A multi-stage grouting hollow anchor rod

Abstract

This utility model relates to the field of mine engineering support technology, specifically disclosing a multi-stage grouting hollow anchor bolt, comprising: an anchor bolt body, wherein the anchor bolt body has an axially continuous grouting channel inside, a grouting interface is provided at the first end of the anchor bolt body, and a sealing and plugging structure is provided at the second end, and a fixed sealing component is installed on the outer periphery of the anchor bolt body near the first end; at least two grouting units are distributed axially at intervals on the pipe wall of the anchor bolt body, and a one-way valve is provided between each pair of adjacent grouting units, wherein the opening and closing pressure threshold of the one-way valve increases progressively from the first end to the second end; during grouting, this utility model allows the grout to automatically and layer-wise achieve an orderly process of "shallow plugging, middle filling, and deep high-pressure splitting", effectively avoiding grout leakage and ensuring the reliability of deep reinforcement, significantly improving the support effect on broken coal walls.

Description

Technical Field

[0001] This utility model belongs to the field of mining engineering support technology, specifically relating to a hollow anchor bolt with multi-stage grouting. Background Technology

[0002] During coal mining, the coal face or roadway sides are prone to sheet-like spalling due to factors such as mining stress, geological structure, and the mechanical properties of the coal. This spalling deteriorates the working environment, reduces production efficiency, and threatens the safety of personnel and equipment, making it a problem that needs to be addressed in coal mining. Currently, commonly used prevention and control methods fall into two categories: one is passive support using ordinary anchor bolts, metal mesh, etc., which uses external structures to prevent coal spalling; the other is active reinforcement using traditional grouting anchor bolts. "Grouting" refers to injecting grout (such as cement grout, resin grout, etc.) into the coal wall fissures through the channels inside the anchor bolt. The strength of the grout after solidification fills the fissures and bonds the broken coal, thereby enhancing the integrity of the coal wall.

[0003] However, when traditional hollow grouting anchors are used to grout the coal face, all grout outlets release grout simultaneously. Because grout flows along the path of least resistance, it preferentially flows into the loose, fractured areas of the shallow coal face; while the deeper coal seam is more compacted and has greater fracture resistance, making it difficult for grout to be effectively injected. This results in sufficient grout filling in the shallow areas of the coal face, but insufficient grout in the deeper, fractured areas requiring reinforcement, creating a "solid outside, hollow inside" situation that fails to fundamentally suppress spalling. Furthermore, traditional anchors use a single grouting pressure, which is difficult to adapt to the differences in the degree of fracture and stress state of different areas of the coal face from shallow to deep, affecting the reinforcement effect. Utility Model Content

[0004] The purpose of this invention is to provide a multi-stage grouting hollow anchor bolt to solve the problems of traditional hollow grouting anchor bolts where all grout outlets simultaneously discharge grout, causing the grout to preferentially flow to the shallow and deep parts of the coal wall, making effective injection difficult, and the single pressure is not suitable for different areas of the coal wall. This invention facilitates multi-stage, orderly, and controllable reinforcement of broken coal walls.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A multi-stage grouting hollow anchor bolt, comprising:

[0007] The anchor bolt body has an axially continuous grouting channel inside. The first end of the anchor bolt body has a grouting interface, and the second end has a sealing and plugging structure. A fixed sealing component is installed on the outer periphery of the anchor bolt body near the first end.

[0008] At least two slurry discharge units are distributed axially at intervals on the pipe wall of the anchor body. A one-way valve is provided between two adjacent sets of slurry discharge units. The opening and closing pressure threshold of the one-way valve increases step by step from the first end to the second end.

[0009] The slurry discharge unit is used to discharge the slurry in the grouting channel to the coal face.

[0010] Preferably, the grouting unit is composed of multiple grout diffusion components arranged axially at equal intervals. The grout diffusion components include multiple grouting holes opened on the wall of the anchor bolt body, and the grouting holes are connected to the grouting channel.

[0011] Preferably, the axial spacing between two adjacent discharge units is equal.

[0012] Preferably, no one-way valve is installed at the grouting channel closest to the second end.

[0013] Preferably, the fixing sealing assembly consists of a tray, a nut, and a grout stop plug for connecting the grouting pump, arranged sequentially from the second end to the first end.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] Automatic and orderly grouting: During grouting, this structure forces the grout to first open the shallowest valve at low pressure, sealing the borehole and preventing grout leakage; then, the pressure can continue to rise within the sealed borehole, gradually opening deeper valves with higher pressure thresholds. This process is entirely achieved by the anchor bolt's own structure, requiring no complex operations.

[0016] Improved the reliability of reinforcement: ensured that the grout could effectively penetrate the deep part of the coal wall that needed reinforcement the most, avoiding the drawbacks of traditional grouting that was "solid on the outside and hollow on the inside", and forming a continuous and complete reinforcement body from shallow to deep.

[0017] Improved grouting efficiency: A single grouting operation can achieve complex layered reinforcement effects, simplifying construction and improving efficiency.

[0018] Effective suppression of spalling: By effectively modifying the coal wall in both depth and breadth, the integrity and strength of the coal body are significantly improved, thereby effectively controlling the occurrence of spalling. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0020] Figure 2 for Figure 1 Sectional view of AA;

[0021] Figure 3 for Figure 2 Enlarged view of the structure at point B.

[0022] In the diagram: 1. Anchor bolt body; 2. Grouting channel; 3. Grout outlet unit; 4. One-way valve; 5. Nut; 6. Tray; 7. Grout stop plug;

[0023] 11. First end; 12. Second end; 31. Slurry outlet. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more. Example

[0026] Please see Figures 1-3 As shown, a multi-stage grouting hollow anchor bolt includes:

[0027] An anchor body 1 has an internal axially penetrating grouting channel 2. The first end 11 of the anchor body 1 has a grouting interface, and the second end 12 has a sealing and plugging structure. A fixed sealing assembly is installed on the outer periphery of the anchor body 1 near the first end 11. The fixed sealing assembly consists of a tray 6, a nut 5, and a grout stop plug 7 for connecting the grouting pump, arranged sequentially from the second end 12 to the first end 11.

[0028] At least two grouting units 3 are distributed axially on the pipe wall of the anchor body 1. A one-way valve 4 is provided between two adjacent sets of grouting units 3. The opening and closing pressure threshold of the one-way valve 4 increases gradually from the first end 11 to the second end 12. No one-way valve 4 is provided at the grouting channel 2 closest to the second end 12.

[0029] The design of the axial spacing (L) between two adjacent rows of slurry holes (31) is mainly based on the following formula:

[0030]

[0031] In the formula: n is the total number of rows of slurry outlet holes, in rows; Dp is the potential spalling depth of the coal wall, in meters.

[0032] The design of the opening pressure threshold (Pi) of the one-way valve 4 is determined based on the in-situ stress, tensile strength, and slurry flow resistance of the coal body at its location. To ensure that the slurry can be effectively injected into or split the coal body at this location, its value should satisfy the following relationship:

[0033]

[0034] In the formula: T 0 The value represents the tensile strength (MPa) of the coal and rock mass at the valve location. This represents the minimum principal stress at that location. ΔP This refers to the viscous resistance (MPa) that the slurry must overcome to flow through pipes and fissures.

[0035] Depend on Figure 3 It is known that the slurry discharge unit 3 is used to discharge the slurry in the grouting channel 2 to the coal wall. The slurry discharge unit 3 is composed of multiple slurry diffusion components arranged axially at equal intervals. The slurry diffusion components include multiple slurry discharge holes 31 opened on the wall of the anchor body 1. The slurry discharge holes 31 are connected to the grouting channel 2.

[0036] Specifically, along the axial direction of the anchor bolt body 1, three rows of radial grout outlet holes (31a, 31b, 31c) are sequentially arranged from the first end 11 to the second end 12. Except for the third grout outlet hole (31c) closest to the second end 12, each of the first grout outlet hole (31a) and the second grout outlet hole (31b) is fitted with an independent one-way valve (4a, 4b). In this embodiment, the opening pressure of each one-way valve is set as follows: the opening pressure of the first row of one-way valves (4a) is P1 = 1.0 MPa, and the opening pressure of the second row of one-way valves (4b) is P2 = 1.8 MPa, satisfying P1... <P2。

[0037] The working principle of this anchor bolt is as follows:

[0038] Once the anchor body 1 is installed in place, the grouting pump begins to pump grout into the grouting channel 2, and the pressure inside the channel begins to rise.

[0039] 1. First stage (shallow reinforcement): Grout flows out from the grout outlet (31a), quickly filling and sealing the loose cracks around the orifice. At this time, because P1 and P2 are much higher than the current pressure, the intermediate and deep valves remain closed.

[0040] 2. Second stage (central reinforcement): After the grout outlet (31a) is blocked, the grout cannot flow out, and the system pressure continues to rise steadily. When the pressure reaches 1.0MPa, the first row of one-way valves (4a) opens, and the grout continues to flow out from the grout outlet (31b) to split or penetrate the coal wall in the central area.

[0041] 3. Third stage (deep reinforcement): After the slurry outlet (31b) is sealed, the system pressure continues to increase to 1.8MPa, the second row of one-way valves (4b) is opened, and the slurry continues to flow out from the slurry outlet (31c), effectively reinforcing the deepest part of the coal wall and the area with the highest ground stress.

[0042] Through the aforementioned automatic process guided by the anchor bolt's own structure, a continuous and reliable reinforcement zone is ultimately formed within the coal face, from shallow to deep, effectively preventing spalling.

[0043] Specifically, regarding the above, please refer to... Figure 2 As shown, the axial spacing between two adjacent discharge units 3 is equal.

[0044] As can be seen from the above, the equal axial spacing between adjacent slurry outlet units 3, combined with the characteristic that the slurry outlet unit 3 itself is composed of multiple slurry diffusion components (including slurry outlet holes 31) arranged at equal axial spacing, can ensure that the diffusion range of slurry in the axial direction of the coal wall is evenly distributed, avoiding insufficient or excessive grouting in local areas due to uneven spacing. With the graded grouting sequence controlled by the one-way valve 4, the slurry can eventually form a continuous and evenly distributed reinforcement area in the coal wall from shallow to deep, further improving the overall reinforcement effect of the coal wall.

[0045] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hollow anchor bolt with multi-stage grouting, characterized in that, include: An anchor body (1) has an axially penetrating grouting channel (2) inside. The first end (11) of the anchor body (1) is provided with a grouting interface, and the second end (12) is provided with a sealing and plugging structure. A fixed sealing component is installed on the outer periphery of the anchor body (1) near the first end (11). At least two slurry discharge units (3) are distributed axially on the pipe wall of the anchor body (1). A one-way valve (4) is provided between two adjacent sets of slurry discharge units (3). The opening and closing pressure threshold of the one-way valve (4) increases step by step from the first end (11) to the second end (12). The slurry discharge unit (3) is used to discharge the slurry in the grouting channel (2) to the coal wall.

2. The hollow anchor bolt with multi-stage grouting according to claim 1, characterized in that: The grouting unit (3) is composed of multiple grout diffusion components arranged axially at equal intervals. The grout diffusion components include multiple grouting holes (31) opened on the wall of the anchor body (1). The grouting holes (31) are connected to the grouting channel (2).

3. A hollow anchor bolt with multi-stage grouting according to claim 1, characterized in that: The axial spacing between two adjacent discharge units (3) is equal.

4. A hollow anchor bolt with multi-stage grouting according to claim 1, characterized in that: No check valve (4) is installed at the grouting channel (2) closest to the second end (12).

5. A hollow anchor bolt with multi-stage grouting according to claim 1, characterized in that: The fixed sealing assembly consists of a tray (6), a nut (5), and a grout stop plug (7) for connecting the grouting pump, arranged sequentially from the second end (12) to the first end (11).

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