Reusable concrete preformed hole device

Abstract

The invention relates to the technical field of concrete processing, in particular to a reusable concrete preformed 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, and the two short seamless steel pipes are symmetrically distributed in the length direction of the long seamless steel pipe; the short seamless steel pipe is vertically crossed and meshed with the long seamless steel pipe, through long holes are formed in the middle of the long seamless steel pipe and the middle of the short seamless steel pipe, the connecting assembly comprises a screw rod, a nut and a gasket, and the screw rod penetrates through the through long holes to transversely and longitudinally connect and reinforce the short seamless steel pipe and the long seamless steel pipe into a whole. The device adopts a detachable connection structure, and each part can be drawn out without damage after concrete pouring. And the performance is not obviously attenuated. Compared with a traditional disposable material, secondary processing is not needed after the material is on site, the material is directly installed and used, the processing cost and time are saved, the total cost is reduced, and meanwhile construction waste is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of concrete processing, in particular to a reusable concrete reserved hole device. Background Art

[0002] As we all know, in concrete structure construction, reserved holes are a key step to ensure the smooth implementation of subsequent projects. They are widely used in scenarios such as equipment installation, pipeline routing, steel bar connection and hoisting operations. Traditional reserved hole construction methods mainly rely on buried casing, wooden boxes or PVC pipe + four-way combination methods. However, these methods have difficult to overcome technical defects in actual application, as shown below:

[0003] The traditional method has low hole precision and poor stability: In the traditional method, the core problem is the lack of 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 3-4GPa. During the concrete pouring process, it is subjected to 3-5kN / m 2 When subjected to lateral pressure, radial deformations of 10-20mm are likely to occur, causing the reserved hole size deviation to far exceed the ±5mm range allowed by the specification. At the same time, due to the low material strength and poor sealing of the connection between the PVC pipe and the cross, the leakage rate is as high as over 30%. The inner wall of the channel is often rough, partially blocked, or even completely blocked, seriously affecting the subsequent pipeline installation or equipment installation. Additional manpower is required for secondary dredging, and the dredging cost accounts for 20%-30% of the construction cost of a single hole. Wooden boxes are highly absorbent and easily expand due to moisture after concrete pouring. This not only causes the hole shape to deform, but also bonds tightly to the concrete, making it difficult to remove and easy to break.

[0004] Non-reusable materials and high costs: Traditional pre-drilled hole materials are single-use. A single wooden box costs approximately 20 yuan, while a PVC pipe + cross-connect combination costs approximately 15 yuan. If a project requires 500 pre-drilled holes, the material cost alone can reach 7,500-10,000 yuan. Furthermore, these materials require secondary processing upon arrival, including cutting, splicing, and polishing. This processing time accounts for over 40% of the construction time for a single hole, further increasing labor costs and project time. Materials cannot be recycled after use due to deformation, damage, or bonding, resulting in a waste of resources and failing to meet green construction requirements.

[0005] Poor construction adaptability and complex operations: Traditional materials have weak adaptability to the construction environment. PVC pipes are prone to softening and deformation in high-temperature environments (above 35°C) and brittle cracking in low-temperature environments (below 5°C). Wooden boxes are greatly affected by humidity, with their strength dropping sharply in humid environments and easily collapsing during the pouring process. Furthermore, installation requires cumbersome fixing of the casing or wooden box (such as tying and supporting), but displacement during pouring is still difficult to avoid. Disassembly requires destructive methods such as crushing and cutting due to the adhesion of the material to the concrete. This is not only time-consuming (single-hole disassembly takes more than 20 minutes) but may also damage the concrete structure itself, affecting construction quality. Therefore, it is necessary to propose a solution to this technical problem. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In view of the deficiencies in the prior art, the present invention provides a reusable concrete pre-hole device.

[0008] (2) Technical solution

[0009] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a reusable concrete pre-hole device, comprising a seamless steel pipe assembly and a connecting assembly, wherein the seamless steel pipe assembly comprises two short seamless steel pipes and one 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 cross-engaged with the long seamless steel pipe, and the middle parts of the long seamless steel pipe and the short seamless steel pipe are both provided with through-length holes, and the connecting assembly comprises a screw, a nut and a gasket, and the screw passes through the through-length hole to connect the short seamless steel pipe and the long seamless steel pipe horizontally and vertically to reinforce them into a whole.

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

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

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

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

[0014] Furthermore, the present invention is improved in that after the concrete pouring is completed, the device is disassembled about 1 to 3 hours after the concrete pouring is completed.

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

[0016] Furthermore, the present invention is improved in that the extracted seamless steel pipe, screw, nut and gasket can be put into use again after cleaning.

[0017] Furthermore, the present invention has the following improvements: the seamless steel pipe is a high-strength rigid steel pipe, which can withstand the side pressure of concrete during the concrete pouring process and maintain a stable shape and position.

[0018] Furthermore, the present invention is improved in that, by adjusting the length and the cross angle of the seamless steel pipe, it is suitable for the requirements of reserved holes of different specifications and shapes.

[0019] (3) Beneficial effects

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

[0021] The core components of this reusable concrete reserved hole device are made of high-strength seamless steel pipes, which have a lateral pressure resistance 5-8 times higher than that of PVC pipes of the same specifications. They can effectively resist lateral pressure during the concrete pouring process and ensure the stability of the shape and position of the device. In actual construction, the size deviation of the reserved holes can be controlled to ≤3mm, and the position offset can be ≤2mm, which fully meets the requirements of high-precision construction (such as the strict requirements for precision of lifting holes). Compared with the deformation and leakage problems caused by insufficient rigidity of traditional PVC pipes + four-way joints, this device forms an overall force system through the "cross-shaped interlocking rigid frame + tension bolt locking" structure, which eliminates the problems of channel blockage and dimensional deviation, and greatly improves the reliability of construction quality.

[0022] The device features a detachable connection structure, allowing components to be removed without damage after concrete pouring. Field verification has shown that each component can be reused 10 or more times after cleaning, with no noticeable performance degradation. Compared to traditional disposable materials, this method eliminates the need for secondary processing upon arrival and allows for direct installation, saving processing costs and time. This reuse reduces the amortized cost per use to one-fifth of that of traditional methods. For example, in a project involving 500 pre-retained holes, total costs can be reduced by over 80%, while also reducing construction waste and aligning with green construction principles.

[0023] Installation requires only tightening the nuts with an electric wrench, with a single installation time of 10 minutes or less. Disassembly requires only loosening the nuts and extracting the screws. Leveraging the rigidity and smooth surface of the steel pipe, the pipe can be easily removed, with a single removal time of 5 minutes or less. Compared to traditional methods (installation taking over 30 minutes and disassembly taking over 20 minutes), construction efficiency has increased by over 300%, significantly reducing the proportion of man-hours spent on pre-drilled holes and accelerating overall construction progress.

[0024] By adjusting the length (short tubes 40-70cm, long tubes 80-120cm), diameter (30-50mm), and intersection angle (60°-90°) of the seamless steel pipe, the device can adapt to various sizes of reserved holes, such as cross-shaped, rectangular, and circular, to meet the construction requirements of different components such as prefabricated wall panels, prefabricated bridge beams, and small prefabricated blocks. At the same time, the material properties of seamless steel pipes enable them to maintain stable performance in high-temperature (above 35°C) or low-temperature (below 5°C) environments, solving the problem of traditional PVC pipes softening at high temperatures and becoming brittle at low temperatures, and their application scenarios are not restricted by climatic conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 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 It is a schematic diagram of the structural combination of the present invention;

[0029] Figure 5 It is a schematic side cross-sectional view of the structure of the present invention;

[0030] Figure 6 This is a schematic diagram of a front cross-section of the structural combination of the present invention;

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

[0032] In the figure: 1. Short seamless steel pipe; 2. Long seamless steel pipe; 3. Through-length hole; 4. Screw; 5. Nut; 6. Gasket. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] See also Figures 1 to 7 The present invention is a reusable concrete pre-hole device, including a seamless steel pipe assembly and a connecting assembly, wherein the seamless steel pipe assembly includes two short seamless steel pipes 1 and a long seamless steel pipe 2, the two short seamless steel pipes 1 are symmetrically distributed along the length direction of the long seamless steel pipe 2, and are vertically cross-engaged with the long seamless steel pipe 2, and the middle parts of the long seamless steel pipe 2 and the short seamless steel pipe 1 are both provided with a through-length hole 3, and the connecting assembly includes a screw 4, a nut 5 and a gasket 6, and the screw 4 passes through the through-length hole 3 to connect the short seamless steel pipe 1 and the long seamless steel pipe 2 horizontally and vertically to reinforce them to form a whole.

[0035] In this solution, 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. After a large number of experiments and engineering practice verifications, it was determined that the seamless steel pipes in this size range can achieve the best balance in strength, rigidity and compatibility with concrete. Seamless steel pipes with too small a diameter are not rigid enough to resist the side pressure of concrete and are prone to deformation; those with too large a diameter will increase material costs, and the friction with concrete will increase during the extraction process, which is not conducive to the disassembly and reuse of the device. The length range setting of the short seamless steel pipe 1 and the long seamless steel pipe 2 is based on a comprehensive consideration of the common concrete pre-set hole sizes and the convenience of construction operations, and can meet the needs of pre-set holes of various specifications. Seamless steel pipes in this size range improve the versatility of the device while ensuring the stability and strength of the device. It can be flexibly applied to the construction of concrete reserved holes of different sizes and shapes. Whether it is the reserved holes of small prefabricated components or the reserved holes in large building structures, it can be assembled by selecting seamless steel pipes of appropriate sizes to achieve precise reserved hole construction, while reducing the cost increase caused by customizing special-sized steel pipes.

[0036] In this solution, the size of the through-length hole 3 is 8mm to 12mm, and the size of the through-length hole 3 is adapted to the diameter of the screw 4. The hole size of 8mm to 12mm can ensure that the screw 4 with a diameter of 8mm to 12mm can pass through smoothly. At the same time, after the screw 4 is tightened, an appropriate gap is maintained between the hole and the screw 4. The steel pipe will not slide relative to the screw 4 during the pouring process due to the gap being too large, affecting the stability of the device, nor will the screw 4 be difficult to pass through or cause damage to the steel pipe due to the gap being too small. This precise size matching is obtained through multiple tests and optimizations to ensure that the connection assembly can function effectively. The appropriate size of the through-length hole 3 makes the installation and disassembly of the connection assembly more convenient and efficient, while ensuring the stability of the device during the concrete pouring process. During the construction process, construction workers can quickly and accurately pass the screw 4 through the hole for installation, which improves construction efficiency; during disassembly, the screw 4 can also be easily removed, facilitating the recycling and reuse of the device. In addition, the stable connection can effectively prevent the displacement and deformation of the steel pipe during concrete pouring, further ensuring the accuracy of the reserved holes.

[0037] In this solution, in the connection assembly, the diameter of the screw 4 is 8mm to 12mm, the size of the nut 5 is 18mm to 22mm, and the gasket 6 is a double-layer steel gasket 6 with a thickness of 1.5mm to 2.5mm. The selection of the diameter of the screw 4 is based on the need to provide sufficient tightening force to ensure that the seamless steel pipes are firmly connected and resist the side pressure of the concrete. The diameter of the screw 4 of 8mm to 12mm matches the size of the through-length hole 3 while meeting the strength requirements. The size of the nut 5 should be set to match the screw 4. The nut 5 of 18mm to 22mm can provide sufficient torque application area, which is convenient for construction workers to tighten the nut 5 and achieve the required tightening force. The design of the double-layer steel gasket 6 is to disperse the pressure of the nut 5 on the steel pipe to avoid deformation of the steel pipe surface due to excessive local pressure. The thickness of 1.5mm to 2.5mm can not only ensure that the gasket 6 has sufficient strength, but also compensate for the unevenness of the steel pipe surface through micro-deformation, so that the pressure is evenly distributed. This meticulously designed connection assembly significantly enhances the joint strength and stability of the device. During the concrete pouring process, it effectively prevents loosening and displacement between the steel pipes, ensuring the position and shape accuracy of the reserved holes. Furthermore, the use of double-layer steel gaskets (6) extends the service life of the steel pipes, reduces damage to the device caused by local deformation, increases the number of device reuses, and reduces construction costs.

[0038] In this solution, before the concrete pouring operation, the device is installed to the designated position of the reserved hole, and the seamless steel pipe is firmly reinforced by tightening the nut 5. Accurately installing the device and reinforcing it before concrete pouring is a key step in assembling seamless steel pipes into a stable structure using a connecting assembly. By tightening the nut 5, the screw 4 generates axial tension, tightly connecting the two short seamless steel pipes 1 and the long seamless steel pipe 2 together to form a rigid whole, thereby having the ability to resist the lateral pressure of concrete. Installation to the designated position ensures that the reserved hole can be formed at the position required by the design. Strictly following this step can ensure the position accuracy of the reserved hole and avoid the position deviation of the reserved hole due to improper installation of the device. The firmly reinforced device can remain stably in place during the concrete pouring process, effectively resisting the lateral pressure of concrete, ensuring that the size and shape of the reserved hole meet the design requirements, and creating good conditions for the smooth development of subsequent projects.

[0039] In this solution, after the concrete pouring is completed, the device is disassembled after about 1 to 3 hours. After the concrete pouring is completed, it is necessary to wait for a certain time for the concrete to reach the initial setting state, but it cannot be waited too long, so as to avoid the concrete from being too tightly bonded to the device after hardening and being difficult to disassemble. The time range of 1 to 3 hours is based on the initial setting characteristics of concrete and a large number of engineering practices. During this time period, the concrete has a certain strength and can maintain the shape of the reserved hole. At the same time, the bonding force between the concrete and the device is relatively small, which is convenient for disassembly of the device. The specific time is determined in combination with the temperature because the temperature will affect the initial setting time of the concrete. The initial setting time is shortened when the temperature is high and prolonged when the temperature is low. Disassembling the device at the appropriate time can not only ensure the molding quality of the reserved hole, but also easily remove the device from the concrete, which is convenient for reuse of the device. It avoids the problem of the reserved hole collapsing due to premature disassembly and the device being difficult to remove or even damaged due to too late disassembly, thereby improving construction efficiency and reducing construction costs.

[0040] In this solution, during disassembly, the operator loosens the nut 5, takes out the screw 4, and extracts the seamless steel pipe from the concrete. By loosening the nut 5, the tightening force of the screw 4 on the seamless steel pipe is released, and the connection between the seamless steel pipes is loosened. Since the seamless steel pipe is coated with a release agent before pouring the concrete and is disassembled at an appropriate time, the bonding force between the seamless steel pipe and the concrete is relatively small. The operator can use the rigidity of the steel pipe itself to extract the seamless steel pipe from the concrete manually or with the help of simple tools. This disassembly method is simple and convenient, does not require the use of complex tools or destructive operations, and will not cause damage to the concrete structure and the device itself. The device can be disassembled quickly, which improves construction efficiency, while ensuring the integrity of the device and providing a guarantee for subsequent reuse.

[0041] In this solution, the extracted seamless steel pipe, screw 4, nut 5 and gasket 6 can be put into use again after cleaning. The various components of the device are made of durable materials and are not easily damaged during normal construction and disassembly. After cleaning and removing impurities such as concrete residues attached to the surface, the strength and rigidity of the seamless steel pipe can still meet the use requirements, and the screw 4, nut 5 and gasket 6 can also play a normal connecting role, so they can be put into new reserved hole construction projects again. The reuse of the device is achieved, which greatly reduces the construction cost. Compared with the traditional disposable reserved hole device, it reduces the waste of materials and conforms to the green and environmentally friendly construction concept. Repeated use also proves the reliability and durability of the device, further enhancing its value in engineering applications.

[0042] In this solution, 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 a stable shape and position. The high-strength rigid seamless steel pipe is selected as the main material of the device, and its material properties determine that it has high strength and rigidity. During the concrete pouring process, the lateral pressure generated by the concrete on the device will cause the device to be squeezed and deformed, while the high-strength rigid steel pipe can resist this force through its own material properties, maintain its original shape and position, and no obvious deformation or displacement occurs. The accuracy of the reserved holes during the concrete pouring process is guaranteed, and the size deviation and inaccurate position of the reserved holes caused by deformation or displacement of the device are avoided. Compared with the reserved hole device made of traditional low-strength materials, the construction quality is greatly improved, the subsequent rework and repair work caused by the reserved hole problem is reduced, and the construction time and cost are saved.

[0043] In this solution, by adjusting the length of the seamless steel pipe and the intersection angle of the pipe mouth, it is suitable for the requirements of reserved holes of different specifications and shapes. Different concrete structures may need to reserve holes of different specifications (such as round, rectangular, square, etc.) and shapes (such as straight holes, curved holes, cross-shaped holes, etc.). By changing the length of the seamless steel pipe, the size requirements of reserved holes of different sizes can be adapted; by adjusting the intersection angle of the pipe mouth, the device can be combined into different shapes to match the reserved holes of specific shapes. This flexible design is based on the cross-shaped bite structure and adjustable connection method of the device. It greatly improves the versatility and applicability of the device. Whether it is a simple reserved hole in a small construction project or a special shape reserved hole in a large and complex building structure, the construction requirements can be met by adjusting the length and intersection angle of the seamless steel pipe. It reduces the cost and time of customizing special reserved hole devices for specific projects, improves construction efficiency, and expands the scope of application of the device.

[0044] The working process of this device is as follows: Installation stage: Before the concrete pouring operation, accurately install this device to the designated position of the reserved hole, and firmly reinforce the seamless steel pipe by tightening the nut. During installation, the full-length hole in the middle of the steel pipe and the screw adopt a "clearance fit", and the gap is controlled at 0.5-1mm (verified by 5 groups of different gap tests: when the gap is <0.5mm, it is difficult to pass the screw, and when it is >1mm, the steel pipe is easy to slide relative to each other), to ensure that the position of the device is stable during the pouring process. Pouring stage: During the concrete pouring process, the seamless steel pipe is made of Q235 material, which has a lateral compressive strength 20% higher than that of the welded steel pipe of the same specification, and the inner wall is smooth, which reduces the friction with the concrete by 30%. With its own high strength and rigidity, it can effectively resist the lateral pressure of the concrete, maintain the stability of the shape and position, thereby ensuring the accuracy of the reserved hole. Disassembly stage: When the concrete pouring is completed about 1 to 3 hours later (the specific time is determined in combination with the on-site temperature), this time range is based on the concrete initial setting strength test: at this time, the initial setting strength of the concrete reaches 1-2MPa (determined by the penetration resistance test), which can not only ensure the stable forming of the reserved hole, but also not form a hardened bond, and the extraction force is <500N (much lower than the yield strength of the steel pipe ≥235MPa). The operator loosens the nut, takes out the screw, uses a short-pitch wrench to penetrate the reserved hole of the steel pipe and rotates clockwise to smoothly extract the seamless steel pipe from the concrete. Reuse: The extracted seamless steel pipe, screw, nut and gasket can be put into use again after a simple cleaning. After testing, after the device was reused 15 times, the curvature of the seamless steel pipe was <1mm / m, there was no thread slippage on the screw and nut, and the connection strength remained above 95% of the initial value, achieving stable reuse.

[0045] Preliminary preparation: According to the location and size of the reserved holes in the concrete formwork, determine the specific specifications of the seamless steel pipe (diameter 30mm to 50mm, short pipe length 40cm to 70cm, long pipe length 80cm to 120cm), and open a full-length hole of 8mm to 12mm in the middle of the steel pipe; prepare screws with a diameter of 8mm to 12mm, nuts with a diameter of 18mm to 22mm and double-layer steel gaskets with a thickness of 1.5mm to 2.5mm, and apply mold release agent to the seamless steel pipe before use. Figure 7 、 4 As shown, first pass the long steel pipe from the A end to the B end of the template through the reserved hole of the template, with both ends of the steel pipe exposed 10cm-15cm outside the ends of the template A and B; then pass the screw from the C end to the D end of the template through the reserved hole of the template vertically into the long hole reserved for the long steel pipe; then pass the two short steel pipes through the screw from the C and D ends of the template respectively, and assemble the steel pipes into a cross shape in the template, and adjust the cross angle of the pipe mouth to meet the requirements of the reserved hole (the cross angle can be adjusted within the range of 60°-90° according to the hole shape requirements); finally, install double-layer steel washers and nuts at both ends of the screw at the same time, and use an electric wrench to tighten the nuts to complete the fixation. Device disassembly: As shown in the figure, first pass the long steel pipe from the A end to the B end of the template through the reserved hole of the template; then pass the two short steel pipes through the screw from the C and D ends of the template respectively, and assemble the steel pipes into a cross shape in the template, and adjust the cross angle of the pipe mouth to meet the requirements of the reserved hole (the cross angle can be adjusted within the range of 60°-90° according to the hole shape requirements); finally, install double-layer steel washers and nuts at both ends of the screw at the same time, and use an electric wrench to tighten the nuts to complete the fixation. Figure 1As shown, when disassembling, loosen the nuts on both sides of the short steel pipe, remove the gasket, pull out the screw, use a short-length wrench to penetrate the reserved hole of the short steel pipe, and rotate it clockwise to pull out the short steel pipe; Figure 2 As shown in the figure, when removing the long steel pipe, use a short-length wrench to insert it into the reserved hole at one end of the long steel pipe, and rotate it clockwise to pull out the long steel pipe.

[0046] Reuse: Clean the extracted seamless steel pipes, screws, nuts and gaskets, store them for future use and put them into use directly during the next construction.

[0047] Example 1: Precast concrete wall panel hoisting hole reservation scenario. In a precast concrete wall panel production project, a cross-shaped hoisting hole with a diameter of 80mm needs to be reserved for the connection of the hoisting equipment during the hoisting and transportation of the wall panel. A Q235 seamless steel pipe with a diameter of 40mm is selected (the lateral pressure resistance meets the requirements and it is easy to pull out). The short seamless steel pipe is 55cm long and the long seamless steel pipe is 1m long. The connection components use 10mm screws, 20mm nuts and 2mm thick double-layer steel washers. The size of the full-length hole in the middle of the steel pipe is 10mm. After the wall panel formwork is installed, the long steel pipe is inserted into the preset position along the length of the formwork, with both ends protruding 12cm outside the formwork. The screw is inserted vertically into the middle hole of the long steel pipe, and then the two short steel pipes are inserted into the screw from the width of the formwork, so that the long and short steel pipes form a 90° cross bite in the formwork. Tighten the nuts at both ends of the screw with an electric wrench, and use double-layer washers to ensure uniform transmission of the locking force. After the device is fixed, check that the verticality deviation is ≤2mm. During the concrete pour, the steel pipe resisted lateral pressure without deformation. Two hours after pouring (at a site temperature of 25°C), the nut was loosened and the screw was removed. A short-pitch wrench was inserted into the hole of the short steel pipe and rotated clockwise to easily remove the short pipe. The long pipe was then removed in the same manner. The deviation in the reserved hole size was tested to be only 1.5mm, and the inner wall was smooth and leak-free. After cleaning, the device was directly used for the next wall panel, reducing the material cost per hole by 80%.

[0048] Example 2: Prefabricated bridge beam pipeline hole scenario: A prefabricated bridge beam requires a 300×200mm rectangular pipeline hole for later cable routing. This hole must be unobstructed and free of offset. The steel pipe specifications are adjusted based on the rectangular hole size: the short seamless steel pipe is 70cm long, the long seamless steel pipe is 120cm long, and both have a diameter of 50mm (to meet the larger hole stiffness requirements). The connection components use a 12mm screw (for enhanced locking force), a 22mm nut, and a 2.5mm thick double-layer steel gasket. The full-length hole in the middle of the steel pipe is 12mm in size, and the intersection angle (the angle between the short and long seamless steel pipes) is adjusted to 60°. The hole position is marked in the prefabricated beam template, and the long steel pipe is arranged along the length of the beam, with 15cm exposed from the template at both ends; after the screw is inserted into the hole of the long steel pipe, the two short steel pipes are inserted from the width of the beam and adjusted to a 60° cross angle to ensure that the combined outline of the steel pipe matches the rectangular hole; when tightening the nut, the preload force is controlled by a torque wrench to ensure that the steel pipe is not loose. 3 hours after the concrete is poured (the temperature on site is 18°C), the initial setting strength of the concrete reaches 1.5MPa. At this time, the nut is loosened and the screw is pulled out. Due to the large diameter of the steel pipe, it can be easily pulled out with the help of the torque generated by the rotation of the wrench, and there is no concrete bonding. The reserved hole is precisely formed to meet the requirements for pipeline installation. After being reused 10 times, there is still no obvious deformation, avoiding the hole offset problem caused by insufficient rigidity of traditional PVC pipes.

[0049] Example 3: Scenario of reserved holes for small prefabricated blocks in low-temperature environments. In small concrete prefabricated block projects constructed in low temperatures in winter (below 5°C), circular reserved holes with a diameter of 50mm need to be reserved for later steel bar connections. A seamless steel pipe with a diameter of 30mm is selected (for lightweight requirements of small channels), with a short steel pipe length of 40cm and a long steel pipe length of 80cm. The connection components use 8mm screws, 18mm nuts and 1.5mm thick double-layer steel washers. The full-length hole size is 8mm and the cross angle is 90°. The prefabricated block template is small in size. During installation, the long steel pipe and the short steel pipe are pre-assembled into a cross structure outside the template and placed in the reserved position of the template as a whole, ensuring that both ends of the steel pipe are exposed to 10cm from the template. Because the initial setting of concrete in a low-temperature environment is slow, temporary supports are used to assist in fixing after the nuts are tightened (to avoid accidental collision and displacement). Three hours after the concrete pour is complete (initial setting time is extended in low-temperature environments), the concrete surface is checked for signs of flow and disassembly begins. At this point, the concrete strength reaches 1 MPa. After loosening the nuts, there is no frozen bond between the steel pipe and the concrete, allowing manual extraction of the pipe. The deviation in the reserved hole position is ≤ 2 mm. After cleaning, the device can be directly reused in subsequent batches of precast blocks, resolving the high cost and poor forming properties of traditional disposable materials in low-temperature environments.

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

[0051]

[0052] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A reusable concrete reserved hole device, characterized in that: The invention comprises a seamless steel pipe assembly and a connection assembly, wherein the seamless steel pipe assembly comprises two short seamless steel pipes (1) and one long seamless steel pipe (2), wherein the two short seamless steel pipes (1) are symmetrically distributed along the length direction of the long seamless steel pipe (2) and vertically cross-engage with the long seamless steel pipe (2), wherein the middle parts of the long seamless steel pipe (2) and the short seamless steel pipe (1) are both provided with a through-length hole (3), and the connection assembly comprises a screw (4), a nut (5) and a gasket (6), wherein the screw (4) passes through the through-length hole (3) to connect and reinforce the short seamless steel pipe (1) and the long seamless steel pipe (2) in a transverse and longitudinal direction to form a whole.

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

3. The reusable concrete pre-hole device according to claim 1, characterized in that: The size of the through-length hole (3) is 8 mm to 12 mm.

4. A reusable concrete reserved hole device according to claim 1, characterized in that: In the connection assembly, the diameter of the screw (4) is 8 mm to 12 mm, the size of the nut (5) is 18 mm to 22 mm, and the gasket (6) is a double-layer steel gasket (6) with a thickness of 1.5 mm to 2.5 mm.

5. The reusable concrete pre-hole device according to claim 1, characterized in 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 reinforced by tightening the nut (5).

6. The reusable concrete pre-hole device according to claim 1, characterized in that: After the concrete pouring is completed, about 1 to 3 hours after the concrete pouring is completed, the device is disassembled.

7. The reusable concrete pre-hole device according to claim 1, characterized in that: During disassembly, the operator loosens the nut (5), takes out the screw (4), and extracts the seamless steel pipe from the concrete.

8. The reusable concrete pre-hole device according to claim 7, characterized in that: The extracted seamless steel pipe, screw (4), nut (5) and gasket (6) can be put into use again after being cleaned.

9. The reusable concrete pre-hole device according to claim 1, characterized in that: The seamless steel pipe is a high-strength rigid steel pipe that can withstand the side pressure of concrete during concrete pouring and maintain stable shape and position.

10. The reusable concrete pre-hole device according to claim 1, characterized in that: By adjusting the length and the cross angle of the seamless steel pipe, it is suitable for the requirements of reserved holes of different specifications and shapes.

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