Grouting method for room-and-pillar mining area

Abstract

The application provides a house pillar type goaf grouting method, which comprises the following steps: performing directional drilling operation in the roof area of the house pillar type goaf to form multiple unconnected horizontal directional drill holes; the height of the horizontal directional drill hole is higher than the highest height of the coal pillar in the house pillar type goaf; performing hydraulic fracturing operation on each horizontal directional drill hole to generate at least one crack connected with the horizontal directional drill hole; and performing grouting operation on each horizontal directional drill hole to inject grout into the house pillar type goaf through each crack. The house pillar type goaf grouting method provided by the application generates multiple horizontal directional drill holes, generates multiple cracks by using the fracturing method, connects the horizontal directional drill hole with the goaf, uses the cracks as grouting points, realizes common grouting of multiple grouting points, makes the injected grout more uniform, and achieves better grouting effect.

Description

Technical Field

[0001] This invention relates to the field of goaf management technology, and in particular to a room-and-pillar type goaf grouting method. Background Technology

[0002] Coal mining leaves behind a large number of room-and-pillar goaf areas. Over time, the coal pillars supporting the goaf areas will gradually become unstable, leading to surface subsidence. Therefore, it is necessary to reinforce the goaf areas by grouting.

[0003] Traditional room-and-pillar grouting methods for goaf typically involve drilling vertical holes in the ground and injecting grout through these holes. However, with existing grouting techniques, firstly, the grout tends to inject into the coal pillars instead of the goaf; secondly, even if the grout does inject into the goaf, it is difficult to ensure that the grout is injected sufficiently and evenly. In summary, existing grouting methods have poor grouting effectiveness. Summary of the Invention

[0004] This invention provides a method for grouting room-column goaf, which solves the problem of poor grouting effect in the prior art, realizes grouting at multiple grouting points, makes the injected grout more uniform, and improves the grouting effect.

[0005] This invention provides a method for grouting a room-and-column type goaf, comprising:

[0006] Directional drilling is carried out in the roof area of ​​the room-and-pillar goaf to form multiple non-connected horizontal directional boreholes; the height of the horizontal directional boreholes is higher than the highest height of the coal pillars in the room-and-pillar goaf.

[0007] Hydraulic fracturing operations are performed on each of the horizontal directional boreholes to generate at least one fracture communicating with the horizontal directional borehole.

[0008] Grouting operations are performed on each of the horizontal directional boreholes to inject grout into the room-and-column goaf through each of the cracks.

[0009] According to a method for grouting a room-and-pillar type goaf provided by the present invention, the step of performing hydraulic fracturing operation on each of the horizontal directional boreholes to generate at least one fracture communicating with the horizontal directional boreholes includes:

[0010] Based on the water injection string, the fracturing tool string is fed into the end of the horizontal directional borehole;

[0011] During the retraction of the fracturing tool string, hydraulic fracturing operations are performed on the horizontal directional borehole segment by segment to generate at least one fracture connected to the horizontal directional borehole.

[0012] According to a method for grouting a room-and-pillar goaf provided by the present invention, the step of performing segment-by-segment hydraulic fracturing operations on the horizontal directional borehole during the retraction of the fracturing tool string to generate at least one fracture communicating with the horizontal directional borehole includes:

[0013] The fracturing tool string is retracted from the first position to the second position; the distance between the first position and the second position is the first distance;

[0014] Hydraulic fracturing is performed at the second location to generate at least one fracture communicating with the horizontal directional borehole.

[0015] According to a method for grouting a room-and-pillar type goaf provided by the present invention, the step of performing hydraulic fracturing operation at the second location to generate at least one fracture communicating with the horizontal directional borehole includes:

[0016] Hydraulic fracturing operations are performed at the second location, and the water pressure of the injection tubing is monitored.

[0017] If the water pressure in the injection string drops beyond a first threshold within a first time period, the hydraulic fracturing operation at the second position shall be stopped.

[0018] According to a method for grouting a room-and-pillar goaf provided by the present invention, the step of retracting the fracturing tool string from a first position to a second position includes:

[0019] Reduce the water pressure in the injection tubing so that the fracturing tool string retracts from the first position to the second position.

[0020] According to a method for grouting a room-and-pillar goaf provided by the present invention, before retracting the fracturing tool string from the first position to the second position, the method further includes:

[0021] The first distance is determined based on the fluidity of the slurry and / or the geometric characteristics of the room-and-pillar goaf.

[0022] According to a method for grouting a goaf in a room-and-pillar type according to the present invention, the first distance is 30 to 50 meters.

[0023] According to a method for grouting a room-and-pillar type goaf provided by the present invention, the plurality of horizontal directional boreholes are located on the same horizontal plane.

[0024] According to a method for grouting a room-and-pillar type goaf provided by the present invention, the plurality of horizontal directional boreholes are parallel to each other.

[0025] According to a method for grouting a goaf in a room-and-pillar type according to the present invention, the plurality of horizontal directional boreholes are distributed at equal intervals.

[0026] The room-and-pillar type goaf grouting method provided by the present invention generates multiple horizontal directional boreholes. In each horizontal directional borehole, a fracturing tool is used to generate multiple cracks in the roof area of ​​the goaf where each horizontal directional borehole is located. Among all the cracks, multiple cracks can connect the horizontal directional boreholes and the goaf. The cracks connecting the horizontal directional boreholes and the goaf are used as grouting points to achieve grouting at multiple grouting points, so that the injected grout is more uniform and the grouting effect is better. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is one of the flowcharts of the room-and-column type goaf grouting method provided by the present invention;

[0029] Figure 2 This is a schematic diagram of the process of directional drilling in the grouting method for room-and-column goaf provided by the present invention;

[0030] Figure 3 This is a schematic diagram of the process of hydraulic fracturing operation in the room-and-column goaf grouting method provided by the present invention;

[0031] Figure 4 This is a schematic diagram of the grouting process in the room-and-column goaf grouting method provided by the present invention;

[0032] Figure 5 This is a top view schematic diagram of the horizontal directional borehole distribution of the grouting method for room-and-column type goaf provided by the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] The following is combined Figures 1-5 Specific embodiments of the present invention are described below.

[0035] Figure 1 This is a schematic flowchart of the room-and-column type goaf grouting method provided by the present invention. Figure 1As shown, the method includes steps 101, 102 and 103.

[0036] Step 101: Conduct directional drilling operations in the roof area of ​​the room-and-pillar goaf to form multiple unconnected horizontal directional boreholes; the height of the horizontal directional boreholes is higher than the highest height of the coal pillars in the room-and-pillar goaf.

[0037] Specifically, the roof area of ​​the room-and-pillar goaf 202 is the area located above the room-and-pillar goaf 202. This area is unmined, relatively flat, and suitable for drilling operations. The roof area of ​​the room-and-pillar goaf 202 can be a large area or a small area.

[0038] The highest height of the coal pillar 203 in the room-and-pillar goaf 202 is the height of the tallest coal pillar 203 among all the coal pillars 203 below the roof area of ​​the selected room-and-pillar goaf 202.

[0039] Alternatively, a horizontal directional drilling rig 204 can be used to drill multiple non-connected horizontal directional boreholes 201 in the roof area of ​​the room-and-pillar goaf 202, that is, there is no connection between any two horizontal directional boreholes 201.

[0040] The process of drilling in the roof area of ​​the room-and-pillar goaf 202 using a horizontal directional drilling rig 204 can be described as follows: Figure 2 As shown.

[0041] Optionally, the horizontal directional drilling rig 204 can be a high-torque directional drilling rig, or other drilling tools capable of horizontal directional drilling 201. This embodiment of the invention does not specifically limit the type of horizontal directional drilling rig 204.

[0042] The height of the horizontal directional borehole 201 is higher than the highest height of the coal pillar 203 in the room-and-pillar goaf 202. This is to ensure that all horizontal directional boreholes 201 are completely within the roof area of ​​the room-and-pillar goaf 202, so that all horizontal directional boreholes 201 do not intersect with the goaf 202.

[0043] Step 102: Perform hydraulic fracturing on each horizontal directional borehole to generate at least one fracture connected to the horizontal directional borehole.

[0044] Specifically, the fracturing tool can be a fracturing tool string, packer, pressure-guided sandblasting device, or hydraulic anchor, or other fracturing tools that can perform hydraulic fracturing. The embodiments of the present invention do not specifically limit the type of fracturing tool.

[0045] In a horizontally oriented borehole 201, a fracturing tool is used to compress the borehole, thereby creating a fracture 303 connected to it. This process constitutes a hydraulic fracturing operation. The fracture 303 connected to the horizontally oriented borehole 201 may or may not be connected to the goaf 202. Hydraulic fracturing operations can be performed on each horizontally oriented borehole 201 individually or on multiple horizontally oriented boreholes 201 simultaneously.

[0046] Fracturing tools can be arranged in the horizontal directional borehole 201. Water is introduced into the fracturing tools, causing them to exert pressure on the horizontal directional borehole 201. When the pressure reaches the fracturing condition, a fracture 303 connected to the horizontal directional borehole 201 will be generated. According to the laws of hydraulic fracture initiation and propagation, fracture 303 will extend towards the stress concentration goaf 202, eventually forming a fracture 303 connected to the horizontal directional borehole 201. By using fracturing, the fracture 303 is made more likely to occur above the goaf 202, thus connecting the horizontal directional borehole and the goaf 202.

[0047] Each horizontal directional borehole 201 can generate multiple cracks 303. In this embodiment of the invention, the number of cracks 303 generated by each horizontal directional borehole 201 is not specifically limited.

[0048] Step 103: Perform grouting operations on each horizontal directional borehole to inject grout into the room-and-column goaf through each crack.

[0049] Specifically, the fracturing tool is withdrawn from the horizontal directional borehole 201, and a grouting pipe is connected to the borehole opening of the horizontal directional borehole 201 for grouting operations. After the grout 401 is injected into the horizontal directional borehole 201, due to the fluidity of the grout 401, it can flow to the location of the fracture 303, and the grout 401 can be injected into the room-and-pillar goaf 202 through the fracture 303 to complete the grouting task.

[0050] Optionally, grouting operations can be performed on each horizontal directional borehole 201 in turn, or grouting operations can be performed on multiple horizontal directional boreholes 201 simultaneously. This embodiment of the invention does not specifically limit the specific method of grouting operations.

[0051] Compared with the traditional room-and-pillar goaf grouting method, the present invention can generate multiple grouting points in a single borehole, and grouting can be performed at multiple points simultaneously. This avoids the problem that the horizontal directional borehole cannot be connected to the goaf due to a crack being located above the coal pillar, thus preventing grouting operations from being carried out. It also avoids the defect in the traditional room-and-pillar goaf grouting method where grouting cannot be performed because the borehole is drilled above the coal pillar.

[0052] This invention generates multiple horizontally oriented boreholes. In each horizontally oriented borehole, a fracturing tool is used to create multiple cracks in the roof area of ​​the goaf where each horizontally oriented borehole is located. Among all the cracks, multiple cracks can connect the horizontally oriented boreholes and the goaf. The cracks connecting the horizontally oriented boreholes and the goaf are used as grouting points to achieve grouting at multiple grouting points, making the injected grout more uniform and the grouting effect better.

[0053] Based on any of the above embodiments, hydraulic fracturing is performed on each horizontal directional borehole to generate at least one fracture communicating with the horizontal directional borehole, including: feeding a fracturing tool string into the end of the horizontal directional borehole based on a water injection string.

[0054] Specifically, the process of generating fracture 303 through hydraulic fracturing can be described as follows: Figure 3 As shown, a water injection string 301 can be arranged in the horizontal directional borehole 201, and the fracturing tool string 302 can be sent to the end of the horizontal directional borehole 201 through the water injection string 301. The end of the horizontal directional borehole 201 is the farthest point of the horizontal directional borehole 201.

[0055] During the retreating fracturing tool string process, hydraulic fracturing operations are performed on the horizontal directional borehole segment by segment, resulting in multiple fractures in the horizontal directional borehole.

[0056] Specifically, such as Figure 3 As shown, the fracturing tool string 302 is gradually moved backward. After moving backward a certain distance, water is introduced into the fracturing tool string 302 to perform hydraulic fracturing operation on the horizontal directional borehole 201, thereby generating a fracture 303 that connects the horizontal directional borehole 201 and the goaf 202.

[0057] Repeating the fracturing process described above can generate multiple fractures 303 connected to the horizontal directional borehole 201. These multiple fractures 303 can then be... Figure 4 As shown.

[0058] The embodiments of the present invention generate multiple grouting points by creating multiple cracks connected to the horizontal directional borehole, which can improve grouting efficiency, make grouting more uniform, and achieve better grouting effect.

[0059] Based on any of the above embodiments, during the process of retracting the fracturing tool string, hydraulic fracturing operations are performed on the horizontal directional borehole segment by segment to generate at least one fracture communicating with the horizontal directional borehole, including: retracting the fracturing tool string from a first position to a second position; the distance between the first position and the second position is a first distance.

[0060] Specifically, the first position is the current position of the horizontal directional borehole 201 where the fracturing tool string 302 is located, and the second position is the target position of the horizontal directional borehole 201 to which the fracturing tool string 302 retreats.

[0061] The distance between the first position and the second position is the first distance. The size of the first distance is set based on the actual situation such as the distance of the coal pillar 203 and the properties of the slurry 401. In this embodiment of the invention, the size of the first distance is not specifically limited.

[0062] The first distance can be a fixed value determined based on the actual situation; or the first distance can be different each time it is retreated. This embodiment of the invention does not specifically limit this.

[0063] Using a fixed value for the first distance eliminates the need to manually change the retraction distance of the fracturing tool string 302 each time it retracts after setting the first distance once, reducing manual operation and improving work efficiency.

[0064] The first distance uses different values. The distance to retreat of each fracturing tool string 302 can be determined according to the actual distribution of coal pillars 203 in the goaf 202. With the distribution of the goaf 202 detected in advance, the cracks 303 generated by each fracturing operation can be above the goaf 202, generating as many cracks 303 as possible that connect the horizontal directional borehole 201 and the goaf 202, thereby improving grouting efficiency.

[0065] Hydraulic fracturing is performed at a second location to create at least one fracture that communicates with the horizontal directional borehole.

[0066] Specifically, when the fracturing tool string 302 is in the second position, water is injected into the fracturing tool string 302, and the fracturing tool string 302 performs fracturing operations, generating a fracture 303 in the second position.

[0067] Multiple cracks 303 can be generated by repeating the above method. The number of cracks 303 can be set according to the actual situation. In this embodiment of the invention, the number of cracks is not specifically limited.

[0068] By setting a first distance, the location of the fracturing operation is made to meet the actual requirements. The resulting cracks can improve grouting efficiency, make grouting more uniform, and improve the grouting effect.

[0069] Based on any of the above embodiments, performing hydraulic fracturing operations at a second location to generate at least one fracture communicating with a horizontally directional borehole includes: performing hydraulic fracturing operations at a second location and monitoring the water pressure within the injection tubing.

[0070] Specifically, water is injected into the fracturing tool string 302 at the second position to perform hydraulic fracturing. The water pressure of the tubing string is monitored and recorded during water injection.

[0071] Water pressure monitoring of the water injection string 301 can be performed using a water pressure sensor, pressure gauge, or other tools for measuring water pressure. This embodiment of the invention does not specifically limit the type of tool used for measuring water pressure.

[0072] If the water pressure in the injection tubing 301 drops beyond a first threshold within a first time period, the hydraulic fracturing operation at the second position is stopped.

[0073] Specifically, the first duration is a very short period of time. The specific value of the first duration can be determined according to the actual situation, for example, it can be 0.1s, 1s, or other very short values. This embodiment of the invention does not specifically limit the specific value of the first duration.

[0074] The first threshold is a threshold for measuring the magnitude of water pressure drop. The first threshold can be determined according to actual conditions, and the embodiment of the present invention does not specifically limit the value of the first threshold.

[0075] When the fracturing tool string 302 is in the second position, water is injected into it. The water pressure in the tubing gradually increases, generating pressure that creates a fracture 303 connecting to the horizontal directional borehole 201 and thus to the goaf 202. At this point, water enters the goaf 202, and the pressure in the tubing drops significantly within a short time. A first threshold is set based on this pressure drop. The first threshold is determined according to actual conditions. When the water pressure drop exceeds the first threshold, it is determined that a fracture 303 has occurred in the second position.

[0076] If the water pressure in the injection tubing 301 drops beyond a first threshold within a first time period, and it is determined that a crack 303 has been generated at the second location, then hydraulic fracturing operations at the second location will be stopped.

[0077] This invention, through monitoring the magnitude of water pressure changes within a very short time in the injection pipe, determines whether a crack has occurred at the second location, thus enabling a more convenient and accurate assessment of whether a hydraulic fracturing operation has been completed.

[0078] Based on any of the above embodiments, retracting the fracturing tool string from the first position to the second position includes: reducing the water pressure in the water injection string so that the fracturing tool string retracts from the first position to the second position.

[0079] Specifically, by reducing the water pressure inside the injection tubing 301, the fracturing tool string 302 can be retracted from the first position to the second position. After reaching the second position, the water pressure inside the injection tubing 301 can be increased to continue the fracturing operation.

[0080] This invention reduces the water pressure inside the injection tubing, allowing the fracturing tool string to retract and continue fracturing operations.

[0081] Based on any of the above embodiments, before retracting the fracturing tool string from the first position to the second position, the method further includes: determining a first distance based on the fluidity of the slurry and / or the geometric characteristics of the room-and-pillar goaf.

[0082] Specifically, the first distance can be determined based on the fluidity of the grout 401 and / or the geometric characteristics of the room-and-pillar goaf 202, controlling the distance between the cracks 303 to ensure that the distance between the grouting points meets the requirements of the grouting effect.

[0083] The geometric features of the goaf 202 may include at least one of the distance between adjacent coal pillars 203 within the goaf 202 and the total length of the goaf 202 in one direction. The distance between the coal pillars 203 within the goaf 202 is used to indicate the sparseness of the coal pillars 203 within the goaf 202. The geometric features of the goaf 202 may also include other features of the goaf 202 that can affect the grouting effect.

[0084] Optionally, the first distance can be determined based on the fluidity of the grout 401. The stronger the fluidity of the grout 401, the easier it is for the grout 401 to spread to the surroundings after grouting, and the greater the distance between grouting points can be, thus the greater the first distance can be; the weaker the fluidity of the grout 401, the less likely it is to spread to the surroundings after grouting, and the closer the distance between grouting points can be, thus the closer the first distance can be.

[0085] Optionally, the first distance can be determined based on the distance between adjacent coal pillars 203 within the room-and-pillar goaf 202. The sparser the coal pillars 203 within the goaf 202, the easier it is for the injected grout 401 to diffuse to the surrounding area and fill the goaf 202, and the interval between grouting points can be greater, and the first distance can be greater; the denser the coal pillars 203 within the goaf 202, the less likely the injected grout 401 is to diffuse to the surrounding area, and the less likely the grout 401 is to fill the goaf 202, and the interval between grouting points can be closer, and the first distance can be closer.

[0086] The embodiments of the present invention determine the first distance and the interval of the grouting points based on the fluidity of the grout and / or the geometric characteristics of the room-and-pillar goaf, so as to ensure that the grout can uniformly fill the goaf and achieve better grouting effect.

[0087] Based on any of the above embodiments, the first distance is 30 to 50 meters.

[0088] Specifically, the first distance can be determined to be 30-50 meters. Based on the fluidity, solidification and other properties of the grout 401 used for grouting in the existing commonly used room-and-pillar goaf 202, as well as the geometric characteristics of the goaf 202 left by the commonly used mining methods, the first distance can generally be selected between 30 meters and 50 meters, that is, the interval between grouting points can be between 30 meters and 50 meters.

[0089] This invention provides a commonly used option for selecting the first distance by setting it between 30 and 50 meters. This simplifies the process of determining the first distance and ensures that the distance between the grouting points meets the needs of commonly used grouts, resulting in better grouting effects.

[0090] Based on any of the above embodiments, multiple horizontal directional boreholes are located on the same horizontal plane.

[0091] Specifically, a horizontal directional borehole 201 can be created during drilling. Based on this borehole, the horizontal directional drilling rig 204 can be translated and / or rotated on the horizontal plane where the horizontal directional borehole 201 is located before performing the next directional drilling operation to create the next horizontal directional borehole 201. With the direction the drill bit of the horizontal directional drilling rig 204 is pointing forward as the front, the translation direction can be left or right, and the rotation direction can be left or right, with the horizontal directional drilling rig 204 moving on the same horizontal plane. The above operation is repeated to create multiple horizontal directional boreholes 201 on the same horizontal plane.

[0092] Multiple horizontal directional boreholes 201 can be located on the same horizontal plane, making the distance between the horizontal directional boreholes 201 and the ground of the goaf 202 more uniform. During grouting, the diffusion speed of grout 401 in various areas is relatively uniform, the state of grout 401 is more stable, and the grouting effect is better.

[0093] This invention, by placing multiple horizontal directional boreholes on the same horizontal plane, ensures that the grout spreads at a relatively uniform speed in different areas during grouting, resulting in a more stable grout state and better grouting effect.

[0094] Based on any of the above embodiments, multiple horizontal directional boreholes are parallel to each other.

[0095] Specifically, such as Figure 5 As shown, multiple horizontal directional boreholes 201 can be made parallel to each other, ensuring that the horizontal directional boreholes 201 located on the same horizontal plane will not be connected. During fracturing operations, the pressure can be monitored normally, and the grout 401 can be evenly passed through each grouting hole during grouting.

[0096] A horizontally oriented borehole 201 can be created first during drilling. Based on this borehole, the horizontally oriented drilling rig 204 is then moved horizontally along the same horizontal plane, with the direction of the drill bit of the horizontally oriented drilling rig 204 as the forward direction. The direction of movement can be left or right. The horizontally oriented drilling rig 204 moves along the same horizontal plane, maintaining the same drilling direction as the previous borehole, i.e., the drilling direction is the same each time, thus creating the next borehole. This process is repeated to create multiple parallel horizontally oriented boreholes 201 on the same horizontal plane.

[0097] This invention ensures the normal execution of fracturing operations and grouting by making multiple horizontal directional boreholes on the same horizontal plane parallel to each other, thus achieving better grouting results.

[0098] Based on any of the above embodiments, multiple horizontally oriented boreholes are distributed at equal intervals.

[0099] Specifically, such as Figure 5 As shown, multiple horizontal directional boreholes 201 that are parallel to each other on the same horizontal plane can be distributed at equal intervals, making the distribution of the horizontal directional boreholes 201 more uniform. The distance between the grouting points generated by fracturing can be distributed more uniformly, and grout can be injected evenly into the entire goaf 202 during grouting to achieve the best grouting effect.

[0100] Based on the parallel nature of multiple horizontal directional boreholes 201, after generating the first horizontal directional borehole 201, the drill bit of the horizontal directional drilling machine 204 can move a fixed distance to the left each time to perform drilling operations, generating multiple horizontal directional boreholes 201 with equal distances; alternatively, after generating the first horizontal directional borehole 201, the drill bit of the horizontal directional drilling machine 204 can move a fixed distance to the right each time to perform drilling operations, generating multiple horizontal directional boreholes 201 with equal distances; or alternatively, after generating the first horizontal directional borehole 201, the drill bit of the horizontal directional drilling machine 204 can move a fixed distance to the left each time to perform drilling operations, generating multiple horizontal directional boreholes 201 with equal distances. After generating several horizontal directional boreholes 201 with equal distances, the drill bit of the horizontal directional drilling machine 204 can be moved back to the first horizontal directional borehole 201, and the drill bit of the horizontal directional drilling machine 204 can move the same fixed distance to the right as when moving to the left each time to perform drilling operations, generating multiple horizontal directional boreholes 201 with equal distances.

[0101] In this embodiment of the invention, multiple horizontally oriented boreholes that are parallel to each other on the same horizontal plane are distributed at equal intervals, so that the grouting points are distributed more evenly, allowing the grout to be injected into the goaf more uniformly, resulting in a better grouting effect.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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 grouting method for a room-and-column type goaf, characterized in that, include: Directional drilling operations were carried out in the roof area of ​​the room-and-pillar goaf to form multiple unconnected horizontal directional boreholes; The height of the horizontal directional borehole is higher than the highest height of the coal pillar in the room-and-pillar goaf. Hydraulic fracturing operations are performed on each of the horizontal directional boreholes to generate at least one fracture communicating with the horizontal directional borehole. Grouting operations are performed on each of the horizontal directional boreholes to inject grout into the room-and-column goaf through each of the cracks; The hydraulic fracturing operation performed on each of the horizontally directional boreholes to generate at least one fracture communicating with the horizontally directional borehole includes: Based on the water injection string, the fracturing tool string is fed into the end of the horizontal directional borehole; During the retraction of the fracturing tool string, hydraulic fracturing operations are performed on the horizontal directional borehole in segments to generate at least one fracture communicating with the horizontal directional borehole. During the retraction of the fracturing tool string, segment-by-segment hydraulic fracturing operations are performed on the horizontally directional borehole to generate at least one fracture communicating with the horizontally directional borehole, including: The fracturing tool string is retracted from the first position to the second position; the distance between the first position and the second position is the first distance; Hydraulic fracturing is performed at the second location to generate at least one fracture communicating with the horizontal directional borehole; The hydraulic fracturing operation performed at the second location to generate at least one fracture in the horizontal directional borehole includes: Hydraulic fracturing operations are performed at the second location, and the water pressure inside the injection tubing is monitored. If the water pressure in the injection string drops beyond a first threshold within a first time period, the hydraulic fracturing operation at the second position shall be stopped.

2. The grouting method for room-and-column type goaf according to claim 1, characterized in that, The step of retracting the fracturing tool string from the first position to the second position includes: Reduce the water pressure in the injection tubing so that the fracturing tool string retracts from the first position to the second position.

3. The grouting method for room-and-column type goaf according to claim 1, characterized in that, Before retracting the fracturing tool string from the first position to the second position, the method further includes: The first distance is determined based on the fluidity of the slurry and / or the geometric characteristics of the room-and-pillar goaf.

4. The grouting method for room-and-column type goaf according to claim 1, characterized in that, The first distance is 30 to 50 meters.

5. The grouting method for room-and-column type goaf according to any one of claims 1 to 4, characterized in that, The multiple horizontal directional boreholes are located on the same horizontal plane.

6. The grouting method for room-and-column type goaf according to claim 5, characterized in that, The multiple horizontally directional boreholes are parallel to each other.

7. The grouting method for room-and-column type goaf according to claim 6, characterized in that, The multiple horizontally oriented boreholes are distributed at equal intervals.

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