Mortar anchor rod construction device and mortar anchor rod construction method

Abstract

The invention relates to a mortar anchor rod construction device and a mortar anchor rod construction method. The construction device comprises a drill rod, an impactor and a drill bit which are sequentially connected, and is further provided with a wall protection sleeve, the rear end of the drill rod is connected with an output shaft of the rotary driving device, the wall protection sleeve is arranged on the outer side of the drill rod in a sleeving mode, a rotary fit clearance is reserved between the wall protection sleeve and the drill rod, the rear end of the wall protection sleeve is connected with an output shaft flange of the rotary driving device, and an annular drill bit structure is arranged at the front end of the wall protection sleeve. The construction device is used for drilling an anchor rod hole, after drilling is completed, the protection casing pipe is disconnected from the driving shaft of the rotary driving device, the mortar anchor rod construction device is returned, and the protection casing pipe is reserved in the anchor rod hole in situ. The device is suitable for occasions where surface layer covering soil is thick or loose, hole collapse can be effectively avoided, and the working efficiency can be improved.

Description

Technical Field

[0001] The invention relates to a mortar anchor rod construction device and a mortar anchor rod construction method. Background Art

[0002] Mortar anchors are full-length cemented anchors anchored with cement mortar. They are primarily used in tunnel construction and for slope protection in areas with intact rock structures. The rod body typically utilizes ribbed steel bars, which are integrally bonded to the surrounding rock through grouting. Existing mortar anchor construction typically involves a step-by-step process, including drilling, rebar planting, mortar filling, and bolt formation. For example, Chinese patent document CN115492134A discloses a grouting anchor construction process for shallow slope support, which includes the following steps: S1: construction preparation, all materials and equipment used for construction are on site; S2: drilling, the anchor hole position deviation, drilling inclination, direction angle error, and hole depth should be strictly controlled during drilling; S3: hole cleaning, the hole channel should be cleaned with pressurized air; S4: anchor hole grouting, the grouting pipe should be inserted to the bottom of the hole, and then withdrawn 5cm to 10cm to start grouting, and the grouting pipe should be slowly and uniformly pulled out as the mortar is injected to fill the hole with mortar; S5: anchor installation, the anchor body should be inserted in time after the anchor hole is filled with mortar; S6: quality inspection personnel and supervision engineers inspect and accept the constructed anchor. Chinese patent document CN113250721A discloses a method for constructing mortar anchor bolts. The method involves accurately positioning the anchor bolt holes according to design requirements, drilling with a pneumatic rock drill, and clearing the holes with high-pressure air. A single-tube grouting system is employed, where a grouting tube is directly inserted into the bottom of the anchor bolt hole. After grouting begins, the grouting tube is repeatedly fed toward the bottom of the hole, allowing the mortar to squeeze excess water out of the hole. The grouting tube is then withdrawn while grouting is ongoing, preparing for bolt insertion. After grouting, the anchor bolts should be promptly placed, and additional grouting may be required after placement. These existing methods are not only complex and time-consuming, but also prone to collapse when the surface soil is thick or loose, after the hole is extracted and squeezed dry.

[0003] On the other hand, down-the-hole drills, particularly pneumatic down-the-hole drills, can effectively drill anchor holes. For example, Chinese patent document CN116607878A discloses a hammer and down-the-hole drill, which includes a power head, a drill rod, and a hammer, wherein the drill rod is connected to the output end of the power head, and the end of the drill rod away from the power head is connected to the hammer, and the drill bit is mounted on the hammer. The hammer includes an outer sleeve, the rear end of the outer sleeve is connected to a joint, and the front end of the outer sleeve is connected to the drill bit via a clamp sleeve; a gas distribution rod fixedly disposed in the outer sleeve and connected to the high-pressure air passage of the joint; a piston slidably mounted on the outer side of the gas distribution rod, the outer side of the piston being mounted with an inner sleeve, a first air chamber formed between the joint, the piston, the inner sleeve, and the gas distribution rod, and a second air chamber formed between the drill bit, the piston, the outer sleeve, and the gas distribution rod; and an exhaust passage disposed in the joint, wherein the piston moves along the axis of the gas distribution rod so that the exhaust passage is alternately connected to the first and second air chambers. Chinese patent document CN114541961A discloses a pneumatic down-the-hole hammer drilling device comprising a drill rod, an impactor, and a drill bit. The impactor's rear connector is fixedly connected to the drill rod, and its drill bit holder is connected to the drill bit. The impactor housing defines a slag collection chamber, the opening of which is located on the outer circumference of the housing. The housing also includes a guide plate and a first drive mechanism. The guide plate is positioned directly above the opening of the slag collection chamber, with the end of the guide plate away from the housing axis tilted downward. The first drive mechanism is used to drive the guide plate to slide out of the housing or slide back into the housing. These existing technologies can only effectively drill holes but do not help prevent hole collapse. Summary of the Invention

[0004] The purpose of the present invention is to reduce or avoid the hole collapse phenomenon.

[0005] The technical solution of the present invention is: a mortar anchor construction device, comprising a drill rod, an impactor and a drill bit (or main drill bit) connected in sequence, and a wall protection casing. The rear end (input end) of the drill rod is connected to the output shaft of a rotary drive device. The wall protection casing is sleeved on the outside of the drill rod, and a rotational fit gap (a small annular gap allowing relative rotation) is left between the drill rod and the wall protection casing. A wall protection casing connecting flange is provided on the output shaft of the rotary drive device, the rear end of the wall protection casing is flange-connected to the wall protection casing connecting flange (connected by a flange connection method), and an annular drill bit structure (or annular drill bit) is provided at the front end.

[0006] Preferably, the width of the rotational fit clearance between the wall protection sleeve and the drill rod is 3-5 mm.

[0007] Preferably, the annular drill bit structure is a hard alloy tooth (annular tooth) embedded in the front end of the wall protection sleeve.

[0008] Preferably, the rear end of the drill rod is connected to the output shaft of the rotary drive device via a fixed coupling or a universal joint.

[0009] Preferably, the drill bit is a cross-shaped impact drill bit.

[0010] Preferably, the drill bit is made of alloy material.

[0011] Preferably, the wall protection sleeve is a rigid sleeve.

[0012] Preferably, the wall protection sleeve is made of high-strength alloy steel.

[0013] Preferably, the drill bit is provided with six 45° inclined slag discharge holes.

[0014] Preferably, the front end of the impactor is provided with a clamping sleeve for spline connection with the drill bit, and a spline structure that cooperates with each other is provided between the clamping sleeve and the drill bit (connecting section). A limit pin can be used to limit the range of motion (forward sliding range) of the drill bit.

[0015] Preferably, the rotation drive device is an electric motor or a pneumatic motor.

[0016] The rotary drive device can be provided with a transmission device according to actual needs, for example, a gear reducer.

[0017] A mortar anchor construction method adopts any one of the mortar anchor construction devices disclosed in the present invention to drill an anchor hole. After the drilling is completed, the connection between the wall protection sleeve and the drive shaft of the rotary drive device is disassembled, and the mortar anchor construction device is retracted (withdrawn). The wall protection sleeve remains in place in the anchor hole and is permanently retained in the hole.

[0018] Preferably, after drilling to the set depth, the rotation is stopped (the rotary drive device is shut down), and the impactor continues to maintain the impact action for a certain period of time (for example, 30 seconds) to form a hole bottom enlargement head (for example, relying on the drill bit impact to increase the hole bottom diameter by 50 mm).

[0019] The impact frequency of the impactor (when working, including continued impact after the rotary drive device is shut down) can be 800-1200 times / minute.

[0020] The beneficial effects of the present invention are as follows: since the wall protection sleeve is provided, the wall protection sleeve is retained in the hole after the hole is formed, and the collapse of the hole is effectively avoided and prevented by relying on the support of the wall protection sleeve; since the wall protection sleeve connecting flange is provided on the rotating drive shaft, the connection between the wall protection sleeve and the rotating drive shaft is achieved by the flange connection method, which facilitates the disassembly of the wall protection sleeve; since the wall protection sleeve is retained in the hole, there is no need or basically no need to implement hole cleaning operations, and the planting of reinforcement and mortar filling of the hole are smoother, thereby simplifying the construction process, reducing the construction difficulty, and shortening the construction time.

[0021] According to field experiments, compared with traditional processes (existing methods), the present invention has significant advantages such as high hole quality (hole diameter deviation <3%), fast construction efficiency (shift progress increased by 40%), and excellent anchoring performance (standard deviation of pull-out force <5KN). It is particularly suitable for slope control projects with Class IV-V surrounding rocks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the mortar anchor rod construction device of the present invention.

[0023] Markings in the figure: 1. Drill bit; 2. Carbide teeth; 3. Wall protection casing; 4. Guide ring; 5. Drill rod; 6. Wall protection casing connecting flange; 7. Output shaft of the rotary drive device; 8. Air inlet; 9. Rotary drive device; 10. Hydraulic push rod; 11. Fixed ring; 12. Machine base; 13. Guide mechanism; 14. Impactor; 15. Drill holder; 16. Air outlet. DETAILED DESCRIPTION

[0024] See also Figure 1 The wall protection sleeve 3 of this device is a rigid sleeve that fits over the outside of the drill rod (or percussion drill rod) 5, leaving a slight gap between the two to prevent friction or interference with relative motion. The wall protection sleeve is made of high-strength alloy steel and can be customized to meet specific requirements. For example, in one embodiment, the wall protection sleeve has a wall thickness of 8 mm and an outer diameter of 168 mm. The front end of the wall protection sleeve is inlaid with carbide teeth 2, which serve as a casing drill bit.

[0025] The front end of the drill rod is connected to a cross-shaped percussion drill bit, serving as the drill bit 1, via an impactor 14. The front end of the impactor is provided with a drill sleeve 15 for splined connection to the drill bit. A mating spline structure is provided between the drill sleeve and the drill bit (connecting section). This allows the drill bit to have a certain impact movement relative to the impactor and ensures that the impactor can always drive the drill bit to rotate synchronously. In practice, the impact frequency of the impact drill bit can be 800-1200 times per minute. Typically, the anchor rod body (or anchor rod) required for construction can be made of HRB500 grade threaded steel (32mm diameter), with a spiral grouting groove on the surface to facilitate grouting.

[0026] The power system can adopt the power system of conventional pneumatic down-the-hole drill, with an electric motor or pneumatic motor as the rotary drive device 9, and high-pressure air is prepared to provide power for the impactor. The working air pressure can be 1.2-2.5MPa. The impactor can adopt the impactor of existing pneumatic down-the-hole drill, with high-pressure air as the impact power.

[0027] The output shaft 7 of the rotary drive device can be connected to the drill rod through a universal joint to adapt to the construction conditions.

[0028] Transmission Connection: The output shaft of the rotary drive device can be provided with a protective sleeve connecting flange 6 for mounting the protective sleeve, with a matching flange provided at the rear end of the protective sleeve. The two flanges can be connected by a trapezoidal thread (the pitch can be 12mm) to facilitate disassembly. The protective sleeve connecting flange can be directly mounted on the output shaft of the rotary drive device (for example, fixedly mounted on the front-center portion of the output shaft), or an output sleeve can be mounted on the outside of the output shaft, with the rear end of the output sleeve fixedly connected to the output shaft (main body) (for example, via an annular connector with inner and outer circles connecting the output shaft and the output sleeve, respectively). The protective sleeve connecting flange is fixedly mounted at the front end of the output sleeve.

[0029] Maintain an annular gap of 3-5mm between the drill pipe and the casing.

[0030] The drill bit is an alloy drill with six 45° angled slag removal holes (up to 20mm in diameter) at the front. The impactor and drill rod (where they connect) feature a tapered threaded connection (with a taper of 1:10). The rear of the impactor can be designed as a cylindrical shape with external threads, while the front end of the drill rod has corresponding internal threads. By properly aligning the dimensions, the drill bit is positioned in front of the wall casing (the annular drill bit structure at the front) to ensure effective impact crushing.

[0031] The drill rod adopts a hollow structure, an air inlet 8 is provided on the output shaft of the rotary drive device, and an air outlet (air outlet) 16 is provided on the drill bit. The air inlet and the air outlet are connected through corresponding channels on the output shaft, the drill rod and the drill bit. The high-pressure air introduced from the air inlet drives the impactor to operate and then flows out from the air outlet to blow away impurities at the bottom of the hole.

[0032] A hydraulic push rod (hydraulic cylinder) 10 can be used as a thrust mechanism, and the rod body of the hydraulic push rod can be fixedly installed on the machine base 12. The front end of the piston rod is connected to the rear end of the rotary drive device, thereby driving the rotary drive device and the drill rod to move back and forth. The base of the hydraulic push rod can be threadedly connected to the frame according to actual conditions. If necessary, a clamp or a fixing ring (ring-mounted fixing connector) 11 can be provided to achieve / enhance the fixation of the cylinder body.

[0033] The rotary drive unit is connected to the surface of the frame for linear movement (a guide connection). A guide mechanism (e.g., a guide rail and supporting structure) 13 can be provided on the frame to restrict the rotary drive unit to linear movement (e.g., sliding) relative to the frame to achieve feed and retraction of the drill bit. If necessary, a guide ring (sliding ring) 4 can be provided at the front of the frame to guide / restrict the wall protection sleeve, restricting the wall protection sleeve to linear sliding within the guide ring.

[0034] Working process: 1) Synchronous Drilling Phase: After startup, the casing and drill pipe rotate at 20-30 rpm, driven by the rotary drive motor. This in turn drives the drill bit and annular drill structure. The drill bit also impacts the rock formation at a frequency of 15 Hz, driven by the impactor. Pressurized air (typically 0.8 MPa) used to drive the impactor flows out of the air outlet on the drill bit to remove slag.

[0035] 2) Hole-forming and holding stage: After drilling to the set depth / design depth (for example, 6m), stop the rotation and continue the impact action for 30 seconds to form an enlarged head at the bottom of the hole (the diameter increases by 50mm).

[0036] 3) Anchor Grouting Stage: First, disconnect the threaded connection between the retaining wall casing and the output shaft of the rotary drive unit (threaded connection). Remove the drill bit and drill rod (including the impactor) from the hole, leaving the retaining wall casing stationary. Grouting can then be performed using existing methods. If appropriate, grouting can also be performed through the hollow channel of the drill rod without removing the drill bit, drill rod, etc. After grouting is complete, only the drill bit, impactor, and drill rod are removed, leaving the retaining wall casing permanently in the hole as a retaining wall structure.

[0037] C40 cement slurry (water-cement ratio 0.45) can be used for grouting, and the grouting pressure is gradually increased to 2MPa and maintained stable for 5 minutes.

[0038] Working principle: 1) Dynamic wall protection mechanism: The casing moves synchronously with the drill pipe at a follow-up speed of 0.5 m / min (the specific follow-up speed depends on actual needs). The circumferential friction resistance (calculated by the formula: F = πDLμσn, where μ is 0.25) balances the radial stress of the hole wall in real time, reducing the risk of hole collapse by 83%.

[0039] 2) Optimized energy transfer: A dual-medium transmission design allows for linear transmission of impact energy (with a transfer efficiency of 85%), while the rotational torque is primarily borne by the retaining wall casing. This avoids the energy loss and / or product damage that would otherwise occur if the drill pipe were to simultaneously bear the entire load as in traditional processes.

[0040] 3) Anchorage enhancement mechanism: A rock penetration depth of 6 m (or other appropriate depth) allows the anchor rod (anchoring section) to penetrate the strongly weathered layer and enter the moderately weathered rock mass (uniaxial compressive strength > 15 MPa). Calculated based on τ = 0.1σc, the pull-out coefficient is increased by 1.5 times.

[0041] 4) Aging control system: The presence of the wall protection casing reduces the hole cleaning time constant from τ1=Kγh² / μ to τ2=Kγh² / (μ+Δμ), where Δμ is the casing friction correction term, and the hole cleaning probability is reduced from 80% to 15%.

[0042] In an engineering example of the present invention, the slope of the power station was severely damaged by water, and the entire slope collapsed and slid. The exposed slope soil also had a house load on top. The bottom slope was constructed using conventional technology, and the pull-out test met the design requirement of 60kKN pull-out force. However, when constructing the upper slope anchor, the soil quality of the upper and lower slopes was different. The lower part was a hard rock layer, the upper surface was covered with soil for about 2 meters, and then there was weathered porphyry for 1 meter, and then there was porphyry at a deeper level. If conventional technology was continued, the hole would collapse and be blocked, and the probability of clearing the hole was estimated to be 80%. The device and method of the present invention were used for construction. Three randomly selected locations were drilled, and the one-time hole completion rate was 100%. Then the holes were emptied, tested, rebar planted, and grouting was performed. A third-party testing unit was asked to conduct tensile strength tests. The three tensile strength data were 88KN, 86KN, and 87KN, respectively, and no hole collapse occurred in any of the drilled holes.

[0043] Unless otherwise specified or when one preferred or optional technical means is a further limitation of another technical means, the preferred and optional technical means disclosed in the present invention can be arbitrarily combined to form several different specific implementation methods.

Claims

1. A mortar anchor construction device, comprising a drill rod, an impactor and a drill bit connected in sequence, wherein the rear end of the drill rod is connected to the output shaft of a rotary drive device, characterized in that A wall protection casing is also provided, which is sleeved on the outside of the drill rod, leaving a rotational fit gap between the wall protection casing and the drill rod. A wall protection casing connecting flange is provided on the output shaft of the rotary drive device. The rear end of the wall protection casing is connected to the wall protection casing connecting flange, and a ring drill bit structure is provided at the front end.

2. The mortar anchor construction device according to claim 1, characterized in that The width of the rotational fit clearance between the wall protection casing and the drill rod is 3-5mm.

3. The mortar anchor construction device according to claim 1, characterized in that The rear end of the drill pipe is connected to the output shaft of the rotary drive device through a fixed coupling or a universal joint.

4. The mortar anchor construction device according to claim 1, characterized in that The drill bit is a cross-shaped impact drill bit.

5. The mortar anchor construction device according to claim 1, characterized in that The wall protection casing is a rigid casing.

6. The mortar anchor construction device according to claim 1, characterized in that There are 6 45° inclined slag discharge holes on the drill bit.

7. The mortar anchor construction device according to claim 1, characterized in that The front end of the impactor is provided with a clamping sleeve for spline connection with the drill bit, and a spline structure that cooperates with each other is provided between the clamping sleeve and the drill bit.

8. The mortar anchor construction device according to claim 1, characterized in that The rotary drive device is an electric motor or a pneumatic motor.

9. A mortar anchor construction method, characterized in that The anchor hole is drilled using the mortar anchor construction device described in any one of claims 1-8. After the drilling is completed, the connection between the wall protection sleeve and the drive shaft of the rotary drive device is disconnected, the mortar anchor construction device is returned, and the wall protection sleeve remains in place in the anchor hole.

10. The mortar anchor construction method according to claim 9, characterized in that After drilling to the set depth, the rotation stops and the hammer continues to maintain the impact action for a certain period of time to form an enlarged head at the bottom of the hole.

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