Rotary jet grouting anchor cable variable-diameter drill bit and construction method

Abstract

The invention discloses a variable-diameter drill bit for a rotary jet grouting anchor cable and a construction method, and the variable-diameter drill bit comprises a drill rod, an outer pipe, a jack, an adjustable drill bit and a supporting assembly; the fixed end of the jack is connected to the end of the drill rod, and the movable end of the jack is hinged to one end of the adjustable drill bit. A blade is arranged at the other end of the adjustable drill bit, and the cutting diameter of the adjustable drill bit can be adjusted through the jack; the supporting assembly is arranged on the outer side of the outer pipe. A supporting assembly is arranged on the outer side of the outer pipe, the movable end of the supporting assembly is connected with the adjustable drill bit, and when the adjustable drill bit conducts angle adjustment, the supporting assembly is configured to change the outer diameter of the supporting assembly, so that the hole channel is adaptively supported. The problems that in the prior art, the hole forming diameter of the rotary jet grouting anchor cable is uncontrollable, holes are prone to collapsing under the complex geology, the construction efficiency is low, and the anchor cable failure risk is high are solved, and the technical purposes of precise hole forming of the rotary jet grouting anchor cable and safe and efficient construction are achieved.

Description

Technical Field

[0001] This application relates to the field of jet grouting anchor technology, and in particular to a variable diameter drill bit for jet grouting anchors and a construction method thereof. Background Technology

[0002] In the engineering field, foundation pit support is a core technical measure to ensure the stability of foundation pits during underground engineering construction. With the deepening of urban underground space development, the geological conditions faced by foundation pit projects are becoming increasingly complex. For example, the proportion of soft strata such as saturated soft loess, silt, and quicksand layers is increasing, and the requirements of the surrounding environment for controlling support deformation are becoming increasingly stringent. This has placed higher standards on anchor cable support technology.

[0003] As a key component of composite soil nailing walls, pile anchors, and other support structures, anchor cables, by fixing one end to the slope surface and the other end to stable soil (rock), can directly generate anti-sliding resistance on the slope sliding surface, significantly improving the mechanical properties of the rock mass and effectively controlling soil (rock) displacement. They are a core component for ensuring slope stability. Among them, high-pressure jet grouting anchor cables, leveraging the characteristics of high-pressure jet grouting in improving weak strata, can form cement-soil bodies with a diameter of 0.5-1.5m, greatly enhancing anchoring force. They are suitable for scenarios where ordinary prestressed anchor cables are prone to failure, such as high water levels and quicksand layers. With good applicability and economic benefits under various geological conditions, they have become the preferred solution for complex foundation pit support.

[0004] Despite the significant advantages of jet grouting anchors, the existing method of enlarging the borehole section has a key flaw: traditional borehole formation relies on cement grout or water at a pressure of at least 20 MPa to impact and scour the soil inside the hole, and the same pressure parameter is used for all soil types. This method results in a completely uncontrollable borehole diameter, making it difficult to guarantee the quality of the enlarged section, often resulting in a "skewer-like" enlarged end. The actual diameter of such substandard enlarged ends often fails to meet design requirements, directly leading to insufficient anchoring force and, in severe cases, anchor failure, posing a significant safety hazard to the project.

[0005] Meanwhile, in complex geological conditions such as soft plastic silty clay layers, sandy soil layers, and artificial fill layers, traditional drilling methods also face problems such as easy hole collapse, difficulty in drilling, and large deviations in hole diameter. The traditional approach of simply controlling the grouting pressure to change the hole diameter cannot adapt to the mechanical properties of different soil layers, and also results in a large waste of cement grout, leading to low construction efficiency.

[0006] Therefore, there is an urgent need for a jet grouting anchor cable drilling tool and construction method that can accurately control the hole diameter and adapt to complex geological conditions, in order to solve many of the pain points of existing technologies. Summary of the Invention

[0007] This application provides a variable-diameter drill bit and construction method for jet grouting anchor cables, which solves the problems of uncontrollable hole diameter, easy hole collapse in complex geological conditions, low construction efficiency, and high risk of anchor cable failure in the prior art, and achieves the technical goal of precise hole formation and safe and efficient construction of jet grouting anchor cables.

[0008] In a first aspect, embodiments of the present invention provide a variable-diameter drill bit for jet grouting anchor cables, comprising a drill rod, an outer tube, a jack, an adjustable drill bit, and a support assembly; the fixed end of the jack is connected to the end of the drill rod, and the movable end of the jack is hinged to one end of the adjustable drill bit; the other end of the adjustable drill bit is provided with a cutting blade, and the cutting diameter of the adjustable drill bit can be adjusted by the jack; the outer tube is connected to the outside of the drill rod, and a slot is formed on the outer tube; the support assembly is disposed on the outside of the outer tube; the support assembly is disposed on the outside of the outer tube, and the movable end of the support assembly is connected to the adjustable drill bit; when the adjustable drill bit is angled, the support assembly is configured to change the outer diameter of the support assembly, thereby providing adaptive support for the borehole.

[0009] In conjunction with the first aspect, in one possible implementation, the adjustable drill bit includes a support steel plate, a cutting steel plate, and a drill rod sleeve; one end of the support steel plate is hinged to the movable end of the jack, the other end of the support steel plate is hinged to one end of the cutting steel plate, and the other end of the cutting steel plate is hinged to the drill rod sleeve; the drill rod sleeve is connected to the end of the drill rod; and the cutting steel plate is provided with a cutting blade.

[0010] In conjunction with the first aspect, in one possible implementation, the support assembly includes a mounting sleeve, a sliding sleeve, a connecting rod, and a support plate; the mounting sleeve is fitted onto the outside of the outer tube; one end of the sliding sleeve abuts against the support steel plate; the sliding sleeve is fitted onto the outside of the mounting sleeve and slidably connected to it; one end of the connecting rod is hinged to the outside of the sliding sleeve, and the other end of the connecting rod is connected to the support plate; when the angle between the support steel plate and the drill rod axis changes, the sliding sleeve can be pushed to slide on the mounting sleeve, and the connecting rod can be driven to rotate, and the connecting rod can drive the support plate to move closer to or further away from the drill rod, thereby providing adaptive support for the borehole.

[0011] In conjunction with the first aspect, in one possible implementation, the adjustable drill bit further includes a movable sleeve, a first baffle, and a first pin; the movable sleeve is sleeved on the movable end of the jack; the first baffle is disposed on the outside of the movable sleeve; and the supporting steel plate is rotatably connected to the first baffle via the first pin.

[0012] In conjunction with the first aspect, in one possible implementation, the adjustable drill bit further includes a second baffle and a second pin; the second baffle is connected to the outside of the drill rod sleeve; the cutting steel plate is rotatably connected to the second baffle via the second pin.

[0013] In conjunction with the first aspect, in one possible implementation, the support assembly further includes a telescopic rod and an elastic element; one end of the telescopic rod is connected to the outside of the outer tube, and the other end of the telescopic rod is connected to the inside of the support plate; one end of the elastic element is connected to the end of the sliding sleeve away from the adjustable drill bit, and the other end of the elastic element is connected to the telescopic rod.

[0014] In conjunction with the first aspect, one possible implementation also includes a thrust bearing; the drill rod is disposed inside the jack, and the drill rod and the jack are connected via the thrust bearing; this is used to keep the jack fixed when the drill rod rotates.

[0015] Secondly, embodiments of the present invention provide a construction method for a variable-diameter drill bit for jet grouting anchor cables, characterized in that the variable-diameter drill bit for jet grouting anchor cables, implemented in accordance with the first aspect or any combination thereof, includes the following steps: S1: Construction preparation: completing site clearing, hole positioning, equipment debugging, and grout preparation; S2: Variable-diameter adjustment and drill bit positioning: adjusting the adjustable drill bit to a preset initial diameter using jacks, with the support components adapting synchronously; S3: Drilling and dynamic diameter adjustment: starting the drill rod to rotate and cut the soil, dynamically adjusting the hole diameter according to design requirements, with the support components adapting to the hole wall support in real time; S4: Jet grouting curing: after drilling to the design depth, spraying grout and lifting the drill rod to form a variable-diameter solidified body; S5: Anchor cable installation and grouting: placing the anchor cable body, and replenishing grout if necessary; S6: Support component recovery and borehole protection: recovering the drill bit after the grout has initially set, and protecting the borehole opening; S7: Curing and inspection: curing as required and completing quality inspection.

[0016] In conjunction with the second aspect, in one possible implementation, step S3 includes the following steps: S31: Start the drill rod rotation system and adjust the speed to 10-30 r / min to drive the adjustable drill bit's blades to cut the soil; S32: During drilling, adjust the jack extension speed to 5-15 mm / s through the hydraulic control system to achieve dynamic hole diameter adjustment: During diameter expansion: the jack slowly extends, pushing the support steel plate and the cutting steel plate outward, increasing the blade cutting diameter to the design value, simultaneously driving the sliding sleeve to slide along the axial direction of the mounting sleeve, and the connecting rod drives the support plate to expand outward until the support plate fits against the hole wall, with a fitting gap ≤ 2 mm. mm; During diameter reduction: the jack slowly retracts, the adjustable drill bit retracts inward, the sliding sleeve resets, and the support plate retracts inward with the connecting rod to maintain a support that matches the current hole diameter; S33: Real-time monitoring of drill rod verticality, with deviation controlled within ≤1%. When encountering hard soil layers, reduce the drilling speed to 5-10 cm / min and simultaneously increase the jack extension and retraction frequency to avoid overload damage to the cutting tool; S34: After drilling to the designed hole depth, pause drilling, keep the drill rod rotating, and recalibrate the hole diameter using the jack to ensure that the diameter of the anchoring section meets the design requirements.

[0017] In conjunction with the second aspect, in one possible implementation, step S4 includes the following steps: S41: Adjust the adjustable drill bit to the designed diameter of the anchoring section, expand the support plate of the support assembly to fit against the borehole wall, and lock the position of the support plate with the telescopic rod to ensure support stability; S42: Start the grout delivery equipment, control the grout injection pressure to 15MPa-25MPa, and the grout flow rate to 30L / min-50L / min, and spray the grout onto the borehole wall through the drill pipe inner channel and the drill bit injection port; S43: During the injection process, at a rate of 5cm / min- Slowly raise the drill rod at a speed of 10cm / min, keeping the rotation speed of the drill rod matched with the injection pressure during the raising process; S44: If the design requires the anchoring section to be a variable diameter structure, pause raising the drill rod at the corresponding depth position, adjust the drill bit hole diameter to the design diameter of the enlarged head by using a jack, maintain injection for 30s-60s, and then continue raising at the preset speed to ensure the quality of the solidified body forming at the enlarged head; S45: When the rotary spray reaches the hole opening, increase the slurry injection pressure to 20MPa-30MPa and continue spraying for 1min-2min to ensure the solidified body at the hole opening is full.

[0018] One or more technical solutions provided in this application have at least the following technical effects: The embodiments of the present invention effectively solve the technical problems of uncontrollable hole diameter, easy hole collapse in complex geological conditions, low drilling efficiency, and insufficient anchoring reliability of existing jet grouting anchor cables by combining hydraulic jacks, foldable steel plates, double-plane thrust bearings, and adaptive support components.

[0019] 1. Precise and controllable hole diameter: The hole diameter can be adjusted arbitrarily within the range of 150mm-500mm by means of hydraulic jack extension and retraction, which can perfectly match the different diameter requirements of the free section, the non-enlarged head anchoring section and the enlarged head section, and alleviate the "candied hawthorn" shaped hole formation defect; 2. Improved construction safety: The simultaneous drilling and reaming operation, combined with adaptive support components, can significantly reduce the collapse rate in soft strata and reduce the risk of stuck drill bit. At the same time, the precisely shaped reaming head ensures that the anchoring force meets the design requirements and avoids anchor cable failure. 3. Optimized construction efficiency and economy: Adaptable to various complex geological conditions, eliminating the need for frequent equipment changes or process adjustments, reducing drilling resistance; reducing cement slurry waste, and the drill bit is a steel assembly that is simple to process, reusable, and easy to maintain; 4. High degree of standardization in construction: Equipment parameters, process steps and quality control standards are clearly defined. With the help of special anchor drilling rigs and precision positioning tools, the consistency of construction quality is ensured and the overall reliability of the project is improved. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the jet grouting anchor cable under ideal conditions, provided in the embodiments of this application. Figure 2 This is a schematic diagram illustrating the actual effect of the conventional hole-forming method provided in the embodiments of this application; Figure 3 A schematic diagram of a variable diameter drill bit for jet grouting anchor cables provided in an embodiment of this application; Figure 4 for Figure 3 Enlarged view of point A; Figure 5 A schematic diagram of a variable diameter drill bit for jet grouting anchor cables provided in an embodiment of this application; Figure 6 A schematic diagram of the movable sleeve, the first baffle, and the first pin provided in an embodiment of this application; Figure 7 A flowchart illustrating a method for constructing a jet grouting anchor cable with a variable diameter drill bit, as provided in this application embodiment; Figure 8 A flowchart illustrating a method for constructing a jet grouting anchor cable with a variable diameter drill bit, as provided in this application embodiment; Figure 9 A flowchart illustrating a method for constructing a jet grouting anchor cable with a variable diameter drill bit, as provided in this application embodiment.

[0022] Reference numerals: 1-Drill rod; 2-Outer tube; 3-Thrust bearing; 4-Jack; 5-Adjustable drill bit; 51-Support steel plate; 52-Soil cutting steel plate; 53-Drill rod sleeve; 54-Modible sleeve; 55-First pin; 56-Second baffle; 57-Second pin; 58-First baffle; 6-Support assembly; 61-Mounting sleeve; 62-Sliding sleeve; 63-Connecting rod; 64-Support plate; 65-Telescopic rod; 66-Elastic element; 7-Blade. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for 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. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0025] This invention provides a variable diameter drill bit for jet grouting anchor cables, such as... Figure 1-6As shown, the system includes a drill rod 1, an outer tube 2, a jack 4, an adjustable drill bit 5, and a support assembly 6. The fixed end of the jack 4 is connected to the end of the drill rod 1, and the movable end of the jack 4 is hinged to one end of the adjustable drill bit 5. The other end of the adjustable drill bit 5 is equipped with a blade 7, and the cutting diameter of the adjustable drill bit 5 can be adjusted by the jack 4. The outer tube 2 is connected to the outside of the drill rod 1, and a slot is opened on the outer tube 2. The support assembly 6 is located on the outside of the outer tube 2. The movable end of the support assembly 6 is connected to the adjustable drill bit 5. When the adjustable drill bit 5 is adjusted in angle, the support assembly 6 is configured to change its outer diameter, thereby providing adaptive support for the borehole.

[0026] For example, the jack 4 is a double-acting hollow jack 4, and its specifications meet the following parameters: hollow diameter not less than 45mm, cylinder outer diameter 150mm, stroke not less than 250mm, and load-bearing capacity not less than 30T; the drill rod 1 is a hollow structure, and the two are connected by threaded connections. The drilling depth is adjusted by increasing or decreasing the number of drill rods 1. The front end of the drill rod sleeve 53 is provided with a hole for high-pressure mud to be sprayed out; all welded parts of the drill bit are fully welded, and the weld quality grade is not lower than level 2, which complies with the provisions of the "Code for Welding of Steel Structures".

[0027] like Figure 1-2 As shown, in the existing technology, during the construction of drill pipe 1, Lf is the free section; Ld is the non-enlarged head anchoring section; and LD is the enlarged head section.

[0028] In the embodiments of this application, such as Figure 1-6 As shown, the adjustable drill bit 5 includes a support steel plate 51, a cutting steel plate 52, and a drill rod sleeve 53; one end of the support steel plate 51 is hinged to the movable end of the jack 4, the other end of the support steel plate 51 is hinged to one end of the cutting steel plate 52, and the other end of the cutting steel plate 52 is hinged to the drill rod sleeve 53; the drill rod sleeve 53 is connected to the end of the drill rod 1; the cutting steel plate 52 is provided with a cutting blade 7.

[0029] For example, the cutting steel plate 52 is made of high-speed steel, with a thickness of not less than 6mm and a length of not less than 300mm, and has a blade-shaped structure on the cutting side; the supporting steel plate 51 is a strip steel plate with a length of not less than 300mm.

[0030] In the embodiments of this application, such as Figure 1-6As shown, the support assembly 6 includes a mounting sleeve 61, a sliding sleeve 62, a connecting rod 63, and a support plate 64. The mounting sleeve 61 is fitted onto the outside of the outer tube 2. One end of the sliding sleeve 62 abuts against the support steel plate 51. The sliding sleeve 62 is fitted onto the outside of the mounting sleeve 61 and is slidably connected to the mounting sleeve 61. One end of the connecting rod 63 is hinged to the outside of the sliding sleeve 62, and the other end of the connecting rod 63 is connected to the support plate 64. When the angle between the support steel plate 51 and the axis of the drill rod 1 changes, it can push the sliding sleeve 62 to slide on the mounting sleeve 61 and drive the connecting rod 63 to rotate. The connecting rod 63 can drive the support plate 64 to move closer to or further away from the drill rod 1, thereby providing adaptive support for the borehole.

[0031] In the embodiments of this application, such as Figure 1-6 As shown, the adjustable drill bit 5 also includes a movable sleeve 54, a first baffle 58, and a first pin 55; the movable sleeve 54 is sleeved on the movable end of the jack 4; the first baffle 58 is located on the outside of the movable sleeve 54; the support steel plate 51 is rotatably connected to the first baffle 58 through the first pin 55.

[0032] In the embodiments of this application, such as Figure 1-6 As shown, the adjustable drill bit 5 also includes a second baffle 56 and a second pin 57; the second baffle 56 is connected to the outside of the drill rod sleeve 53; the cutting steel plate 52 is rotatably connected to the second baffle 56 via the second pin 57.

[0033] In the embodiments of this application, such as Figure 1-6 As shown, the support assembly 6 also includes a telescopic rod 65; one end of the telescopic rod 65 is connected to the outside of the outer tube 2, and the other end of the telescopic rod 65 is connected to the inside of the support plate 64.

[0034] For example, it also includes a hydraulic pipe connected to the jack 4 for transmitting hydraulic power to control the extension and retraction of the jack 4.

[0035] In the embodiments of this application, such as Figure 1-6 As shown, it also includes a planar thrust bearing 3; the drill rod 1 is disposed inside the jack 4, and the drill rod 1 and the jack 4 are connected by the planar thrust bearing 3; it is used to keep the jack 4 fixed when the drill rod 1 rotates.

[0036] This invention provides a construction method for a variable-diameter drill bit for jet grouting anchor cables, such as... Figure 1-7 As shown, using a variable diameter drill bit for jet grouting anchor cables includes the following steps: S1: Construction preparation: Complete site clearing, hole location marking, equipment debugging and slurry preparation; S2: Diameter adjustment and drill bit positioning: The adjustable drill bit 5 can be adjusted to the preset initial diameter by jack 4, and the support component 6 adapts and supports synchronously. S3: Drilling and dynamic diameter adjustment: Start the drill rod 1 to rotate and cut the soil, dynamically adjust the hole diameter according to the design requirements, and the support component 6 adapts to the hole wall support in real time. S4: Spray grouting curing: After drilling to the designed depth, spray grout and lift drill rod 1 to form a variable diameter solidified body; S5: Anchor cable installation and grouting: Insert the anchor cable body and add grout if necessary; S6: Support component 6 recovery and borehole protection: After the slurry initially sets, recover the drill bit and protect the borehole. S7: Maintenance and Inspection: Perform maintenance as required and complete quality inspection.

[0037] For example, in step S1, the hole positioning needs to be controlled by a level and a steel ruler to control the hole elevation and horizontal spacing, and the hole positions are marked according to the design requirements.

[0038] For example, in step S2, a special anchor drilling machine is used to align the hole position, and the drilling angle is adjusted. Drilling can only begin after the quality inspector has inspected and approved the machine.

[0039] For example, in step S8, after all drilling tasks are completed, the drill bit and drill rod 1 are thoroughly cleaned, disassembled, maintained, and stored for future use.

[0040] For example, in step S3, while the drill rod 1 is rotating and cutting, the drill bit diameter is adjusted in real time by the jack 4 to reduce drilling resistance and the risk of stuck drill bit, thereby reducing the hole collapse rate.

[0041] In the embodiments of this application, such as Figure 1-8 As shown, step S3 includes the following steps: S31: Start the rotation system of drill rod 1, adjust the rotation speed to 10r / min-30r / min, and drive the blade 7 of adjustable drill bit 5 to cut the soil; S32 During drilling, adjust the extension speed of jack 4 to 5mm / s-15mm / s through the hydraulic control system to achieve dynamic adjustment of the hole diameter: When expanding the diameter: jack 4 slowly extends, pushing the support steel plate 51 and the cutting steel plate 52 to unfold outward, the cutting diameter of blade 7 is expanded to the design value, and simultaneously drives the sliding sleeve 62 to slide along the axial direction of the mounting sleeve 61, and the connecting rod 63 drives the support plate 64 to expand outward until the support plate 64 Fitting against the borehole wall with a fitting gap ≤2mm; During diameter reduction: Jack 4 slowly retracts, adjustable drill bit 5 retracts inward, sliding sleeve 62 resets, support plate 64 retracts inward with connecting rod 63 to maintain a suitable support for the current borehole diameter; S33: Real-time monitoring of drill rod 1 verticality, with deviation controlled within ≤1%. When encountering hard soil layers, reduce drilling speed to 5cm / min-10cm / min, and simultaneously increase the extension and retraction frequency of jack 4 to avoid overload damage to the cutting tool 7; S34: After drilling to the designed borehole depth, pause drilling, keep drill rod 1 rotating, and recalibrate the borehole diameter using jack 4 to ensure that the diameter of the anchoring section meets the design requirements.

[0042] In the embodiments of this application, such as Figure 1-8 As shown, step S4 includes the following steps: S41: Adjust the adjustable drill bit 5 to the designed diameter of the anchoring section; the support plate 64 of the support assembly 6 expands and fits against the hole wall; the telescopic rod 65 locks the position of the support plate 64 to ensure support stability; S42: Start the grout delivery equipment, control the grout injection pressure to 15MPa-25MPa, and the grout flow rate to 30L / min-50L / min; the grout is injected into the hole wall through the inner channel of the drill rod 1 and the grout injection port of the drill bit; S43: During the injection process, the grout flow rate is 5cm / min-10cm / min. S44: If the design requires the anchoring section to be a variable diameter structure, pause the lifting of drill rod 1 at the corresponding depth position, adjust the drill bit hole diameter to the design diameter of the enlarged head by using jack 4, maintain the spraying for 30s-60s, and then continue lifting at the preset speed to ensure the quality of the solidified body forming at the enlarged head; S45: When the slurry is sprayed to the hole opening, increase the slurry spraying pressure to 20MPa-30MPa and continue spraying for 1min-2min to ensure the solidified body at the hole opening is full.

[0043] For example, when encountering a layer of sand and gravel or a layer of backfill soil, a "segmented drilling-segmented support" operation is added in step S3: after drilling 50cm-80cm, drilling is paused and the support assembly 6 is adjusted so that the support plate 64 is completely in contact with the hole wall. After stabilizing the hole wall, drilling continues to avoid hole collapse.

[0044] For example, in step S5, lubricant needs to be applied to the surface of the anchor cable before it is placed in, and the placement speed is controlled at 1m / min-2m / min to avoid scratching the anchor cable or disturbing the grout in the hole; after placement, the verticality of the anchor cable is calibrated with a spirit level to ensure that the deviation is ≤0.5%.

[0045] For example, when the ambient temperature is below 5°C, in step S7, the opening needs to be covered with a heat-insulating cotton blanket, and a heating device needs to be set around the cured body to ensure that the curing temperature is not lower than 5°C and the curing time is extended to 1.5 times the design requirement. For example, in step S7, in addition to routine testing, ultrasonic testing is used to check the integrity of the solidified body of the variable diameter anchoring section, and a pull-out test is used to test the anchoring force of the anchor cable. The test load is 1.2-1.5 times the design anchoring force, the holding time is ≥10min, and no obvious displacement is considered qualified.

[0046] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0047] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A variable diameter drill bit for jet grouting anchor cables, characterized in that, Includes drill pipe (1), outer tube (2), jack (4), adjustable drill bit (5) and support assembly (6); The fixed end of the jack (4) is connected to the end of the drill rod (1), and the movable end of the jack (4) is hinged to one end of the adjustable drill bit (5). The other end of the adjustable drill bit (5) is provided with a blade (7), and the cutting diameter can be adjusted by the jack (4). The drill rod (1) is connected to an outer tube (2) on the outside, and the outer tube (2) has a slot. The support component (6) is disposed on the outside of the outer tube (2); A support component (6) is provided on the outer side of the outer tube (2). The movable end of the support component (6) is connected to the adjustable drill bit (5). When the adjustable drill bit (5) is adjusted in angle, the support component (6) is configured to change the outer diameter of the support component (6) so as to provide adaptive support for the duct.

2. The variable diameter drill bit for jet grouting anchor cables according to claim 1, characterized in that, The adjustable drill bit (5) includes a support steel plate (51), a cutting steel plate (52), and a drill rod sleeve (53). One end of the support steel plate (51) is hinged to the movable end of the jack (4), the other end of the support steel plate (51) is hinged to one end of the soil cutting steel plate (52), and the other end of the soil cutting steel plate (52) is hinged to the drill rod sleeve (53). The drill pipe sleeve (53) is connected to the end of the drill pipe (1); The cutting steel plate (52) is equipped with a blade (7).

3. The variable diameter drill bit for jet grouting anchor cables according to claim 2, characterized in that, The support assembly (6) includes a mounting sleeve (61), a sliding sleeve (62), a connecting rod (63), and a support plate (64). The mounting sleeve (61) is fitted onto the outside of the outer tube (2); One end of the sliding sleeve (62) abuts against the supporting steel plate (51); The sliding sleeve (62) is sleeved on the outside of the mounting sleeve (61) and is slidably connected to the mounting sleeve (61); One end of the connecting rod (63) is hinged to the outside of the sliding sleeve (62), and the other end of the connecting rod (63) is connected to the support plate (64); When the angle between the support plate (51) and the drill rod (1) axis changes, the sliding sleeve (62) can be pushed to slide on the mounting sleeve (61) and drive the connecting rod (63) to rotate. The connecting rod (63) can drive the support plate (64) to move closer to or further away from the drill rod (1), thereby providing adaptive support for the duct.

4. The variable diameter drill bit for jet grouting anchor cables according to claim 2, characterized in that, The adjustable drill bit (5) also includes a movable sleeve (54), a first baffle (58) and a first pin (55); The movable sleeve (54) is fitted onto the movable end of the jack (4); The first baffle (58) is disposed on the outside of the movable sleeve (54); The supporting steel plate (51) is rotatably connected to the first baffle (58) by the first pin (55).

5. The variable diameter drill bit for jet grouting anchor cables according to claim 2, characterized in that, The adjustable drill bit (5) also includes a second baffle (56) and a second pin (57); The second baffle (56) is connected to the outside of the drill pipe sleeve (53); The cutting steel plate (52) is rotatably connected to the second baffle (56) by the second pin (57).

6. The variable diameter drill bit for jet grouting anchor cables according to claim 3, characterized in that, The support assembly (6) also includes a telescopic rod (65) and an elastic element (66). One end of the telescopic rod (65) is connected to the outside of the outer tube (2), and the other end of the telescopic rod (65) is connected to the inside of the support plate (64); One end of the elastic element (66) is connected to the end of the sliding sleeve (62) away from the adjustable drill bit (5), and the other end of the elastic element (66) is connected to the telescopic rod (65).

7. The variable diameter drill bit for jet grouting anchor cables according to claim 1, characterized in that, It also includes thrust bearings (3); The drill rod (1) is installed inside the jack (4). The drill rod (1) and the jack (4) are connected by the thrust bearing (3); this is used to keep the jack (4) fixed when the drill rod (1) rotates.

8. A construction method for a variable-diameter drill bit for jet grouting anchor cables, characterized in that, Using the variable-diameter drill bit for jet grouting anchors as described in any one of claims 1-7, the method includes the following steps: S1: Construction preparation: Complete site clearing, hole location marking, equipment debugging and slurry preparation; S2: Diameter adjustment and drill bit positioning: Adjust the adjustable drill bit (5) to the preset initial diameter by using jack (4), and the support component (6) will adapt and support it synchronously; S3: Drilling and dynamic diameter change: Start the drill rod (1) to rotate and cut the soil, dynamically adjust the hole diameter according to the design requirements, and the support component (6) adapts to the hole wall support in real time; S4: Spray grouting: After drilling to the designed depth, spray grout and lift the drill rod (1) to form a variable diameter solidified body; S5: Anchor cable installation and grouting: Insert the anchor cable body and add grout if necessary; S6: Support component (6) recovery and orifice protection: After the slurry has initially set, recover the drill bit and protect the orifice. S7: Maintenance and Inspection: Perform maintenance as required and complete quality inspection.

9. The construction method of the variable diameter drill bit for jet grouting anchor cables according to claim 8, characterized in that, Step S3 includes the following steps: S31: Start the drill rod (1) rotation system, adjust the speed to 10r / min-30r / min, and drive the blade (7) of the adjustable drill bit (5) to cut the soil; During the S32 drilling process, the extension and retraction speed of the jack (4) is adjusted to 5mm / s-15mm / s through the hydraulic control system to achieve dynamic adjustment of the hole diameter. During the expansion: the jack (4) slowly extends, pushing the support steel plate (51) and the cutting steel plate (52) outward, the blade (7) expands the cutting diameter to the design value, and simultaneously drives the sliding sleeve (62) to slide along the axial direction of the mounting sleeve (61), the connecting rod (63) drives the support plate (64) to expand outward until the support plate (64) fits against the hole wall, with a fitting gap ≤2mm; When reducing the diameter: the jack (4) slowly retracts, the adjustable drill bit (5) retracts inward, the sliding sleeve (62) resets, and the support plate (64) retracts inward with the connecting rod (63) to maintain the support that is compatible with the current hole diameter; S33: Real-time monitoring of drill rod (1) verticality, deviation controlled within ≤1%, when encountering hard soil layer, reduce drilling speed to 5cm / min-10cm / min, and simultaneously increase the extension frequency of jack (4) to avoid overload damage to the cutting tool (7); S34: After drilling to the designed hole depth, stop drilling, keep the drill rod (1) rotating, and recalibrate the hole diameter using the jack (4) to ensure that the diameter of the anchoring section meets the design requirements.

10. The construction method of the variable diameter drill bit for jet grouting anchor cables according to claim 8, characterized in that, Step S4 includes the following steps: S41: Adjust the adjustable drill bit (5) to the design diameter of the anchoring section, the support plate (64) of the support assembly (6) expands and fits against the hole wall, and the telescopic rod (65) locks the position of the support plate (64) to ensure support stability; S42: Start the slurry delivery equipment, control the slurry injection pressure to 15MPa-25MPa, and the slurry flow rate to 30L / min-50L / min. The slurry is injected into the hole wall through the channel inside the drill rod (1) and the slurry nozzle of the drill bit. S43: During the injection process, slowly lift the drill rod (1) at a speed of 5cm / min-10cm / min, and keep the rotation speed of the drill rod (1) matched with the injection pressure during the lifting process; S44: If the design requires the anchoring section to be a variable diameter structure, pause the lifting of the drill rod (1) at the corresponding depth position, adjust the drill bit hole diameter to the design diameter of the enlarged head by using the jack (4), maintain the spray for 30s-60s, and then continue to lift at the preset speed to ensure the quality of the solidified body of the enlarged head. S45: When spraying the slurry to the orifice, increase the slurry spraying pressure to 20MPa-30MPa and continue spraying for 1min-2min to ensure that the solidified body at the orifice is full.

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