A grouting anchor rod construction system and method for fractured rock mass in a confined space

Abstract

The application provides a grouting anchor rod construction system and method for fissure rock mass in a limited space, comprising: a roadway excavated in surrounding rock and a YT-28 drilling machine and a grouting device arranged in the roadway; a water supply pipe is connected to a water delivery end of the YT-28 drilling machine, and an air supply pipe is connected to a gas delivery end; when drilling a hole in a position of the surrounding rock with a rock mass fissure, the output end of the YT-28 drilling machine is connected to a drill rod, the end of the drill rod is connected to a drill bit, and the surrounding rock is drilled; when grouting in the position of the rock mass fissure, the grouting device is connected to a hollow grouting anchor rod assembly, the hollow grouting anchor rod assembly is inserted into the drilled hole, grouting is performed, and slurry is filled into the rock mass fissure. The technical problem of complex construction and poor effect of the traditional non-prestressed grouting anchor rod support method in the design of grouting support for the roadway or chamber with limited operation space and developed rock mass fissure in the underground mine is solved.

Description

Technical Field

[0001] This invention relates to the field of rock strata control technology in geotechnical engineering, and particularly to the field of anchor bolt support technology in underground mines. Specifically, it relates to a hollow grouting anchor bolt construction system and construction method for fractured rock masses in confined spaces. Background Technology

[0002] As deep mining becomes more routine, passive support techniques used in shallow mining, such as timber support, steel support, and masonry arch support, are rarely used alone in deep mining roadways, chambers, or stopes. This is because as mining depth increases, ground stress increases significantly, making roadways or chambers with poor surrounding rock properties prone to deformation phenomena such as roof subsidence, sidewall protrusion, and floor bulging. Using the aforementioned passive support techniques alone is ineffective in such cases, and the support costs are high. At this point, rock bolt support technology, a type of flexible support, has gradually been adopted in the support engineering of deep roadways, chambers, or stopes due to its low cost and good support effect. The main function of rock bolts is to connect the unstable rock strata at the top and sides of the roadway with the stable rock strata above, acting as a suspension to ensure the stability of the surrounding rock of the roadway or chamber.

[0003] Anchor bolt support is classified into non-prestressed anchor bolts and prestressed anchor bolt support based on whether prestressing is applied. A representative example of non-prestressed anchor bolt support is ordinary grouting anchor bolt support. Its construction process includes drilling, inspecting and cleaning the borehole, pushing the anchor bolt, installing the air duct, grouting pipe and sealing plug, and finally grouting through the grouting pump connected to the grouting pipe. After the grout solidifies, it works together with the anchor bolt to suspend the loosened surrounding rock. Prestressed anchor bolt support comes in various forms, with prestressed resin anchor bolt support and prestressed grouting anchor bolt support being the most commonly used. The general construction process for prestressed resin anchor bolt support includes drilling, cleaning the borehole, inserting the resin anchoring agent, inserting the anchor bolt, installing the tray and nut, and stirring the anchor bolt. The mixer, connected to the anchor drilling rig, uniformly stirs the resin anchoring agent and simultaneously tightens the nut to apply prestress to the entire anchor, thus forming active support for the loose surrounding rock. The main difference between prestressed grouting anchors and non-prestressed grouting anchors lies in the anchor and its bottom structure. Prestressed grouting anchors are hollow grouting anchors, while non-prestressed grouting anchors are ordinary threaded steel anchors. The bottom structure of non-prestressed grouting anchors consists of a sealing wooden plug, a grouting pipe, and a venting pipe, while the bottom structure of prestressed grouting anchors consists of a tray and a nut. After the prestressed grouting anchor is installed, the nut needs to be tightened with a wrench to ensure that the tray is tightly attached to the rock mass, thus applying prestress to the entire anchor.

[0004] Currently, the construction of anchor bolt support in confined spaces in mines faces drilling challenges. Specifically, anchor bolt trolleys cannot operate normally in confined spaces such as roadways, chambers, or stopes. In such cases, the YT-28 pneumatic leg drilling rig is widely used for drilling operations in confined spaces in mines due to its portability, low cost, and fast drilling speed. For unstable fractured rock masses, grouting support is a commonly used reinforcement method. However, non-prestressed grouting anchor bolt support methods are complex to construct, have poor effectiveness, and cannot meet the safety requirements of the construction site. Summary of the Invention

[0005] This invention provides a method for constructing hollow grouting anchor bolts in fractured rock masses within confined spaces. The method aims to address the technical problems of complex construction and poor effectiveness of traditional non-prestressed grouting anchor bolt support methods in mine roadways or chambers with well-developed rock fractures and limited working space when designing grouting support.

[0006] Specifically, this includes: tunnels excavated inside the surrounding rock and YT-28 drilling rigs and grouting devices installed inside the tunnels;

[0007] The YT-28 drilling rig has a water supply pipe connected to the water delivery end and an air supply pipe connected to the air delivery end.

[0008] When drilling into locations with rock fissures within the surrounding rock, connect the output end of the YT-28 drilling rig to the drill rod, and connect the end of the drill rod to the drill bit to drill into the surrounding rock.

[0009] When grouting at the location of rock fissures, the grouting device is connected to the hollow grouting anchor assembly, which is then inserted into the borehole for grouting, allowing the grout to fill the rock fissures.

[0010] It should be further noted that the hollow grouting anchor bolt assembly includes: a threaded hollow anchor bolt, with a tray connected to the first end of the threaded hollow anchor bolt via a threaded connection. The tray is snapped onto the inner side of the tunnel wall and fixed to the threaded hollow anchor bolt with a nut. The first end of the threaded hollow anchor bolt is connected to the air pressure pipe or the grouting pipe via a connector. The second end of the threaded hollow anchor bolt is connected to a grouting valve.

[0011] It should be further noted that the end of the grouting valve is connected to a wind pressure expansion anchor head; the grouting valve is equipped with a piston, which is sleeved on the second end of the hollow threaded steel anchor rod; the piston has an external overflow hole and an internal overflow hole for the grouting valve.

[0012] It should be further noted that the YT-28 drilling rig is connected to a YT-28 drilling rig air leg.

[0013] The inner walls of the tunnel are equipped with steel anchor mesh and shotcrete.

[0014] It should be further noted that the drill rods include 1m, 2m, and 3m models. A wrench is included as a connector.

[0015] This invention also provides a method for constructing hollow grouting anchors in fractured rock masses within confined spaces, the method comprising:

[0016] S1. After the tunnel excavation is completed, shotcrete support is carried out; after the shotcrete solidifies, the YT-28 drilling rig and grouting equipment are transported to the site.

[0017] S2. Before drilling, connect the air arch pipe and water arch pipe to the YT-28 drilling rig respectively, and set up the YT-28 drilling rig air leg for wet drilling.

[0018] During drilling, the YT drilling machine connects the m-rod, m-rod, and m-rod in sequence, and connects the drill bit to the end of the rod to carry out drilling operations in order to meet the drilling requirements;

[0019] S3. After drilling is completed, the hollow grouting anchor assembly is assembled by connecting the air pressure expansion anchor head, grouting valve, and threaded steel hollow anchor in sequence through internal thread connection. During the assembly process, the overflow hole inside the grouting valve and the overflow hole outside the grouting valve are set to be in an uneven state.

[0020] S4. After the hollow grouting anchor bolt assembly is assembled, it is manually inserted into the borehole. A connector is installed on the exposed section of the threaded steel hollow anchor bolt and connected to the air pressure pipe. High-pressure air is introduced to cause the air pressure expansion anchor head at the top of the threaded steel hollow anchor bolt to expand, and the threaded steel hollow anchor bolt is fixed in the borehole as a whole.

[0021] S5. Use a wrench to turn the connector to rotate and rise the hollow anchor rod of the threaded steel, thereby pushing the piston inside the grouting valve so that the overflow hole inside the grouting valve is flush with the overflow hole outside the grouting valve.

[0022] S6. Tighten the wrench to remove the connector, and install the tray and nut in sequence. Tighten the nut with the wrench until the tray is flush against the surrounding rock.

[0023] S7. Install the connector again on the exposed section of the hollow anchor rod of the threaded steel. The pre-mixed grout is injected into the hollow anchor rod of the threaded steel through the grouting pump and the grouting pipe. The grouting pipe is then connected to the connector. The grout flows out through the overflow hole inside the grouting valve connected above the hollow anchor rod of the threaded steel, and the overflow hole outside the grouting valve is flush with the overflow hole, thus filling the borehole and rock fissures. Stop grouting when the grout begins to overflow from the borehole.

[0024] S8. After grouting is completed, the construction of prestressed hollow grouting anchor rods is finished.

[0025] As can be seen from the above technical solutions, the present invention has the following advantages:

[0026] This invention provides a prestressed hollow grouting anchor bolt construction method for fractured rock masses in confined spaces. This addresses the problem of anchor bolt trolleys being unable to operate normally due to space constraints when constructing anchor bolt support in small cross-section roadways or chambers in mines. Compared to similar drilling rigs, the YT-28 pneumatic leg drilling rig is widely used in mines due to its advantages such as light weight, ease of carrying and operation, low drilling noise, high efficiency, and fast speed. For unstable fractured rock masses, grouting support is a commonly used reinforcement method. However, traditional non-prestressed grouting anchor bolt support methods are complex to construct and have poor effectiveness. Based on this, the proposed prestressed hollow grouting anchor bolt support method effectively solves the technical challenges of grouting support for fractured rock masses by expanding the end air pressure expansion anchor head and applying prestress through full-length grouting and tightening the nut. This invention features simple operation, good support effect, low cost, and wide applicability. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 Schematic diagram for drilling a hole with a 1m drill rod attached to a YT-28 drilling rig;

[0029] Figure 2 Schematic diagram for drilling holes with a 2m drill rod attached to a YT-28 drilling rig;

[0030] Figure 3 Schematic diagram for drilling holes with a 3m drill rod attached to a YT-28 drilling rig;

[0031] Figure 4 Schematic diagram for drilling holes with a 3m drill rod attached to a YT-28 drilling rig;

[0032] Figure 5 This is a schematic diagram of a novel prestressed hollow grouting anchor structure.

[0033] Figure 6 This is a partial cross-sectional schematic diagram of the grouting valve for a novel prestressed hollow grouting anchor.

[0034] Figure 7 A schematic diagram showing the completion of drilling a 3m hole and the installation of the steel reinforcement anchor mesh;

[0035] Figure 8 This is a schematic diagram of anchor delivery;

[0036] Figure 9 This is a schematic diagram of the expansion of the wind pressure expansion anchor head;

[0037] Figure 10A schematic diagram showing the grout overflow holes inside and outside the grouting valve being flush;

[0038] Figure 11 Diagram showing the installation of the tray and nuts;

[0039] Figure 12 This is a schematic diagram of grouting.

[0040] Figure 13 A schematic diagram showing the completed installation of a new type of prestressed hollow grouting anchor.

[0041] Figure 14 This is a flowchart illustrating the construction method of hollow grouting anchor bolts for fractured rock masses in confined spaces.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1. Surrounding rock; 2. Rock fissure; 3. Tunnel; 4. Reinforcing steel anchor mesh; 5. Shotcrete body; 6. Drill bit; 7. 1m drill rod; 8. YT-28 drilling rig air leg; 9. YT-28 drilling rig; 10. Water supply pipe; 11. Air supply pipe; 12. 2m drill rod; 13. 3m drill rod; 14. Air pressure expansion anchor head; 15. Grouting valve; 16. External overflow hole of grouting valve; 17. Hollow threaded steel anchor rod; 18. Tray; 19. Nut; 20. Internal overflow hole of grouting valve; 21. Piston; 22. 3m borehole; 23. Connector; 24. Air pressure pipe; 25. Wrench; 26. Grouting pipe; 27. Grouting material. Detailed Implementation

[0044] The prestressed hollow grouting anchor bolt construction method for fractured rock masses in confined spaces provided by this invention is mainly applicable to situations in underground mines where there are many rock fractures, grouting support is required, and the working space is limited. This method aims to solve the problems of traditional non-prestressed grouting anchor bolt support methods, which are complex to construct, have poor effectiveness, and cannot meet the safety requirements of construction sites.

[0045] The prestressed hollow grouting anchor bolt construction method for fractured rock masses in confined spaces provided by this invention uses a YT-28 drilling rig 9 and a grouting device for drilling and grouting. Specifically, as... Figures 1 to 14 As shown, the grouting anchor system for fractured rock masses within a confined space includes: a tunnel 3 excavated inside the surrounding rock 1, with a steel mesh 4 and shotcrete 5 installed on the inner wall of the tunnel 3. The steel mesh 4 and shotcrete 5 are configured during the tunnel excavation process. The YT-28 drilling rig 9 and the grouting device are located inside the tunnel 3.

[0046] The YT-28 drilling rig 9 has a water supply pipe 10 connected to the water supply end and an air supply pipe 11 connected to the air supply end; the water supply pipe 10 and the air supply pipe 11 can supply water and air during the drilling process, which can play a role in cooling.

[0047] When drilling into the rock fissures within the surrounding rock 1, the output end of the YT-28 drilling rig 9 is connected to a drill rod, and the end of the drill rod is connected to the drill bit 6 to drill into the surrounding rock 1. The drill rods include: a 1m drill rod 7, a 2m drill rod 12, and a 3m drill rod 13. Drill rods of other lengths can also be used as needed.

[0048] When using the YT-28 drilling rig 9, the YT-28 drilling rig air leg 8 can be installed. The YT-28 drilling rig air leg 8 fixes the YT-28 drilling rig 9 into the tunnel to facilitate drilling operations.

[0049] Thus, due to the limited space for drilling operations on the sides and roof of small cross-section roadways or chambers in mines, anchor cable trolleys cannot operate normally. Under these operating conditions, the YT-28 drilling rig meets the operational requirements to complete the anchor cable support operation for small cross-section roadways or chambers. Taking a roadway cross-section of 3×2.85m and a support depth of 3m as an example, the YT-28 drilling rig uses 1m, 2m, and 3m drill rods in sequence to complete the required drilling depth.

[0050] When grouting at the location of rock fissures, the grouting device is connected to the hollow grouting anchor assembly, which is then inserted into the borehole 22 for grouting, allowing the grout to fill the rock fissures.

[0051] The hollow grouting anchor bolt assembly of the present invention includes: a threaded hollow anchor bolt 17, with a tray 18 threadedly connected to the first end of the threaded hollow anchor bolt 17. The tray 18 is snapped into the inner wall of the tunnel 3 and fixed to the threaded hollow anchor bolt 17 by a nut 19. The first end of the threaded hollow anchor bolt 17 is connected to a pneumatic pipe 24 or a grouting pipe 26 via a connector 23. A grouting valve 15 is connected to the second end of the threaded hollow anchor bolt 17. A pneumatic expansion anchor head 14 is connected to the end of the grouting valve 15. The grouting valve 15 is equipped with a piston 21, which is sleeved on the second end of the threaded hollow anchor bolt 17. The piston 21 has an external overflow hole 16 and an internal overflow hole 20. A wrench 25 is connected to the connector 23.

[0052] After drilling is completed, the grouting device is assembled by connecting the anchor rod with internal threads in the following order: wind pressure expansion anchor head, grouting valve, and threaded steel hollow anchor rod. During the assembly process, it should be ensured that the overflow hole inside the grouting valve and the overflow hole outside the grouting valve are not aligned, so that the entire anchor rod except for the hollow hole of the threaded steel anchor rod at the tail is in a closed state, so that high pressure air can be introduced later to cause the wind pressure expansion anchor head at the top of the anchor rod to expand.

[0053] After the hollow grouting anchor bolt assembly is assembled, it is manually inserted into the borehole. Then, a connector is installed on the exposed section of the anchor bolt and connected to a compressed air pipe. High-pressure air is introduced to cause the top of the anchor bolt to expand, thereby fixing the entire anchor bolt inside the borehole.

[0054] After the air supply is completed, use a wrench to tighten the connector, which will then tighten the threaded steel anchor rod and the grouting valve until the overflow hole inside and outside the grouting valve are flush, facilitating subsequent grouting. Remove the connector and install the tray and nut in sequence. Use a wrench to tighten the nut until the tray is flush with the rock mass. Tightening the nut is equivalent to applying prestress to the entire anchor rod. Reinstall the connector on the exposed section of the anchor rod. Inject the pre-mixed grouting material into the hollow anchor rod through the grouting pump connected to the grouting pipe, which is then connected to the connector. The grouting material flows out through the overflow hole of the grouting valve connected to the top of the threaded steel hollow anchor rod, filling the entire borehole and rock fissures. Stop grouting when the grouting material begins to overflow from the borehole.

[0055] Thus, the grouting anchor bolt construction system for confined spaces in fractured rock masses solves the problem of anchor bolt trolleys being unable to operate normally due to space limitations when constructing anchor bolt support in small cross-section roadways or chambers in mines. Compared with similar drilling rigs, the YT-28 pneumatic leg drilling rig is widely used in mines due to its advantages such as light weight, easy portability and operation, low drilling noise, high efficiency, and fast speed. For unstable fractured rock masses, grouting support is a commonly used reinforcement method. However, traditional non-prestressed grouting anchor bolt support methods are complex to construct and have poor effects. Based on this, the proposed prestressed hollow grouting anchor bolt support method effectively solves the technical difficulties of grouting support for fractured rock masses by expanding the end wind pressure expansion anchor head and applying prestress through full-length grouting and tightening the nut. The construction process of this invention is simple to operate, has good support effect, low cost, and wide applicability.

[0056] The following are embodiments of the hollow grouting anchor bolt construction method for fractured rock masses in confined spaces provided by this disclosure. This construction method belongs to the same inventive concept as the construction systems of the above embodiments. For details not described in detail in the embodiments of the construction method, please refer to the embodiments of the above construction systems.

[0057] The methods include:

[0058] S101. Before construction, prepare the necessary materials and equipment, including YT-28 drilling rig 9, wind pressure expansion anchor head 14, grouting valve 15, threaded steel hollow anchor rod 17, tray 18, nut 19, wrench 25, connector 23, grouting material 27, etc.

[0059] After the excavation of S102 and the fractured rock mass tunnel 3 is completed, shotcrete support is carried out. After the shotcrete 5 solidifies, for the fractured rock mass 2 of the tunnel surrounding rock, the corresponding position is selected according to the prestressed hollow grouting anchor support scheme and the YT-28 drilling rig is used for drilling. Before drilling, the arch air pipe 11 and arch water pipe 10 are connected to the YT-28 drilling rig 9 respectively, and the YT-28 drilling rig air leg 8 is set up for wet drilling. When drilling begins, the YT28 drilling rig 9 is connected in sequence with 1m drill rod 7, 2m drill rod 12, and 3m drill rod 13 and connected with drill bit 6 to drill to achieve the requirement of a 3m drilling depth 22.

[0060] S103. After drilling is completed, the anchor rod is assembled by connecting the wind pressure expansion anchor head 14, the grouting valve 15, and the threaded steel hollow anchor rod 17 in sequence through internal thread connection. During the assembly process, it should be ensured that the overflow hole 20 inside the grouting valve and the overflow hole 16 outside are not flush, so that the entire anchor rod except for the hollow hole of the threaded steel hollow anchor rod 17 at the tail is in a closed state, so that high pressure air can be introduced later to cause the wind pressure expansion anchor head 14 at the top of the anchor rod to expand.

[0061] S104. After the anchor bolt is assembled, it is manually inserted into a 3m borehole 22. Then, a connector 23 is installed on the exposed section of the anchor bolt and connected to a wind pressure pipe 24. High-pressure air is introduced to cause the wind pressure expansion anchor head 14 at the top of the anchor bolt to expand, and the entire anchor bolt is fixed in the 3m borehole 22.

[0062] S105. After the air supply is completed, use wrench 25 to turn connector 23 to drive the hollow anchor rod 17 of threaded steel to rotate and rise, thereby pushing the piston 21 inside the grouting valve so that the overflow hole 20 inside the grouting valve and the overflow hole 16 outside the grouting valve are flush, so that the grouting work can be carried out in the future.

[0063] S106. Tighten the wrench 25 to remove the connector 23, and install the tray 18 and nut 19 in sequence. Tighten the nut 19 with the wrench 25 until the tray 18 is in close contact with the surrounding rock 1. Tightening the nut 19 is equivalent to applying prestress to the anchor rod as a whole.

[0064] S107. Install connector 23 again on the exposed section of the anchor rod. Connect the pre-mixed grouting material 27 to the grouting pipe 26 through the grouting pump. Then connect the grouting pipe 26 to connector 23 and inject it into the hollow threaded steel anchor rod 17. The grouting material 27 flows out through the overflow hole 20 inside the grouting valve 15 connected above the hollow threaded steel anchor rod 17 and the overflow hole 16 outside the grouting valve 15, which are flush with each other, and fills the 3m borehole 22 and the rock mass fissure 2. Stop grouting when the grouting material 27 begins to overflow from the 3m borehole 22.

[0065] S108. After grouting is completed, the construction of the new type of prestressed hollow grouting anchor is finished.

[0066] Based on the above-mentioned method for constructing hollow grouting anchor bolts in confined spaces with fractured rock masses, a YT-28 drilling rig is used instead of the anchor bolt trolley, and the designed hole depth is achieved by replacing the drill rod. Grouting support is a commonly used reinforcement method for unstable fractured rock masses. However, traditional non-prestressed grouting anchor bolt support methods are complex to construct and have poor effectiveness. Therefore, this invention proposes a novel prestressed hollow grouting anchor bolt support method. This method effectively solves the technical challenges of grouting support for fractured rock masses by expanding the end wind-pressure anchor head and applying prestress through full-length grouting and tightening the nut.

[0067] It should be understood that when an element or layer is referred to as being "connected" or "coupled" to another element or layer "on" it may be directly connected or coupled to said other element or layer, or there may be intermediate elements or layers. Conversely, when an element is referred to as being "directly connected" or "directly coupled" to another element or layer "on" it is not an intermediate element or layer. Similar figures in all figures indicate similar elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0068] Spatially relative terms such as “below,” “under,” “lower,” “above,” “above,” etc., may be used here to describe the relationship between one element or feature and another, as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation other than those shown in the figure. For example, if the device in the figure were flipped over, the element described as “below” or “under” other elements or features would be facing “above” other elements or features. Thus, the exemplary term “below” can include both above and below orientations. Other orientations (rotation 90 degrees or other orientations) may be adopted, and the spatially relative terms used herein will be interpreted accordingly.

[0069] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the expression within this document. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that, when used in this specification, the term “comprising” means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0070] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this invention, are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hollow grouting anchor rod construction method for fissure rock mass in a confined space, characterized in that, The water supply pipe (10) is connected to the water delivery end of the YT-28 drill (9), and the air supply pipe (11) is connected to the gas delivery end; The hollow grouting anchor rod assembly used includes a threaded steel hollow anchor rod (17), a tray (18) connected to the first end of the threaded steel hollow anchor rod (17) by threading, the tray (18) is clamped to the inner side of the inner wall of the roadway (3) and is fixed to the threaded steel hollow anchor rod (17) by a nut (19); the first end of the threaded steel hollow anchor rod (17) is connected to the air pressure pipe (24) through the connector (23), or connected to the grouting pipe (26); the second end of the threaded steel hollow anchor rod (17) is connected to the grouting valve (15); The end of the grouting valve (15) is connected to the wind pressure expansion anchor head (14); the grouting valve (15) is provided with a piston (21), the piston (21) is sleeved on the second end of the threaded steel hollow anchor rod (17); the piston (21) is provided with a grouting valve external overflow hole (16) and a grouting valve internal overflow hole (20); The construction method comprises: S1, after the roadway (3) is excavated, the shotcrete support is carried out; after the shotcrete (5) is solidified, the YT-28 drill (9) and the grouting device are transported to the site; S2, before drilling, the air supply pipe (11) and the water supply pipe (10) are connected to the YT-28 drill (9) respectively, and the YT-28 drill air leg (8) is erected for wet drilling; When drilling, the YT28 drill (9) is connected to the 1m drill rod (7), the 2m drill rod (12) and the 3m drill rod (13) in sequence, and the drill bit (6) is connected to the end of the drill rod for drilling operation to meet the drilling requirements; S3, after drilling is completed, the hollow grouting anchor rod assembly is assembled in the order of the wind pressure expansion anchor head (14), the grouting valve (15) and the threaded steel hollow anchor rod (17) through internal thread connection; during the assembly process, the grouting valve internal overflow hole (20) and the grouting valve external overflow hole (16) are set to be uneven; S4, after the hollow grouting anchor rod assembly is assembled, it is manually sent into the drill hole (22); the connector (23) is installed on the exposed section of the threaded steel hollow anchor rod, and the air pressure pipe (24) is connected; high pressure air is sent to make the wind pressure expansion anchor head (14) at the top of the threaded steel hollow anchor rod expand, and the threaded steel hollow anchor rod is fixed in the drill hole (22) as a whole; S5, use the wrench (25) to twist the connector (23) to drive the threaded steel hollow anchor rod (17) to rotate and rise, thereby pushing the internal piston (21) of the grouting valve, so that the internal overflow hole (20) and the external overflow hole (16) of the grouting valve are flush; S6, twist the wrench (25) to remove the connector (23), and install the tray (18) and the nut (19) in sequence, and tighten the nut (19) with the wrench (25) until the tray (18) is tightly attached to the surrounding rock (1). S7, the connector (23) is installed again in the exposed section of the threaded steel hollow anchor rod, the grouting material (27) is injected into the threaded steel hollow anchor rod (17) through the grouting pump connected to the grouting pipe (26), the grouting pipe (26) is connected to the connector (23), the grouting material (27) flows out through the overflow hole flush with the internal overflow hole (20) and the external overflow hole (16) in the grouting valve (15) connected to the top of the threaded steel hollow anchor rod (17) and fills the drill hole (22) and the rock mass fracture (2), and the grouting is stopped when the grouting material (27) starts to overflow the drill hole (22); S8, after the grouting is completed, the prestressed hollow grouting anchor rod construction is completed.

2. The method for the construction of a hollow grouting anchor rod for fractured rock mass in a confined space according to claim 1, characterized in that, The YT-28 drilling machine (9) is connected to the YT-28 drilling machine air leg (8).

3. The method for the construction of hollow grouting anchor rods in fractured rock mass in confined spaces according to claim 1, characterized in that, The inner wall of the roadway (3) is provided with a steel anchor net (4).

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