Variable-diameter drilling sleeve and construction method thereof

Abstract

The invention provides a variable-diameter drilling sleeve and a construction method thereof. The variable-diameter drilling sleeve comprises a drill rod. The drill bit is connected with the drill rod, and the outer diameter of the drill bit shrinks to be smaller than the inner diameter of the pipe shoe during reverse rotation; one end of the pipe shoe is in threaded connection with the drill bit; the drill rod is arranged in an inner cavity of the follow-pipe sleeve, and the other end of the pipe shoe is connected with the follow-pipe sleeve. The invention has the beneficial effects that the drill bit automatically shrinks to be smaller than the inner diameter of the pipe shoe during reverse rotation, so that the drill bit can smoothly withdraw through the sleeve, the problem of drill bit abandonment is thoroughly solved, the construction cost is obviously reduced, and meanwhile, the interference of hole bottom metal residues on subsequent grouting is avoided; the outer diameters of the first section sleeve and the subsequent sleeve are gradually reduced, so that the contact area of the hole bottom section sleeve and the soil layer is minimized, the deep hole pipe drawing resistance is reduced in a cliff mode, and the construction adaptability of the complex stratum is multiplied; grouting and pipe drawing are strictly and synchronously carried out, gaps formed after the casing pipe is withdrawn are filled with grout in real time, the delay time for the grout to wrap the hole wall is shortened, and the reinforcing compactness of the saturated soil layer is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of soil reinforcement, and particularly relates to a variable-diameter drilling casing and a construction method thereof. BACKGROUND

[0002] Retaining walls are common support structure forms in various engineering construction, but in the long-term use process, the retaining walls are greatly affected by natural conditions and various problems affecting the service life occur, such as high water-rich soil layer near the river, rainwater-induced scouring landslide, etc. In the engineering of high water-rich backfill area using traditional anchor reinforcement technology, the traditional following pipe casing adopts equal-diameter design, which causes the friction and gripping force between the casing and the soil layer to increase sharply with the increase of drilling depth, not only reducing the drilling efficiency, but also causing the pipe pulling difficulty after hole forming and even the casing abandonment; at the same time, because the outer diameter of the drill bit is larger than the inner diameter of the shoe and the casing, the drill bit cannot be withdrawn after hole forming and is forced to be left in the hole, which significantly increases the construction cost; in addition, the grouting and pipe pulling processes are separated in the existing process, and the grouting is followed by static setting and then pipe pulling, which easily causes the slurry to sink and form a cavity around the casing, thereby weakening the soil reinforcement effect. Therefore, there is an urgent need for a variable-diameter drilling casing and a construction method thereof to solve the above problems. SUMMARY

[0003] To solve the above technical problems, the present application provides a variable-diameter drilling casing and a construction method thereof, which are particularly suitable for soil reinforcement in high water-rich backfill areas.

[0004] The technical solution adopted by the present application is as follows: in the first aspect, a variable-diameter drilling casing is provided, which comprises:

[0005] a drill rod;

[0006] a drill bit, which is connected with the drill rod, and the outer diameter of the drill bit is contracted to be smaller than the inner diameter of the shoe when the drill bit is reversed;

[0007] the shoe, one end of the shoe is connected with the drill bit through threads;

[0008] a following pipe casing, the drill rod is arranged in the inner cavity of the following pipe casing, and the other end of the shoe is connected with the following pipe casing.

[0009] Further, the outer diameter of the following pipe casing decreases along the drilling direction.

[0010] Further, the following pipe casing comprises:

[0011] a first following pipe casing, one end of the first following pipe casing is connected with the other end of the shoe;

[0012] at least one second following pipe casing, each second following pipe casing is connected in sequence through threads, and the other end of the first following pipe casing is connected with one end of the second following pipe casing through threads.

[0013] The first and second casing have the same inner diameter, and the outer diameter of the first casing and multiple sections of the second casing decreases along the drilling direction.

[0014] Furthermore, the other end of the first tube sleeve is provided with an internal thread, one end of the second tube sleeve is provided with an external thread, and the other end of the second tube sleeve is provided with an internal thread.

[0015] Secondly, a construction method for a variable-diameter borehole casing is provided, comprising the following steps:

[0016] Partial assembly of the first casing;

[0017] Drilling is performed using the assembled first casing.

[0018] When the first casing is drilled to the end, the second casing is connected.

[0019] When drilling reaches the designed depth, the drill rod and drill bit are pulled out by reversing the drill rod.

[0020] Insert the anchor cable and grouting pipe into the inner cavities of the second and first root casings;

[0021] Grouting is performed through the grouting pipe, and the second and first root pipe sleeves are simultaneously pulled out.

[0022] Once the grouting is complete, both the second and first root tube sleeves are completely removed.

[0023] Furthermore, the partial assembly of the first sleeve includes the following steps:

[0024] Connect the drill bit to the drill rod;

[0025] Connect the boot to the drill bit;

[0026] The drill pipe is inserted through the inner cavity of the first heel sleeve, and the first heel sleeve is connected to the tube shoe;

[0027] Connect the drill pipe to the drilling rig.

[0028] The advantages and positive effects of this invention are as follows: Due to the adoption of the above technical solution, the drill bit automatically retracts to a size smaller than the inner diameter of the casing shoe during reversal, allowing it to smoothly retract through the casing, completely solving the problem of drill bit abandonment, significantly reducing construction costs, and avoiding interference from residual metal at the bottom of the hole to subsequent grouting; the drill bit is threaded at the front end of the casing shoe and the casing is fixed at the rear end, ensuring the stability of drilling force transmission and serving as the first passage after the drill bit retracts, preventing jamming during retraction and improving system reliability; the outer diameter of the first casing section gradually decreases with subsequent casing sections, forming a layout of "large end near the borehole opening, small end deep to the bottom of the hole," minimizing the contact area between the casing at the bottom of the hole and the soil layer, resulting in a sharp decrease in deep hole casing pull-out resistance and significantly increasing adaptability to complex geological formations; grouting and casing pull-out are strictly synchronized, with grout filling the gaps after casing removal in real time, reducing the delay time of grout coating the borehole wall and effectively increasing the compaction of saturated soil layers. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a drill casing according to an embodiment of the present invention.

[0030] Figure 2 This is a partial schematic diagram of a drill casing according to an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of a variable diameter drilling casing according to an embodiment of the present invention.

[0032] Figure 4 This is a partial schematic diagram of a variable diameter drilling casing according to an embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram of the construction method of a variable diameter borehole casing according to an embodiment of the present invention.

[0034] In the picture:

[0035] 10 drill pipe 20 drill bit 30 shoe 40 back-up casing 41 first back-up casing 42 second back-up casing Detailed Implementation

[0036] The present disclosure will now be described more fully with reference to the accompanying drawings, which illustrate exemplary embodiments of the present disclosure. The technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative effort are within the scope of protection of the present disclosure.

[0037] like Figures 1-2 As shown, the present invention provides a variable diameter drilling casing, comprising:

[0038] Drill pipe 10;

[0039] Preferably, one end of the drill rod 10 (the end connected to the drill bit) is provided with an external hexagonal tenon, and the side wall of the tenon is provided with a pin hole. The other end (the end connected to the drilling machine) is provided with a standard drilling machine interface with a torque transmission groove.

[0040] Drill bit 20 is connected to drill rod 10. When the drill bit 20 reverses, its outer diameter shrinks to be smaller than the inner diameter of the shoe 30.

[0041] Preferably, the connection end between the drill bit 20 and the drill rod 10 is provided with an internal hexagonal sleeve, which is fitted onto one end of the drill rod 10 and the pin hole is locked by a through pin to achieve a connection that prevents detachment; the connection end between the drill bit 20 and the tube shoe 30 is provided with an external thread.

[0042] The tube shoe 30 has one end connected to the drill bit 20 via a thread;

[0043] Preferably, one end of the tube shoe 30 is provided with an internal thread that engages with the external thread at the bottom of the drill bit 20, and a flange is provided at the connection between the tube shoe 30 and the casing 40. In order to avoid the friction and gripping force of the high water-rich soil layer from damaging the tube shoe, the wall thickness of the tube shoe 30 is increased.

[0044] The casing 40 and drill pipe 20 are located inside the casing 40, and the other end of the shoe 30 is connected to the casing 40.

[0045] Using the above-mentioned device, the drill bit automatically retracts to a size smaller than the inner diameter of the shoe when it reverses, allowing it to smoothly pass through the casing for retraction. This completely solves the problem of drill bit abandonment, significantly reduces construction costs, and avoids interference from residual metal at the bottom of the hole to subsequent grouting. The drill bit is threaded at the front end of the shoe and the casing is fixed at the rear end, which not only ensures the stability of drilling force transmission but also serves as the first passage after the drill bit retracts, preventing the drill bit from getting stuck during retraction and improving system reliability.

[0046] To address the problem of excessive pull-out resistance of traditional equal-diameter casing in water-rich formations, this embodiment provides an implementation method.

[0047] In one embodiment, the outer diameter of the casing decreases along the drilling direction.

[0048] Preferably, in order to further reduce frictional resistance, a lubricant (such as a polytetrafluoroethylene anti-friction coating) is sprayed onto the outer surface of the casing.

[0049] Using the above-mentioned device, the outer diameter of the casing decreases step by step along the drilling direction, forming an inverted conical structure. During drilling, the contact area with the soil is reduced, which greatly reduces frictional resistance and increases the efficiency of deep hole drilling several times. When pulling out the casing, the energy consumption is greatly reduced due to the decrease in resistance gradient. In particular, it can prevent the casing from getting stuck or breaking in highly water-saturated soil layers.

[0050] To address the challenge of transporting and constructing excessively long single-pipe systems, a continuous variable-diameter system composed of multiple sections is required, while maintaining a constant inner diameter to ensure consistent construction. This embodiment provides a solution for this problem.

[0051] like Figures 3-4 As shown, in one embodiment, the heel sleeve includes:

[0052] The first sleeve 41, one end of the first sleeve 41 is connected to the other end of the shoe 30;

[0053] At least one second tube sleeve 42, and each second tube sleeve 42 is connected in sequence by threads. The other end of the first tube sleeve 41 is connected to one end of the second tube sleeve 42 by threads.

[0054] The inner diameters of the first casing 41 and the second casing 42 are the same, and the outer diameters of the first casing 41 and the multiple sections of the second casing 42 decrease along the drilling direction.

[0055] Using the above-mentioned device, the outer diameter of the first casing section and subsequent casing sections gradually decreases, forming a layout of "large end near the borehole opening and small end deep to the bottom of the borehole". This minimizes the contact area between the casing section at the bottom of the borehole and the soil layer, resulting in a sharp drop in the resistance to pull out the casing in deep holes and greatly increasing the adaptability to construction in complex strata. The inner diameter of all casing units is strictly consistent, ensuring that there is no interference when the drill rod rotates, no obstruction when the anchor cable is lowered, and no deviation when the grouting pipe is inserted. In particular, it ensures the smooth insertion of ultra-long anchor cables (>30m). By increasing or decreasing the number of second casing sections, it can be freely adapted to different hole depth requirements of 5 to 50m, greatly reducing the equipment customization cost and improving the versatility of the project.

[0056] To address the problem that traditional sleeve welding or flange connections cannot meet the rapid assembly and disassembly requirements of variable diameter systems and are prone to failure under vibration, this embodiment provides an implementation method.

[0057] In one embodiment, the other end of the first tube sleeve 41 is provided with an inner thread, one end of the second tube sleeve 42 is provided with an outer thread, and the other end of the second tube sleeve 42 is provided with an inner thread.

[0058] Using the above device, the outer diameter of the external thread end is precisely matched with the inner diameter of the front sleeve, and the connection is smoothly transitioned, avoiding the step protrusion from scraping the hole wall and reducing the risk of hole collapse.

[0059] like Figure 5 As shown, to facilitate the use of the reducing borehole casing provided in this disclosure, this disclosure also provides a construction method for the reducing borehole casing, including the following steps:

[0060] S100. Partially assemble the first casing;

[0061] S200, Drilling is carried out using the first assembled casing;

[0062] S300. When the first casing reaches the end during drilling, connect the second casing.

[0063] S400: When drilling reaches the designed depth, the drill rod and drill bit are pulled out by reversing the drill rod.

[0064] S500, Insert the anchor cable and grouting pipe into the inner cavity of the second and first casing pipes;

[0065] S600, Grouting is performed through the grouting pipe and the second and first casing pipes are pulled out simultaneously;

[0066] S700, until grouting is completed, pull out the second and first casing pipes.

[0067] Using the above method, grouting and casing removal are strictly synchronized. The grout fills the gap after the casing is removed in real time, which reduces the delay time of the grout covering the borehole wall and effectively increases the compactness of the saturated soil layer. The borehole wall is wrapped with grout the moment the casing is pulled out, forming a "liquid film support effect" and completely eliminating the risk of borehole collapse in water-rich strata.

[0068] In one embodiment, partial assembly of the first bushing includes the following steps:

[0069] Connect the drill bit to the drill pipe;

[0070] Connect the shoe to the drill bit;

[0071] The drill pipe is inserted into the inner cavity of the first casing, and the first casing is connected to the casing shoe;

[0072] Connect the drill pipe to the drilling rig.

[0073] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0074] The construction workers first inserted the external hexagonal tenon at the lower end of the drill pipe into the internal hexagonal sleeve at the top of the drill bit, and hammered the through pin to lock it in place. Then, they screwed the internal thread at the front end of the pipe shoe into the external thread at the bottom of the drill bit to a preload torque of 800 N·m. Next, the drill pipe passed through the inner cavity of the first casing (inner diameter ∅104 mm), and the rear flange of the pipe shoe was welded to the beginning of the first casing. After passing ultrasonic testing, the upper end of the drill pipe was then... Connect the 3418 interface to the drill rig's power head, and calibrate the concentricity deviation with laser alignment to ≤0.3°. Drive the drill bit at 25 rpm to cut the soil layer. The first casing (outer diameter ∅120mm) follows the drill. When the end of the casing is 0.3m from the borehole opening, stop the drill to clean the slag. Apply hydrogenated nitrile butadiene sealant to the external thread of the front end of the first section of the second casing (outer diameter ∅115mm), and screw it into the internal thread of the rear end of the first casing until the metal sealing surface is fully engaged. Repeat connecting subsequent second casing sections (outer diameter decreasing progressively to ∅100mm for the last section) until the designed depth is reached. At a depth of 25m, reverse the drill rod 5 turns to trigger the drill bit's inclined groove push rod to retract the cutting blade, reducing the outer diameter from ∅130mm to ∅102mm (less than the inner diameter of the pipe shoe ∅105mm). The drill rod system is then pulled back without resistance. Insert the steel strand anchor cable and grouting pipe to the bottom of the hole, start the 0.5MPa pressure grouting pump, and simultaneously pull back the casing section by section at a speed of 0.8m / min. The grout fills the gaps in the casing in real time. When the grouting volume reaches 120% of the design value, stop the pump and continue pulling the pipe until it is completely removed, finally forming a dense anchoring section (grout filling rate ≥98%).

[0075] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A variable diameter drilling casing, characterized in that, include: Drill pipe; A drill bit connected to the drill rod, wherein the outer diameter of the drill bit contracts to a size smaller than the inner diameter of the tube shoe when the drill bit is reversed; The tube shoe, one end of which is threadedly connected to the drill bit; The drill pipe is disposed in the inner cavity of the casing, and the other end of the shoe is connected to the casing.

2. The variable diameter drilling casing according to claim 1, characterized in that: The outer diameter of the casing decreases along the drilling direction.

3. The variable diameter drill casing according to claim 1, characterized in that, The casing includes: The first tube sleeve, one end of which is connected to the other end of the tube shoe; At least one second helix sleeve, and each second helix sleeve is connected in sequence by threads, and the other end of the first helix sleeve is connected to one end of the first second helix sleeve by threads; The first and second casing have the same inner diameter, and the outer diameter of the first casing and multiple sections of the second casing decreases along the drilling direction.

4. The variable diameter drilling casing according to claim 3, characterized in that: The first tube sleeve has an internal thread at one end, the second tube sleeve has an external thread at one end, and the second tube sleeve has an internal thread at the other end.

5. A method for constructing a variable diameter drilling casing, using the variable diameter drilling casing as described in claim 4, characterized in that, Includes the following steps: Partial assembly of the first casing; Drilling is performed using the assembled first casing. When the first casing is drilled to the end, the second casing is connected. When drilling reaches the designed depth, the drill rod and drill bit are pulled out by reversing the drill rod. Insert the anchor cable and grouting pipe into the inner cavities of the second and first root casings; Grouting is performed through the grouting pipe, and the second and first root pipe sleeves are simultaneously pulled out. Once the grouting is complete, both the second and first root tube sleeves are completely removed.

6. The construction method of the variable diameter borehole casing according to claim 5, characterized in that, The partial assembly of the first sleeve includes the following steps: Connect the drill bit to the drill rod; Connect the boot to the drill bit; The drill pipe is inserted through the inner cavity of the first heel sleeve, and the first heel sleeve is connected to the tube shoe; Connect the drill pipe to the drilling rig.

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