Bottom sealing treatment method for prefabricated pipe pile

Abstract

The invention provides a bottom sealing treatment method for a prefabricated pipe pile, which is characterized in that a bottom sealing device is adopted to seal the bottom end of the prefabricated pipe pile in advance, and soil and water can be effectively prevented from entering an inner hole of the prefabricated pipe pile when the prefabricated pipe pile sinks into a foundation soil body; after the prefabricated pipe pile sinks in place, the bottom sealing device can be simply and quickly separated from the bottom of the prefabricated pipe pile in a hammering or extruding mode, the pipe pile is not damaged, and a channel is formed to facilitate subsequent carrier construction; the bottom sealing device is fixedly connected with an end plate at the bottom end of the prefabricated pipe pile, and the bottom sealing device comprises a bottom sealing steel plate or a prefabricated pile tip.

Description

Technical Field

[0001] The invention relates to pile foundation construction in the field of civil engineering, and in particular to a bottom sealing processing method for a prefabricated pipe pile. Background Art

[0002] In the field of construction engineering, prefabricated pipe piles are a type of pile that is often used in foundation treatment. They are produced by manufacturers in major cities across the country. At present, prefabricated pipe piles are mainly driven into the foundation soil by diesel hammers, hydraulic hammers and static pressure pile drivers. The advantages are simple construction process, fast speed and moderate cost. The disadvantage is that the pile body is easily damaged. Especially when the diesel hammer method is used, the tensile stress generated during the transmission of the pile body stress wave often cracks the pile body concrete. It is more difficult to drive the pile when encountering hard plastic clay, interlayer silt, silt sand and pebble soil layers. When the pressure and kinetic energy used exceed the strength that the pile body can withstand, it will cause the pile head to break and the pile body to crack. This damaged prefabricated pile will cause the corrosion of the prestressed tendons and the strength of the concrete to be damaged in the presence of groundwater or corrosive minerals. In addition, the bearing capacity of prefabricated pipe piles is mostly derived from the friction force on the pile side, and its pile end resistance value is relatively low, so the overall bearing capacity is relatively low.

[0003] Patent document No. ZL200410102711.6 discloses a method for constructing concrete piles, in which the pile body is made of prestressed pipe piles, and operations such as packing compaction and concrete pouring are directly carried out in the middle hole of the pipe piles, which effectively forms a composite carrier and can ensure the quality of the pile end joint, improve the qualified rate of the piles, and reduce the settlement of the piles. This technology effectively brings into play the advantages of prefabricated pipe piles and carriers, and has the advantages of high single pile bearing capacity and reliable quality. However, due to the lack of key processes for closing and opening the bottom of the pipe piles, the pipe piles are easily distorted or leaked during sinking, and water and soil are easily intruded into the bottom of the pipes during the carrier construction, which seriously affects the construction effect and even causes waste piles, so it cannot be widely used in engineering.

[0004] The combination of prefabricated pipe piles and carrier piles is a very good combination that can give full play to their respective advantages, but it is not a very simple process combination, and corresponding innovation and adjustment of processes and equipment are required. The closing and opening of the bottom of the prefabricated pipe pile is a very critical process, because the inner hole of the pipe pile will be used for filling and tamping construction later, which requires that the inner hole of the prefabricated pipe pile is clean when it sinks to the set depth. In addition to preventing the soil, it is also necessary to prevent the water in the soil from entering the inner hole. At the same time, because the inner hole of the pipe pile will be used for filling and tamping construction later, the bottom of the prefabricated pipe pile cannot be closed after it sinks into place. Therefore, the requirements for the closure of the bottom of the pipe pile are twofold, that is, it requires considerable sealing and requires that it can be easily and quickly detached from the bottom of the pipe pile.

[0005] Therefore, people hope to provide a bottom sealing treatment method for prefabricated pipe piles that meets the high bearing capacity requirements and is applicable to various geological soil layers and is applicable to the application in combination with the carrier pile process. Summary of the invention

[0006] The present invention is proposed to solve the above-mentioned problems, and aims to provide a bottom sealing processing method for prefabricated pipe piles. According to the need of combining the prefabricated pipe piles with carrier piles, a special bottom sealing steel plate or a prefabricated pile tip is used to seal the bottom end of the prefabricated pipe pile by a special process. After reaching the designed depth, the prefabricated pipe pile can be easily and conveniently separated from the prefabricated pipe pile without causing damage to the pipe pile itself, thereby improving construction efficiency and ensuring project quality.

[0007] In order to achieve the above-mentioned purpose, a bottom sealing device of a prefabricated pipe pile of the present invention is characterized in that: the bottom sealing device is used to seal the bottom end of the prefabricated pipe pile in advance, and the prefabricated pipe pile can effectively prevent soil and water from entering the inner hole of the prefabricated pipe pile when the prefabricated pipe pile is sunk into the foundation soil; after the prefabricated pipe pile is sunk into place, the bottom sealing device can be easily and quickly separated from the bottom of the prefabricated pipe pile by hammering or squeezing, without causing damage to the pipe pile, so as to form a channel for subsequent carrier construction; The bottom sealing device is fixedly connected to the end plate at the bottom of the prefabricated pipe pile, and the bottom sealing device includes two forms: a bottom sealing steel plate or a prefabricated pile tip; Specifically, one method of using a bottom cover steel plate for bottom cover processing is: Specifications of bottom steel plate: The bottom steel plate is circular or polygonal, the diameter of the steel plate is more than 3cm larger than the inner hole diameter of the prefabricated pipe pile, the thickness of the steel plate is not less than 6mm, and the thickness of the steel plate increases according to the increase of the area to ensure that the bottom steel plate does not deform when sinking into the prefabricated pipe pile; Sealing method of bottom steel plate: When the prefabricated pipe pile is only required to prevent soil gushing, the bottom steel plate and the end plate of the pipe pile are welded by spot welding, with 3-8 welding points; when the prefabricated pipe pile is required to prevent soil gushing and water ingress, the bottom steel plate and the end plate of the pipe pile are welded by full welding, the weld is airtight and leak-proof, and the weld strength is lower than the conventional standard requirements; to ensure that the bottom steel plate can be easily separated from the bottom of the pile by moderate impact, and does not cause damage to the prefabricated pipe pile; Separation method of bottom steel plate: After the prefabricated pipe pile sinks to the designed depth, for the bottom steel plate that adopts the spot welding method, a column hammer with a weight of not less than 2t and a diameter less than 2cm in the inner hole is placed in the inner hole of the prefabricated pipe pile, and the column hammer is lifted to tamp the bottom steel plate to separate it from the end plate of the pipe pile; for the bottom steel plate that adopts the full welding method, first fill the bottom of the inner hole of the prefabricated pipe pile with a cement sand mixture with a height of less than 100cm, and then place a column hammer with a diameter less than 2cm in the inner hole of the prefabricated pipe pile. The weight of the column hammer is The pressure per square meter generated by the column hammer is not less than 2t and is greater than the fa value of the soil at the pile end. Then the column hammer is slowly slid to the surface of the cement sand, and then the cement sand mixture is rammed with a low drop distance and small energy to squeeze the bottom steel plate to separate it from the pile end plate. In this method, a diesel hammer or hydraulic hammer connected to an inner ramming pipe can be used instead of the column hammer, or a static press connected to an inner pipe can be used to directly extrude the bottom steel plate or the pre-filled cement sand mixture in the inner hole of the prefabricated pile to separate the bottom steel plate from the pile end plate. Another method of using prefabricated pile tips for bottom sealing is: Specifications of prefabricated pile tip: The prefabricated pile tip is prefabricated as a whole with a lower concrete pile tip and an upper flat steel plate. The diameter of the concrete pile tip is not larger than the diameter of the prefabricated pipe pile, and the cross section is circular or polygonal. The lower concrete pile tip is a cone or a platform, and the diameter of the upper flat steel plate is larger than the inner hole diameter of the prefabricated pipe pile by more than 3 cm. Prefabricated pile tip sealing method: the upper flat steel plate of the prefabricated pile tip is butt-jointed with the end plate of the prefabricated pipe pile and welded into one piece. The specific welding method is the same as the above-mentioned bottom steel plate sealing method; Prefabricated pile tip detachment method: The specific detachment method is the same as the detachment method of the above-mentioned bottom steel plate.

[0008] In engineering applications, you can choose bottom steel plates or prefabricated pile tips according to different geological conditions. When the geological soil layer is relatively hard, you can choose prefabricated pile tips, which can reduce resistance when drilling and have higher efficiency. When the geological soil layer is relatively soft, choose bottom steel plates, which are relatively easier to purchase and have lower costs.

[0009] Preferably, the prefabricated pipe piles include prestressed pipe piles, prefabricated hollow bamboo piles, and prefabricated hollow square piles.

[0010] Preferably, the subsequent carrier construction is to fill the central channel of the prefabricated pipe pile with cement-sand mixture, and reinforce and compact the soil at the bottom of the pile with the cement-sand mixture by hammering with a column hammer or squeezing with an inner pipe.

[0011] It is best to avoid the outer edge of the bottom steel plate from coinciding with the screw hole position on the end plate of the prefabricated pipe pile, firstly to avoid affecting the welding quality, and secondly to avoid affecting the operation of adding anti-pullout reinforcement at the screw hole.

[0012] Preferably, a conical or cross-shaped steel body can be added to one side of the bottom steel plate to facilitate the sinking of the prefabricated pipe piles into the foundation soil.

[0013] Preferably, the above-mentioned weld strength lower than the conventional standard requirement means: the weld strength is lower than 50% of the tensile strength of the precast pipe pile end plate, the tensile strength of the precast pipe pile end plate is referenced according to the specific specifications of the selected precast pipe pile, or the weld angle height is less than 50% of the thickness of the bottom steel plate. The purpose of reducing the weld strength is to ensure that the bottom steel plate can be easily separated from the pile bottom by moderate impact and does not cause damage to the precast pipe pile.

[0014] Preferably, the square meter pressure generated by the column hammer is greater than the fa value of the soil at the pile end, where the square meter pressure generated by the column hammer is calculated by dividing the weight of the column hammer by the bottom area of ​​the column hammer. The fa value is the bearing capacity characteristic value corrected by the depth of the soil, and the calculation formula is f a =f ak ﹢η d γ0(d﹣0.5),where f ak is the characteristic value of the foundation bearing capacity of the reinforced soil layer, i.e. the soil layer at the bottom of the pile, η d is the foundation bearing capacity correction coefficient for the foundation depth, γ0 is the weighted average weight of the soil above the base, and d is the foundation embedment depth. Generally speaking, the larger the bearing capacity characteristic value fa after the depth of the reinforced soil layer is, the greater the weight of the selected column hammer should be. The larger the bottom area of ​​the column hammer, that is, the thicker the hammer body, the greater the weight of the selected column hammer should be.

[0015] Preferably, in the above-mentioned method of disengaging the bottom steel plate, a column hammer may be placed in the inner hole of the prefabricated pipe pile first and then a cement-sand mixture may be filled into the bottom of the inner hole of the prefabricated pipe pile.

[0016] The beneficial effects of the bottom sealing treatment method of the above-mentioned prefabricated pipe pile are: ① providing a variety of bottom sealing treatment forms to meet the needs of different engineering and geological conditions, improving work efficiency and saving costs; ② good sealing effect, when the prefabricated pipe pile is sunk in the soil, it can effectively prevent the soil and water in the foundation soil from entering the inner hole, and after the prefabricated pipe pile is sunk into place, the bottom sealing device can be easily and quickly separated from the bottom end of the pipe pile by hammering in the inner hole of the pipe pile; ③ by reducing the number of welding points or the strength requirements of the weld, it is ensured that the prefabricated pipe pile is not damaged when it is separated from the bottom end of the pipe pile; ④ simple material acquisition and production, easy to purchase, extremely low cost, and convenient assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic structural diagram of an embodiment of a method for processing the bottom sealing of a prefabricated pipe pile according to the present invention. Figure 2 Schematic diagram of the construction process of this embodiment.

[0018] Figure 1 , Figure 2Among them, 1 is a prefabricated pipe pile, 2 is the inner hole of the pipe pile, 3 is a bottom steel plate, 4 is an end plate of the pipe pile, 5 is a welding angle, 6 is a column hammer, and 7 is a cement-sand mixture. DETAILED DESCRIPTION

[0019] Figure 1 Schematic diagram of an embodiment of the bottom sealing treatment method of prefabricated pipe piles of the present invention. In this embodiment, the geological soil layer is relatively weak and there is groundwater, and the prefabricated pipe piles have dual requirements of preventing soil gushing and preventing water ingress, so a steel plate bottom sealing is adopted; Figure 1 As shown, the model of the prefabricated pipe pile 1 is PHC500 (100) B, the diameter of the inner hole 2 of the pipe pile is 300 mm, the specifications of the bottom steel plate 3 are circular, 360 mm in diameter and 8 mm in thickness, and the bottom steel plate 3 is concentrically fitted with the pipe pile end plate 4 and then welded by full welding. The weld is required to be continuous and full, and the height of the weld angle 5 of the weld is less than 4 mm, so as to ensure that the bottom steel plate is airtight and leak-proof and can be easily separated from the pile bottom without causing damage to the prefabricated pipe pile.

[0020] Figure 2 Schematic diagram of the construction process of this embodiment. Figure 2 As shown in a, the prefabricated pipe pile 1 with bottom sealing treatment is sunk into the foundation soil to the designed depth; then, as shown in Figure 2 As shown in b, fill the inner hole 2 of the pipe pile with cement sand mixture 7, the height of the cement sand mixture 7 in the inner hole 2 of the pipe pile is 60cm; then, as shown in Figure 2 As shown in Figure c, a column hammer 6 is placed in the inner hole 2 of the pile. The column hammer 6 has a diameter of 260 mm and a weight of 3.8 tons. The column hammer 6 is slowly lowered down; then, Figure 2 d, the cement sand mixture 7 is rammed with a small energy at a drop distance of no more than 2m and the bottom steel plate 1 is squeezed, and then, as shown in FIG. Figure 2 As shown in e, the bottom steel plate 1 is separated from the pile end plate 4; then, Figure 2 As shown in f, continue to fill in the cement sand mixture and use the column hammer to hammer, gradually forming the pile end carrier.

[0021] The above embodiments are merely illustrative rather than restrictive, and the protection scope of the present invention cannot be limited thereto. Other different forms of changes or modifications derived from the above descriptions are still within the protection scope of the present invention.

Claims

1. A method for bottom sealing of prefabricated pipe piles, characterized in that: The bottom sealing device is used to seal the bottom of the prefabricated pipe pile in advance, which can effectively prevent soil and water from entering the inner hole of the prefabricated pipe pile when the prefabricated pipe pile is sunk into the foundation soil. After the prefabricated pipe pile is sunk into place, the bottom sealing device can be easily and quickly detached from the bottom of the prefabricated pipe pile by hammering or squeezing without causing damage to the pipe pile, forming a channel to facilitate subsequent carrier construction. The bottom sealing device is fixedly connected to the end plate at the bottom of the prefabricated pipe pile, and the bottom sealing device includes two forms: a bottom sealing steel plate or a prefabricated pile tip; Specifically, one method of using a bottom cover steel plate for bottom cover processing is: Specifications of bottom steel plate: The bottom steel plate is circular or polygonal, and the diameter of the steel plate is more than 3cm larger than the inner diameter of the prefabricated pipe pile. The outer edge of the bottom steel plate should not overlap with the screw holes on the end plate of the prefabricated pipe pile. The thickness of the steel plate is not less than 6mm, and the thickness of the steel plate increases according to the increase of the area to ensure that the bottom steel plate does not deform when it is sunk into the prefabricated pipe pile. Sealing method of bottom steel plate: When the prefabricated pipe pile is only required to prevent soil gushing, the bottom steel plate and the end plate of the pipe pile are welded by spot welding, with 3-8 welding points; when the prefabricated pipe pile is required to prevent soil gushing and water ingress, the bottom steel plate and the end plate of the pipe pile are welded by full welding, the weld is airtight and leak-proof, and the weld strength is lower than the conventional standard requirements; to ensure that the bottom steel plate can be easily separated from the bottom of the pile by moderate impact, and does not cause damage to the prefabricated pipe pile; Separation method of bottom steel plate: After the prefabricated pipe pile sinks to the designed depth, for the bottom steel plate that adopts the spot welding method, a column hammer with a weight of not less than 2t and a diameter less than 2cm in the inner hole is placed in the inner hole of the prefabricated pipe pile, and the column hammer is lifted to tamp the bottom steel plate to separate it from the end plate of the pipe pile; for the bottom steel plate that adopts the full welding method, first fill the bottom of the inner hole of the prefabricated pipe pile with a cement sand mixture with a height of less than 100cm, and then place a column hammer with a diameter less than 2cm in the inner hole of the prefabricated pipe pile. The weight of the column hammer is The pressure per square meter generated by the column hammer is not less than 2t and is greater than the fa value of the soil at the pile end. The column hammer is then slowly slid to the cement sand surface, and then the cement sand mixture is rammed with a low drop distance and small energy to squeeze the bottom steel plate to separate it from the pile end plate. In this method, a diesel hammer or hydraulic hammer connected to an inner ramming pipe can be used instead of a column hammer, or a static press connected to an inner pipe can be used to directly squeeze the bottom steel plate or the pre-filled cement sand mixture in the inner hole of the prefabricated pile to separate the bottom steel plate from the pile end plate. Another method of using prefabricated pile tips for bottom sealing is: Specifications of prefabricated pile tip: The prefabricated pile tip is prefabricated as a whole with a lower concrete pile tip and an upper flat steel plate. The diameter of the concrete pile tip is not larger than the diameter of the prefabricated pipe pile, and the cross section is circular or polygonal. The lower concrete pile tip is a cone or a platform, and the diameter of the upper flat steel plate is larger than the inner hole diameter of the prefabricated pipe pile by more than 3 cm. Prefabricated pile tip sealing method: the upper flat steel plate of the prefabricated pile tip is butt-jointed with the end plate of the prefabricated pipe pile and welded into one piece. The specific welding method is the same as the above-mentioned bottom steel plate sealing method; The method of detaching the prefabricated pile tip is the same as the method of detaching the above-mentioned bottom steel plate.

2. The bottom sealing treatment method of the prefabricated pipe pile according to claim 1 is characterized in that The above-mentioned prefabricated pipe piles include prestressed pipe piles, prefabricated hollow bamboo piles, and prefabricated hollow square piles.

3. The bottom sealing treatment method of the prefabricated pipe pile according to claim 1 is characterized in that The subsequent carrier construction mentioned above refers to: filling the central channel of the prefabricated pipe pile with a cement-sand mixture, and reinforcing and compacting the soil at the bottom of the pile with the cement-sand mixture by hammering with a column hammer or squeezing with an inner pipe.

4. The bottom sealing treatment method of the prefabricated pipe pile according to claim 1 is characterized in that A conical or cross-shaped steel body can be added to one side of the bottom steel plate to facilitate the sinking of the prefabricated pipe piles into the foundation soil.

5. The bottom sealing treatment method of prefabricated pipe pile according to claim 1, characterized in that The above-mentioned weld strength being lower than the conventional standard requirements means that the weld strength is lower than 50% of the tensile strength of the prefabricated pipe pile end plate, or the weld angle height is less than 50% of the thickness of the bottom steel plate.

6. The bottom sealing treatment method of the prefabricated pipe pile according to claim 1, characterized in that The square meter pressure generated by the above-mentioned column hammer is greater than the fa value of the soil at the pile end. The square meter pressure generated by the column hammer is calculated by dividing the weight of the pile hammer by the bottom area of ​​the pile hammer. The fa value is the bearing capacity characteristic value corrected by the depth of the soil. The calculation formula is f a =f ak ﹢η d γ0(d﹣0.5),where f ak is the characteristic value of the foundation bearing capacity of the reinforced soil layer, η d is the foundation bearing capacity correction coefficient for the foundation burial depth, γ0 is the weighted average density of the soil above the base, and d is the foundation burial depth.

7. The bottom sealing treatment method of prefabricated pipe pile according to claim 1, characterized in that In the above-mentioned method of detaching the bottom steel plate, a column hammer can also be placed in the inner hole of the prefabricated pipe pile first and then a cement sand mixture is filled into the bottom of the inner hole of the prefabricated pipe pile.

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