A coal mine underground soft coal seam directional hole bottom anchoring device and a use method thereof

Abstract

The application discloses a kind of coal mine underground soft coal seam directional hole bottom anchoring device and use method, including the anchoring head assembly of splicing and outer tube, the anchoring head assembly in the outer tube is connected with expansion inner core assembly, the axial rear end of the outer tube is connected with limit joint;The anchoring head assembly includes body, and the body includes cone, stepped cylindrical platform and cylinder sequentially in axial direction, by setting anchoring head assembly and expansion inner core assembly, two different principles of anchoring method of mechanical anchor jaw anchoring and chemical expansion plug anchoring are integrated, can provide greater anchoring force, the tensile capacity of single mechanical anchor jaw anchoring can be improved by 1 to 3 times, and the mechanical anchoring and chemical expansion plug anchoring of the anchoring device in hole is triggered by compressed gas drive, control is simple and reliable, without additional push force, anchoring depth is not limited, solve the technical problems of small anchoring force,'anchor pull'ability weak, poor reliability of existing mechanical anchor jaw.

Description

Technical Field

[0001] This invention belongs to the field of directional drilling technology in coal mines, and relates to a bottom anchoring device, specifically a bottom anchoring device for directional holes in soft coal seams in coal mines and its usage method. Background Technology

[0002] Soft and fractured coal seams are widely distributed in major coal mining areas across my country. Many high-gas mines and coal and gas outburst mines primarily utilize soft and fractured coal seams. For a long time, the directional drilling of long boreholes along the seam for gas drainage in soft and fractured coal seams has been a difficult problem that has not been well solved in the field of tunnel drilling both domestically and internationally. In recent years, the domestically pioneered pneumatic directional drilling technology for underground coal mines has gradually broken through the technical bottleneck of long borehole construction along the seam in soft and fractured coal seams. In typical mining areas, the borehole completion rate for long boreholes with depths exceeding 300m has reached over 75%, with the maximum borehole depth exceeding 600m. Using long boreholes along the seam as drainage channels has laid the foundation for achieving progressive and efficient regional gas drainage and control in soft and fractured coal seams.

[0003] However, when using long boreholes along the seam to manage gas in soft and fractured coal seams, the poor integrity and low mechanical strength of these seams make it easy for borehole walls to collapse and block gas flow channels during extraction in the bare borehole state after drilling, thus affecting extraction efficiency and borehole utilization. Therefore, using protective screens is an effective way to ensure unobstructed extraction channels. Currently, various methods for lowering screens in directional coal seam boreholes generally involve pushing the organic material screen into the borehole using external force at the borehole opening and pressurized water jetting through a dedicated drill rod center channel. However, as the borehole depth and pipe length increase, the anchoring force required to keep the screen in the borehole becomes increasingly greater. Existing mechanical anchor claw devices cannot meet the requirements for anchoring long screens because the borehole walls in soft and fractured coal seams are often irregular, lack integrity, and have low mechanical strength, leading to slippage of the mechanical anchor claws under excessive force. This results in problems such as low anchoring force, weak anchoring capacity, and poor reliability of mechanical anchor claws. In addition, the process of placing the screen tube in the long branch hole of the multi-branch directional hole by relatively 'pulling' requires a larger capacity hole bottom anchoring device, which objectively requires innovation in the structure of the hole bottom anchoring device.

[0004] Therefore, there is an urgent need for a hole bottom anchoring device and usage method suitable for pneumatic directional hole lower protection screen pipes in soft coal seams, in order to overcome the above-mentioned defects. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a bottom anchoring device and method for directional holes in soft coal seams in underground coal mines, so as to solve the technical problems of low anchoring force, weak 'anchoring' ability and poor reliability of existing mechanical anchor claws.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] An anchoring device for the bottom of a directional hole in a soft coal seam in an underground coal mine includes an insertable anchoring head assembly and an outer tube. An expansion inner core assembly is connected to the anchoring head assembly located inside the outer tube, and a limit joint is connected to the axial rear end of the outer tube. The anchor head assembly includes a body, which comprises a cone, a stepped cylindrical platform, and a cylinder arranged sequentially along the axial direction. The outer wall of the axial front end of the stepped cylindrical platform is provided with multiple anchor claw through slots at equal intervals. A fixing pin is provided on one side of the anchor claw through slot. An anchor claw is rotatably sleeved on one end of the fixing pin, and a V-shaped elastic element is sleeved on the other end of the fixing pin. One side of the V-shaped elastic element is in close contact with the bottom interior of the anchor claw through slot, and the other side of the V-shaped elastic element is fixed to the side wall of the anchor claw. The cylinder has a pair of symmetrically distributed strip-shaped locking holes on its side wall. A horizontal pin is provided inside the cylinder, and a V-shaped elastic frame is fitted on the horizontal pin. A cylindrical locking pin is provided at each end of the V-shaped elastic frame, and the two cylindrical locking pins extend into the strip-shaped locking holes respectively. Multiple spring mounting holes are provided at equal intervals on the axial rear end face of the cylinder. Limiting springs are installed in the spring mounting holes, and the ends of the limiting springs are in contact with the expansion inner core assembly. The outer tube that is inserted into the anchor head assembly has two guide slots that correspond to the circumferential positions of the strip-shaped lock hole, and two round holes that are respectively set on the axial rear side of the two guide slots. A cylindrical locking pin is set in each of the two round holes. The expansion core assembly includes a cylindrical rod, on which a first liquid storage cylinder, a fiber bag, and a second liquid storage cylinder are sequentially mounted from front to back along the axial direction. A pair of first injection holes are provided on the axial rear end face of the first liquid storage cylinder, and a pair of second injection holes are provided on the axial front end face of the second liquid storage cylinder. Each of the first and second injection holes is equipped with a sealing stud. Symmetrical strip-shaped liquid flow grooves are provided on the outer walls at both ends of the cylindrical rod. The first liquid storage cylinder is provided with a first end cap and the second liquid storage cylinder is provided with a second end cap at the axial front end and the second liquid storage cylinder, respectively. The cylindrical rod is provided with a first piston and a second piston at the axial front end and the axial rear end, respectively. The first piston and the second piston are in corresponding contact with the first end cap and the second end cap, respectively. A trigger is provided on the first end cap. The trigger includes a connected U-shaped opening and a connecting post. The connecting post is fixedly connected to the first end cap. A strip-shaped hole connecting plate is provided on the side of the U-shaped opening. The cross pin is provided in the strip hole of the strip-shaped hole connecting plate. The second end cap is provided with a plunger and a flexible cable assembly in sequence. The flexible cable assembly includes a flexible cable tube, and a flexible cable connected to the plunger is provided inside the flexible cable tube. A screen tube connector is inserted into the axial rear end of the flexible cable tube, and the axial rear end of the screen tube connector extends into the limiting joint. The screen tube connector is provided with a radial airflow channel and a central airflow cavity, and the radial airflow channel and the central airflow cavity are connected.

[0008] This invention also includes the following technical features: The outer wall of the cone is provided with multiple guide grooves at equal intervals.

[0009] A guide cover is provided at the axial front end of the anchor claw through groove.

[0010] The plunger and the flexible cable are connected by bolts.

[0011] A method for using a bottom anchoring device for directional holes in soft, fractured coal seams in underground coal mines includes the following steps: Step 1: Install the bottom anchoring device of the directional hole in the soft coal seam of the coal mine at one end of the downpipe drill rod and lower it into the borehole. Then, connect multiple downpipe drill rods and multiple screen pipes to the other end of the downpipe drill rod in sequence until the bottom anchoring device of the directional hole in the soft coal seam of the coal mine is pushed into the predetermined anchoring position in the borehole. All the aforementioned down-tube drill rods form a down-tube drill rod column, and all the aforementioned screen pipes form a screen pipe string; Step 2: High-pressure gas is injected into the hole through the center of the lower drill string. The high-pressure gas enters the outer tube through the central airflow chamber and radial airflow channel of the screen pipe connector. The high-pressure gas acts on the plunger to generate axial thrust, which pushes the expansion inner core assembly to move towards the bottom of the hole and compress the limiting spring. The U-shaped opening on the trigger moves into the anchor head assembly, causing the V-shaped elastic frame to contract. The cylindrical locking pin moves radially inward until it exits the round hole on the outer tube. The anchor head assembly is unlocked and disengaged from the outer tube. The anchor claws on the anchor head assembly open under the action of the V-shaped elastic element. Step 3: The high-pressure gas continues to push the anchor head assembly and the expansion inner core assembly into the borehole until the plunger extends out of the outer tube and the anchor claws embed into the borehole wall to achieve mechanical anchoring. Step 4: The drilling rig pulls back the lower pipe drill rod column inside the hole. The anchoring force of the anchoring head assembly at the bottom of the hole acts on the first liquid storage cylinder through the trigger and the first end cap. The frictional resistance between the screen pipe string and the lower pipe drill rod column acts on the second liquid storage cylinder through the screen pipe connector, flexible cable, plunger and the second end cap. After being subjected to force, the first and second liquid storage cylinders move in opposite directions along the cylindrical rod. The strip-shaped liquid flow channels on the cylindrical rod extend out of the first and second liquid storage cylinders respectively. The two chemical slurries in the first and second liquid storage cylinders flow out into the fiber bag through the corresponding strip-shaped liquid flow channels. They mix and react chemically in the fiber bag to generate bubble-like solids, causing the fiber bag to expand and form a chemical expansion plug, which is supported on the irregular hole wall. Step 5: After the chemical expansion plug has formed for 3 to 4 hours, it is anchored together with the anchoring head assembly. The screen tube string is pulled by the flexible cable and the screen tube connector, and then the lower tube drill rod is withdrawn one by one. Finally, the limiting joint and the outer tube are withdrawn out of the hole together.

[0012] Compared with the prior art, the beneficial technical effects of this invention are: (I) In this invention, by setting up an anchoring head assembly and an expansion core assembly, two different anchoring methods, mechanical anchor claw anchoring and chemical expansion plug anchoring, are integrated into one, which can provide greater anchoring force. The tensile strength can be increased by 1 to 3 times compared with the single mechanical anchor claw anchoring. Moreover, the mechanical anchoring and chemical expansion plug anchoring in the hole are triggered and driven by compressed gas, which is simple and reliable to control. No additional pushing force is required, and the anchoring depth is not limited. This solves the technical problems of low anchoring force, weak 'anchoring pull' ability and poor reliability of existing mechanical anchor claws.

[0013] (II) The chemical expansion plug of the present invention is formed at the anchoring position inside the borehole, and the corresponding chemical reaction occurs under controlled conditions outside the borehole. The chemical anchoring is not limited by the depth and duration of the screen tube lowering, resulting in better flexibility and usability. The chemical expansion plug of the present invention is formed inside a flexible fiber bag. The maximum diameter of the expansion plug is 1.8 times the theoretical diameter of the borehole. Under the constraint of the flexible fiber bag, the chemical expansion plug can be "shaped" and attached to the borehole wall of irregular, soft coal seams and anchored by compression. The anchoring force can be changed within the range of 0.2 tons to 0.6 tons by adjusting the amount of polyurethane material and the length of the expansion plug core component, thus meeting the requirements for anchoring screen tube strings of different lengths.

[0014] (III) The bottom hole anchoring device of the present invention is pushed to the anchoring position by the lowering drill rod, and the lowering and anchoring reliability is high, with an anchoring success rate of over 98%. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the anchor head assembly in this invention; Figure 3 This is a schematic diagram of the outer tube in this invention; Figure 4 This is a schematic diagram of the structure of the expanded inner core assembly in this invention; Figure 5 This is a schematic diagram of the trigger element in the present invention; Figure 6 This is a schematic diagram of the structure of the chemical expansion plug in this invention; Figure 7 This is a schematic diagram of the connection between the anchor head assembly and the expansion inner core assembly in this invention. Figure 8 This is a schematic diagram of the structure inside the anchor claw through groove in this invention.

[0016] The meanings of the labels in the diagram are as follows: 1. Anchor head assembly; 2. Outer tube; 3. Expansion inner core assembly; 4. Limiting connector; 5. Trigger; 6. Chemical expansion plug. Body 101, anchor claw through groove 102, fixing pin 103, anchor claw 104, V-shaped elastic element 105, strip-shaped locking hole 106, horizontal pin 107, V-shaped elastic frame 108, cylindrical locking pin 109, spring mounting hole 1010, guide groove 1012, guide cover 1013. Cone 10101, stepped truncated cylinder 10102, cylinder 10103; Guide groove 201, round hole 202; Cylindrical rod 301, first liquid storage cylinder 302, fiber bag 303, second liquid storage cylinder 304, first injection hole 305, second injection hole 306, sealing stud 307, strip-shaped liquid flow channel 308, first end cap 309, second end cap 3010, first piston 3011, second piston 3012, plunger 3013, flexible cable assembly 3014, flexible cable cylinder 3015, flexible cable 3016, screen tube connector 3017, radial airflow channel 3018, central airflow chamber 3019; U-shaped opening 501, connecting post 502, strip hole connecting plate 503, bolt 504.

[0017] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, all components in this invention are those known in the art.

[0019] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0020] This invention provides a bottom anchoring device for directional holes in soft, fractured coal seams in underground coal mines, such as... Figures 1 to 8 As shown, it includes an anchor head assembly 1 and an outer tube 2 that are inserted into each other. An expansion inner core assembly 3 is connected to the anchor head assembly 1 located inside the outer tube 2. A limit joint 4 is connected to the axial rear end of the outer tube 2. The anchor head assembly 1 includes a body 101, which includes a cone 10101, a stepped cylindrical platform 10102 and a cylinder 10103 arranged sequentially along the axial direction. Multiple anchor claw through slots 102 are evenly spaced on the outer wall of the axial front end of the stepped cylindrical platform 10102. A fixing pin 103 is provided on one side of the anchor claw through slot 102. An anchor claw 104 is rotatably sleeved on one end of the fixing pin 103, and a V-shaped elastic element 105 is sleeved on the other end of the fixing pin 103. One side of the V-shaped elastic element 105 is in close contact with the bottom interior of the anchor claw through slot 102, and the other side of the V-shaped elastic element 105 is fixed to the side wall of the anchor claw 104. A pair of symmetrically distributed strip-shaped locking holes 106 are provided on the side wall of the cylinder 10103. A horizontal pin 107 is provided inside the cylinder 10103. A V-shaped elastic frame 108 is fitted on the horizontal pin 107. A cylindrical locking pin 109 is provided at each end of the V-shaped elastic frame 108. The two cylindrical locking pins 109 extend into the strip-shaped locking holes 106 respectively. A plurality of spring mounting holes 1010 are provided at equal intervals on the axial rear end face of the cylinder 10103. Limiting springs are installed in the spring mounting holes 1010. The ends of the limiting springs are in contact with the expansion inner core assembly 3. The outer tube 2, which is inserted into the anchor head assembly 1, has two guide slots 201 that correspond to the circumferential positions of the strip-shaped locking hole 106, and two round holes 202 that are respectively provided on the axial rear side of the two guide slots 201. A cylindrical locking pin 109 is provided in each of the two round holes 202. The expansion core assembly 3 includes a cylindrical rod 301. A first liquid storage cylinder 302, a fiber bag 303, and a second liquid storage cylinder 304 are sequentially mounted on the cylindrical rod 301 from front to back along the axial direction. A pair of first injection holes 305 are opened on the axial rear end face of the first liquid storage cylinder 302, and a pair of second injection holes 306 are opened on the axial front end face of the second liquid storage cylinder 304. A sealing stud 307 is provided in both the first injection hole 305 and the second injection hole 306. Symmetrical strip-shaped liquid flow grooves 308 are provided on the outer walls at both ends of the cylindrical rod 301. The first end cap 309 and the second end cap 3010 are respectively provided at the axial front end of the first liquid storage cylinder 302 and the axial rear end of the second liquid storage cylinder 304. The first piston 3011 and the second piston 3012 are respectively provided at the axial front end and the axial rear end of the cylindrical rod 301. The first piston 3011 and the second piston 3012 are respectively in contact with the first end cap 309 and the second end cap 3010. A trigger 5 is provided on the first end cover 309. The trigger 5 includes a connected U-shaped opening 501 and a connecting post 502. The connecting post 502 is fixedly connected to the first end cover 309. A strip-shaped hole connecting plate 503 is provided on the side of the U-shaped opening 501. A horizontal pin 107 is provided in the strip-shaped hole of the strip-shaped hole connecting plate 503. The second end cap 3010 is provided with a plunger 3013 and a flexible cable assembly 3014 in sequence. The flexible cable assembly 3014 includes a flexible cable cylinder 3015. A flexible cable 3016 connected to the plunger 3013 is provided inside the flexible cable cylinder 3015. A screen tube connector 3017 is inserted into the axial rear end of the flexible cable cylinder 3015. The axial rear end of the screen tube connector 3017 extends into the limiting connector 4. The screen tube connector 3017 has a radial airflow channel 3018 and a central airflow cavity 3019, which are connected.

[0021] In the above technical solution, chemical slurry is injected into the first liquid storage cylinder 302 and the second liquid storage cylinder 304 through the first injection hole and the second injection hole, respectively.

[0022] The other end of the limiting spring installed in the spring mounting hole 1010 of the anchor head assembly 1 abuts against the first end cover 309. The anchor claw 104 on the anchor head is manually retracted into the anchor claw through groove 102, and at the same time the cylindrical locking pin 109 is aligned with the guide through groove 201 on the outer tube 2. The anchor head assembly 1 is pushed into the outer tube until the cylindrical locking pin 109 enters the round hole 202, thereby locking the anchor head assembly 1 and the outer tube 2.

[0023] By setting up the anchoring head assembly 1 and the expansion inner core assembly 3, two different anchoring methods, mechanical anchor claw anchoring and chemical expansion plug anchoring, are integrated into one, which can provide greater anchoring force. The tensile strength can be increased by 1 to 3 times compared with the single mechanical anchor claw anchoring. Moreover, the mechanical anchoring and chemical expansion plug anchoring in the hole are triggered and driven by compressed gas, which is simple and reliable to control, requires no additional pushing force, and has no limitation on anchoring depth. It solves the technical problems of low anchoring force, weak 'anchoring pull' ability, and poor reliability of existing mechanical anchor claws.

[0024] Specifically, multiple guide grooves 1012 are equally spaced on the outer wall of the cone 10101.

[0025] In the above technical solution, a strip-shaped guide groove is provided on the surface of the cone to avoid the accumulation of drill cuttings in the hole at the front end of the anchor head assembly during the lowering of the screen tube, which would increase the resistance.

[0026] Specifically, a guide cover 1013 is provided at the axial front end of the anchor claw through groove 102.

[0027] In the above technical solution, the guide cover 102 is fitted onto the anchor head body, and its functions include: 1. supporting and reducing drag, reducing the contact area between the anchoring device and the hole wall, and reducing friction; 2. covering part of the anchor claw groove, preventing drill cuttings from entering the anchor claw groove during the lowering process and affecting the opening action of the anchor claw.

[0028] Specifically, the plunger 3013 and the flexible cable 3016 are connected by bolts 504.

[0029] This invention also provides a method for using a bottom anchoring device for directional holes in soft coal seams underground in coal mines, specifically including the following steps: Step 1: Install the bottom anchoring device of the directional hole in the soft coal seam of the coal mine at one end of the downpipe drill rod and lower it into the borehole. Then, connect multiple downpipe drill rods and multiple screen pipes to the other end of the downpipe drill rod in sequence until the bottom anchoring device of the directional hole in the soft coal seam of the coal mine is pushed into the predetermined anchoring position in the borehole. All the down-tube drill rods form a down-tube drill rod column, and all the screen pipes form a screen pipe string; Step 2: High-pressure gas is injected into the hole through the center of the lower drill string. The high-pressure gas enters the outer tube 2 through the central airflow chamber 3019 and radial airflow channel 3018 on the screen pipe connector 3017. The high-pressure gas acts on the plunger 3013 to generate axial thrust, which pushes the expansion inner core assembly 3 to move towards the bottom of the hole and compress the limiting spring. The U-shaped opening 501 on the trigger 5 moves into the anchor head assembly 1, causing the V-shaped elastic frame 108 to contract. The cylindrical locking pin 109 moves radially inward until it exits the circular hole 202 on the outer tube 2. The anchor head assembly 1 is unlocked and disengaged from the outer tube 2. The anchor claw 104 on the anchor head assembly 1 opens under the action of the V-shaped elastic element 105. Step 3: The high-pressure gas continues to push the anchor head assembly 1 and the expansion inner core assembly 3 into the borehole until the plunger 3013 extends out of the outer tube 2 and the anchor claw 104 is embedded in the borehole wall to achieve mechanical anchoring. Step 4: The drilling rig pulls back the lower pipe drill rod in the hole. The anchoring force of the anchoring head assembly 1 at the bottom of the hole acts on the first liquid storage cylinder 302 through the trigger 5 and the first end cap 309. The frictional resistance between the screen pipe string and the lower pipe drill rod acts on the second liquid storage cylinder 304 through the screen pipe connector 3017, the flexible cable 3016, the plunger 3013 and the second end cap 3010. After being subjected to force, the first liquid storage cylinder 302 and the second liquid storage cylinder 304 move in opposite directions along the cylindrical rod 301. The strip-shaped liquid flow channel 308 on the cylindrical rod 301 extends out of the first liquid storage cylinder 302 and the second liquid storage cylinder 304 respectively. The two chemical slurries in the first liquid storage cylinder 302 and the second liquid storage cylinder 304 flow out into the fiber bag 303 through the corresponding strip-shaped liquid flow channel 308. They mix and react chemically in the fiber bag 303 to generate bubble-like solids, causing the fiber bag 303 to expand and form a chemical expansion plug 6, which is supported on the irregular hole wall. Step 5: After the chemical expansion plug 6 has been formed for 3 to 4 hours, it is jointly anchored with the anchoring head assembly 1. The screen tube string is pulled by the flexible cable 3016 and the screen tube connector 3017. Then, the lower tube drill rod is withdrawn one by one. Finally, the limiting connector 4 and the outer tube 2 are withdrawn out of the hole together.

[0030] In the above technical solution, the chemical expansion plug is formed at the anchoring position inside the borehole, and the corresponding chemical reaction occurs under controlled conditions outside the borehole. The chemical anchoring is not limited by the depth and duration of screen pipe lowering, resulting in better flexibility and usability. The chemical expansion plug of this invention is formed inside a flexible fiber bag. The maximum diameter of the expansion plug is 1.8 times the theoretical diameter of the borehole. Under the constraint of the flexible fiber bag, the chemical expansion plug can conform to the irregular, soft coal seam borehole wall and be anchored by compression. The anchoring force can be changed within the range of 0.2 tons to 0.6 tons by adjusting the amount of polyurethane material and the length of the expansion plug's inner core assembly, meeting the requirements for anchoring screen pipe strings of different lengths.

[0031] The bottom anchoring device is pushed to the anchoring position by the downhole drill rod, and the reliability of the lowering and anchoring is high, with an anchoring success rate of over 98%.

Claims

1. A bottom anchoring device for directional holes in soft, fractured coal seams in underground coal mines, characterized in that, It includes an anchor head assembly (1) and an outer tube (2), with an expansion inner core assembly (3) connected to the anchor head assembly (1) located inside the outer tube (2), and a limit joint (4) connected to the axial rear end of the outer tube (2). The anchor head assembly (1) includes a body (101), which includes a cone (10101), a stepped cylindrical platform (10102), and a cylinder (10103) arranged sequentially along the axial direction. Multiple anchor claw through slots (102) are evenly spaced on the outer wall of the axial front end of the stepped cylindrical platform (10102). A fixing pin (103) is provided on one side of the anchor claw through slot (102). An anchor claw (104) is rotatably sleeved on one end of the fixing pin (103). A V-shaped elastic element (105) is sleeved on the other end of the fixing pin (103). One side of the V-shaped elastic element (105) is in close contact with the bottom interior of the anchor claw through slot (102), and the other side of the V-shaped elastic element (105) is fixed on the side wall of the anchor claw (104). The cylinder (10103) has a pair of symmetrically distributed strip-shaped locking holes (106) on its side wall. A horizontal pin (107) is provided inside the cylinder (10103). A V-shaped elastic frame (108) is fitted on the horizontal pin (107). A cylindrical locking pin (109) is provided at each end of the V-shaped elastic frame (108). The two cylindrical locking pins (109) extend into the strip-shaped locking holes (106). A plurality of spring mounting holes (1010) are provided at equal intervals on the axial rear end face of the cylinder (10103). Limiting springs are installed in the spring mounting holes (1010). The ends of the limiting springs are in contact with the expansion inner core assembly (3). The outer tube (2) that is inserted into the anchor head assembly (1) is provided with two guide slots (201) that correspond to the circumferential position of the strip lock hole (106) respectively, and two round holes (202) respectively provided on the axial rear side of the two guide slots (201). A cylindrical locking pin (109) is provided in each of the two round holes (202). The expansion core assembly (3) includes a cylindrical rod (301), on which a first liquid storage cylinder (302), a fiber bag (303), and a second liquid storage cylinder (304) are sequentially mounted from front to back along the axial direction. A pair of first injection holes (305) are provided on the axial rear end face of the first liquid storage cylinder (302), and a pair of second injection holes (306) are provided on the axial front end face of the second liquid storage cylinder (304). A sealing stud (307) is provided in both the first injection hole (305) and the second injection hole (306). Symmetrical strip-shaped liquid flow grooves (308) are provided on the outer walls at both ends of the cylindrical rod (301). The first liquid storage cylinder (302) is provided with a first end cap (309) and the second end cap (3010) at its axial front end and the second liquid storage cylinder (304) at its axial rear end, respectively. The cylindrical rod (301) is provided with a first piston (3011) and a second piston (3012) at its axial front end and the second end cap (3010) at its axial rear end, respectively. The first piston (3011) and the second piston (3012) are in corresponding contact with the first end cap (309) and the second end cap (3010), respectively. A trigger (5) is provided on the first end cap (309). The trigger (5) includes a connected U-shaped opening (501) and a connecting post (502). The connecting post (502) is fixedly connected to the first end cap (309). A strip-shaped hole connecting plate (503) is provided on the side of the U-shaped opening (501). The cross pin (107) is provided in the strip-shaped hole of the strip-shaped hole connecting plate (503). The second end cap (3010) is sequentially provided with a plunger (3013) and a flexible cable assembly (3014). The flexible cable assembly (3014) includes a flexible cable cylinder (3015). The flexible cable cylinder (3015) is provided with a flexible cable (3016) connected to the plunger (3013). A screen tube connector (3017) is inserted into the axial rear end of the flexible cable cylinder (3015). The axial rear end of the screen tube connector (3017) extends into the limiting joint (4). The screen tube connector (3017) is provided with a radial airflow channel (3018) and a central airflow cavity (3019), and the radial airflow channel (3018) and the central airflow cavity (3019) are connected.

2. The bottom anchoring device for directional holes in soft coal seams underground in coal mines as described in claim 1, characterized in that, The outer wall of the cone (10101) is provided with multiple guide grooves (1012) at equal intervals.

3. The bottom anchoring device for directional holes in soft coal seams underground in coal mines as described in claim 1, characterized in that, The axial front end of the anchor claw through groove (102) is provided with a guide cover (1013).

4. The bottom anchoring device for directional holes in soft coal seams underground in coal mines as described in claim 1, characterized in that, The plunger (3013) and the flexible cable (3016) are connected by bolts (504).

5. A method of using the bottom anchoring device for directional holes in soft coal seams underground in coal mines as described in any one of claims 1 to 4, characterized in that, Specifically, the following steps are included: Step 1: Install the bottom anchoring device of the directional hole in the soft coal seam of the coal mine at one end of the downpipe drill rod and lower it into the borehole. Then, connect multiple downpipe drill rods and multiple screen pipes to the other end of the downpipe drill rod in sequence until the bottom anchoring device of the directional hole in the soft coal seam of the coal mine is pushed into the predetermined anchoring position in the borehole. All the aforementioned down-tube drill rods form a down-tube drill rod column, and all the aforementioned screen pipes form a screen pipe string; Step 2: High-pressure gas is injected into the hole through the center of the lower tube drill string. The high-pressure gas enters the outer tube (2) through the central airflow chamber (3019) and radial airflow channel (3018) on the screen tube connector (3017). The high-pressure gas acts on the plunger (3013) to generate axial thrust, which pushes the expansion inner core assembly (3) to move towards the bottom of the hole to compress the limiting spring. The U-shaped opening (501) on the trigger (5) moves into the anchor head assembly (1), causing the V-shaped elastic frame (108) to contract. The cylindrical locking pin (109) moves radially inward until it exits the round hole (202) on the outer tube (2). The anchor head assembly (1) is unlocked and disengaged from the outer tube (2). The anchor claw (104) on the anchor head assembly (1) opens under the action of the V-shaped elastic element (105). Step 3: The high-pressure gas continues to push the anchor head assembly (1) and the expansion inner core assembly (3) into the borehole until the plunger (3013) extends out of the outer tube (2) and the anchor claw (104) embeds into the borehole wall to achieve mechanical anchoring; Step 4: The anchoring force of the anchoring head assembly (1) at the bottom of the hole is applied to the first reservoir cylinder (302) through the trigger (5) and the first end cap (309) by pulling back the drill rod in the hole. The frictional resistance between the screen pipe string and the drill rod is applied to the second reservoir cylinder (304) through the screen pipe connector (3017), the flexible cable (3016), the plunger (3013), and the second end cap (3010). After being subjected to force, the first reservoir cylinder (302) and the second reservoir cylinder (304) move along the cylindrical rod (301) towards... Moving in opposite directions, the strip-shaped liquid flow channels (308) on the cylindrical rod (301) extend out of the first liquid storage cylinder (302) and the second liquid storage cylinder (304) respectively. The two chemical slurries in the first liquid storage cylinder (302) and the second liquid storage cylinder (304) flow out into the fiber bag (303) through the corresponding strip-shaped liquid flow channels (308). They mix and react chemically in the fiber bag (303) to generate bubble-like solids, causing the fiber bag (303) to expand and form a chemical expansion plug (6), which is supported on the irregular hole wall. Step 5: After the chemical expansion plug (6) is formed for 3 to 4 hours, it is jointly anchored with the anchoring head assembly (1). The screen tube string is pulled by the flexible cable (3016) and the screen tube connector (3017). Then, the lower tube drill rod is withdrawn one by one. Finally, the limiting connector (4) and the outer tube (2) are withdrawn from the hole together.

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