Elastic steel hoop hole protection technology and supporting equipment for drilling in complex formations in underground coal mines

Abstract

This invention belongs to the field of coal mining and relates to the process and supporting equipment for using elastic steel hoop protection in drilling through complex strata underground. When encountering complex strata during drilling, the drill is withdrawn, and the connecting protection device and other equipment are sent into the complex strata section of the hole. The elastic opening steel hoop is released, and the drill bit rotates to expand the elastic steel hoop until it can be pulled back to compress the steel hoop device. The compressing steel hoop device is then expanded by water pressure to press the elastic steel hoop into the hole wall, achieving dense elastic steel hoop embedding into the hole wall layer to protect the hole and prevent hole obstruction due to broken coal and rock blocks or fault displacement. The protection equipment is then withdrawn and removed, and conventional drilling equipment is used to drill into the complex strata again, continuing forward until the next section of soft and fractured strata is encountered. A similar operation method is used to complete the passage through the complex strata until the hole is completed. In use, the hole protection effect is good, the stability is strong, the safety is high, there is no pollution, the process is simple, the cost is low, and it can effectively guarantee the hole protection effect at fixed points.

Description

Technical Field

[0001] This invention belongs to the field of coal mining and relates to the process and supporting equipment for using elastic steel hoop hole protection in drilling in complex underground strata of coal mines. Background Technology

[0002] my country's coal mines have complex geological conditions, and drilling operations often encounter complex strata. Drilling in these complex strata can easily lead to borehole collapse, diameter reduction, and stuck drill bits, resulting in poor borehole formation, shallow borehole depth, and frequent accidents. Although research institutes have made technological breakthroughs in recent years, developing techniques such as branching around fractured strata, steep-angle drilling through fractured strata, segmented enlargement drilling, composite directional drilling, casing installation, grouting reinforcement, and mud circulation, these methods have not effectively solved the problems encountered in deep-hole directional drilling in complex strata. Borehole protection is poor, and the work is intensive and inefficient. Grouting reinforcement and mud circulation drilling, in particular, cause significant pollution, resulting in a poor underground working environment. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a process and supporting equipment for drilling in complex formations in coal mines using elastic steel hoop protection, which solves the problems of poor protection effect, complex process and high pollution in current deep and shallow hole construction in coal mines through complex formations.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a process for using elastic steel hoop hole protection in drilling in complex formations underground in coal mines, employing supporting equipment for this process. This equipment comprises a drill rod, a hole protection device, a transition joint, a pressing steel hoop device, and a drill bit connected sequentially. The hole protection device consists of a female joint, a steel hoop seat, an elastic steel hoop assembly, a steel hoop clamp, a shearing pin, a piston cylinder, a male joint, and a sealing ring. The pressing steel hoop device consists of a central tube body, a limiting sleeve, pressing slips, a return spring, a push-pull cylinder sleeve, a connecting screw, a spring seat, a plug ring, and a sealing ring. The process includes the following steps:

[0005] S1, in coal mines, long boreholes are drilled from stable strata to complex strata. When phenomena such as borehole collapse or stuck drill occur, the borehole is washed and the drill is withdrawn.

[0006] S2. After retracting the drill bit, connect the hole protection device, the compression steel hoop device and the transition joint between the drill bit and the drill rod. Start the drilling rig and drill bit assembly to send it into the complex formation section of the hole and continue drilling until it passes through the complex formation section or the jamming pressure is too great to continue drilling. Then stop drilling forward.

[0007] S3, increase the water pressure in the drill string's internal flow channel. When the water pressure reaches a certain value, the internal mechanism of the borehole protection device shears off its shearing pin through the water pressure transmitted from the drill string's internal flow channel. After the steel hoop seat is moved into place, i.e., the end of the hoop seat contacts the shoulder of the female connector, the elastic steel hoop group is released. Each elastic steel hoop in the elastic steel hoop group unfolds to support the borehole wall under the action of elastic force. Decrease the water pressure in the drill string's internal flow channel. Rotate the drill string to agitate the elastic steel hoop group to further expand radially until the inner channel diameter of the elastic steel hoop can retract the length of the squeeze slip and pull back the drill string. The retraction distance is the length of the squeeze slip of the steel hoop device.

[0008] S4. Gradually increase the water pressure. Under the action of water pressure, the push-pull cylinder sleeve of the squeezing steel hoop device pushes the squeezing slips to achieve radial expansion along the dovetail groove guide, and rotates the drill bit. The elastic steel hoop in the elastic steel hoop group, under the radial expansion pressure and rotational impact of the squeezing slips, is pressed into the hole wall until the diameter of the elastic steel hoop annular cavity is larger than the drill bit diameter. Then, decrease the water pressure, and the squeezing slips retract and reset. At this time, pull back the squeezing slips again, gradually increase the water pressure again, and rotate the drill bit to press the elastic steel hoop into the hole wall. At this time, the elastic steel hoop group is either attached to the hole wall or pressed into the hole wall. Repeat the operation until the drill bit is completely withdrawn from the steel hoop protection section.

[0009] After exiting S5, the conventional drilling tool is reinserted to pass through the borehole protection section and continue drilling forward. If complex strata are encountered again, the same process is used to pass through the complex strata until the borehole is completed.

[0010] Optionally, multiple borehole protection devices or compression steel hoop devices can be connected in series based on the estimated length of the borehole section in complex strata and specific geological conditions. They can be connected in staggered series (or one borehole protection device, one compression steel hoop device, another borehole protection device, another compression steel hoop device, and so on; or a series of elastic steel hoop borehole protection devices can be connected in series, and then one or a series of compression steel hoop devices can be connected on top).

[0011] Optionally, in step S4, the drill bit needs to be rotated continuously, and the combined action of unfolding and rotating compresses the elastic steel hoop, causing it to continuously impact the borehole wall of the complex formation, so that the elastic steel hoop can be smoothly pressed into the borehole wall.

[0012] Optionally, in step S4, the water pressure is gradually increased. Under the action of the water pressure, the slip extends radially continuously under the drive of the push-pull cylinder liner. When the water pressure is decreased, the spring seat is driven to reset under the action of the reset spring. At this time, the push-pull cylinder liner, which is integrated with the spring seat, resets synchronously. The dovetail cooperation and guidance between the push-pull cylinder liner and the squeezing slip achieves radial retraction of the slip.

[0013] Optionally, the dovetail grooves at both ends of the extrusion slip can be matched with the dovetail groove of the limiting sleeve and the dovetail block of the push-pull cylinder liner, respectively, to realize the guiding movement, unfolding and retracting of the extrusion slip.

[0014] The supporting equipment for the elastic steel hoop borehole protection process in complex formations of underground coal mines includes drill rods, borehole protection devices, transition joints, extrusion steel hoop devices, and drill bits connected in sequence. The borehole protection device includes a female joint, a steel hoop seat, an elastic steel hoop assembly, a steel hoop retainer, a shearing pin, a piston cylinder, a male joint, and a sealing ring. The steel hoop seat is welded to the surface of the male and female welded pipe bodies. The steel hoop retainer is placed inside the steel hoop seat, in an axially sliding state, and is axially fixed by the shearing pin. The extrusion steel hoop device includes a central pipe body, a limiting sleeve, extrusion slips, a return spring, a push-pull cylinder sleeve, connecting screws, and a spring seat. The plug ring and sealing ring, along with the limiting sleeve, are used to circumferentially limit the extrusion slip and are machined with guide dovetail grooves. They are welded to the central tube body. The extrusion slip is installed in the slip groove formed by the limiting sleeve and the central tube body. One end is machined with a dovetail block, and the other end is machined with a dovetail groove, which respectively cooperates with the dovetail groove of the limiting sleeve and the dovetail block of the push-pull cylinder sleeve to realize the guiding movement, expansion, and contraction of the extrusion slip. The end of the push-pull cylinder sleeve is machined with a dovetail block. The push-pull cylinder sleeve is fixed to the spring seat by connecting screws to realize the axial movement of the three as a whole. Under the action of water pressure, the push-pull cylinder sleeve pushes the extrusion slip to slide along the dovetail groove to realize radial expansion.

[0015] Optionally, the female and male connectors are joined together by friction welding, and the internal and external weld marks are machined off.

[0016] Optionally, the elastic steel hoop assembly is wrapped with an elastic steel wire mesh, and each elastic steel hoop has an opening groove at both ends. The diameter of the opening ring of the elastic steel hoop in its natural state is larger than the maximum outer diameter of the drill bit.

[0017] Optionally, the steel hoop seat is similar to a channel steel structure, with equally spaced round holes machined on the steel plates on both sides. The steel hoop clamp seat is similar to a channel steel structure, with equally spaced semi-circular notches arranged on the steel plates on both sides. One end of the steel hoop clamp seat contacts the piston cylinder. In the fixed state, each elastic steel hoop on the elastic steel hoop assembly passes through the round hole of the steel hoop seat and is clamped on the steel plates on both sides of the steel hoop clamp seat.

[0018] Optionally, one end of the spring seat is positioned by a plug ring, and the other end is in contact with the return spring. After being compressed by the push-pull cylinder liner, the spring seat is reset under the action of the spring, thereby realizing the retraction of the squeeze slip.

[0019] The beneficial effects of this invention are as follows: The elastic steel hoop hole protection process and supporting equipment for drilling in complex strata in coal mines are as follows: When drilling encounters complex strata, the drill is withdrawn, and the hole protection device and other equipment are sent into the complex strata section. The elastic opening steel hoop is released, and the drill bit rotates to expand the elastic steel hoop until it can be pulled back to compress the steel hoop device. Water pressure is used to unfold the compressing steel hoop device, pressing the elastic steel hoop into the borehole wall, achieving dense elastic steel hoop embedding into the borehole wall layer for hole protection, preventing coal and rock blocks from obstructing the hole. The hole protection equipment is then removed, and conventional drilling equipment is used to drill into the complex strata again, continuing forward until the next section of fractured and soft strata is encountered. A similar operation method is used to complete the complex strata crossing until the borehole is completed. During use, the hole protection effect is good, the stability is strong, the safety is high, there is no pollution, the process is simple, and the cost is low, which can effectively guarantee the hole protection effect at fixed points.

[0020] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0022] Figure 1 This is a schematic diagram of the long borehole of the present invention;

[0023] Figure 2 This is a schematic diagram of the hole protection device of the present invention being inserted into the bottom of the hole;

[0024] Figure 3 This is a schematic diagram of the insertion of the protective elastic steel bar according to the present invention;

[0025] Figure 4 This is a schematic diagram of the complex formation borehole protection method according to the present invention;

[0026] Figure 5 This is a schematic diagram of the hole protection device of the present invention;

[0027] Figure 6 for Figure 5 AA section view;

[0028] Figure 7 This is a schematic diagram of the elastic steel hoop of the present invention;

[0029] Figure 8 This is a schematic diagram of the steel hoop seat of the present invention;

[0030] Figure 9 This is a schematic diagram of the steel hoop holder of the present invention;

[0031] Figure 10 This is a schematic diagram of the compressed steel hoop device of the present invention in its contracted state;

[0032] Figure 11 for Figure 10 EE sectional view;

[0033] Figure 12 This is a schematic diagram of the unfolded state of the extrusion steel hoop device of the present invention;

[0034] Figure 13 This is a schematic diagram of the extrusion clamp of the present invention;

[0035] Figure 14 This is a schematic diagram of the push-pull cylinder liner of the present invention;

[0036] Figure 15 This is a schematic diagram of the limiting sleeve of the present invention;

[0037] Figure 16 This is a schematic diagram of the water entering the push-pull cylinder liner flow channel of the present invention. Figure 10 Enlarged view of F in the middle.

[0038] Reference numerals: 1. Drill pipe; 2. Hole protection device; 21. Female connector; 22. Steel hoop seat; 23. Elastic steel hoop assembly; 24. Steel hoop clamp seat; 25. Shearing pin; 26. Piston cylinder; 27. Male connector; 28. Elastic wire mesh; 3. Transition joint; 4. Extrusion steel hoop device; 41. Central tube body; 42. Limiting sleeve; 43. Extrusion slip; 44. Return spring; 45. Push-pull cylinder sleeve; 46. Connecting screw; 47. Spring seat; 48. Plug ring; 5. Drill bit. Detailed Implementation

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0040] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0041] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0042] Please see Figures 1 to 15 This invention relates to the technology and equipment for using elastic steel hoop hole protection in complex formations in underground coal mines.

[0043] (1) The hole protection process is as follows Figure 1-4 As shown, the state of long underground boreholes in coal mines from stable strata to complex strata is as follows: Figure 1 As shown, I represents a stable formation, and II represents a complex formation. When phenomena such as borehole collapse or stuck drill occur, the borehole is flushed and the drill is withdrawn.

[0044] (2) After retracting the drill bit, connect the borehole protection device 2 (multiple borehole protection devices 2 are connected in series according to the estimated length of the complex formation and specific geological conditions), the compression steel hoop device 4 (multiple can be connected in series as needed), and the transition joint 3 between the drill bit and the drill pipe. At this time, the drilling tool composition is as follows: Figure 2 As shown, the system consists of drill rod 1, borehole protection device 2, transition joint 3, clamping steel hoop device 4, and drill bit. The drilling rig is started, and the drill bit is fed into a complex formation section along the borehole. Drilling continues until it passes through a complex formation section or the jamming pressure becomes too high to continue. At this point, drilling stops, and the water pressure in the drill string's internal flow channel is increased. When the water pressure reaches a certain value, the internal mechanism of the borehole protection device 2 shears its shearing pin 25 through the water pressure transmitted from the drill string's internal flow channel. This pushes the steel hoop holder 24 into place, releasing the elastic steel hoop assembly 23. Each elastic steel hoop in the elastic steel hoop assembly 23 unfolds under the action of elastic force to support the borehole wall. The water pressure in the drill string's internal flow channel is then reduced, and the drill string is rotated to agitate the elastic steel hoop assembly 23 radially until it can retract the clamping slip 43 a certain distance (at this point, the drill bit 5 is jammed and cannot retract further). The water pressure is gradually increased, and the push-pull cylinder sleeve 45 of the clamping steel hoop device 4 is activated by the water pressure (water flows into the channel as shown). Figure 16Under the action of (as shown), the squeezing slip 43 is pushed to radially unfold along the dovetail groove guide, and the drill bit is continuously rotated (the continuous rotation of the drill bit, the combined action of unfolding and rotation squeezing, causes the elastic steel hoop to continuously impact the borehole wall of the complex formation, so that the elastic steel hoop is smoothly pressed into the borehole wall). The elastic steel hoop in the elastic steel hoop group 23 located under the action of the squeezing slip 43 is pressed into the borehole wall until the diameter of the elastic steel hoop annular cavity is larger than the diameter of the drill bit 5. The water pressure is reduced, the squeezing slip 43 retracts and resets. At this time, the squeezing slip 43 is pulled back again, the water pressure is gradually increased again, and the drill bit is rotated to press the elastic steel hoop into the borehole wall. The state at this time is as shown in the figure. Figure 3 As shown (elastic steel hoop group 23a is the group that adheres to the hole wall, and elastic steel hoop group 23b is the group that is pressed into the hole wall), repeat the operation until the drill bit 5 is completely withdrawn from the steel hoop protection section. At this time, as shown... Figure 4 As shown.

[0045] (3) Depending on the complex strata crossing situation, if the crossing length is insufficient, remove all drilling tools, add elastic steel hoop group 23 again, and cross the complex strata behind in the same way until the complex strata are completely crossed.

[0046] (4) When encountering the next complex stratum, the same steps are followed to construct the tunnel through the complex stratum until the hole is completed.

[0047] The main devices developed to achieve the above process include the hole protection device 2 and the extrusion steel hoop device 4. The hole protection device 2 is as follows: Figures 5-6 As shown, it consists of a female connector 21, a steel hoop seat 22, a flexible steel hoop assembly 23, a steel hoop clamp seat 24, a shear pin 25, a piston cylinder 26, a male connector 2, and a sealing ring. The female connector 21 and the male connector 27 are joined together by friction welding, and the inner and outer weld scars are machined off. The steel hoop seat 22 is as follows... Figure 8 As shown, it resembles a channel steel structure, with equally spaced circular holes machined on both sides of the steel plates. Figure 5 The cross-sectional view on the left shows the welding on the surface of the male and female welded pipe bodies; the steel hoop holder 24 is as shown. Figure 9 As shown, similar to a channel steel structure, the steel plates on both sides have equidistant semi-circular notches, which are placed inside the steel hoop seat 22 and are axially slidable with the steel hoop seat 25. They are axially fixed by shear pins 25. One end of the steel hoop seat 24 contacts the piston cylinder 26. In the fixed state, each elastic steel hoop on the elastic steel hoop assembly 23 is clamped onto the steel plates on both sides of the steel hoop seat; each elastic steel hoop of the elastic steel hoop assembly 23 is as follows: Figure 7 As shown, the elastic steel hoop assembly 23 is externally wrapped with an elastic steel wire mesh 28. The elastic steel hoop has opening slots at both ends (the diameter of the opening ring of the elastic steel hoop in its natural state is larger than the maximum outer diameter of the drill bit). When installed in the hole protection device 2, it is as follows: Figure 5As shown in the cross-sectional view, it is clamped on the clamping plate of the steel hoop clamping seat 24. When the water pressure inside the pipe protection device is increased to a certain value, the piston cylinder 26 pushes the steel hoop clamping seat 24 to move axially until the shearing pin 25 is cut off. When one end of the steel hoop clamping seat 24 contacts the shoulder of the female connector 21, the semi-circular notch of the clamping plate of the steel hoop clamping seat 24 is aligned with the circular hole of the steel hoop seat 22, and each elastic steel hoop in the elastic steel hoop group 23 is radially ejected under the action of elasticity.

[0048] The compression steel hoop device 4 is in the contracted state as follows: Figures 10-11 As shown, the unfolded state is as follows Figure 12 As shown, it consists of a central tube body 41, a limiting sleeve 42, a pressing slip 43, a return spring 44, a push-pull cylinder sleeve 45, a connecting screw 46, a spring seat 47, a plug ring 48, and a sealing ring.

[0049] The limiting sleeve 42 is used to circumferentially limit the extrusion slip 43, and is machined with a guide dovetail groove and welded to the central tube 41. The extrusion slip 43, as... Figure 13 As shown, the slip 43 is installed in the slip groove formed by the limiting sleeve 42 and the central tube 41. One end is machined with a dovetail block, and the other end with a dovetail groove, which respectively cooperate with the dovetail groove of the limiting sleeve 42 and the dovetail block of the push-pull cylinder sleeve 45 to achieve the guiding movement, expansion, and contraction of the extrusion slip 43; the push-pull cylinder sleeve 45 is as follows... Figure 14 As shown, the end is machined with a dovetail block. The push-pull cylinder sleeve 45 is fixed to the spring seat 47 by the connecting screw 46, realizing the axial movement of the three as a whole. Under the action of water pressure, the push-pull cylinder sleeve 45 pushes the extrusion slip 43 to slide along the dovetail groove, realizing radial expansion. One end of the spring seat 47 is positioned by the plug ring 48, and the other end is in contact with the return spring 44. After being compressed by the push-pull cylinder sleeve 45, the spring seat 47 is reset under the action of the spring, realizing the retraction of the extrusion slip 43. In use, the water pressure is gradually increased, and the slip extends radially under the action of water pressure. When the water pressure is decreased, the spring seat 47 is driven to reset under the action of the return spring 44. At this time, the push-pull cylinder sleeve 45, which is integrated with the spring seat 47, is reset synchronously. With the dovetail cooperation and guidance of the push-pull cylinder sleeve 45 and the extrusion slip 43, the radial retraction of the slip is realized.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for using elastic steel hoop protection in drilling through complex formations in underground coal mines, characterized in that, This invention relates to the supporting equipment for the elastic steel hoop hole protection technology used in drilling in complex formations of underground coal mines. The equipment consists of drill rods, a hole protection device, a transition joint, a steel hoop compression device, and the drill bit connected in sequence. The hole protection device comprises a female joint, a steel hoop seat, an elastic steel hoop assembly, a steel hoop clamp, a shear pin, a piston cylinder, a male joint, and a sealing ring. The female and male joints are friction-welded together to form a male-female welded pipe body. The steel hoop seat is welded to the surface of the male-female welded pipe body. The steel hoop clamp is placed inside the steel hoop seat, allowing it to slide axially, and is axially fixed by the shear pin. The steel hoop seat is similar to a channel steel structure, with equally spaced circular holes on both sides of the steel plates. The steel hoop clamp is also similar to a channel steel structure, with equally spaced semi-circular holes on both sides of the steel plates. The notch, one end of the steel hoop holder contacts the piston cylinder. In the fixed state, each elastic steel hoop on the elastic steel hoop assembly passes through the round hole of the steel hoop holder and is clamped on the steel plates on both sides of the steel hoop holder; the extrusion steel hoop device consists of a central tube body, a limiting sleeve, extrusion slips, a return spring, a push-pull cylinder sleeve, connecting screws, a spring seat, a plug ring, and a sealing ring. The limiting sleeve is used to circumferentially limit the extrusion slips and is machined with a guide dovetail groove, which is welded to the central tube body. The extrusion slips are installed in the slip groove formed by the limiting sleeve and the central tube body. One end is machined with a dovetail block, and the other end is machined with a dovetail groove, which respectively cooperates with the dovetail groove of the limiting sleeve and the dovetail block of the push-pull cylinder sleeve to realize the guiding movement, unfolding, and retraction of the extrusion slips; the end of the push-pull cylinder sleeve is machined with a dovetail block, and the push-pull cylinder sleeve is fixed to the spring seat by connecting screws; including the following steps: S1, in coal mines, long boreholes are constructed from stable strata to complex strata. When borehole collapse or stuck drill occurs, the borehole is cleaned and the drill is withdrawn. S2. After retracting the drill bit, connect the hole protection device, the compression steel hoop device and the transition joint between the drill bit and the drill rod. Start the drilling rig and drill bit assembly to send it into the complex formation section of the hole and continue drilling until it passes through the complex formation section or the jamming pressure is too great to continue drilling. Then stop drilling forward. S3, increase the water pressure in the drill string's internal flow channel. When the water pressure reaches a certain value, the internal mechanism of the borehole protection device shears off its shearing pin through the water pressure transmitted from the drill string's internal flow channel. This pushes the steel hoop seat into place, where the end of the steel hoop seat contacts the shoulder of the female connector. The semi-circular notch of the steel hoop seat aligns with the circular hole of the steel hoop seat, and the elastic steel hoop group is released. Each elastic steel hoop in the elastic steel hoop group unfolds to support the borehole wall under the action of elastic force. Decrease the water pressure in the drill string's internal flow channel, rotate the drill string to agitate the elastic steel hoop group, and further expand radially until the inner channel diameter of the elastic steel hoop can retract the length of the squeeze slip and pull back the drill string. The retraction distance is the length of the squeeze slip of the steel hoop device. S4. Gradually increase the water pressure. Under the action of water pressure, the push-pull cylinder sleeve of the squeezing steel hoop device pushes the squeezing slips to achieve radial expansion along the dovetail groove guide, and rotates the drill bit. The elastic steel hoop in the elastic steel hoop group, under the radial expansion pressure and rotational impact of the squeezing slips, is pressed into the hole wall until the diameter of the elastic steel hoop annular cavity is larger than the drill bit diameter. Then, decrease the water pressure, and the squeezing slips retract and reset. At this time, pull back the squeezing slips again, gradually increase the water pressure again, and rotate the drill bit to press the elastic steel hoop into the hole wall. At this time, the elastic steel hoop group is either attached to the hole wall or pressed into the hole wall. Repeat the operation until the drill bit is completely withdrawn from the steel hoop protection section. After exiting S5, the conventional drilling tool is reinserted to pass through the borehole protection section and continue drilling forward. If complex strata are encountered again, the same process is used to pass through the complex strata until the borehole is completed.

2. The elastic steel hoop hole protection technology for drilling in complex formations underground in coal mines according to claim 1, characterized in that: Based on the estimated length of the borehole section in complex strata and specific geological conditions, multiple borehole protection devices or compression steel hoop devices are connected in series.

3. The elastic steel hoop hole protection technology for drilling in complex formations in coal mines according to claim 1, characterized in that: In step S4, the drill bit needs to be rotated continuously. The combined action of unfolding and rotating compresses the elastic steel hoop, causing it to continuously impact the borehole wall in the complex formation, so that the elastic steel hoop can be smoothly pressed into the borehole wall.

4. The elastic steel hoop hole protection technology for drilling in complex formations in coal mines according to claim 1, characterized in that: In step S4, the water pressure is gradually increased. Under the action of the water pressure, the slip extends radially continuously under the drive of the push-pull cylinder liner. When the water pressure is reduced, the spring seat is driven to reset under the action of the reset spring. At this time, the push-pull cylinder liner, which is integrated with the spring seat, resets synchronously. The dovetail cooperation and guidance between the push-pull cylinder liner and the squeezing slip achieves radial retraction of the slip.

5. The elastic steel hoop hole protection technology for drilling in complex formations underground in coal mines according to claim 1, characterized in that: The elastic steel hoop assembly is wrapped with an elastic steel wire mesh. Each elastic steel hoop has an opening groove at both ends. The diameter of the opening ring of the elastic steel hoop in its natural state is larger than the maximum outer diameter of the drill bit.

6. The elastic steel hoop hole protection technology for drilling in complex formations underground in coal mines according to claim 1, characterized in that: One end of the spring seat is positioned by a plug ring, and the other end is in contact with the return spring. After being compressed by the push-pull cylinder liner, the spring seat is reset under the action of the spring, thus realizing the retraction of the squeeze slip.

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