A reusable concrete hole preparation device

Abstract

The present application relates to the technical field of concrete processing, in particular to a reusable concrete reserved hole device, which comprises a seamless steel pipe assembly and a connecting assembly, the seamless steel pipe assembly comprises two short seamless steel pipes and a long seamless steel pipe, the two short seamless steel pipes are symmetrically distributed along the length direction of the long seamless steel pipe, and are vertically crossed and occluded with the long seamless steel pipe, the middle part of the long seamless steel pipe and the short seamless steel pipe is provided with a through hole, the connecting assembly comprises a screw rod, a nut and a gasket, the screw rod passes through the through hole to horizontally and vertically connect and reinforce the short seamless steel pipe and the long seamless steel pipe to form an integrated whole, the device adopts a detachable connecting structure, and each component can be extracted without damage after concrete pouring. It can be reused, and the performance does not obviously attenuate. Compared with the traditional disposable material, the material does not need secondary processing after being delivered, and can be directly installed and used, thereby saving the processing cost and time, reducing the total cost, and reducing the generation of construction waste.

Description

Technical Field

[0001] This invention relates to the field of concrete processing technology, specifically to a reusable concrete pre-drilled hole device. Background Technology

[0002] As is well known, in concrete structure construction, pre-reserved holes are a crucial step in ensuring the smooth implementation of subsequent works, and are widely used in equipment installation, pipeline laying, rebar connection, and hoisting operations. Traditional methods for constructing pre-reserved holes mainly rely on methods such as embedding sleeves, wooden boxes, or PVC pipes combined with four-way connectors. However, these methods have insurmountable technical defects in practical applications, specifically as follows:

[0003] Traditional methods suffer from low precision and poor stability in pre-drilled holes: the core problem lies in the insufficient rigidity of materials such as PVC pipes and wooden boxes. Taking the commonly used PVC pipe + four-way combination as an example, the elastic modulus of PVC pipe is only 3-4 GPa, and during concrete pouring, it is subjected to 3-5 kN / m... 2 Under lateral pressure, radial deformation of 10-20mm is prone to occur, causing the deviation of the reserved hole size to far exceed the allowable range of ±5mm. At the same time, due to the low strength and poor sealing of the material, the grout leakage rate at the connection between the PVC pipe and the four-way joint is as high as 30% or more. It often results in rough inner walls of the channel, partial blockage, or even complete blockage, which seriously affects the subsequent pipeline laying or equipment installation. Additional manpower is required for secondary unblocking, and the unblocking cost accounts for 20%-30% of the construction cost of a single hole. Wooden boxes, due to their high water absorption, are prone to moisture expansion after concrete pouring, which not only causes the hole shape to deform, but also adheres tightly to the concrete, making them difficult to remove and easily broken.

[0004] The materials are not reusable and are costly: traditional pre-drilled hole materials are all for single use. A single wooden box costs approximately 20 yuan, and a PVC pipe + four-way combination costs approximately 15 yuan. If a project requires 500 pre-drilled holes, the material cost alone would reach 7,500-10,000 yuan. Furthermore, these materials require secondary processing upon arrival, including cutting, splicing, and grinding, which takes up more than 40% of the construction time per hole, further increasing labor costs and project delays. After use, the materials cannot be recycled due to deformation, damage, or adhesion, resulting in resource waste and failing to meet the requirements of green construction.

[0005] Poor construction adaptability and complex operation: Traditional materials have weak adaptability to the construction environment. PVC pipes are prone to softening and deformation in high-temperature environments (above 35℃) and brittleness and cracking in low-temperature environments (below 5℃). Wooden boxes are greatly affected by humidity, and their strength drops sharply in humid environments, making them prone to collapse during pouring. At the same time, the installation of sleeves or wooden boxes requires cumbersome fixing (such as binding and supporting), but displacement during pouring is still difficult to avoid. During disassembly, because the materials are bonded to the concrete, destructive methods such as crushing and cutting are required, which is not only time-consuming (disassembly of a single hole takes more than 20 minutes) but may also damage the concrete structure and affect the construction quality. Therefore, it is necessary to propose a solution to this technical problem. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a reusable concrete pre-drilled hole device.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a reusable concrete pre-drilled hole device, comprising a seamless steel pipe assembly and a connecting assembly. The seamless steel pipe assembly includes two short seamless steel pipes and one long seamless steel pipe. The two short seamless steel pipes are symmetrically distributed along the length of the long seamless steel pipe and interlock perpendicularly with the long seamless steel pipe. Both the long seamless steel pipe and the short seamless steel pipe have a through-hole in the middle. The connecting assembly includes a screw, a nut, and a washer. The screw passes through the through-hole to connect and reinforce the short seamless steel pipe and the long seamless steel pipe horizontally and vertically to form a whole.

[0010] Furthermore, the present invention is improved in that the diameter of the seamless steel pipe is 30mm to 50mm; the length of the two short seamless steel pipes is 40cm to 70cm, and the length of the long seamless steel pipe is 80cm to 120cm.

[0011] Furthermore, an improvement of the present invention is that the size of the through-hole is 8mm to 12mm.

[0012] Furthermore, the present invention is improved in that, in the connecting assembly, the diameter of the screw is 8mm to 12mm, the size of the nut is 18mm to 22mm, and the washer is a double-layer steel washer with a thickness of 1.5mm to 2.5mm.

[0013] Furthermore, an improvement of the present invention is that, before the concrete pouring operation, the device is installed at the designated position of the reserved hole, and the seamless steel pipe is firmly secured by tightening the nut.

[0014] Furthermore, an improvement of the present invention is that, after the concrete pouring is completed, the device is disassembled approximately 1 to 3 hours later.

[0015] Furthermore, an improvement of the present invention is that, during disassembly, the operator loosens the nut, removes the screw, and pulls the seamless steel pipe out of the concrete.

[0016] Furthermore, an improvement of the present invention is that the extracted seamless steel pipe, screw, nut and washer can be reused after cleaning.

[0017] Furthermore, the present invention is improved in that the seamless steel pipe is a high-strength rigid steel pipe, which can resist the lateral pressure of concrete during the concrete pouring process and maintain its shape and position stability.

[0018] Furthermore, the present invention is improved by adjusting the length of the seamless steel pipe and the pipe end intersection angle to accommodate the requirements of reserved holes of different specifications and shapes.

[0019] (III) Beneficial Effects

[0020] Compared with the prior art, the present invention provides a reusable concrete pre-drilled hole device, which has the following beneficial effects:

[0021] This reusable concrete pre-drilled hole device uses high-strength seamless steel pipes as its core components. Its lateral pressure resistance is 5-8 times higher than that of PVC pipes of the same specifications, effectively resisting lateral pressure during concrete pouring and ensuring the stability of the device's shape and position. In actual construction, the dimensional deviation of the pre-drilled hole can be controlled within ≤3mm, and the positional offset within ≤2mm, fully meeting the stringent precision requirements of high-precision construction (such as the stringent precision requirements of lifting holes). Compared to the deformation and grout leakage problems caused by insufficient rigidity of traditional PVC pipes + four-way fittings, this device, through a "cross-shaped interlocking rigid frame + tie bolt locking" structure, forms an integrated force-bearing system, eliminating hole blockage and dimensional deviations, and significantly improving the reliability of construction quality.

[0022] The device employs a detachable connection structure, allowing each component to be extracted without damage after concrete pouring. Practical verification has shown that each component can be reused ≥10 times after cleaning without significant performance degradation. Compared to traditional disposable materials, the material requires no secondary processing upon arrival and can be directly installed and used, saving processing costs and time. Reusability reduces the amortization cost per use to 1 / 5 of traditional methods. Taking a project with 500 pre-drilled holes as an example, the total cost can be reduced by more than 80%, while also reducing construction waste, aligning with green construction principles.

[0023] Installation is simple; just tighten the nuts with an electric wrench to secure the device, with a single unit installation time of ≤10 minutes. Disassembly is equally straightforward; simply loosen the nuts and pull out the screw. The steel pipe itself, with its rigidity and smooth surface, can be easily removed, with a single unit disassembly time of ≤5 minutes. Compared to traditional methods (installation takes over 30 minutes, disassembly over 20 minutes), this method increases construction efficiency by over 300%, significantly reducing the time required for pre-drilled holes and accelerating the overall construction progress.

[0024] The device can adapt to various specifications of pre-drilled holes, such as cross-shaped, rectangular, and circular, by adjusting the length (40-70cm for short pipes, 80-120cm for long pipes), diameter (30-50mm), and intersection angle (60°-90°) of the seamless steel pipes. This meets the construction requirements of different components such as precast wall panels, bridge precast beams, and small precast blocks. Furthermore, the material properties of seamless steel pipes allow them to maintain stable performance in both high-temperature (above 35℃) and low-temperature (below 5℃) environments, solving the problems of high-temperature softening and low-temperature embrittlement of traditional PVC pipes. Therefore, its application is not limited by climatic conditions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the short seamless steel pipe of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the long seamless steel pipe of the present invention;

[0027] Figure 3 This is a schematic diagram of the combined structure of the short seamless steel pipe of the present invention;

[0028] Figure 4 This is a schematic diagram of the structural assembly of the present invention;

[0029] Figure 5 This is a schematic diagram of the side cross-section of the structure of the present invention;

[0030] Figure 6 This is a front cross-sectional view of the structural assembly of the present invention;

[0031] Figure 7 This is a schematic diagram of the structural template combination of the present invention.

[0032] In the diagram: 1. Short seamless steel pipe; 2. Long seamless steel pipe; 3. Continuous hole; 4. Screw; 5. Nut; 6. Washer. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figures 1 to 7 This invention relates to a reusable concrete pre-drilled hole device, comprising a seamless steel pipe assembly and a connecting assembly. The seamless steel pipe assembly includes two short seamless steel pipes 1 and one long seamless steel pipe 2. The two short seamless steel pipes 1 are symmetrically distributed along the length of the long seamless steel pipe 2 and interlock perpendicularly with the long seamless steel pipe 2. Both the long seamless steel pipe 2 and the short seamless steel pipes 1 have a through hole 3 in the middle. The connecting assembly includes a screw 4, a nut 5, and a washer 6. The screw 4 passes through the through hole 3 to connect and reinforce the short seamless steel pipes 1 and the long seamless steel pipe 2 horizontally and vertically to form a whole.

[0035] In this design, the diameter of the seamless steel pipe is 30mm to 50mm; the lengths of the two short seamless steel pipes 1 are both 40cm to 70cm, and the length of the long seamless steel pipe 2 is 80cm to 120cm. Extensive experiments and engineering practice have verified that this size range of seamless steel pipes achieves the best balance in terms of strength, rigidity, and compatibility with concrete. Seamless steel pipes with excessively small diameters lack sufficient rigidity to resist the lateral pressure of concrete and are prone to deformation; excessively large diameters increase material costs and increase friction with concrete during extraction, hindering disassembly and reuse of the device. The length range of the short seamless steel pipes 1 and the long seamless steel pipes 2 is determined based on a comprehensive consideration of common concrete pre-drilled hole sizes and ease of construction, meeting the needs of various pre-drilled hole specifications. This size range of seamless steel pipes improves the versatility of the device while ensuring its stability and strength. It can be flexibly applied to the construction of concrete pre-reserved holes of different sizes and shapes. Whether it is a pre-reserved hole in a small precast component or a pre-reserved hole in a large building structure, it can achieve precise pre-reserved hole construction by selecting seamless steel pipes of appropriate size for assembly, while reducing the cost increase caused by customizing special-sized steel pipes.

[0036] In this design, the size of the through-hole 3 is 8mm to 12mm. The size of the through-hole 3 is compatible with the diameter of the screw 4. The 8mm to 12mm hole size ensures that the screw 4, with a diameter of 8mm to 12mm, can pass through smoothly. Simultaneously, after the screw 4 is tightened, a suitable gap is maintained between the hole and the screw 4. This prevents the steel pipe from slipping relative to the screw 4 during pouring due to excessive gap, affecting the stability of the device, while also preventing the screw 4 from being difficult to insert or damaging the steel pipe due to insufficient gap. This precise dimensional fit was achieved through multiple tests and optimizations to ensure the effective functioning of the connecting components. The suitable size of the through-hole 3 makes the installation and disassembly of the connecting components more convenient and efficient, while ensuring the stability of the device during concrete pouring. During construction, workers can quickly and accurately insert the screw 4 through the hole for installation, improving construction efficiency; during disassembly, the screw 4 can also be easily removed, facilitating the recycling and reuse of the device. In addition, a stable connection can effectively prevent the displacement and deformation of the steel pipe during concrete pouring, further ensuring the accuracy of the reserved hole.

[0037] In this design, the connecting assembly includes a screw 4 with a diameter of 8mm to 12mm, a nut 5 with a size of 18mm to 22mm, and a double-layered steel washer 6 with a thickness of 1.5mm to 2.5mm. The screw 4 diameter is chosen to provide sufficient tightening force to ensure a firm connection between seamless steel pipes and resist lateral pressure from concrete. The 8mm to 12mm diameter of the screw 4 meets strength requirements while matching the size of the continuous hole 3. The nut 5 size is designed to match the screw 4; an 18mm to 22mm nut 5 provides sufficient torque application area, facilitating tightening by construction personnel to achieve the required tightening force. The double-layered steel washer 6 is designed to distribute the pressure of the nut 5 on the steel pipe, preventing deformation of the pipe surface due to excessive local pressure. The 1.5mm to 2.5mm thickness ensures sufficient strength for the washer 6 while compensating for unevenness on the steel pipe surface through slight deformation, resulting in uniform pressure distribution. This meticulously designed connection assembly significantly enhances the connection strength and stability of the device. During concrete pouring, it effectively prevents loosening and displacement between steel pipes, ensuring the position and shape accuracy of the pre-drilled holes. Simultaneously, the use of double-layer steel gaskets extends the service life of the steel pipes, reduces damage to the device caused by localized deformation, increases the number of times the device can be reused, and lowers construction costs.

[0038] In this scheme, before concrete pouring, the device is installed at the designated position of the pre-drilled hole, and the seamless steel pipe is firmly secured by tightening the nut 5. Accurate installation and reinforcement of the device before concrete pouring is a crucial step in assembling the seamless steel pipes into a stable structure using the connecting components. Tightening the nut 5 generates axial tension in the screw 4, tightly connecting the two short seamless steel pipes 1 and one long seamless steel pipe 2 together, forming a rigid whole that can resist the lateral pressure of the concrete. Installation at the designated position ensures that the pre-drilled hole is formed in the designed location. Strict adherence to this procedure guarantees the positional accuracy of the pre-drilled hole and prevents misalignment due to improper device installation. The securely reinforced device remains stably in place during concrete pouring, effectively resisting the lateral pressure of the concrete and ensuring that the size and shape of the pre-drilled hole meet design requirements, creating favorable conditions for the smooth progress of subsequent projects.

[0039] In this scheme, the device is disassembled approximately 1 to 3 hours after concrete pouring. A certain time is needed after concrete pouring to allow it to reach its initial setting state, but the waiting period cannot be too long, otherwise the hardened concrete will bond too tightly to the device, making disassembly difficult. The 1-3 hour timeframe is based on the initial setting characteristics of concrete and extensive engineering practice. Within this timeframe, the concrete has sufficient strength to maintain the shape of the pre-reserved hole, while the adhesion between the concrete and the device is relatively weak, facilitating disassembly. The specific time is determined in conjunction with the temperature, as temperature affects the initial setting time of concrete; higher temperatures shorten the initial setting time, while lower temperatures prolong it. Disassembling the device at the appropriate time ensures the quality of the pre-reserved hole's formation and allows for easy removal of the device from the concrete, facilitating reuse. This avoids the problems of premature disassembly leading to pre-reserved hole collapse and delayed disassembly resulting in difficulty in removal or even damage to the device, thus improving construction efficiency and reducing construction costs.

[0040] In this solution, during disassembly, the operator loosens the nut 5, removes the screw 4, and pulls the seamless steel pipe out of the concrete. Loosening the nut 5 releases the tightening force of the screw 4 on the seamless steel pipe, thus loosening the connection between the seamless steel pipes. Because a release agent was applied to the seamless steel pipe before concrete pouring, and disassembly is performed at an appropriate time, the adhesion between the seamless steel pipe and the concrete is relatively weak. The operator can utilize the rigidity of the steel pipe itself to manually or with simple tools pull the seamless steel pipe out of the concrete. This disassembly method is simple and convenient, requiring no complex tools or destructive operations, and will not damage the concrete structure or the device itself. It enables rapid disassembly, improves construction efficiency, and ensures the integrity of the device, providing a guarantee for subsequent reuse.

[0041] In this solution, the extracted seamless steel pipe, screw 4, nut 5, and washer 6 can be reused after cleaning. The components of the device are made of durable materials, making them resistant to damage during normal construction and disassembly. After cleaning to remove surface contaminants such as concrete residue, the strength and rigidity of the seamless steel pipe still meet the usage requirements, and the screw 4, nut 5, and washer 6 can still function properly, thus allowing them to be reused in new pre-drilled hole construction projects. This achieves device reuse, significantly reducing construction costs. Compared to traditional disposable pre-drilled hole devices, it reduces material waste and aligns with green and environmentally friendly construction principles. Multiple reuses also demonstrate the device's reliability and durability, further enhancing its value in engineering applications.

[0042] In this design, the seamless steel pipe is a high-strength rigid steel pipe, capable of resisting the lateral pressure of concrete during pouring and maintaining its shape and position stability. The selection of high-strength rigid seamless steel pipe as the main material of the device ensures its high strength and rigidity. During concrete pouring, the lateral pressure exerted by the concrete on the device causes compression and deformation. The high-strength rigid steel pipe resists this force through its material properties, maintaining its original shape and position without significant deformation or displacement. This guarantees the accuracy of the pre-drilled holes during concrete pouring, avoiding dimensional deviations and inaccuracies in the holes caused by device deformation or displacement. Compared to traditional pre-drilled hole devices made of low-strength materials, this design significantly improves construction quality, reduces rework and repair work caused by pre-drilled hole problems, and saves construction time and costs.

[0043] In this solution, by adjusting the length of the seamless steel pipe and the intersection angle of the pipe ends, it can accommodate the needs for pre-drilled holes of different specifications and shapes. Different concrete structures may require pre-drilled holes of different specifications (such as round, rectangular, square, etc.) and shapes (such as straight holes, bent holes, cross-shaped holes, etc.). By changing the length of the seamless steel pipe, it can adapt to the size requirements of pre-drilled holes of different sizes; by adjusting the intersection angle of the pipe ends, the device can be combined into different shapes to match pre-drilled holes of specific shapes. This flexible design is based on the device's cross-shaped interlocking structure and adjustable connection method. This greatly improves the versatility and applicability of the device. Whether it is a simple pre-drilled hole in a small building project or a special-shaped pre-drilled hole in a large, complex building structure, the construction requirements can be met by adjusting the length and intersection angle of the seamless steel pipe. This reduces the cost and time of customizing a special pre-drilled hole device for a specific project, improves construction efficiency, and expands the application range of the device.

[0044] The working process of this device is as follows: Installation stage: Before concrete pouring, accurately install the device at the designated position of the pre-drilled hole and secure the seamless steel pipe by tightening the nuts. During installation, the continuous hole in the middle of the steel pipe and the screw rod adopt a "clearance fit," with the clearance controlled between 0.5-1mm (verified by 5 sets of different clearance tests: when the clearance is <0.5mm, the screw rod is difficult to insert; when the clearance is >1mm, the steel pipe is prone to relative slippage), ensuring the stability of the device's position during pouring. Pouring stage: During concrete pouring, the seamless steel pipe is made of Q235 material, which has 20% higher lateral pressure resistance than welded steel pipes of the same specification, and its smooth inner wall reduces friction with concrete by 30%. With its high strength and rigidity, it can effectively resist the lateral pressure of the concrete, maintaining the stability of its shape and position, thereby ensuring the accuracy of the pre-drilled hole. Disassembly Stage: Approximately 1 to 3 hours after concrete pouring (the exact time depends on the site temperature), based on the initial concrete setting strength test: at this time, the initial concrete setting strength reaches 1-2 MPa (determined by penetration resistance test), ensuring stable pre-drilled hole formation without hardening adhesion, and the pull-out force is <500N (far lower than the steel pipe yield strength ≥235MPa). The operator loosens the nut, removes the screw, and uses a short-range wrench inserted into the pre-drilled hole in the steel pipe to rotate clockwise, smoothly pulling the seamless steel pipe out of the concrete. Reuse: The extracted seamless steel pipe, screw, nut, and gasket can be reused after simple cleaning. Tests show that after 15 reuses, the seamless steel pipe bending is <1mm / m, the screw and nut show no stripping, and the connection strength remains above 95% of the initial value, achieving stable reuse.

[0045] Preliminary Preparation: Based on the location and size of the pre-reserved holes in the concrete formwork, determine the specific specifications of the seamless steel pipes (diameter 30mm to 50mm, short pipe length 40cm to 70cm, long pipe length 80cm to 120cm), and drill a continuous hole of 8mm to 12mm in the middle of the steel pipe; prepare threaded rods with a diameter of 8mm to 12mm, nuts with a diameter of 18mm to 22mm, and double-layer steel washers with a thickness of 1.5mm to 2.5mm. Apply a release agent to the seamless steel pipes before use. Installation: (The text abruptly ends here, so the translation stops as well.) Figure 7 , 4 As shown, first insert the long steel pipe from end A to end B of the template into the pre-drilled hole in the template, with both ends of the steel pipe protruding 10cm-15cm beyond the outer sides of ends A and B. Then, insert the screw rod from end C to end D of the template vertically through the pre-drilled hole in the long steel pipe. Next, insert two short steel pipes into the screw rod from ends C and D of the template respectively, assembling the pipes into a cross shape inside the template. Adjust the angle of the pipe ends to meet the requirements of the pre-drilled hole (the angle can be adjusted within the range of 60°-90° depending on the hole shape). Finally, simultaneously install double-layer steel washers and nuts at both ends of the screw rod, and tighten the nuts with an electric wrench to complete the fixation. Disassembly of the device: As shown... Figure 1As shown, during disassembly, loosen the nuts on both sides of the short steel pipe, remove the washers, and pull out the screw in sequence. Use a short-throw wrench inserted into the pre-drilled hole in the short steel pipe and turn it clockwise to pull out the short steel pipe; as shown... Figure 2 As shown, when disassembling a long steel pipe, use a short-pitch wrench to insert into the pre-drilled hole at one end of the long steel pipe and turn it clockwise to pull out the long steel pipe.

[0046] Reuse: After cleaning the extracted seamless steel pipes, screws, nuts and washers, store them for later use and put them directly into use during the next construction.

[0047] Example 1: Scenario for reserving lifting holes for precast concrete wall panels. In a precast concrete wall panel production project, 80mm diameter cross-shaped lifting holes need to be reserved for connecting lifting equipment during wall panel lifting and transportation. 40mm diameter Q235 seamless steel pipes (meeting lateral pressure strength requirements and easy to pull out) are selected, with the short seamless steel pipes being 55cm long and the long seamless steel pipes being 1m long. The connecting components use 10mm screws, 20mm nuts, and 2mm thick double-layer steel washers. The through-hole size in the middle of the steel pipe is 10mm. After the wall panel template is installed, the long steel pipe is inserted into the preset position along the template length, with both ends protruding 12cm outside the template. The screw is vertically inserted into the hole in the middle of the long steel pipe, and then two short steel pipes are inserted into the screw from the template width direction, so that the long and short steel pipes form a 90° cross-interlock within the template. The nuts at both ends of the screw are tightened using an electric wrench, and the double-layer washers ensure even transmission of locking force. After the device is fixed, the verticality deviation is checked to be ≤2mm. During concrete pouring, the steel pipe resisted lateral pressure without deformation. Two hours after pouring (at an ambient temperature of 25°C), the nut was loosened, the screw was removed, and a short-range wrench was inserted into the hole of the short steel pipe and turned clockwise to easily pull out the short steel pipe. The long steel pipe was then pulled out in the same way. The dimensional deviation of the reserved hole was only 1.5mm, and the inner wall was smooth with no grout leakage. After cleaning, the device could be directly used for the construction of the next wall panel, reducing the material cost per hole by 80%.

[0048] Example 2: Scenario of reserved holes for pipelines in precast bridge beams. A bridge project requires reserved 300×200mm rectangular pipeline holes in precast beams for subsequent cable installation. The holes must be unobstructed and without deviation. The steel pipe specifications are adjusted according to the rectangular hole size: the short seamless steel pipe is 70cm long, and the long seamless steel pipe is 120cm long, both with a diameter of 50mm (to match the stiffness requirements of the larger hole). The connecting components are 12mm screws (to enhance locking force), 22mm nuts, and 2.5mm thick double-layer steel washers. The continuous hole size in the middle of the steel pipe is 12mm, and the intersection angle (the angle between the short and long seamless steel pipes) is adjusted to 60°. The locations of the ducts were marked inside the precast beam formwork. Long steel pipes were arranged along the beam length, with 15cm protruding from both ends of the formwork. After the threaded rod was inserted into the hole in the long steel pipe, two short steel pipes were inserted from the beam width direction and adjusted to a 60° intersection angle to ensure the combined outline of the steel pipes matched the rectangular holes. When tightening the nuts, the pre-tightening force was controlled using a torque wrench to ensure the steel pipes remained secure. Three hours after concrete pouring (at an ambient temperature of 18℃), the initial setting strength of the concrete reached 1.5MPa. At this point, the nuts were loosened and the threaded rod was pulled out. Due to the large diameter of the steel pipes, they were easily pulled out using the torque generated by rotating the wrench, without any concrete adhesion. The pre-drilled holes were precisely sized to meet pipeline installation requirements. The device showed no significant deformation after 10 reuses, avoiding the duct misalignment problem caused by insufficient rigidity of traditional PVC pipes.

[0049] Example 3: Scenario for pre-drilled holes in small precast blocks under low-temperature conditions. In small precast concrete block projects constructed in winter at low temperatures (below 5℃), 50mm diameter circular pre-drilled holes are required for later reinforcement connections. Seamless steel pipes with a diameter of 30mm are selected (to meet the lightweight requirements of small holes), with short pipes 40cm long and long pipes 80cm long. The connecting components use 8mm threaded rods, 18mm nuts, and 1.5mm thick double-layer steel washers. The overall hole size is 8mm, and the intersection angle is 90°. Due to the small size of the precast block template, the long and short steel pipes are pre-assembled into a cross structure outside the template during installation, and then placed into the pre-drilled position on the template, ensuring that both ends of the steel pipe protrude 10cm from the template. Because the initial setting of concrete is slow in low-temperature environments, temporary supports are used for additional fixation after tightening the nuts (to prevent accidental displacement due to collisions). Three hours after concrete pouring (the initial setting time is longer in low-temperature environments), dismantling begins after checking that there is no flow on the concrete surface. At this point, the concrete strength reaches 1 MPa. After loosening the nuts, there is no frozen adhesion between the steel pipe and the concrete, and the steel pipe can be manually pulled out with assistance. The deviation of the reserved hole position is ≤2mm. After cleaning, the device can be directly reused in the construction of subsequent batches of precast blocks, solving the problems of high cost and poor molding of traditional disposable materials in low-temperature environments.

[0050] The following is a comparison table of the effects of this structure and the traditional pre-drilled hole method:

[0051]

[0052] Although embodiments of the 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 invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A reusable concrete pre-drilled hole device, characterized in that, The assembly includes a seamless steel pipe assembly and a connecting assembly. The seamless steel pipe assembly includes two short seamless steel pipes (1) and one long seamless steel pipe (2). The two short seamless steel pipes (1) are symmetrically distributed along the length of the long seamless steel pipe (2) and interlock perpendicularly with the long seamless steel pipe (2). Both the long seamless steel pipe (2) and the short seamless steel pipes (1) have a through hole (3) in the middle. The connecting assembly includes a screw (4), a nut (5), and a washer (6). The screw (4) passes through the through hole (3) to connect and reinforce the short seamless steel pipes (1) and the long seamless steel pipe (2) in a horizontal and vertical manner to form a whole. In the connecting assembly, the diameter of the screw (4) is 8mm to 12mm, and the size of the nut (5) is... The thickness of the gasket (6) is 18mm to 22mm. The gasket (6) is a double-layer steel gasket (6) with a thickness of 1.5mm to 2.5mm. The seamless steel pipe assembly is a high-strength rigid steel pipe that can resist the side pressure of concrete during concrete pouring and maintain the stability of shape and position. By adjusting the length of the seamless steel pipe and the cross angle of the pipe opening, it is suitable for the requirements of reserved holes of different specifications and shapes. During installation, first insert the long seamless steel pipe (2) from end A to end B of the template into the reserved hole of the template. Both ends of the long seamless steel pipe (2) are exposed outside the ends A and B of the template. Then insert the screw (4) from end C to end D of the template through the reserved hole of the template and vertically into the reserved hole of the long seamless steel pipe (2). Next, insert the two short seamless steel pipes (1) into the screw (4) from end C and end D of the template respectively. Finally, install the gasket (6) and nut (5) at both ends of the screw (4) and tighten the nut (5) to complete the fixation.

2. The reusable concrete pre-drilled hole device according to claim 1, characterized in that, The diameter of the seamless steel pipe is 30mm to 50mm; the length of the two short seamless steel pipes (1) is 40cm to 70cm, and the length of the long seamless steel pipe (2) is 80cm to 120cm.

3. The reusable concrete pre-drilled hole device according to claim 1, characterized in that, After the concrete is poured, wait 1 to 3 hours before disassembling the device.

4. The reusable concrete pre-drilled hole device according to claim 1, characterized in that, During disassembly, the operator loosens the nut (5), removes the screw (4), and pulls the seamless steel pipe out of the concrete.

5. The reusable concrete pre-drilled hole device according to claim 4, characterized in that, The extracted seamless steel pipe, screw (4), nut (5) and gasket (6) can be reused after cleaning.

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