A device and method for maintaining pressure on horizontally frozen drilling mud wall

Abstract

The present invention discloses a device and method for maintaining pressure of a horizontal frozen drilling mud wall. The device comprises an orifice pipe installed on the inner wall of a construction pit, a horizontal drill rod being rotatably sealed in the orifice pipe, a first connecting pipe being connected and installed on the orifice pipe, a check valve being installed on the first connecting pipe, and fluid in the first connecting pipe flowing unidirectionally into the orifice pipe through the check valve, and a mud balance supply pipeline being installed on the other end of the first connecting pipe. The present invention provides a check valve, and pumps mud through a mud pump during drilling. Under the working pressure of the mud pump, the check valve can automatically close to ensure the correct flow direction of the mud. When drilling is stopped, the mud pump stops working, and the mud in the ground mud box can be supplied to the horizontal hole through the natural height difference pressure, thereby balancing the mud pressure inside the wall-protecting mud cake and the formation water pressure outside the wall-protecting mud cake, effectively improving the stability of the horizontal hole and avoiding hole collapse.

Description

Technical Field

[0001] The present invention relates to the technical field of horizontal stratum drilling, and in particular to a device and method for maintaining pressure by protecting a horizontal frozen drilling mud wall. Background Art

[0002] Horizontal freeze-drilled holes in foundation pits or tunnels are typically located in soft soil layers, such as silty clay or sandy formations. Drilling is performed under the protection of a blowout preventer (BOP) at the borehole. When the mud pump is operating, the mud in the horizontal (frozen) borehole, protected by the mud wall, will not collapse. Once the mud pump stops, the mud in the horizontal borehole loses external pressure support and can only rely on the compression device of the BOP to maintain a certain level of pressure. While the pump is stopped and the drill pipe is extended, a certain amount of leakage may occur at the borehole, despite the BOP maintaining compression. This leakage results in a loss of mud in the borehole, causing a drop in mud pressure. In soft soil layers, such as silty clay or sandy formations, the internal and external pressure balance of the mud cake in the retaining wall of some sections of the borehole is disrupted, leading to collapse.

[0003] Under the existing technology, when the mud pump stops pumping, the mud lost in the horizontal borehole cannot be replenished, the mud pressure in the borehole drops, and the mud cannot play the role of wall protection. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a horizontal freezing drilling mud wall protection and pressure maintaining device and method which automatically replenishes mud into the horizontal hole during drilling stoppage.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a horizontal freezing drilling mud wall protection and pressure maintaining device, comprising an orifice pipe installed on the inner wall surface of a construction pit, a horizontal drill rod rotatably sealed in the orifice pipe, a first connecting pipe installed on the orifice pipe, a check valve installed on the first connecting pipe, the fluid in the first connecting pipe flows unidirectionally into the orifice pipe through the check valve, a mud balance supply pipeline is installed on the other end of the first connecting pipe, the other end of the mud balance supply pipeline is fluid-connected to a ground mud box, the position of the ground mud box is higher than the position of the orifice pipe; the tail end of the horizontal drill rod is connected to a mud pump through a pump slurry pipeline, and the mud pump is fluid-connected to the ground mud box.

[0006] The above-mentioned horizontal freezing drilling mud wall protection and pressure maintaining device has a first gate valve installed on the first connecting pipe between the check valve and the orifice pipe, and a first interface pipe is fixedly installed on the end of the first connecting pipe away from the orifice pipe, and the first interface pipe is connected to the end of the mud balance supply pipeline.

[0007] In the above-mentioned horizontal freezing drilling mud wall protection and pressure maintaining device, a second connecting pipe is installed on the orifice pipe, and a second gate valve and a safety valve are installed on the second connecting pipe.

[0008] The above-mentioned horizontal freezing drilling mud wall protection and pressure maintaining device has a valve fixedly installed on the end of the orifice pipe, and a first-level orifice clamping mechanism and a second-level orifice clamping mechanism are installed in sequence on the end of the valve. A horizontal tunnel drilling rig is installed in the construction foundation pit, and the horizontal drill rod is driven and installed on the horizontal tunnel drilling rig. The front end of the horizontal drill rod passes through the second-level orifice clamping mechanism, the first-level orifice clamping mechanism and the valve in sequence and then enters the orifice pipe. The inner walls of the first-level orifice clamping mechanism and the second-level orifice clamping mechanism are sealed and fitted with the outer wall of the horizontal drill rod.

[0009] The above-mentioned horizontal freezing drilling mud wall protection and pressure maintaining device, the first-level orifice pressing mechanism includes a first outer retaining ring, a second outer retaining ring and a sealing cylinder sleeved on the horizontal drill rod, the first outer retaining ring and the second outer retaining ring are respectively attached to the two ends of the sealing cylinder, the side wall of the first outer retaining ring is fixedly connected to the end of the valve, convex rings are provided on both ends of the outer wall of the sealing cylinder, the second inner retaining ring and the first inner retaining ring are respectively sleeved on the sealing cylinder, the convex ring at one end of the sealing cylinder is located between the first inner retaining ring and the first outer retaining ring, and the convex ring at the other end of the sealing cylinder is located between the first inner retaining ring and the first outer retaining ring. The convex ring is located between the second outer retaining ring and the second inner retaining ring. The sealing cylinder is provided with an inner cylinder and an outer cylinder between the second inner retaining ring and the first inner retaining ring. The inner diameter of the outer cylinder matches the outer diameter of the inner cylinder. The outer cylinder is sleeved on the inner cylinder. One end of the inner cylinder is fixedly connected to the side wall of the second inner retaining ring, and one end of the outer cylinder is fixedly connected to the side wall of the first inner retaining ring. The first outer retaining ring and the first inner retaining ring are detachably fixedly connected by a first bolt, and the first inner retaining ring and the second inner retaining ring are detachably fixedly connected by a second bolt.

[0010] The above-mentioned horizontal freezing drilling mud wall pressure maintaining device, the secondary orifice pressing mechanism includes a support ring plate, an outer sleeve, a sealing packing and a pressing plug sleeved on the horizontal drill pipe, the support ring plate is fitted with the second outer retaining ring, and a through hole is opened on the side wall of the second inner retaining ring, the side wall of the second outer retaining ring and the side wall of the support ring plate, the second inner retaining ring, the second outer retaining ring and the support ring plate are connected to each other by a third bolt. One end of the sealing packing fits the side wall surface of the support ring plate. The outer sleeve is sleeved on the sealing packing, one end of the outer sleeve is fixedly connected to the side wall of the support ring plate, one end of the pressing plug is inserted into the outer sleeve and fits the other end of the sealing packing, the other end of the pressing plug protrudes from the outer sleeve and is fixedly installed with a second flange, the outer sleeve is fixedly connected to the first flange at one end away from the support ring plate, and the first flange and the second flange are detachably fixedly connected by a fourth bolt.

[0011] The above-mentioned horizontal freezing drilling mud wall protection and pressure maintaining device, a pit bottom mud sedimentation tank is provided in the construction foundation pit, the ground mud box is installed on the ground, a ground mud sedimentation box is installed on one side of the ground mud box, the upper part of one side of the ground mud sedimentation box is connected to the ground mud box through a pipeline, a sludge pump is provided in the pit bottom mud sedimentation tank, and the outlet end of the sludge pump is connected to the ground mud sedimentation box fluid through the ground mud sedimentation box pipeline.

[0012] A method for maintaining pressure by protecting the wall of a horizontally frozen drilling mud using the aforementioned device for protecting the wall of a horizontally frozen drilling mud including the following steps:

[0013] Step A: Start the mud pump and pump mud into the horizontal drill pipe through the pump slurry pipeline. The mud flows into the drill bit at the bottom of the horizontal drill pipe and enters the bottom of the horizontal borehole from the drill bit water hole. The mud is pumped to the bottom of the horizontal borehole, carrying the rock powder at the bottom of the hole toward the hole mouth, maintaining the mud wall pressure in the horizontal hole. The mud enters the hole mouth pipe, and the check valve closes under the action of the mud pump pressure. When the mud pressure in the horizontal borehole reaches the design value, the safety valve on the hole mouth pipe opens, causing mud overflow. The horizontal drill pipe is driven to drill the horizontal hole.

[0014] Step B: After drilling stops, the mud pump stops running and supplying pressure. The mud in the ground mud box is supplied to the first connecting pipe through the mud balance supply pipeline and pushes the check valve to open. Then the mud enters the orifice pipe and enters the horizontal hole to replenish the wall protection mud in the horizontal hole and maintain the wall protection mud pressure in the horizontal hole.

[0015] The technical solution of the present invention achieves the following beneficial technical effects:

[0016] 1. The present invention provides a check valve, and during drilling, slurry is pumped by a mud pump. Under the working pressure of the mud pump, the check valve can be automatically closed to ensure the correct flow of mud. When drilling is stopped, the mud pump stops working, and the mud in the ground mud box can provide mud to the horizontal hole through the natural height difference pressure. The mud balance supply pipeline can fully supply the mud in the horizontal hole during the pump stop period, and can also maintain the pressure value of the horizontal hole from decreasing. The wall protection mud cake on the wall of the horizontal hole is supported by the supplementary mud, so as to achieve the effect of balancing the mud pressure inside the wall protection mud cake and the formation water pressure outside the wall protection mud cake, effectively improving the stability of the horizontal hole and avoiding the collapse of the hole.

[0017] 2. The present invention sets a ground mud box on the formation. The height difference between the ground mud box and the horizontal hole is close to the burial depth of the horizontal hole in the formation, so that the pressure provided by the ground mud box can be close to the water pressure in the formation at the position of the horizontal hole, thereby achieving the purpose of automatic pressure balance. In addition, the density of the mud in the ground mud box is higher than the density of water in the formation, so that the pressure provided by the ground mud box is greater than the water pressure in the formation, thereby maintaining the mud wall protection pressure in the horizontal hole.

[0018] 3. The present invention maintains a fixed mud pressure value by setting a safety valve. When the pressure value is greater than the set value of the safety valve, overflow will occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the installation of the horizontal freezing drilling mud wall protection and pressure maintaining device of the present invention;

[0020] Figure 2 Schematic diagram of the connection between the first interface pipe, the second connecting pipe and the orifice pipe of the present invention;

[0021] Figure 3 Cross-sectional views of the primary and secondary orifice clamping mechanisms of the present invention.

[0022] The reference numerals in the figure are as follows: 1-construction pit; 2-orifice pipe; 3-first connecting pipe; 4-first gate valve; 5-check valve; 6-first interface pipe; 7-mud balance slurry supply pipeline; 8-first orifice clamping mechanism; 801-first outer retaining ring; 802-second outer retaining ring; 803-second inner retaining ring; 804-inner cylinder; 805-first inner retaining ring; 806-outer cylinder; 807-sealing cylinder; 808-convex ring; 809-first bolt; 810-second bolt; 811-third bolt; 812-fourth bolt; 9-second Stage orifice clamping mechanism; 901-support ring plate; 902-outer sleeve; 903-sealing packing; 904-compression plug; 905-first flange; 906-second flange; 10-horizontal tunnel drilling rig; 11-pump slurry pipeline; 12-mud pump; 13-ground mud box; 14-ground mud sedimentation box; 15-pit bottom mud sedimentation tank; 16-ground mud sedimentation box pipeline; 17-sludge pump; 18-second connecting pipe; 19-second gate valve; 20-safety valve; 21-second interface pipe; 22-horizontal drill pipe; 23-valve. DETAILED DESCRIPTION

[0023] Example 1

[0024] In this embodiment, a horizontal freezing drilling mud wall protection and pressure maintaining device is provided. Figure 1-2, including an orifice pipe 2 installed on the inner wall of a construction foundation pit 1, a first connecting pipe 3 is installed on the orifice pipe 2, the first connecting pipe 3 is communicated with the orifice pipe 2, a check valve 5 is installed on the first connecting pipe 3, the fluid in the first connecting pipe 3 flows unidirectionally into the orifice pipe 2 through the check valve 5, a mud balance slurry supply pipeline 7 is installed on the other end of the first connecting pipe 3, the other end of the mud balance slurry supply pipeline 7 is fluidly communicated with a ground mud box 13, the position of the ground mud box 13 is higher than the position of the orifice pipe 2; a horizontal drill rod 22 is rotatably sealed in the orifice pipe 2, the tail end of the horizontal drill rod 22 is connected to a mud pump 12 through a pump slurry pipeline 11, and the mud pump 12 is connected to the ground The mud box 13 is fluid-conductive, and by setting a check valve 5, the mud is pumped by the mud pump 12 during drilling. Under the working pressure of the mud pump 12, the check valve 5 can be automatically closed to ensure the correct flow of mud. When drilling is stopped, the mud pump 12 stops working, and the mud in the ground mud box 13 can provide mud to the horizontal hole through the natural height difference pressure. The mud balance supply pipeline 7 can fully supply the mud loss in the horizontal hole during the pump stop period, and can also maintain the pressure value of the horizontal hole from decreasing. The wall protection mud cake on the wall of the horizontal hole is supported by the supplementary mud, so as to achieve the effect of balancing the mud pressure inside the wall protection mud cake and the formation water pressure outside the wall protection mud cake, effectively improving the stability of the horizontal hole and avoiding hole collapse.

[0025] A pit bottom mud sedimentation tank 15 is provided in the construction foundation pit 1, and the ground mud box 13 is installed on the ground. A ground mud sedimentation tank 14 is installed on one side of the ground mud box 13, and the upper part of one side of the ground mud sedimentation tank 14 is connected to the ground mud box 13 through a pipeline. A sludge pump 17 is provided in the pit bottom mud sedimentation tank 15, and the outlet end of the sludge pump 17 is fluid-connected with the ground mud sedimentation tank 14 through a ground mud sedimentation tank pipeline 16. By arranging the ground mud box 13 on the formation, the height difference between the ground mud box 13 and the horizontal hole is similar to the burial depth of the horizontal hole in the formation, so that the pressure provided by the ground mud box 13 can be close to the water pressure in the formation at the position of the horizontal hole, which plays the purpose of automatic pressure balance, and the density of the mud in the ground mud box 13 is higher than the water density in the formation, so that the pressure provided by the ground mud box 13 is greater than the water pressure in the formation, which plays the role of maintaining the mud wall protection pressure in the horizontal hole.

[0026] A first gate valve 4 is installed on the first connecting pipe 3 between the check valve 5 and the orifice pipe 2, and a first interface pipe 6 is fixedly installed on the end of the first connecting pipe 3 away from the orifice pipe 2. The first interface pipe 6 is connected to the end of the mud balance supply pipeline 7.

[0027] A second connecting pipe 18 is installed on the orifice pipe 2, and a second gate valve 19 and a safety valve 20 are installed on the second connecting pipe 18. By setting the safety valve 20, the mud is kept at a fixed mud pressure value. When the pressure value is greater than the set value of the safety valve, overflow will occur.

[0028] A valve 23 is fixedly installed on the end of the orifice pipe 2, and a first-level orifice clamping mechanism 8 and a second-level orifice clamping mechanism 9 are installed in sequence on the end of the valve 23. A horizontal tunnel drilling rig 10 is installed in the construction foundation pit 1, and the horizontal drill rod 22 is driven and installed on the horizontal tunnel drilling rig 10. The front end of the horizontal drill rod 22 passes through the second-level orifice clamping mechanism 9, the first-level orifice clamping mechanism 8 and the valve 23 in sequence and then penetrates into the orifice pipe 2. The inner walls of the first-level orifice clamping mechanism 8 and the second-level orifice clamping mechanism 9 are sealed and fitted with the outer wall of the horizontal drill rod 22.

[0029] like Figure 3 As shown, the primary orifice clamping mechanism 8 includes a first outer retaining ring 801, a second outer retaining ring 802 and a sealing cylinder 807 sleeved on the horizontal drill rod 22, the first outer retaining ring 801 and the second outer retaining ring 802 are respectively attached to the two ends of the sealing cylinder 807, the side wall of the first outer retaining ring 801 is fixedly connected to the end of the valve 23, and convex rings 808 are provided on both ends of the outer wall of the sealing cylinder 807. The second inner retaining ring 803 and the first inner retaining ring 805 are respectively sleeved on the sealing cylinder 807. The convex ring 808 at one end of the sealing cylinder 807 is located between the first inner retaining ring 805 and the first outer retaining ring 801, and the convex ring 808 at the other end of the sealing cylinder 807 is located at the second outer retaining ring 8 02 and the second inner stop ring 803, an inner cylinder 804 and an outer cylinder 806 are sleeved on the sealing cylinder 807 between the second inner stop ring 803 and the first inner stop ring 805, the inner diameter of the outer cylinder 806 matches the outer diameter of the inner cylinder 804, the outer cylinder 806 is sleeved on the inner cylinder 804, one end of the inner cylinder 804 is fixedly connected to the side wall of the second inner stop ring 803, and one end of the outer cylinder 806 is fixedly connected to the side wall of the first inner stop ring 805; the first outer stop ring 801 and the first inner stop ring 805 are detachably fixedly connected by a first bolt 809, and the first inner stop ring 805 and the second inner stop ring 803 are detachably fixedly connected by a second bolt 810.

[0030] The secondary orifice clamping mechanism 9 includes a support ring plate 901, an outer sleeve 902, a sealing packing 903 and a pressing plug 904 sleeved on the horizontal drill rod 22, the support ring plate is fitted with the second outer retaining ring 802, and through holes are provided on the side wall of the second inner retaining ring 803, the side wall of the second outer retaining ring 802 and the side wall of the support ring plate 901. The second inner retaining ring 803, the second outer retaining ring 802 and the support ring plate 901 are connected to each other by a third bolt 811. One end of the sealing packing 903 is fitted with the side wall surface of the support ring plate 901. The sealing packing 903 is covered with an outer sleeve 902, one end of the outer sleeve 902 is fixedly connected to the side wall of the support ring plate 901, one end of the compression plug 904 is inserted into the outer sleeve 902 and fits with the other end of the sealing packing 903, the other end of the compression plug 904 protrudes from the outer sleeve 902 and is fixedly installed with a second flange 906, and the end of the outer sleeve 902 away from the support ring plate 901 is fixedly connected to a first flange 905, and the first flange 905 and the second flange 906 are detachably fixedly connected by a fourth bolt 812.

[0031] Example 2

[0032] A horizontal freezing drilling mud wall protection and pressure maintenance method in this embodiment uses the horizontal freezing drilling mud wall protection and pressure maintenance device in Example 1 to perform horizontal freezing drilling mud wall protection and pressure maintenance, including the following steps:

[0033] Step A: Start the mud pump 12, pump mud into the horizontal drill pipe 22 through the pump slurry pipeline 11, flow into the drill bit at the bottom of the horizontal drill pipe 22, enter the bottom of the horizontal borehole from the drill bit water hole, pump mud to the bottom of the horizontal borehole, and move the rock powder at the bottom of the hole toward the hole mouth, maintaining the mud wall pressure in the horizontal hole. The mud enters the hole mouth pipe 2, and the check valve 5 is closed under the pressure of the mud pump 12; when the mud pressure in the horizontal borehole reaches the design value, the safety valve 20 on the hole mouth pipe 2 opens, causing mud overflow; drive the horizontal drill pipe 22 to drill the horizontal hole;

[0034] Step B: After drilling stops, the mud pump 12 stops running and supplying pressure, and the mud in the ground mud box 13 is supplied into the first connecting pipe 3 through the mud balance supply pipeline 7 and pushes the check valve 5 to open. Then the mud enters the orifice pipe 2 and enters the horizontal hole, replenishing the wall protection mud in the horizontal hole and maintaining the wall protection mud pressure in the horizontal hole.

[0035] Working process: Start the sludge pump 17 to pump the mud in the pit bottom mud sedimentation tank 15 into the ground mud sedimentation box 14 for sedimentation. The upper mud in the ground mud sedimentation box 14 flows into the ground mud box 13. During drilling, start the mud pump 12 and the horizontal tunnel drilling rig 10. The horizontal tunnel drilling rig 10 drives the horizontal drill rod 22 to drill a horizontal hole. The mud pump 12 pumps the mud in the ground mud box 13 into the horizontal drill rod 22 and inputs it into the horizontal hole to maintain the mud pressure. Under the action of the working pressure of the mud pump 12, the check valve 5 is pushed in the reverse direction to close.

[0036] After drilling is stopped and the mud pump 12 is turned off, the pressure that pushes the check valve 5 to close disappears, and the pressure in the ground mud box 13 enters the first connecting pipe 3 through the mud balance slurry supply pipeline 7 and pushes the check valve 5 to open, enters the orifice pipe 2, and is supplied to the horizontal hole.

[0037] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the claims of this patent application.

Claims

1. A horizontal frozen drilling mud wall protection and pressure maintaining device, comprising an orifice pipe (2) installed on the inner wall surface of a construction pit (1), wherein a horizontal drill rod (22) is rotatably sealed in the orifice pipe (2), characterized in that: A first connecting pipe (3) is installed on the orifice pipe (2), a check valve (5) is installed on the first connecting pipe (3), and the fluid in the first connecting pipe (3) flows unidirectionally into the orifice pipe (2) through the check valve (5). A mud balance supply pipeline (7) is installed on the other end of the first connecting pipe (3), and the other end of the mud balance supply pipeline (7) is fluid-connected to a ground mud box (13), and the position of the ground mud box (13) is higher than the position of the orifice pipe (2); the tail end of the horizontal drill pipe (22) is connected to a mud pump (12) through a pump slurry pipeline (11), and the mud pump (12) is fluid-connected to the ground mud box (13); A valve (23) is fixedly mounted on the end of the orifice tube (2), and a primary orifice pressing mechanism (8) and a secondary orifice pressing mechanism (9) are sequentially mounted on the end of the valve (23); The first-level orifice clamping mechanism (8) comprises a first outer retaining ring (801), a second outer retaining ring (802) and a sealing cylinder (807) sleeved on the horizontal drill rod (22); the first outer retaining ring (801) and the second outer retaining ring (802) are respectively fitted on the two ends of the sealing cylinder (807); the side wall of the first outer retaining ring (801) is fixedly connected to the end of the valve (23); convex rings (808) are provided on both ends of the outer wall of the sealing cylinder (807); the second inner retaining ring (803) and the first inner retaining ring (805) are respectively sleeved on the sealing cylinder (807); the convex ring (808) at one end of the sealing cylinder (807) is located between the first inner retaining ring (805) and the first outer retaining ring (801); and the convex ring (808) at the other end of the sealing cylinder (807) is located between the second outer retaining ring (802) and the second inner retaining ring (803); The secondary orifice clamping mechanism (9) comprises a support ring plate (901) sleeved on the horizontal drill rod (22), an outer sleeve (902), a sealing packing (903) and a clamping plug (904), wherein the support ring plate is fitted with the second outer retaining ring (802); the sealing packing (903) is sleeved with the outer sleeve (902), one end of the outer sleeve (902) is fixedly connected to the side wall of the support ring plate (901), one end of the clamping plug (904) is inserted into the outer sleeve (902) and fitted with the other end of the sealing packing (903), and the other end of the clamping plug (904) protrudes from the outer sleeve (902) and is fixedly mounted with a second flange (906).

2. A horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 1, characterized in that: A first gate valve (4) is installed on the first connecting pipe (3) between the check valve (5) and the orifice pipe (2), and a first interface pipe (6) is fixedly installed on the end of the first connecting pipe (3) away from the orifice pipe (2), and the first interface pipe (6) is connected to the end of the mud balance slurry supply pipeline (7).

3. The horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 1 is characterized in that: A second connecting pipe (18) is connected and installed on the orifice pipe (2), and a second gate valve (19) and a safety valve (20) are installed on the second connecting pipe (18).

4. The horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 1, characterized in that: A horizontal tunnel drilling rig (10) is installed in the construction foundation pit (1), and the horizontal drill rod (22) is driven and installed on the horizontal tunnel drilling rig (10). The front end of the horizontal drill rod (22) passes through the secondary orifice clamping mechanism (9), the primary orifice clamping mechanism (8) and the valve (23) in sequence and then enters the orifice pipe (2). The inner walls of the primary orifice clamping mechanism (8) and the secondary orifice clamping mechanism (9) are sealed and fitted with the outer wall of the horizontal drill rod (22).

5. The horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 4 is characterized in that: An inner cylinder (804) and an outer cylinder (806) are sleeved on the sealing cylinder (807) between the second inner retaining ring (803) and the first inner retaining ring (805); the inner diameter of the outer cylinder (806) matches the outer diameter of the inner cylinder (804); the outer cylinder (806) is sleeved on the inner cylinder (804); one end of the inner cylinder (804) is fixedly connected to the side wall of the second inner retaining ring (803); and one end of the outer cylinder (806) is fixedly connected to the side wall of the first inner retaining ring (805); the first outer retaining ring (801) and the first inner retaining ring (805) are detachably fixedly connected by a first bolt (809); and the first inner retaining ring (805) and the second inner retaining ring (803) are detachably fixedly connected by a second bolt (810).

6. A horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 5, characterized in that: Through holes are provided on the side wall of the second inner retaining ring (803), the side wall of the second outer retaining ring (802) and the side wall of the support ring plate (901); the second inner retaining ring (803), the second outer retaining ring (802) and the support ring plate (901) are connected to each other by a third bolt (811); one end of the sealing packing (903) is in contact with the side wall of the support ring plate (901); a first flange (905) is fixedly connected to the end of the outer sleeve (902) away from the support ring plate (901); the first flange (905) and the second flange (906) are detachably fixedly connected by a fourth bolt (812).

7. The horizontal freezing drilling mud wall protection and pressure maintaining device according to claim 1, characterized in that: A pit bottom mud sedimentation tank (15) is provided in the construction foundation pit (1), the ground mud box (13) is installed on the ground, a ground mud sedimentation tank (14) is installed on one side of the ground mud box (13), an upper part of one side of the ground mud sedimentation tank (14) is connected to the ground mud box (13) through a pipeline, a sludge pump (17) is provided in the pit bottom mud sedimentation tank (15), and the outlet end of the sludge pump (17) is fluidically connected to the ground mud sedimentation tank (14) through a ground mud sedimentation tank pipeline (16).

8. A method for maintaining pressure by protecting the wall of a horizontally frozen drilling mud, using a device for protecting the wall of a horizontally frozen drilling mud according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step A: Start the mud pump (12), pump mud into the horizontal drill pipe (22) through the pump slurry pipeline (11), flow into the drill bit at the bottom end of the horizontal drill pipe (22), enter the bottom of the horizontal drill hole from the drill bit water hole, pump mud into the bottom of the horizontal drill hole, and move the rock powder at the bottom of the hole toward the hole mouth to maintain the mud wall pressure in the horizontal hole; the mud enters the hole mouth pipe (2), and the check valve (5) is closed under the pressure of the mud pump (12); when the mud pressure in the horizontal drill hole reaches the design value, the safety valve (20) on the hole mouth pipe (2) opens, resulting in mud overflow; Driving the horizontal drill rod (22) to perform horizontal hole drilling; Step B: After drilling stops, the mud pump (12) stops running and supplying pressure, and the mud in the ground mud box (13) is supplied to the first connecting pipe (3) through the mud balance supply pipeline (7) and pushes the check valve (5) to open. Then the mud enters the orifice pipe (2) and enters the horizontal hole, replenishing the wall protection mud in the horizontal hole and maintaining the wall protection mud pressure in the horizontal hole.

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