A method for grouting and reinforcing a non-homogeneous coal pillar

Abstract

The embodiment of the present application provides a kind of non-homogeneous coal column grouting reinforcement method, hydraulic fracturing is carried out after roadway coal column construction stop grout layer;Through the reverse water absorption operation of hydraulic fracturing grouting pipe, then through the way of shallow hole grouting, middle-deep hole grouting, finally deep hole grouting, the fissure of surrounding rock is blocked. In this way, the present application prevents a large amount of grout running or leaking during grouting by the stop grout layer first, then improves the coal column rock mass characteristics by hydraulic fracturing, and through the reverse water absorption operation, the influence of the subsequent residual water on the grouting material can be avoided, solving the problem of subsequent grouting borehole collapse, thereby improving the integrity of surrounding rock;The pore characteristics of non-homogeneous coal column are effectively improved by hydraulic fracturing technology, the hydraulic fracturing technology and grouting reinforcement technology are combined, the reinforcement effect is improved, and the short circuit effect problem in the subsequent grouting process is solved.

Description

Technical Field

[0001] This invention relates to the field of coal mine roadway coal pillar treatment and reinforcement technology, and to, but is not limited to, a method for grouting reinforcement of heterogeneous coal pillars. Background Technology

[0002] Coal pillars in coal mine roadways not only support the roadway structure but also effectively isolate goaf areas, preventing accidents and collapses. However, due to changes in the stress field caused by deep burial and high-intensity mining, coal pillar breakage and instability have become common, leading to a decrease in the pillar's load-bearing capacity and affecting its safety and stability. Currently, reinforcement methods for coal pillar stability and strength mainly include improving the stress state and enhancing the strength of the surrounding rock. Common technical means include mechanical support, shotcrete reinforcement, reinforced concrete support, and grouting reinforcement technology.

[0003] Grouting reinforcement is considered an effective technique for improving the strength of the surrounding rock of coal pillars and controlling the stability of coal pillars in roadways. By injecting a special grout into the coal pillar, cracks and pores can be filled, increasing the overall stability of the coal pillar. However, in heterogeneous coal pillars, the uneven distribution of porosity and strength severely affects the bearing capacity and overall stability of the coal pillar, and the grouting effect is extremely poor. The main difficulty is the short-circuit effect. In complex areas such as geological anomaly zones or weak layers, due to the uneven distribution of porosity and strength of the coal pillar, the grout is prone to a short-circuit effect during injection, preventing it from fully filling the voids in the coal pillar. This directly leads to a weakened reinforcement effect and a decrease in the overall stability of the coal seam. Therefore, targeted grouting reinforcement methods for heterogeneous coal pillars are particularly important. Summary of the Invention

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

[0005] The technical method of this invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a method for grouting reinforcement of heterogeneous coal pillars, the method comprising:

[0007] Based on the obtained coal seam porosity φ, original rock stress q0, and tensile strength R of the coal and rock mass sample... t Given the lateral stress coefficient λ of the rock strata, 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] The borehole height and depth are determined based on the width and height of the coal pillar.

[0009] A measured amount of concrete grout is sprayed onto the coal pillar in the roadway to provide a grout-stopping layer for the coal pillar.

[0010] After the grout-stopping layer has solidified, based on the borehole height and depth, a borehole is drilled in the coal pillar of the roadway to obtain a hydraulic fracturing hole. After the grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed. After sealing, water is injected through the grouting pipe. When the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure, the hydraulic fracturing operation ends. The water remaining in the rock mass fracture is back-suctioned out using the grouting pipe. After the water is drained, the grouting pipe is sealed.

[0011] After the grouting pipe is sealed, shallow grouting holes with a depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, shallow grouting pipes are installed in the shallow grouting holes to seal them. After sealing, grouting material is injected. When the grouting pressure reaches 1.0 to 2.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0012] After shallow hole grouting is completed, medium-deep grouting holes with a depth of 5.0 to 10.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, medium-deep hole grouting pipes are installed in the medium-deep grouting holes to seal them. After sealing, the grouting material is injected. When the grouting pressure reaches 3.0 to 4.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0013] After the medium-deep hole grouting is completed, deep grouting holes with a depth of 11.0 to 16.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, deep hole grouting pipes are installed in the deep grouting holes to seal them. After sealing, the grouting material is injected. When the grouting pressure reaches 5.0 to 7.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0014] Repeat the above grouting process until the coal pillar reinforcement construction in the roadway 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 characteristics of the coal pillar rock mass, and then use shallow hole grouting, medium-deep hole grouting and deep hole grouting to reinforce the coal pillar.

[0017] In some embodiments, the hydraulic fracturing grouting pipe is constructed by first injecting water and then reverse-suctioning water to avoid the influence of residual moisture on the grouting material.

[0018] The heterogeneous coal pillar grouting reinforcement method provided in this invention effectively reinforces heterogeneous roadway coal pillars in areas with large variations in mining-induced stress caused by deep or high-intensity mining, achieving long-term stability of the roadway coal pillars. By first grouting shallow holes, then medium-deep holes, and finally deep holes, a shielding grout-stopping layer is formed at different depths, improving the integrity of the surrounding rock within the grouting range and solving the problem of borehole collapse during subsequent grouting. The hydraulic fracturing technology effectively improves the porosity characteristics of the heterogeneous coal pillar, enhances the reinforcement effect, and solves the short-circuit effect problem during subsequent grouting.

[0019] This method employs hydraulic fracturing first, which effectively improves the rock mass characteristics of heterogeneous coal pillars with uneven distribution of porosity and strength, ensuring a smooth grouting process. After grouting, the integrity of the surrounding rock within the grouting area is improved. By improving the porosity characteristics of the coal pillar through hydraulic fracturing technology, the grout can be distributed more evenly, improving the reinforcement effect and solving the short-circuit effect problem in subsequent grouting processes. By first grouting shallow holes, then medium-deep holes, and finally deep holes, a shielding grout-stopping layer is formed at different depths, ensuring that the grouting pressure of the coal pillar continuously increases, effectively reinforcing the roadway coal pillar, sealing the fissures in the surrounding rock, and improving the integrity of the surrounding rock. It has the characteristics of wide applicability, safety, and high efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for grouting and reinforcing heterogeneous coal pillars provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of hydraulic fracturing for the heterogeneous coal pillar grouting reinforcement method provided in this embodiment of the invention;

[0022] Figure 3 This 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 in the embodiments of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on 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.

[0024] In the following description, references to "some embodiments" refer to a subset of all possible embodiments; however, it is understood that "some embodiments" may be the same 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 invention have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the invention pertain. The terminology used in the embodiments of the invention is for the purpose of describing the embodiments of the invention only and is not intended to limit the invention.

[0025] This invention provides a method for grouting reinforcement of heterogeneous coal pillars. See [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic flowchart of the heterogeneous coal pillar grouting reinforcement method provided in this embodiment of the invention, which will be combined with... Figure 1 The steps shown are explained.

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

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

[0028] In some embodiments, coal seam porosity represents the degree of pore development in the coal seam, and its size affects fluid penetration and pressure transmission during fracturing; the original stress of the coal seam represents the original stress state of the coal pillar before mining, and is an important parameter determining the initial stability of the coal pillar; the tensile strength of the coal-rock mass sample reflects the ability of the coal pillar material to resist tensile failure; and the lateral stress coefficient of the rock strata is related to the stress distribution characteristics of the rock strata surrounding the coal pillar. By comprehensively considering these parameters, the calculated critical initiation pressure value can accurately determine the minimum pressure required to initiate fractures in the coal pillar during hydraulic fracturing, providing a crucial pressure basis for subsequent hydraulic fracturing operations.

[0029] Step S120: Determine the borehole height and borehole depth based on the width and height of the coal pillar.

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

[0031] Step S130: A measured amount of concrete slurry is sprayed onto the coal pillar in the roadway to provide a slurry-stopping layer for the coal pillar.

[0032] In some embodiments, a measured amount of concrete grout is sprayed onto the surface of the coal pillar in the roadway to form a grout-stopping layer. The main function of the grout-stopping layer is to prevent the grout from overflowing during subsequent hydraulic fracturing and grouting processes, ensuring that the grout can play a reinforcing and modifying role inside the coal pillar. Its thickness and quality directly affect the grout-stopping effect. Through experiments and experience, the appropriate amount of concrete grout and the spraying method can be determined to ensure that the grout-stopping layer can effectively solidify and achieve the required strength and impermeability.

[0033] Step S140: After the grout-stopping layer has solidified, a hole is drilled in the coal pillar of the roadway based on the borehole height and the borehole depth to obtain a hydraulic fracturing hole; after the grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed; after sealing the hole, water is injected through the grouting pipe, and the hydraulic fracturing operation ends when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure; the water remaining in the rock mass fissure is back-suctioned out using the grouting pipe, and the grouting pipe is sealed after the water is drained.

[0034] In some embodiments, after the grout-stopping layer has solidified, boreholes are drilled into the coal pillar of the roadway according to a predetermined borehole height and depth to obtain hydraulic fracturing holes. The purpose of hydraulic fracturing holes is to generate fractures through high-pressure water injection, thereby altering the internal structure and stress state of the coal pillar and providing a channel for subsequent grouting. After inserting a grouting pipe into the hydraulic fracturing hole, the hole is sealed to ensure a tight seal and prevent pressure and grout leakage. After sealing, water is injected through the grouting pipe. When the fracturing pump's operating pressure reaches the critical value for initiation pressure, fractures will form within the coal pillar. After the hydraulic fracturing operation is completed, the grouting pipe is used to back-suction and drain any remaining water from the fractures, and finally, the grouting pipe is sealed. During this process, hydraulic fracturing increases the porosity and fractures of the coal pillar, providing better conditions for subsequent grouting reinforcement.

[0035] In step S150, after the grouting pipe is sealed, shallow grouting holes with a depth of 2.0 to 4.0 m are made in the coal pillar construction holes in the roadway, and the spacing between the holes is 1.5 to 3.0 m. Then, shallow grouting pipes are installed in the shallow grouting holes to seal them. After sealing, grouting material is injected. When the grouting pressure reaches 1.0 to 2.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0036] Step S160: After shallow hole grouting is completed, medium-deep grouting holes with a depth of 5.0 to 10.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, medium-deep hole grouting pipes are installed in the medium-deep grouting holes to seal them. After sealing, the grouting material is injected. When the grouting pressure reaches 3.0 to 4.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

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

[0038] Step S180: Repeat the above grouting process until the roadway coal pillar reinforcement construction is completed.

[0039] First, after hydraulic fracturing, shallow grouting holes with a depth of 2.0–4.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5–3.0 m between holes. Shallow grouting pipes are installed inside the shallow grouting holes and sealed, followed by the injection of grouting material. When the grouting pressure reaches 1.0–2.0 MPa, it is stabilized for 3–5 minutes. This stabilization process allows the grouting material to fully fill the shallow fractures and pores, ensuring the reinforcement effect.

[0040] After shallow-hole grouting is completed, medium-deep grouting holes are constructed, with a depth of 5.0–10.0 m and a spacing of 1.5–3.0 m between holes. Similarly, medium-deep grouting pipes are installed, the holes are sealed, and grouting material is injected. When the grouting pressure reaches 3.0–4.0 MPa, it is stabilized for 3–5 minutes. This stage mainly reinforces the medium-deep part of the coal pillar. Due to the increased depth, the required grouting pressure also increases accordingly to ensure that the grouting material can overcome the resistance at depth and fill the cracks in the medium-deep part.

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

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

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

[0044] The layered arrangement of shallow, medium, and deep grouting holes and different grouting pressures can adapt to the reinforcement needs of coal pillars at different depths, ensuring that the coal pillars are fully reinforced from the surface to the depths, improving the strength and stability of the coal pillars, thereby significantly enhancing the role of the coal pillars in roadway support and goaf isolation, reducing the risk of coal pillar instability, extending the service life of roadways, and improving the safety and efficiency of coal mining.

[0045] This method employs hydraulic fracturing first, which effectively improves the rock mass characteristics of heterogeneous coal pillars with uneven distribution of porosity and strength, ensuring a smooth grouting process. After grouting, the integrity of the surrounding rock within the grouting area is improved. By improving the porosity characteristics of the coal pillar through hydraulic fracturing technology, the grout can be distributed more evenly, improving the reinforcement effect and solving the short-circuit effect problem in subsequent grouting processes. By first grouting shallow holes, then medium-deep holes, and finally deep holes, a shielding grout-stopping layer is formed at different depths, ensuring that the grouting pressure of the coal pillar continuously increases, effectively reinforcing the roadway coal pillar, sealing the fissures in the surrounding rock, and improving the integrity of the surrounding rock. It has the characteristics of wide applicability, safety, and high efficiency.

[0046] The grouting reinforcement method for heterogeneous coal pillars provided by this invention effectively reinforces heterogeneous roadway coal pillars in areas with large variations in mining-induced stress caused by deep or high-intensity mining, achieving long-term stability of the roadway coal pillars. By first grouting shallow holes, then medium-deep holes, and finally deep holes, a shielding grout-stopping layer is formed at different depths, improving the integrity of the surrounding rock within the grouting range and solving the problem of borehole collapse during subsequent grouting. The hydraulic fracturing technology effectively improves the porosity characteristics of the heterogeneous coal pillar, enhances the reinforcement effect, and solves the short-circuit effect problem during subsequent grouting.

[0047] The following will describe an exemplary application of the embodiments of the present invention in a practical application scenario.

[0048] This invention provides a grouting reinforcement method for heterogeneous coal pillars, solving the problems encountered in the reinforcement and treatment of heterogeneous coal pillars in roadways. This reinforcement method first improves the pore structure of the coal pillar using hydraulic fracturing technology, and then performs effective grouting, thereby enhancing 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 in-situ stress q0, and the tensile strength R of the coal and rock mass samples through geological exploration and drilling tests. t The lateral stress coefficient λ of the rock strata is generally taken as 1.2.

[0050] Calculate the critical value of borehole fracturing 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 P of the fracturing initiation pressure during fracturing operations in roadway coal pillars.

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

[0053] Drilling height h: Drilling depth b:

[0054] Step 2: Spray 0.1-0.2m of concrete grout onto the coal pillar in the roadway to provide a grout-stopping layer for the coal pillar.

[0055] Step 3: After the grout stop layer has solidified, construct hydraulic fracturing holes with a depth of bm in the coal pillar of the roadway, with a horizontal spacing of 1.5m and a drilling height of hm. After the hydraulic fracturing holes are constructed, insert grouting pipes into the holes and seal them with quick-hardening cement and sealing devices. After sealing, inject water through the grouting pipes. When the working pressure of the fracturing pump is not lower than the critical value of the fracturing initiation pressure P MPa, wait for the hydraulic fracturing to end.

[0056] Step 4: After completion, use the grouting pipe to back-suction the water remaining in the rock fissures, remove the water, and then seal the grouting pipe.

[0057] Step 5, Shallow hole grouting: After the grouting pipe is sealed, shallow grouting holes with a depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, 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 and sealing devices. After sealing, grouting is performed. When the grouting pressure reaches 1.0 to 2.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0058] Step 6, Medium-deep hole grouting: After the shallow hole grouting is completed, medium-deep grouting holes with a depth of 5.0 to 10.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, medium-deep hole grouting pipes are installed in the holes, and the holes are sealed with quick-hardening cement and sealing devices. After sealing, grouting is performed. When the grouting pressure reaches 3.0 to 4.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

[0059] Step 7, Deep Hole Grouting: After the medium-deep hole grouting is completed, deep grouting holes with a depth of 11.0 to 16.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, deep hole grouting pipes are installed in the holes, and the holes are sealed with quick-hardening cement and sealing devices. After sealing, grouting is performed. When the grouting pressure reaches 5.0 to 7.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped.

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

[0061] In this embodiment, the depths of shallow hole grouting, medium-deep hole grouting, and deep hole grouting increase sequentially, and the grouting pressure also increases sequentially.

[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 the humid environment after hydraulic fracturing.

[0063] like Figure 2 As shown, 1 represents the roadway, 2 represents the grout stop layer, 3 represents the hydraulic fracturing hole, and 4 represents the hydraulic fracturing grouting pipe. Specifically, a measured amount of concrete slurry is sprayed onto the coal pillar in roadway 1 to provide a grout stop layer 2 for the coal pillar. After the grout stop layer 2 has solidified, a hydraulic fracturing hole 3 is obtained by drilling the coal pillar 1 based on the drilling height and depth. After the hydraulic fracturing hole 3 is inserted into the hydraulic fracturing grouting pipe 4, the hole is sealed. After sealing, water is injected through the grouting pipe. The hydraulic fracturing operation ends when the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure. The water remaining in the rock mass fractures is back-suctioned out using the hydraulic fracturing grouting pipe 4. After the water is drained, the grouting pipe 4 is sealed.

[0064] like Figure 3 As shown, 1 represents the roadway, 2 represents the grout stop layer, 5 represents a deep grouting hole, 6 represents a deep grouting pipe, 7 represents a medium-deep grouting hole, 8 represents a medium-deep grouting pipe, 9 represents a shallow grouting hole, and 10 represents a shallow grouting pipe. Specifically, after the hydraulic fracturing operation is completed, shallow grouting holes 9 with a depth of 2.0–4.0 m are constructed in the coal pillar of roadway 1, with a spacing of 1.5–3.0 m between holes. Then, shallow grouting pipes 10 are installed in the shallow grouting holes to seal them. After sealing, grouting material is injected. When the grouting pressure reaches 1.0–2.0 MPa, the pressure is stabilized for 3–5 minutes before grouting is stopped.

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

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

[0067] It should be noted that, in the embodiments of the present invention, if the above-mentioned heterogeneous coal pillar grouting reinforcement method is implemented in the form of a software functional 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 embodiments of the present invention, or the part that contributes to related technologies, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a terminal to execute all or part of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), magnetic disks, or optical disks. Thus, the embodiments of the present invention are not limited to any specific hardware and software combination.

[0068] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

[0069] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of the invention, the sequence numbers of the above-described processes do not imply a sequential 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 embodiments of the invention. The sequence numbers of the above-described embodiments of the invention are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0070] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not performed.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for grouting reinforcement of heterogeneous coal pillars, characterized in that, The method includes: Based on the obtained original stress q0 of the coal seam, tensile strength Rt of the coal and rock mass sample, and lateral stress coefficient λ of the rock strata, the critical value of borehole fracturing pressure is calculated. The critical value of the initiation pressure is expressed as: ; The borehole height and depth are determined based on the width and height of the coal pillar. A measured amount of concrete grout is sprayed onto the coal pillar in the roadway to provide a grout-stopping layer for the coal pillar. After the grout-stopping layer has solidified, based on the borehole height and depth, a borehole is drilled in the coal pillar of the roadway to obtain a hydraulic fracturing hole. After the grouting pipe is placed in the hydraulic fracturing hole, the hole is sealed. After sealing, water is injected through the grouting pipe. When the working pressure of the fracturing pump is not lower than the critical value of the fracturing pressure, the hydraulic fracturing operation ends. The water remaining in the rock mass fracture is back-suctioned out using the grouting pipe. After the water is drained, the grouting pipe is sealed. After the grouting pipe is sealed, shallow grouting holes with a depth of 2.0 to 4.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, shallow grouting pipes are installed in the shallow grouting holes to seal them. After sealing, grouting material is injected. When the grouting pressure reaches 1.0 to 2.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped. After shallow hole grouting is completed, medium-deep grouting holes with a depth of 5.0 to 10.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, medium-deep hole grouting pipes are installed in the medium-deep grouting holes to seal them. After sealing, the grouting material is injected. When the grouting pressure reaches 3.0 to 4.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped. After the medium-deep hole grouting is completed, deep grouting holes with a depth of 11.0 to 16.0 m are constructed in the coal pillar of the roadway, with a spacing of 1.5 to 3.0 m between holes. Then, deep hole grouting pipes are installed in the deep grouting holes to seal them. After sealing, the grouting material is injected. When the grouting pressure reaches 5.0 to 7.0 MPa, the pressure is stabilized for 3 to 5 minutes and then grouting is stopped. Repeat the above grouting process until the coal pillar reinforcement construction in the roadway is completed. The grouting material is an acrylate grouting material; The principle of the grouting reinforcement method is to first use hydraulic fracturing technology to improve the characteristics of the coal pillar rock mass, and then use shallow hole grouting, medium-deep hole grouting and deep hole grouting to reinforce the coal pillar. During the construction of the hydraulic fracturing grouting pipe, water is injected first and then reversed to avoid the influence of residual moisture on the grouting material.

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