited to a grouting reinforcement method for a heterogeneous coal pillar. Background Art

[0002] Coal pillars in coal mine tunnels not only support the tunnel structure, but also effectively isolate the goaf to prevent accidents and collapse. However, due to the changes in the mining stress field caused by deep burial and high-intensity mining, the breakage and instability of coal pillars have become more common, resulting in a decrease in the bearing capacity of coal pillars, thus affecting their safety and stability. At present, the reinforcement methods for the stability and strength of coal pillars mainly include improving the stress state and enhancing the strength of surrounding rock. Common technical means include: mechanical support, shotcrete reinforcement, reinforced concrete support, grouting reinforcement technology, etc.

[0003] Among them, grouting reinforcement is considered to be an effective technology to improve the strength of the surrounding rock of coal pillars and control the stability of coal pillars in tunnels. By injecting special slurry into the coal pillar, cracks and pores can be filled to increase the overall stability of the coal pillar. However, in heterogeneous coal pillars, the uneven distribution of porosity and strength seriously affects the bearing capacity and overall stability of the coal pillar, and the grouting effect is extremely poor. The main difficulties are: short-circuit effect. In complex areas such as geological anomaly zones or weak layers, due to the uneven distribution of coal pillar porosity and strength, the slurry is prone to short-circuit effect during the injection process, making it impossible to fully fill the voids of the coal pillar. This directly leads to a weakening of the reinforcement effect and a reduction in the overall stability of the coal seam. Therefore, it is particularly important to carry out targeted grouting reinforcement methods based on the characteristics of heterogeneous coal pillars. Summary of the invention

[0004] The present invention provides a grouting reinforcement method for a heterogeneous coal pillar, aiming to solve the technical problems of weak reinforcement effect and low overall stability of coal seams in the reinforcement management of heterogeneous coal pillars in tunnels in the prior art.

[0005] The technical method of the embodiment of the present invention is implemented as follows:

[0006] In a first aspect, an embodiment of the present invention provides a method for reinforcing a heterogeneous coal pillar by grouting, the method comprising:

[0007] Based on the coal seam porosity φ, coal seam original rock stress q0, coal rock sample tensile strength R t and the lateral stress coefficient λ of the rock formation, calculate the critical value P of the borehole fracturing pressure; the critical value of the fracturing pressure is expressed as: P = min{(3-λ)q0+R t +(3λ-1)q0+R t};

[0008] Determine the drilling height and drilling depth based on the width and height of the coal pillar to be retained;

[0009] Spraying a certain amount of concrete slurry on the coal pillars in the roadway to provide a slurry stop layer for the coal pillars in the roadway;

[0010] After the grout-stopping layer is solidified, the tunnel coal pillar is drilled based on the drilling height and the drilling depth to obtain a hydraulic fracturing hole; after a grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed; after the hole is sealed, water is injected through the grouting pipe, and when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure, the hydraulic fracturing operation is completed; the grouting pipe is used to suck out the water remaining in the rock mass fissure, and the grouting pipe is closed after the water is discharged;

[0011] After the grouting pipe is closed, shallow grouting holes with a hole depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, and the spacing between holes is 1.5 to 3.0 m; then, shallow hole grouting pipes are installed in the shallow grouting holes to seal the holes, and grouting materials are injected after the sealing is completed. When the grouting pressure reaches 1.0 to 2.0 Mpa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes;

[0012] After the shallow hole grouting is completed, a medium-deep grouting hole with a hole depth of 5.0 to 10.0 m is constructed in the coal pillar of the roadway, and the hole spacing is 1.5 to 3.0 m. After that, a medium-deep hole grouting pipe is installed in the medium-deep grouting hole to seal the hole. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 3.0 to 4.0 Mpa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes;

[0013] After the grouting of the medium-deep hole is completed, a deep grouting hole with a hole depth of 11.0-16.0m is constructed in the coal pillar of the roadway, and the spacing between holes is 1.5-3.0m. After that, a deep hole grouting pipe is installed in the deep grouting hole to seal the hole. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 5.0-7.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes;

[0014] The above grouting process is repeated until the tunnel coal pillar reinforcement construction is completed.

[0015] In some embodiments, the grouting material is an acrylate grouting material.

[0016] In some embodiments, the principle of the grouting reinforcement method is to first use hydraulic fracturing technology to improve the rock characteristics of the coal pillar, and then use shallow hole grouting, medium-deep hole grouting and deep hole grouting to reinforce the coal pillar.

[0017] In some embodiments, during the construction of the hydraulic fracturing grouting pipe, water is first injected and then back-absorbed to avoid the influence of residual moisture on the grouting material.

[0018] The heterogeneous coal pillar grouting reinforcement method provided in the embodiment of the present invention effectively reinforces the heterogeneous roadway coal pillars in areas with large mining stress changes caused by deep burial or high-intensity mining, thereby achieving long-term stability of the roadway coal pillars; by first grouting in shallow holes, then grouting in medium and deep holes, and finally grouting in deep holes, a shielding grouting layer is formed at different depths, thereby improving the integrity of the surrounding rock within the grouting range and solving the problem of subsequent grouting drilling collapse; by using hydraulic fracturing technology, the pore characteristics of the heterogeneous coal pillars are effectively improved, the reinforcement effect is improved, and the short-circuit effect problem in the subsequent grouting process is solved.

[0019] The method adopts hydraulic fracturing first, which effectively improves the rock characteristics of the uneven distribution of porosity and strength of the heterogeneous coal pillar, ensures the smooth grouting process, and improves the integrity of the surrounding rock within the grouting range after grouting. The pore characteristics of the coal pillar are improved by hydraulic fracturing technology, and the slurry can be more evenly distributed, which improves the reinforcement effect and solves the short-circuit effect problem in the subsequent grouting process; by grouting in shallow holes first, then in medium and deep holes, and finally in deep holes, a shielding grouting layer is formed at different depths to ensure that the grouting pressure of the coal pillar is continuously increased, effectively reinforce the coal pillar of the roadway, seal the cracks in the surrounding rock, and improve the integrity of the surrounding rock; it has the characteristics of wide application, safety and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic flow chart of a method for reinforcing a heterogeneous coal pillar by grouting provided in an embodiment of the present invention;

[0021] Figure 2 It is a schematic diagram of hydraulic fracturing of a heterogeneous coal pillar grouting reinforcement method provided by an embodiment of the present invention;

[0022] Figure 3 It is a schematic diagram of shallow hole grouting, medium-deep hole grouting and deep hole grouting of the heterogeneous coal pillar grouting reinforcement method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present invention. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0024] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meaning as those commonly understood by those skilled in the art to which the embodiments of the present invention pertain. The terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0025] The embodiment of the present invention provides a method for reinforcing a heterogeneous coal pillar by grouting. Figure 1 , Figure 1 is a schematic diagram of a flow chart of a grouting reinforcement method for a heterogeneous coal pillar provided by an embodiment of the present invention, Figure 1 The steps shown are explained.

[0026] Step S110, based on the coal seam porosity φ, coal seam original rock stress q0, coal rock sample tensile strength R t and the lateral stress coefficient λ of the rock formation, calculate the critical value P of the borehole fracturing pressure.

[0027] Here, the critical value of the cracking pressure is expressed as: P = min{(3-λ)q0+R t +(3λ-1)q0+R t}.

[0028] In some embodiments, the coal seam porosity indicates the degree of development of pores in the coal seam, and its size affects the penetration and pressure transmission of fluids during fracturing; the original rock stress of the coal seam represents the original stress state of the coal pillar when it is not affected by mining, and is an important parameter that determines the initial stability of the coal pillar; the tensile strength of the coal rock sample reflects the ability of the coal pillar material to resist tensile failure; and the lateral stress coefficient of the rock formation is related to the stress distribution characteristics of the rock formation around the coal pillar. By comprehensively considering these parameters, the calculated critical value of the initiation pressure can accurately determine the minimum pressure required to cause the coal pillar to begin to crack during hydraulic fracturing, providing a key pressure basis for subsequent hydraulic fracturing operations.

[0029] Step S120, determining the drilling height and drilling depth based on the width and height of the remaining coal pillar.

[0030] In some embodiments, the drilling height and drilling depth can be reasonably determined according to the width and height of the coal pillar. The width and height of the coal pillar are the basic geometric dimensions of the coal pillar, which are closely related to the bearing capacity and stability of the coal pillar. Different coal pillar sizes may require different drilling arrangements to achieve the best reinforcement effect. For example, a wider or taller coal pillar may require deeper or more drilling holes to ensure the uniformity and integrity of the reinforcement.

[0031] Step S130, spraying a certain amount of concrete slurry on the coal pillars in the roadway to provide a slurry stop layer for the coal pillars in the roadway.

[0032] In some embodiments, a fixed amount of concrete slurry is sprayed on the surface of the coal pillar in the tunnel to form a stop grouting layer. The main function of the stop grouting layer is to prevent the slurry from overflowing during the subsequent hydraulic fracturing and grouting process, and to ensure that the slurry can play a role in reinforcing and transforming the coal pillar. Its thickness and quality will directly affect the stop grouting effect. The appropriate amount of concrete slurry and spraying method can be determined through experiments and experience to ensure that the stop grouting layer can be effectively consolidated and achieve the required strength and impermeability.

[0033] Step S140, after the grout-stop layer is solidified, based on the drilling height and the drilling depth, the coal pillar of the tunnel is drilled to obtain a hydraulic fracturing hole; after a grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed; after the hole is sealed, water is injected through the grouting pipe, and the hydraulic fracturing operation is completed when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure; the grouting pipe is used to suck out the residual water in the rock cracks, and the grouting pipe is closed after the water is discharged.

[0034] In some embodiments, after the stop grout layer is solidified, the coal pillar of the tunnel is drilled according to the determined drilling height and depth to obtain a hydraulic fracturing hole. The purpose of the hydraulic fracturing hole is to generate cracks through high-pressure water injection, change the structure and stress state inside the coal pillar, and provide a channel for subsequent grouting. After the grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed. The sealing effect must be guaranteed to prevent the leakage of pressure and slurry. After the hole is sealed, water is injected through the grouting pipe. When the working pressure of the fracturing pump reaches the critical value of the fracture initiation pressure, cracks will be generated in the coal pillar. After the hydraulic fracturing operation is completed, the grouting pipe is used to suck out and drain the residual water in the cracks, and finally the grouting pipe is closed. In this process, hydraulic fracturing can increase the porosity and cracks of the coal pillar, providing better conditions for subsequent grouting reinforcement.

[0035] Step S150, after the grouting pipe is closed, shallow grouting holes with a hole depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, and the hole spacing is 1.5 to 3.0 m; then, shallow hole grouting pipes are installed in the shallow grouting holes to seal the holes. After the sealing is completed, grouting materials are injected, and when the grouting pressure reaches 1.0 to 2.0 MPa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes.

[0036] Step S160, after the shallow hole grouting is completed, medium-deep grouting holes with a hole depth of 5.0-10.0m are constructed in the coal pillar of the tunnel, and the hole spacing is 1.5-3.0m. After that, medium-deep hole grouting pipes are installed in the medium-deep grouting holes to seal the holes. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 3.0-4.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes.

[0037] Step S170, after the completion of the medium-deep hole grouting, deep grouting holes with a hole depth of 11.0 to 16.0 m are constructed in the coal pillar of the roadway, and the hole spacing is 1.5 to 3.0 m. Afterwards, deep hole grouting pipes are installed in the deep grouting holes to seal the holes. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 5.0 to 7.0 MPa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes.

[0038] Step S180, repeat the above grouting process until the tunnel coal pillar reinforcement construction is completed.

[0039] First, after hydraulic fracturing, shallow grouting holes with a depth of 2.0 to 4.0 m are constructed in the coal pillars of the roadway, with a spacing of 1.5 to 3.0 m between holes. Shallow hole grouting pipes are installed in the shallow grouting holes and the holes are sealed, and then grouting materials are injected. When the grouting pressure reaches 1.0 to 2.0 Mpa, the pressure is stabilized for 3 to 5 minutes. This pressure stabilization process allows the grouting material to fully fill the shallow cracks and pores to ensure the reinforcement effect.

[0040] After the shallow hole grouting is completed, the construction of medium-deep grouting holes is carried out, with a hole depth of 5.0-10.0m and a hole spacing of 1.5-3.0m. Similarly, the medium-deep hole grouting pipe is installed, the hole is sealed, and the grouting material is injected. When the grouting pressure reaches 3.0-4.0Mpa, the pressure is stabilized for 3-5 minutes. This stage mainly reinforces the medium-deep part of the coal pillar. As the depth increases, the required grouting pressure also increases accordingly to ensure that the grouting material can overcome the resistance in the deep part and fill the cracks in the medium-deep part.

[0041] Finally, deep grouting holes are constructed with a hole depth of 11.0 to 16.0 m and a hole spacing of 1.5 to 3.0 m. The installation of deep hole grouting pipes, hole sealing and injection of grouting materials are similar to the above, but when the grouting pressure reaches 5.0 to 7.0 MPa, the pressure is stabilized for 3 to 5 minutes. This is because the geological conditions of the deep coal pillar are more complex, and higher grouting pressure can ensure that the grouting material can reach deeper cracks and pores, achieving effective reinforcement of the deep coal pillar.

[0042] Repeating the above grouting process means that through multiple grouting operations at different depths, the coal pillar can be gradually reinforced from shallow to deep, ensuring that different depths of the coal pillar can be fully reinforced and improving the overall performance of the coal pillar.

[0043] The method of the present invention comprehensively considers various physical and mechanical properties of heterogeneous coal pillars, realizes targeted hydraulic fracturing operations by accurately calculating the critical value of fracture initiation pressure, and can open appropriate fractures according to the actual conditions of the coal pillars, providing a good channel for subsequent grouting.

[0044] The setting of hierarchical shallow, medium and deep grouting holes and different grouting pressures can adapt to the reinforcement needs of coal pillars at different depths, ensure that the coal pillars can be fully reinforced from the surface to the deep, improve the strength and stability of the coal pillars, thereby significantly enhancing the role of coal pillars in tunnel support and goaf isolation, reducing the risk of coal pillar instability, extending the service life of tunnels, and improving the safety and efficiency of coal mining.

[0045] The method adopts hydraulic fracturing first, which effectively improves the rock characteristics of the uneven distribution of porosity and strength of the heterogeneous coal pillar, ensures the smooth grouting process, and improves the integrity of the surrounding rock within the grouting range after grouting. The pore characteristics of the coal pillar are improved by hydraulic fracturing technology, and the slurry can be more evenly distributed, which improves the reinforcement effect and solves the short-circuit effect problem in the subsequent grouting process; by grouting in shallow holes first, then in medium and deep holes, and finally in deep holes, a shielding grouting layer is formed at different depths to ensure that the grouting pressure of the coal pillar is continuously increased, effectively reinforce the coal pillar of the roadway, seal the cracks in the surrounding rock, and improve the integrity of the surrounding rock; it has the characteristics of wide application, safety and high efficiency.

[0046] The heterogeneous coal pillar grouting reinforcement method provided by the present invention effectively reinforces the heterogeneous roadway coal pillars in areas with large mining stress changes caused by deep burial or high-intensity mining, thereby achieving long-term stability of the roadway coal pillars; by first grouting shallow holes, then grouting medium and deep holes, and finally grouting deep holes, a shielding grouting layer is formed at different depths, thereby improving the integrity of the surrounding rock within the grouting range and solving the problem of subsequent grouting drilling collapse; by using hydraulic fracturing technology, the pore characteristics of the heterogeneous coal pillars are effectively improved, the reinforcement effect is improved, and the short-circuit effect problem in the subsequent grouting process is solved.

[0047] The following describes an exemplary application of an embodiment of the present invention in a practical application scenario.

[0048] The present invention provides a method for reinforcing a heterogeneous coal pillar by grouting, which solves the problems encountered in reinforcing and managing heterogeneous coal pillars in tunnels. The reinforcement method first uses hydraulic fracturing technology to improve the pore structure of the coal pillar, and then performs effective grouting to enhance the strength and stability of the coal pillar. The method includes the following steps:

[0049] Step 1: Determine the porosity φ of the coal seam, the original rock stress q0, and the tensile strength R of the coal rock sample through geological exploration and drilling tests. t And the lateral stress coefficient λ of the rock formation is generally taken as 1.2.

[0050] Calculate the critical value of drilling fracture pressure P: P = min{(3-λ)q0+R t +(3λ-1)q0+R t};

[0051] The working pressure of the fracturing pump should not be lower than the critical value of the fracturing pressure P during construction in the coal pillar of the roadway.

[0052] If the width of the coal pillar is B and the height of the coal pillar is H, determine the drilling position.

[0053] Drilling height h: Drilling depth b:

[0054] Step 2: Spray 0.1-0.2m of concrete slurry on the coal pillars in the roadway to provide a slurry stop layer for the coal pillars in the roadway.

[0055] Step 3: After the grouting layer is solidified, hydraulic fracturing holes with a depth of bm are constructed in the coal pillars of the roadway, with a horizontal spacing of 1.5m and a drilling height of hm. After the construction of the hydraulic fracturing holes is completed, a grouting pipe is placed in the hole, and the hole is sealed with quick-hardening cement, a hole sealer, etc. After the hole is sealed, water is injected through the grouting pipe. When the working pressure of the fracturing pump is not lower than the critical value of the fracture initiation pressure P Mpa, wait for the hydraulic fracturing to end.

[0056] Step 4: After completion, use the grouting pipe to suck out the remaining water in the rock cracks, and seal the grouting pipe after the water is removed.

[0057] Step 5, shallow hole grouting: After the grouting pipe is closed, shallow grouting holes with a depth of 2.0 to 4.0 m are constructed in the coal pillars of the tunnel, with a spacing of 1.5 to 3.0 m between holes. Then, shallow hole grouting pipes are installed in the holes, and the holes are sealed with quick-hardening cement, hole sealers, etc. After the sealing is completed, grouting is carried out. When the grouting pressure reaches 1.0 to 2.0 MPa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes.

[0058] Step 6, medium-deep hole grouting: After the shallow hole grouting is completed, medium-deep grouting holes with a depth of 5.0-10.0m are constructed in the coal pillar of the tunnel, with a spacing of 1.5-3.0m between holes. Then, medium-deep hole grouting pipes are installed in the holes, and the holes are sealed with quick-hardening cement, sealers, etc. After the sealing is completed, grouting is carried out. When the grouting pressure reaches 3.0-4.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes.

[0059] Step 7, deep hole grouting: After the medium and deep hole grouting is completed, deep grouting holes with a depth of 11.0-16.0m are constructed in the coal pillars of the tunnel, with a spacing of 1.5-3.0m between holes. Then, deep hole grouting pipes are installed in the holes, and the holes are sealed with quick-hardening cement, sealers, etc. After the sealing is completed, grouting is carried out. When the grouting pressure reaches 5.0-7.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes.

[0060] Step 8: As the excavation working face advances, repeat the above steps 2 to 7 until the tunnel coal pillar reinforcement construction is completed.

[0061] The depths of the shallow hole grouting, medium-deep hole grouting, and deep hole grouting described in this embodiment increase successively, and the grouting pressure increases successively.

[0062] The grouting material is an acrylate grouting material, which has good fluidity and durability, can be injected into extremely fine cracks, is insoluble in water, has good water resistance and strength, and can maintain stable performance in a humid environment after hydraulic fracturing.

[0063] like Figure 2 As shown, 1 is a roadway, 2 is a stop layer, 3 is a hydraulic fracturing hole, and 4 is a hydraulic fracturing grouting pipe. Specifically, a certain amount of concrete slurry is sprayed on the coal pillar of the roadway 1 to provide a stop layer 2 for the coal pillar of the roadway; after the stop layer 2 is solidified, the roadway coal pillar 1 is drilled based on the drilling height and the drilling depth to obtain a hydraulic fracturing hole 3; after the hydraulic fracturing grouting pipe 4 is placed in the hydraulic fracturing hole 3, the hole is sealed; after the hole is sealed, water is injected through the grouting pipe, and when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure, the hydraulic fracturing operation is completed; the hydraulic fracturing grouting pipe 4 is used to suck out the water remaining in the rock mass fissures, and the grouting pipe 4 is closed after the water is discharged.

[0064] like Figure 3 As shown, 1 is a tunnel, 2 is a stop layer, 5 is a deep hole grouting hole, 6 is a deep hole grouting pipe, 7 is a medium-deep hole grouting hole, 8 is a medium-deep hole grouting pipe, 9 is a shallow hole grouting hole, and 10 is a shallow hole grouting pipe. Specifically, after the hydraulic fracturing work is completed, shallow grouting holes 9 with a hole depth of 2.0 to 4.0 m are constructed in the tunnel 1 coal pillar, and the row spacing between holes is 1.5 to 3.0 m; then, shallow hole grouting pipes 10 are installed in the shallow grouting holes to seal the holes. After the sealing is completed, grouting materials are injected. When the grouting pressure reaches 1.0 to 2.0 Mpa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes.

[0065] After the shallow hole grouting is completed, medium-deep grouting holes 7 with a hole depth of 5.0-10.0m are constructed in the coal pillar of the tunnel 1, and the spacing between holes is 1.5-3.0m. Afterwards, medium-deep hole grouting pipes 8 are installed in the medium-deep grouting holes to seal the holes. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 3.0-4.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes.

[0066] After the grouting of the medium-deep holes is completed, deep grouting holes 5 with a depth of 11.0-16.0m are constructed in the coal pillar of the tunnel 1, and the spacing between holes is 1.5-3.0m. Afterwards, deep hole grouting pipes 6 are installed in the deep grouting holes to seal the holes. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 5.0-7.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes.

[0067] It should be noted that in the embodiment of the present invention, if the above-mentioned heterogeneous coal pillar grouting reinforcement method is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present invention is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product. The computer software product is stored in a storage medium, including a number of instructions for a terminal to execute all or part of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read Only Memory), disk or optical disk and other media that can store program code. In this way, the embodiment of the present invention is not limited to any specific combination of hardware and software.

[0068] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement and improvement made within the spirit and scope of the present invention are included in the protection scope of the present invention.

[0069] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the size of the serial number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention. The serial numbers of the above-mentioned embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0070] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of further restrictions, an element defined by the sentence "comprises one..." does not exclude the presence of other identical elements in the process, method, article or device including the element. In several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored, or not executed.

[0071] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for reinforcing a heterogeneous coal pillar by grouting, characterized in that: The method comprises: Based on the coal seam porosity φ, coal seam original rock stress q0, coal rock sample tensile strength R t and the lateral stress coefficient λ of the rock formation, calculate the critical value P of the borehole fracturing pressure; the critical value of the fracturing pressure is expressed as: P = min{(3-λ)q0+R t +(3λ-1)q0+R t }; Determine the drilling height and drilling depth based on the width and height of the coal pillar to be retained; Spraying a certain amount of concrete slurry on the coal pillars in the roadway to provide a slurry stop layer for the coal pillars in the roadway; After the grout-stopping layer is solidified, the tunnel coal pillar is drilled based on the drilling height and the drilling depth to obtain a hydraulic fracturing hole; after a grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed; after the hole is sealed, water is injected through the grouting pipe, and when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure, the hydraulic fracturing operation is completed; the grouting pipe is used to suck out the water remaining in the rock mass fissure, and the grouting pipe is closed after the water is discharged; After the grouting pipe is closed, shallow grouting holes with a hole depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, and the spacing between holes is 1.5 to 3.0 m; then, shallow hole grouting pipes are installed in the shallow grouting holes to seal the holes, and grouting materials are injected after the sealing is completed. When the grouting pressure reaches 1.0 to 2.0 Mpa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes; After the shallow hole grouting is completed, a medium-deep grouting hole with a hole depth of 5.0 to 10.0 m is constructed in the coal pillar of the roadway, and the hole spacing is 1.5 to 3.0 m. After that, a medium-deep hole grouting pipe is installed in the medium-deep grouting hole to seal the hole. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 3.0 to 4.0 Mpa, the grouting is stopped after stabilizing the pressure for 3 to 5 minutes; After the grouting of the medium-deep hole is completed, a deep grouting hole with a hole depth of 11.0-16.0m is constructed in the coal pillar of the roadway, and the spacing between holes is 1.5-3.0m. After that, a deep hole grouting pipe is installed in the deep grouting hole to seal the hole. After the sealing is completed, the grouting material is injected. When the grouting pressure reaches 5.0-7.0Mpa, the grouting is stopped after stabilizing the pressure for 3-5 minutes; The above grouting process is repeated until the tunnel coal pillar reinforcement construction is completed.

2. The method according to claim 1, characterized in that The grouting material is an acrylate grouting material.

3. The method according to claim 1, characterized in that: The principle of the grouting reinforcement method is to first use hydraulic fracturing technology to improve the rock characteristics of the coal pillar, and then use shallow hole grouting, medium-deep hole grouting and deep hole grouting to reinforce the coal pillar.

4. The method according to claim 1, characterized in that: During the construction of the hydraulic fracturing grouting pipe, water is first injected and then back-absorbed to avoid the influence of residual moisture on the grouting material.

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