Prestressed high-strength concrete pipe pile anti-pulling connecting device and construction method

Abstract

The invention relates to the technical field of tubular pile foundation engineering, in particular to a prestressed high-strength concrete tubular pile anti-pulling connecting device and a construction method, and the prestressed high-strength concrete tubular pile anti-pulling connecting device comprises an upper-section tubular pile and a lower-section tubular pile, the bottom end of the lower-section pipe pile is provided with a pile tip, and the top end of the lower-section pipe pile is provided with a second connecting end plate and is welded with the first connecting end plate; the core filling concrete is internally provided with a reinforcement cage and is of an integrated structure; the reinforcement cage is placed in the upper-section pipe pile and the lower-section pipe pile, and the core filling concrete is formed after concrete is poured, so that the upper-section pipe pile and the lower-section pipe pile are connected into a whole; the upper-section pipe pile and the lower-section pipe pile are connected in a two-end-plate welding mode, meanwhile, mechanical connection is replaced by core filling concrete formed by concrete core filling in the pipe piles, the welding connection and concrete core filling mode can meet the connection requirement of the pipe piles in the strong corrosion environment, and meanwhile, due to the fact that mechanical connection is not adopted, the connection cost is reduced. The use of mechanical joints is reduced, and the construction cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe pile foundation engineering, and in particular to a prestressed high-strength concrete pipe pile uplift connection device and a construction method thereof. Background Art

[0002] As a commonly used precast component in foundation engineering, pipe piles are widely used in various large-scale infrastructure construction projects due to their strong bearing capacity, convenient construction, good durability, strong adaptability, and good economy. Among them, the single pile of prestressed high-strength concrete pipe piles (PHC pipe piles) has a higher bearing capacity than ordinary pipe piles. Especially in areas with high groundwater levels, when the load of the upper structure cannot balance the groundwater buoyancy, PHC uplift pipe piles are widely used due to their strong uplift resistance, high self-strength, good durability, high construction efficiency, and low cost.

[0003] During pipe pile construction, in some cases, the lateral friction provided by a single pipe pile cannot meet the uplift requirements of the building, and pile splicing is often required. Pile splicing means that since the length of a single pile cannot reach the designed depth, precast piles need to be connected one by one and continue to be driven down until the designed depth is reached.

[0004] The current national "Technical Standard for Prestressed Concrete Pipe Piles" (JGJ / T 406-2017) stipulates that pipe piles used for uplift should preferably adopt special mechanical connection joints or welded joints designed specifically. When mechanical joints are used in a strongly corrosive environment, welded connections should preferably be used at the same time. At present, when connecting uplift pipe piles in a strongly corrosive environment, most of them adopt a combination of mechanical joint connection and welded connection. Mechanical joint connection refers to using unique mechanical components to fix the upper and lower pipe piles together, and welded connection refers to welding at the contact surface of the end plates of the upper and lower pipe piles. However, this method has the following problems:

[0005] First, the mechanical joints and welds will be corroded by substances such as acids, alkalis, and salts in the environment, resulting in the destruction of the connection of the pipe piles.

[0006] Second, the construction cost of the mechanical connection device is relatively high. Under the condition that the welded connection meets the connection strength requirements, the use of mechanical joints will cause waste of materials. In addition, mechanical connection still requires workers to be familiar with the installation and debugging process of the connection device, increasing the construction cost.

[0007] Third, the process of the mechanical connection method is complex, resulting in great restrictions on the application of precast piles in engineering uplift piles. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a prestressed high-strength concrete pipe pile uplift connection device and construction method. By using the methods of welding and concrete core filling to replace the pipe pile connectors for connecting the pipe piles, the connection requirements of the pipe piles in a strong corrosion environment can be met, while reducing the use of connectors and lowering the construction cost. To achieve the above purpose, the present invention is realized through the following technical solutions:

[0009] In the first aspect, the present invention provides a prestressed high-strength concrete pipe pile uplift connection device, including

[0010] The upper pipe pile, with a first connection end plate provided at the bottom end;

[0011] The lower pipe pile, with a pile tip provided at the bottom end and a second connection end plate provided at the top end and welded to the first connection end plate;

[0012] The core-filled concrete, which is an integral structure with a steel reinforcement cage inside; the steel reinforcement cage is placed inside the upper pipe pile and the lower pipe pile, and after pouring concrete, the core-filled concrete is formed to connect the upper pipe pile and the lower pipe pile to form a whole.

[0013] As a further implementation method, the first connection end plate, the second connection end plate and the weld seam between the two are all covered with anti-corrosion coatings.

[0014] As a further implementation method, the steel reinforcement cage includes structural steel bars at the top end, a supporting plate at the bottom end, and main steel bars and stirrups arranged in the middle. The structural steel bars support the steel reinforcement cage to fix it in a preset position.

[0015] As a further implementation method, the penetration length of the steel reinforcement cage is the same as the length of the core-filled concrete, and the lowest filling position of the core-filled concrete is not lower than 3m below the pipe pile connection.

[0016] As a further implementation method, it further includes a foundation cap formed by pouring, located at the top of the upper pipe pile and provided with foundation cap steel bars inside; the top end of the main steel bars is connected with anchor bars, and the anchor bars extend into the foundation cap and are tied and connected with the foundation cap steel bars.

[0017] As a further implementation method, the upper pipe pile is embedded in the foundation cap to a set depth.

[0018] As a further implementation method, the anchor bars are bent outward.

[0019] As a further implementation method, a cushion layer is provided around the top of the upper pipe pile, located between the foundation cap and the foundation soil.

[0020] As a further implementation method, the inner walls of the upper section of the pipe pile and the lower section of the pipe pile are both coated with slightly expanding concrete.

[0021] In a second aspect, the present invention provides a construction method for the anti-pulling connection device of the prestressed high-strength concrete pipe pile according to the first aspect, including the following steps:

[0022] Precast the upper section of the pipe pile and the lower section of the pipe pile in the factory, and transport them to the construction site after passing the acceptance. Set out the center of the pile position, lift the precast pile so that the pile tip aligns with the center point of the pile position, press the lower section of the pipe pile to the bottom by a static pile press and check the verticality. Connect the upper section of the pipe pile to the top of the lower section of the pipe pile, conduct joint acceptance and apply anti-corrosion paint, press the upper section of the pipe pile and check the verticality. Clean the inside of the upper section of the pipe pile and the lower section of the pipe pile, place the steel reinforcement cage after hoisting, then conduct concrete core filling, embed the anchor reinforcement at the pile top, and construct the foundation cap.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. When the present invention connects the upper section of the pipe pile and the lower section of the pipe pile by welding the two end plates, the core filling concrete formed by concrete core filling inside the pipe pile is used to replace mechanical connection. The welding connection and concrete core filling methods can meet the connection requirements of the pipe pile in a strong corrosion environment. In addition, this structure does not use mechanical connection, reducing the use of mechanical joints, greatly reducing the construction cost. And it reduces the construction steps of mechanical connection, reduces the construction difficulty of workers, and reduces the labor cost. Compared with mechanical connection, the core filling concrete can not only strengthen the connection of the pipe pile, but also greatly increase the ability of the pile top to resist horizontal loads, and at the same time can evenly transfer the uplift load to the pile body, with more extensive functions.

[0025] 2. The first connection end plate, the second connection end plate and the weld between the two are all covered with anti-corrosion paint. The anti-corrosion paint can effectively prevent the erosion and damage of the pipe pile connection in a strong corrosion environment, and prevent substances such as acids, alkalis, and salts from penetrating into the pipe pile to cause corrosion of the steel bars and concrete.

[0026] 3. The core filling concrete of the present invention uses non-full-length concrete core filling. Compared with full-length core filling, it effectively saves materials and construction costs under the condition that the calculation meets the requirements.

[0027] 4. The present invention embeds anchor reinforcement at the top of the upper section of the pipe pile, and connects the upper section of the pipe pile to the foundation cap through the anchor reinforcement, enhancing the integrity of the upper section of the pipe pile and the upper structure, and effectively improving the anti-pulling performance of the pipe pile. At the same time, a high-density asphalt concrete cushion is used, which has good waterproof performance and can effectively isolate the penetration of groundwater, and the asphalt concrete cushion has good corrosion resistance. Description of the Drawings

[0028] The accompanying drawings of the specification, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0029] Figure 1 It is a schematic diagram of the upper section of a pipe pile and the structure above it in an embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the uplift connection device in an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the installation of the pile tip in an embodiment of the present invention;

[0032] Figure 4 It is the present invention Figure 1 Schematic diagram of the A-A cross-sectional structure in;

[0033] Figure 5 It is the present invention Figure 1 Schematic diagram of the B-B cross-sectional structure in;

[0034] Figure 6 It is a schematic diagram of the end plate structure in an embodiment of the present invention;

[0035] Figure 7 It is a bottom view of the pile tip structure in an embodiment of the present invention;

[0036] Figure 8 It is a schematic diagram of the welding joint structure in an embodiment of the present invention.

[0037] In the figure: The distances or sizes between each part are exaggerated for showing the positions of each part, and the schematic diagram is only for illustration.

[0038] Wherein: 1, main reinforcement; 2, structural reinforcement; 3, stirrup; 41, free end plate; 42, first connection end plate; 43, second connection end plate; 5, upper section of pipe pile; 6, core filling concrete; 7, supporting plate; 8, pile tip; 9, prestressed steel bar hole; 10, lower section of pipe pile; 11, pile sleeve hoop; 12, anticorrosive coating; 13, foundation cap; 14, cushion layer, 15, anchoring steel bar. Detailed implementation manners

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] Embodiment 1

[0041] In a typical implementation manner of the present invention, referring to Figure 1 , Figure 2 and Figure 3As shown in the figure, a prestressed high-strength concrete pipe pile uplift connection device includes an upper section pipe pile 5, a lower section pipe pile 10, a foundation cap 13, and core filling concrete 6.

[0042] The upper section pipe pile 5 and the lower section pipe pile 10 are prestressed concrete pipe piles, which are precast in a precast component processing factory. After curing to reach the design strength, they are transported to the construction site and pressed into the soil by a pile foundation. Then, the foundation cap 13 is poured on the top of the pile. Compared with other piles, prestressed concrete pipe piles have strong load-bearing capacity, small settlement deformation, simple construction, and high efficiency. A pile tip 8 is connected to the very front end of the lower section pipe pile 10 to facilitate driving into the underground soil layer. The concrete strength of the pile body is determined according to the design requirements. In this embodiment, the cement variety of the pile body is ordinary Portland cement, and the concrete strength of the pile body is C80.

[0043] The bottom end of the upper section pipe pile 5 is provided with a first connection end plate 42, and the top end is provided with a free end plate 41. The bottom end of the lower section pipe pile 10 is provided with a pile tip 8, and the top end is provided with a second connection end plate 43 which is welded to the first connection end plate 42. The free end plate 41, the first connection end plate 42, and the second connection end plate 43 are all made of Q235B steel and have a thickness of 50 mm. As Figure 6 and Figure 8 shown, the aperture of the prestressed steel bar hole 9 on the end plate is determined according to the steel bars in the prestressed concrete pipe pile to ensure that the steel bars can pass through. The end plate, as the medium for welding between pipe piles and between pipe piles and the upper structure, can bear the pile body load and ensure the stability of the structure. When the steel cage in the pipe pile is prestressed and tensioned, the end plate can act as an anchor for the steel bars to bear the role of anchoring the steel bars.

[0044] As Figure 8 shown, a welded joint composed of a pile sleeve hoop 11 and a first connection end plate 42 is used to connect the upper and lower section pipe piles. The welded joint is installed after the pipe pile is formed. The pile sleeve hoop 11 is rolled into a cylindrical shape with a Q235B steel plate, and the joints are welded and the circle is made round. The thickness is between 1.5 and 2.0 mm, and the inner diameter of the pile sleeve hoop 11 is slightly larger than the pile body diameter.

[0045] The core filling concrete 6 is provided with a steel cage and is an integral structure; the steel cage is placed in the upper section pipe pile 5 and the lower section pipe pile 10, and concrete is poured to form the core filling concrete 6 so that the upper section pipe pile 5 and the lower section pipe pile 10 are connected to form a whole.

[0046] In this embodiment, the upper section of the pipe pile 5 and the lower section of the pipe pile 10 are connected by welding the two end plates. At the same time, the core-filled concrete formed by pouring concrete into the pipe pile is used to replace mechanical connection. The welding connection and the concrete core filling method can meet the connection requirements of the pipe pile in a strong corrosion environment. In addition, this structure does not use mechanical connection, reducing the use of mechanical joints and significantly reducing the construction cost. Moreover, it reduces the construction steps of mechanical connection, reduces the construction difficulty of workers, and reduces the labor cost. Compared with mechanical connection, the core-filled concrete can not only strengthen the connection of the pipe pile but also greatly increase the ability of the pile top to resist horizontal loads. At the same time, it can evenly transfer the uplift load to the pile body, with more extensive functions.

[0047] The inner walls of the upper section of the pipe pile 5 and the lower section of the pipe pile 10 are both coated with slightly expanding concrete to improve the integrity of the core-filled concrete 6 and the pile bodies of the upper section of the pipe pile 5 and the lower section of the pipe pile 10.

[0048] The first connecting end plate 42, the second connecting end plate 43, and the weld between the two are all covered with an anti-corrosion coating 12. The anti-corrosion coating 12 can effectively prevent the weak part of the welding from being corroded in a strong corrosion environment, thereby avoiding the corrosion of the inside of the prestressed concrete pipe pile. In this embodiment, a resin glass flake coating is used and brushed three times, and the coating thickness is not less than 1 mm. The resin glass flake coating has good chemical resistance and can effectively prevent the corrosion of metal substances by acids, alkalis, salts, etc. And the coating formed by this coating has a strong adhesion to the metal surface, effectively preventing the coating from falling off.

[0049] As Figure 2 、 Figure 4 and Figure 5 shown, the steel reinforcement cage includes the structural steel bars 2 at the top, the pallet 7 at the bottom, and the main steel bars 1 and stirrups 3 arranged in the middle.

[0050] The main steel bars 1 play a role in enhancing the bonding force and tensile resistance. The steel bar material and specific dimensions are determined according to the design requirements. To ensure the firm connection of the pile body, the main steel bars 1 extend 3 - 5 m below the pipe pile connection, and the specific penetration length is determined by calculation. In this embodiment, HRB400 steel bars are used, with a steel bar diameter of 22 mm and extending 3 m below the pipe pile connection.

[0051] The structural steel bars 2 are used to fix the steel reinforcement cage in the pipe pile and are perpendicularly welded to the top of the main steel bars 1. In this embodiment, HRB400 steel bars are used, with a diameter of 12 mm.

[0052] The stirrups 3 can fix the main steel bars 1 and prevent the main steel bars 1 from shifting. In this embodiment, HPB235 steel bars are used, with a diameter between 6 - 10 mm and arranged at intervals of 200 mm.

[0053] The pallet 7 is made of a circular thin steel plate with a thickness of 5 mm, and the steel plate material is Q235B steel, mainly playing the role of supporting the concrete and preventing the concrete from falling.

[0054] The structural steel bars 2 support the steel reinforcement cage to fix it in the preset position. The depth of the steel reinforcement cage penetration is the same as the length of the core filling concrete 6, and the lowest filling position of the core filling concrete 6 is not less than 3 m below the pipe pile connection. It can be understood that the core filling concrete 6 in this embodiment adopts non-full-length concrete core filling, which can effectively save materials and construction costs under the condition that the calculation meets the requirements. C40 self-compacting concrete is used for non-full-length core filling in this embodiment.

[0055] As Figure 3 and Figure 7 shown, the pile tip 8 is installed at the very front end of the pipe pile and is installed on the pipe pile head during the pipe pile sinking construction, playing the roles of guiding and plugging. A closed cross-shaped pile tip is adopted in this embodiment, and the pile tip material is made of Q235B steel.

[0056] As Figure 1 shown, it also includes a foundation cap 13 formed by pouring at the pile top (located at the top of the upper section of the pipe pile 5), with the foundation cap 13 steel bars built-in; the top end of the main reinforcement 1 is connected with the anchoring steel bars 15, and the anchoring steel bars 15 are bent outward. The anchoring steel bars 15 extend into the foundation cap 13 and are tied and connected with the foundation cap 13 steel bars. The anchoring steel bars 15 are the key structure connecting the upper section of the pipe pile 5 and the foundation cap 13 to ensure the coordinated force of the pipe pile and the upper structure. HRB400 steel bars with a diameter of 22 mm and a length of 800 mm are adopted in this embodiment.

[0057] The upper section of the pipe pile 5 is embedded in the foundation cap 13 to a set depth. The foundation cap 13 is anchored with the anchoring steel bars 15 to connect the upper section of the pipe pile 5 and the upper structure. The current national "Code for Design of Building Foundation" (GB50007-2011) stipulates that the length of the pile top embedded in the cap should not be less than 50 mm, and the anchoring length of the main reinforcement 1 extending into the foundation cap 13 should not be less than 30 times the steel bar diameter (HPB235) and 35 times the steel bar diameter (HRB335 and HRB400). The foundation cap 13 can transfer the load and coordinate the deformation, enabling the prestressed pipe pile to better resist the uplift force.

[0058] C40 concrete is adopted in this embodiment. The concrete cover thickness of the steel bars in the foundation cap 13 is 50 mm, and the surface of the foundation is protected with 10 mm thick polymer cement mortar. This cement mortar can improve the corrosion resistance and crack resistance of the foundation cap 13. The pile top is embedded 50 mm into the foundation cap 13, and the anchoring steel bars 15 are bent and then extend into the foundation cap 13 with an extension length of 800 mm.

[0059] A cushion layer 14 is provided around the top of the upper precast concrete pile 5, located between the foundation cap 13 and the foundation soil, mainly serving the functions of leveling, isolation, drainage, and uniformly transferring loads. In this embodiment, C20 asphalt concrete with a thickness of 150 mm is used. This material is a special flexible material that can effectively relieve the stress concentration on the cap caused by uneven settlement of the foundation or differential deformation of the pile foundation. In addition, asphalt concrete also has the advantages of good waterproof performance, good corrosion resistance, fast construction, and no need for maintenance.

[0060] Embodiment 2

[0061] This embodiment provides a construction method for the anti-pulling connection device of prestressed high-strength concrete pipe piles as described in Embodiment 1, including the following steps:

[0062] S101. The pipe piles are precast in the factory and transported to the construction site after passing the acceptance.

[0063] After the upper precast concrete pile 5 and the lower precast concrete pile 10 are formed in the factory, the upper precast concrete pile 5 is connected to the free end plate 41 and the first connection end plate 42, and the lower precast concrete pile 10 is connected to the second connection end plate 43 and the pile tip 8. After passing the inspection, the connected upper precast concrete pile 5 and the lower precast concrete pile 10 are transported to the construction site for acceptance by the construction party. After the acceptance is correct, the construction begins.

[0064] S102. Set out the center of the pile position and lift the precast pile so that the pile tip aligns with the center point of the pile position.

[0065] According to the design drawings, drive a HPB235 steel bar with a diameter of 6.5 mm and a length of 35 - 40 cm into the ground at the center point of the pile position and mark it with red paint. After the positioning is completed, the static pressure pile driver is in place. After aligning with the pile position, adjust it to be horizontal and stable to ensure that the static pressure pile driver does not tilt or move during the construction process, so as to ensure the safety and stability of the construction process. After the static pressure pile driver is in place, lift the lower precast concrete pile 10, hoist the lower precast concrete pile 10 into the clamp of the static pressure pile driver, align the pile tip 8 with the center point of the pile position, pull out the positioning steel bar, clamp the lower precast concrete pile 10 and place it into the soil, move the pile driver to adjust the verticality of the pile body. After the verticality meets the specification requirements, adjust the pile driver to be horizontal and stable again.

[0066] S103. The static pressure pile driver presses the lower precast concrete pile to the bottom and checks the verticality.

[0067] Start the static pressure pile driver to slowly press the lower precast concrete pile 10 down, and control the pressing progress to meet the design requirements. The pile pressing should be continuous, and it is advisable to press each pile to the bottom at one time. During the pile pressing process, measure the verticality of the pile body. When the deviation of the pile body verticality is greater than the required specification, find out the reasons and try to correct them.

[0068] S104. Connect the upper precast concrete pile to the top of the lower precast concrete pile, conduct joint acceptance and brush anti-corrosion coatings.

[0069] When the lower section of the pipe pile 10 is pressed until the top of the pile is 0.5 - 1 m from the ground surface, the pile pressing is paused, and a guiding hoop is installed on the top of the lower section of the pipe pile 10. The upper section of the pipe pile 5 is hoisted into the clamp of the static pile press. After aligning the bottom of the upper section of the pipe pile 5 with the top of the lower section of the pipe pile 10, it is slowly placed into the guiding hoop. After ensuring that the two are straight, the upper section of the pipe pile 5 and the lower section of the pipe pile 10 are fixed with the guiding hoop. After the fixation is completed, the pile splicing of the upper section of the pipe pile 5 and the lower section of the pipe pile 10 is started. The pile splicing is carried out by electric welding. Before welding, first use a wire brush to remove the dirt and rust on the surfaces of the first connecting end plate 42 and the second connecting end plate 43. After the cleaning is completed, the guiding hoop is removed, and layered welding is carried out at the joint of the first connecting end plate 42 and the second connecting end plate 43. In this embodiment, the number of welding layers is three. After the inner layer welding is completed, the welding slag is first cleaned up before the outer layer welding is carried out. After the welding is completed, it is allowed to cool naturally. After the cooling is completed, the weld is inspected. The weld should be continuous and full. After passing the inspection, an anti-corrosion coating 12 is brushed around the first connecting end plate 42 and the second connecting end plate 43 to ensure that the weld and the areas around the first connecting end plate 42 and the second connecting end plate 43 are completely covered. The anti-corrosion coating can effectively reduce the erosion of substances such as acids, alkalis, and salts in the surrounding environment on the welded part, and can prevent the erosion substances from infiltrating into the interior of the pipe pile through the eroded weld and damaging the core filling concrete 6 and the steel reinforcement cage. In this embodiment, the anti-corrosion coating 12 uses a resin glass flake coating, which is brushed three times, and the brushing thickness is not less than 1 mm. The pile pressing can be continued only when the coating hardness reaches 100%. This coating has the advantages of corrosion resistance, good anti-permeability, wear resistance, simple construction, and easy repair, and can better complete the anti-corrosion and anti-seepage functions in this embodiment.

[0070] S105. Press the upper section of the pipe pile downwards and check the verticality.

[0071] After the anti-corrosion coating is brushed, the pile pressing is continued, and the specific steps are the same as those in step S103.

[0072] S106. Driving the pile or cutting the pile.

[0073] If the elevation of the pile top is lower than the natural elevation, a special steel pile driver is used to press the pile top to the design elevation. If there is a pile section exposed above the ground after the construction of a pile is completed, it needs to be cut off with a saw pile machine before removing the static pile press to prevent the pile head from being damaged during the construction process and ensure the integrity of the pipe pile. At the same time, cutting the pile can ensure that the top of the pipe pile is flat, which is convenient for connecting with the upper structure and improves the overall stability and safety of the structure.

[0074] S107. Clean the interiors of the upper and lower sections of the pipe pile, hoist the steel reinforcement cage, and then carry out concrete core filling.

[0075] Clean the inside of the pipe pile. If there is accumulated water in the pile core, lower the accumulated water to below 2 m. After cleaning, apply slightly expanding concrete to the inner wall of the pipe pile to improve the integrity of the core-filled concrete 6 with the upper section of the pipe pile 5 and the lower section of the pipe pile 10. Lift the steel reinforcement cage made of main reinforcement bars 1, structural reinforcement bars 2, stirrups 3 and bearing plates 7 into the pipe pile. The steel reinforcement cage is supported by the structural reinforcement bars 2 to fix the steel reinforcement cage at the preset position. Then start the pouring of the core-filled concrete 6. After pouring, use a vibrating rod for vibration, with a spacing of 300 - 400 mm and a time of 20 - 30 seconds. The length of the non-full-length concrete core filling is determined according to Clause 5.2.10 of the Standard Technical Standard for Prestressed Concrete Pipe Piles JGJ / T 406 - 2017 and shall not be less than 3 m below the connection of the pipe piles. The depth of the steel bars extending into the core is the same as the length of the concrete core filling. In this embodiment, C40 self-compacting concrete is used, the core filling height is 15 m, and the tensile steel bars extend 3 m downward from the joint. After core filling, check the density of the core-filled concrete 6. Confirm that there are no defects such as cavities and honeycombs by knocking on the pile body or ultrasonic testing. The concrete strength shall reach the design value, and specimens cured under the same conditions shall be taken for strength verification. Use a pneumatic pick or a cutting machine to break the loose concrete within 500 mm of the pile top until a fresh and dense concrete surface is exposed. Clean the crushed slag and floating slurry on the pile head to ensure that the pile top is clean and pollution-free.

[0076] S108. Embed the anchor reinforcement bars at the pile top.

[0077] After the loose concrete at the pile top is broken, use a wire brush to remove the dirt and rust on the surfaces of the anchor reinforcement bars 15 and the main reinforcement bars 1. After cleaning, pre-bend the anchor reinforcement bars 15 to ensure that the axes of the anchor reinforcement bars 15 and the main reinforcement bars 1 are aligned, and the gap between the anchor reinforcement bars 15 and the main reinforcement bars 1 is not greater than 3 mm. After alignment, fix the positions of the anchor reinforcement bars 15 by spot welding. The length of the spot welding is not less than 20 mm, and the spacing is not greater than 500 mm to avoid thermal deformation. After fixing the anchor reinforcement bars 15, carry out layered welding. In this embodiment, the number of welding layers is three. After the inner layer is welded, clean the welding slag first and then carry out the outer layer welding. After welding is completed, let it cool naturally. After cooling is completed, inspect the weld. The weld shall be continuous and full. The length of the weld is not less than 220 mm to ensure reliable connection.

[0078] S109. Carry out the construction of the foundation cap.

[0079] After the embedded anchoring steel bars 15 are completed, level and compact the area around the top of the upper section of the pipe pile 5. Then, lay a 150-mm-thick C20 asphalt concrete cushion 14 around the top of the pile. In this embodiment, the cushion is laid in layers, with each layer having a thickness of no more than 80 mm. After the laying is completed, let it cool naturally. After the temperature drops below 50 °C, inspect the thickness, flatness, and compactness of the cushion 14. The flatness requirement is that the height difference within every 2 m is no more than 5 mm. After the cushion 14 is laid, set up the formwork for the foundation cap 13 according to the design drawings. After the formwork is set up, apply a release agent to the inner side of the formwork and inspect the installation accuracy of the formwork, with the deviation being no more than 5 mm. After the formwork installation is completed, tie the steel bars inside the foundation cap 13 according to the design drawings. The anchoring steel bars 15 at the top of the pile are tied and connected to the steel bars inside the foundation cap 13 to form an integral stress system. After the tying of the anchoring steel bars 15 and the steel bars inside the foundation cap 13 is completed, pour the C40 concrete in layers, with each layer having a thickness of no more than 500 mm. After pouring, vibrate it thoroughly with a vibrator to avoid cold joints or air pockets. After the pouring is completed, cover it with a plastic film for moisture conservation for seven days. After the conservation is completed, remove the formwork, and conduct an in-situ inspection on the foundation cap 13. If it meets the relevant standards after the inspection, apply a 10-mm-thick polymer cement mortar on the surface of the foundation cap 13.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A prestressed high-strength concrete pipe pile pull-out connection device, characterized in that: include: The upper pipe pile has a first connecting end plate at the bottom end; The lower pipe pile has a pile tip at the bottom and a second connecting end plate at the top that is welded to the first connecting end plate; The core-filled concrete has a built-in steel cage and is an integrated structure; the steel cage is placed in the upper section pipe pile and the lower section pipe pile, and the core-filled concrete is formed after pouring concrete to connect the upper section pipe pile and the lower section pipe pile to form a whole.

2. A prestressed high-strength concrete pipe pile pull-out connection device according to claim 1, characterized in that: The first connecting end plate, the second connecting end plate and the weld therebetween are all covered with anti-corrosion coating.

3. The prestressed high-strength concrete pipe pile pull-out connection device according to claim 1, characterized in that: The steel cage comprises structural steel bars at the top, a support plate at the bottom, and main bars and stirrups arranged in the middle. The structural steel bars support the steel cage to fix it in a preset position.

4. A prestressed high-strength concrete pipe pile pull-out connection device according to claim 3, characterized in that: The depth of the steel cage is the same as the length of the core-filling concrete, and the lowest filling position of the core-filling concrete is not less than 3m below the connection point of the pipe piles.

5. The prestressed high-strength concrete pipe pile pull-out connection device according to claim 3, characterized in that: It also includes a foundation cap formed by casting, which is located on the top of the upper section of the pipe pile and has built-in foundation cap steel bars; the top of the main reinforcement is connected to an anchor steel bar, and the anchor steel bar extends into the foundation cap and is tied and connected to the foundation cap steel bar.

6. A prestressed high-strength concrete pipe pile pull-out connection device according to claim 5, characterized in that: The upper pipe pile is embedded in the foundation cap to a set depth.

7. The prestressed high-strength concrete pipe pile pull-out connection device according to claim 5, characterized in that: The anchoring steel bars are bent outwards.

8. The prestressed high-strength concrete pipe pile pull-out connection device according to claim 6, characterized in that: A cushion layer is arranged around the top of the upper pipe pile and is located between the foundation cap and the foundation soil.

9. The prestressed high-strength concrete pipe pile pull-out connection device according to claim 1, characterized in that: The inner walls of the upper pipe pile and the lower pipe pile are both coated with micro-expansive concrete.

10. The construction method of the prestressed high-strength concrete pipe pile pull-out resistant connection device according to any one of claims 1 to 9, characterized in that: The following steps are involved: The upper and lower pipe piles are prefabricated in the factory and transported to the construction site after acceptance. The pile center is determined by laying out the lines, the prefabricated pile is lifted so that the pile tip is aligned with the center point of the pile, the static pile driver presses the lower pipe pile to the bottom and checks the verticality, the upper pipe pile is connected to the top of the lower pipe pile, the joint is inspected and anti-corrosion paint is applied, the upper pipe pile is pressed down and the verticality is checked; the interior of the upper and lower canned pipe piles is cleaned, the steel cage is hoisted and the concrete is poured into the core, the pile top anchor steel bars are embedded, and the foundation cap is constructed.

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