Steel strand cast-in-place pile and construction method thereof

Abstract

The invention discloses a steel strand cast-in-place pile and a construction method thereof.The steel strand cast-in-place pile comprises a concrete pile body, a reinforcement cage and a plurality of steel strands, the reinforcement cage and the steel strands are embedded in the concrete pile body, the peripheries of the steel strands are sleeved with sleeves, the lower ends of the sleeves are provided with plugging pieces, and the plugging pieces are provided with through holes allowing the sleeves to penetrate through. The construction method has the effect of improving the construction efficiency.

Description

Technical Field

[0001] The present application relates to the field of construction engineering, and in particular to a steel strand bored pile and a construction method thereof. Background Art

[0002] In recent years, with the increasing development of urban construction and the widespread exploitation of underground space, underground buildings have required appropriate anti-floating measures. As the primary form of foundation anti-pullout protection, pull-out piles have been widely used in engineering practice. Currently, pull-out piles are mostly cast-in-place piles, buried deep underground to withstand the tensile forces transmitted from the superstructure. While these traditional cast-in-place piles have a strong load-bearing capacity, the low tensile strength of the pile concrete makes them susceptible to external factors, such as groundwater erosion, which reduces their service life.

[0003] The existing solution is to use steel strands in the reinforced cast-in-place piles to improve the structure's bearing capacity and seismic resistance. After the steel cage is installed, concrete is poured. Once the concrete reaches the designed strength, the steel strands are tensioned and fixed. During tensioning, pre-tensioning and the positioning of the tensioning anchor points should be determined according to the design requirements to avoid over-tensioning or under-tensioning. During fixing, it is necessary to ensure that the bond between the steel strands and the concrete is firm and reliable. After the steel strands are tensioned, the bearing capacity of the cast-in-place piles can be significantly improved. The steel strands can achieve the expected strength under lower stress conditions, thus avoiding excessive consumption and waste of materials.

[0004] Regarding the above-mentioned related technologies, there are the following defects: during prestressing, there is bonding between the steel strands and the concrete, which usually requires pre-reserving channels at the steel strand locations and performing grouting operations, which is more troublesome and reduces construction efficiency. Therefore, there is still room for improvement. Summary of the Invention

[0005] In order to improve construction efficiency, the present application provides a steel strand bored pile and a construction method thereof.

[0006] The present application provides a cast-in-place steel strand pile and a construction method thereof, which adopts the following technical solutions: A stranded cast-in-place pile comprises a concrete pile body, a steel cage and a plurality of strands buried in the concrete pile body. A sleeve is sleeved around the steel strands, a blocking piece is provided at the lower end of the sleeve, and a through hole is opened in the blocking piece for the sleeve to pass through.

[0007] By adopting the above technical solution, a sleeve is set around the outer periphery of the steel strand, thereby forming a protective structure around the outer periphery of the steel strand. The steel sleeve can protect the steel strand from erosion and damage by the external environment. It provides favorable conditions for the steel strand to withstand large tensile forces during the prestressing process. A sealing piece is set at both ends of the sleeve, and a through hole is opened in the sealing piece. The through hole is only for the sleeve to pass through. The sealing piece can block the grouting during grouting, reducing the probability of concrete penetrating into the sleeve when pouring concrete piles. The steel sleeve and the steel strand can slide relative to each other, reducing the bonding force between the steel strand and concrete. During the prestressing process, this sliding characteristic allows the steel strand to extend or shorten relatively freely when subjected to stress without being excessively restricted by the steel sleeve, which helps to reduce prestress loss and improve the efficiency of prestress transmission. There is no need to reserve a channel, which simplifies the construction steps of the steel strand pile and is conducive to improving the construction efficiency of the steel strand pile.

[0008] Preferably, the blocking member is a circular steel plate, which is welded and fixed to the end of the sleeve.

[0009] By adopting the above technical solution, a circular steel plate that matches the shape of the sleeve is used as a sealing piece, and the circular steel plate is fixed to the end of the sleeve by welding, which is beneficial to improving the connection stability and sealing between the sleeve and the sealing piece.

[0010] Preferably, the outer peripheral surface of the steel strand is covered with an epoxy resin layer.

[0011] By adopting the above technical solution, the epoxy resin layer protects the steel strand to protect the surface of the steel strand from corrosion and wear. Moreover, since there is a gap between the through hole and the steel strand, the epoxy resin layer can seal the gap between the through hole and the steel strand, which is beneficial to reduce the probability of concrete penetrating into the casing when pouring concrete piles.

[0012] Preferably, the lower end of the sleeve is filled with grouting material.

[0013] By adopting the above technical solution, a small amount of grouting material is filled at the lower end position of the inside of the casing. After the grouting material solidifies, the grouting material forms a sealing layer at the lower end position of the inside of the casing, further improving the sealing effect of the lower end of the casing. At the same time, it also improves the structural strength of the lower end of the through pipe, avoiding the situation where concrete enters the casing and fills the entire casing when pouring the pile body, and a small section of grouting material does not affect the subsequent steel strand tensioning step.

[0014] Preferably, a hole is provided on the peripheral wall of the lower end of the sleeve.

[0015] By adopting the above technical solution, holes are opened on the peripheral wall of the lower end of the casing so that grouting material can be directly injected into the lower end of the through pipe through the holes, which is beneficial to improving the assembly efficiency of the casing and the steel strand.

[0016] A method for constructing a steel strand cast-in-place pile comprises the following steps: S1: Complete the assembly steps of the casing, steel strands, and plugging parts, then transport the steel strands to the construction site, complete the steel cage binding steps at the construction site, and bind and fix several steel strands to the inner side of the steel cage, and fix the lower ends of the steel strands to the anchors; S2: Drilling is performed on the construction ground of the cast-in-place pile to form a construction hole on the construction ground; S3: Hoist the steel cage into the construction hole; S4: Pour concrete into the construction hole until the concrete fills the construction hole to form a concrete pile body. The steel strand is buried in the concrete pile body. The lower end of the steel strand is anchored in the concrete through an anchor, and the upper end of the steel strand extends out of the construction hole. After the concrete reaches the design strength, the steel strand prestressing step is finally carried out.

[0017] By adopting the above technical solution, the steel strands assembled with the casing are tied to the inner side of the steel cage, so that the steel strands can also be stably placed in the construction hole during the process of hanging the steel cage, which is beneficial to improving construction efficiency. After the concrete pouring construction is completed, the casing is firmly in the concrete pile body. After the concrete reaches the design strength, the prestressing step is carried out. During the prestressing process, the steel strands are stressed and can be relatively freely extended or shortened without being excessively restricted by the steel sleeve, which helps to reduce prestress loss and improve the efficiency of prestress transmission. There is no need to reserve channels, which simplifies the construction steps of steel strand cast-in-place piles and is beneficial to improving the construction efficiency of steel strand cast-in-place piles.

[0018] Preferably, in the assembly steps of the sleeve, steel strand and sealing piece of S1, a circular steel plate is used as the sealing piece, by firstly putting the sleeve on the outer periphery of the steel strand, then opening a through hole in the circular steel plate, and then completing the step of passing the steel strand end through the through hole, and finally welding the circular steel plate to the sleeve end.

[0019] By adopting the above technical solution, the sleeve and steel strand are first assembled, then the end of the steel strand is inserted into the through hole, and finally the circular steel plate and the sleeve end are welded, so that the assembly steps of the sleeve, steel strand and sealing piece are carried out in an orderly manner, which is conducive to improving the installation efficiency of the steel strand.

[0020] Preferably, after completing the assembly steps of the sleeve, steel strand and sealing piece of S1, a hole is opened on the peripheral wall of the lower end of the pipe, and the distance between the hole and the sealing piece at the lower end of the sleeve is 200 mm. The steel strand is then kept in an inclined state with an inclination angle of not less than 45°, and the grouting material is then injected into the lower end of the through pipe through the hole until the grouting material overflows from the hole and the injection action is stopped. After the grouting material solidifies and takes shape, the binding steps of the steel strand and the steel cage are completed.

[0021] By adopting the above technical solution, a hole is pre-opened on the peripheral wall of the lower end of the casing. The distance between the hole and the sealing piece at the lower end is the required length of the grouting material in the casing. Then the grouting material is directly injected into the lower end of the through pipe through the hole. The overflow of the grouting material from the hole is used as a prompt signal, which is easier to observe and helps to reduce the occurrence of excessive injection of grouting material.

[0022] In summary, this application includes at least one of the following beneficial technical effects: 1. By arranging a casing around the outer periphery of the steel strand, and providing blocking pieces at both ends of the casing, and opening a through hole in the blocking piece only for the casing to pass through, the blocking piece can block the grout during grouting, reducing the probability of concrete penetrating into the casing when pouring concrete piles, allowing the steel sleeve and the steel strand to slide relative to each other, reducing the bonding force between the steel strand and concrete. During the prestressing process, this sliding characteristic allows the steel strand to extend or shorten relatively freely when subjected to force without being excessively restricted by the steel sleeve, which helps to reduce prestress loss and improve the efficiency of prestress transmission. Without the need to reserve a channel, the construction steps of the steel strand bored pile are simplified, which is conducive to improving the construction efficiency of the steel strand bored pile; 2. The outer surface of the steel strand is covered with an epoxy resin layer to protect the surface of the steel strand from corrosion and wear. In addition, since there is a gap between the through hole and the steel strand, the epoxy resin layer can seal the gap between the through hole and the steel strand, which helps to reduce the probability of concrete penetrating into the casing when pouring concrete piles; 3. By pre-opening a hole in the peripheral wall of the lower end of the casing, the distance between the hole and the sealing piece at the lower end is the required length of the grouting material in the casing, and then directly injecting the grouting material into the lower end of the through pipe through the hole, and taking the overflow of the grouting material from the hole as a prompt signal, it is easier to observe, which is conducive to reducing the occurrence of excessive grouting material injection. A small amount of grouting material is filled at the lower end of the casing. After the grouting material solidifies, the grouting material forms a sealing layer at the lower end of the casing, further improving the sealing effect of the lower end of the casing, and also improving the structural strength of the lower end of the through pipe, avoiding the situation where concrete enters the casing and fills the entire casing when pouring the pile body, and a small section of grouting material does not affect the subsequent steel strand tensioning step. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the overall structure of a steel strand bored pile according to an embodiment of the present application.

[0024] Figure 2 This is a schematic diagram of the connection between the steel strands, casing and sealing members in a steel strand cast-in-place pile according to an embodiment of the present application.

[0025] Figure 3 This is a schematic diagram of the state of injecting grouting material into the casing in a construction method of a steel strand bored pile in an embodiment of the present application.

[0026] Explanation of the accompanying reference numerals: 1. Steel cage; 2. Steel strand; 3. Casing; 31. Hole; 4. Blocking piece; 41. Through hole; 5. Lifting equipment; 6. Articulated seat; 7. Cradle. DETAILED DESCRIPTION

[0027] The following is combined with Figure 1-3 This application is described in further detail.

[0028] The present application discloses a steel strand bored pile, referring to Figures 1 to 3 The invention comprises a concrete pile body, a steel cage 1 and a plurality of steel strands 2 embedded in the concrete pile body. A casing 3 is provided around the outer periphery of the steel strands 2, and a plugging member 4 is provided at the lower end of the casing 3. The casing 3 can be a metal casing 3, such as a stainless steel casing 3, or a non-metallic casing 3, such as a high-density polyethylene (HDPE) casing 3 or a glass fiber reinforced plastic (FRP) casing 3, to ensure sufficient strength and protective effect.

[0029] In this embodiment, the sealing member 4 is specifically a circular steel plate. The circular steel plate is provided with a through hole 41 for the sleeve 3 to pass through along its thickness direction. The circular steel plate and the end pipe mouth of the sleeve 3 are fixed by welding to ensure the stability and sealing of the connection. In addition, the outer peripheral surface of the steel strand 2 is covered with an epoxy resin layer. The epoxy resin layer is formed by immersing the steel strand 2 in epoxy resin. The epoxy resin layer protects the steel strand 2 to protect the surface of the steel strand 2 from corrosion and wear. Moreover, since there is a gap between the through hole 41 and the steel strand 2, the epoxy resin layer can seal the gap between the through hole 41 and the steel strand 2, which is beneficial to reduce the probability of concrete penetrating into the sleeve 3 when pouring concrete piles.

[0030] In this embodiment, the lower end of the sleeve 3 is filled with grouting material. A hole 31 is provided on the peripheral wall of the lower end of the sleeve 3, and the diameter of the hole 31 is 20 mm to ensure that the injection port of the grouting gun can evenly inject the grouting material into the sleeve 3. The distance between the hole 31 and the sealing member 4 at the lower end of the sleeve 3 is 200 mm. The grouting material can be a cement-based grouting material or a chemical grouting material. Cement-based grouting material has good fluidity and strength after hardening and is suitable for general underground environments; chemical grouting material has better corrosion resistance and airtightness. The filling amount of the grouting material is 200 mm from the lower end of the sleeve 3. When the grouting material overflows from the hole 31, an effective sealing layer has been formed inside the sleeve 3. Prevent concrete from penetrating into the sleeve 3.

[0031] This embodiment also provides a construction method for steel strand cast-in-place piles, comprising the following steps: S1: Assemble the casing 3, steel strands 2, and plugging components 4. First, prepare the casing 3, steel strands 2, plugging components 4, epoxy resin, grouting material, and other auxiliary materials. The steel strands 2 are pre-soaked in epoxy resin, so that the surface of the steel strands 2 is covered with a layer of epoxy resin. The casing 3 is then placed around the epoxy-resin-coated steel strands 2. Each casing 3 can accommodate two steel strands 2.

[0032] A suitable plugging member 4 is selected based on the diameter of the casing 3. The plugging member 4 is a circular steel plate with a through-hole 41 formed in the plate for the steel strand 2 to pass through. The steel strand 2 end is then threaded through the through-hole 41, and finally, the circular steel plate is welded to the end of the casing 3. An epoxy resin layer forms a seal between the inner wall of the through-hole 41 and the steel strand 2.

[0033] To further improve the sealing performance of the lower end of the casing 3, grouting material needs to be injected into the interior of the lower end of the casing 3. Before the grouting material injection step, a tire frame 7 is set up at the construction site in advance and a lifting device 5 is prepared. The lifting device 5 can be a crane or a gantry crane. One end of the tire frame 7 is hinged to the ground via an articulated seat 6. Several assembled steel strands 2 are arranged on the surface of the tire frame 7 and temporarily fixed to the tire frame 7 using clips. Then, the construction personnel open holes 31 in the peripheral wall of the lower ends of the several casings 3 on the tire frame 7 one by one. Then, the lifting device 5 is used to lift the tire frame 7 away from the articulated seat 6, so that the steel strands 2 remain tilted at an angle of not less than 45 degrees. The construction personnel then insert a grouting gun into the hole 31 to inject grouting material into the lower end of the casing 3 until the grouting material overflows from the hole 31, ensuring that an effective sealing layer is formed inside the casing 3. After the grouting material solidifies and takes shape, the tire frame 7 is lowered to a horizontal level, and then the steel strand 2 is removed.

[0034] The steel cage 1 is then tied at the construction site, and several steel strands 2 are tied and fixed inside the steel cage 1. The lower ends of the steel strands 2 are fixed to the anchors. By tying the steel strands 2, which have been assembled with the sleeves 3, to the inside of the steel cage 1, the steel strands 2 can be stably placed in place in the construction hole during the subsequent hoisting of the steel cage 1, which helps improve construction efficiency.

[0035] S2: Drill holes at the construction site. Determine the specific location of the holes based on the design drawings and construction requirements. Use professional drilling equipment to drill holes on the construction site. The depth and diameter of the holes should meet the design requirements. After drilling, clean out any debris from the holes 31 to ensure they are clean and tidy.

[0036] S3: After ensuring that the quality of the rebar cage 1 meets the design requirements and is free of deformation or damage, use a lifting device to lower the rebar cage 1 into the drilled hole, ensuring that the rebar cage 1 is vertically centered and its bottom is in stable contact with the bottom of the hole. Install support devices around the rebar cage 1 to prevent it from shifting during concrete pouring.

[0037] S4: Qualified concrete materials are then prepared according to design requirements, ensuring that the concrete's strength, fluidity, and other indicators meet standards. Pumping equipment is used to evenly pour concrete into the drilled hole until it completely fills the hole, forming the concrete pile. During the pouring process, appropriate vibration is applied to remove air bubbles and ensure concrete density. After pouring, appropriate curing is performed to ensure that the concrete reaches the designed strength.

[0038] S5: Prestressing confirms that the concrete has reached the design strength. After the concrete pouring construction is completed, the sleeve 3 is firmly fixed in the concrete pile body, the lower end of the steel strand 2 is anchored in the concrete through the anchor, and the upper end of the steel strand 2 extends out of the construction hole. Prepare the tensioning equipment, such as jacks, pressure gauges, etc., to ensure that the equipment is intact. Carry out prestressing in accordance with the design requirements, and gradually increase the tensioning force until it reaches the predetermined value. After the tensioning is completed, necessary inspections are carried out to ensure that the prestressing transfer effect is good and there are no abnormalities. During the prestressing process, the steel strand 2 is stressed and can be relatively freely extended or shortened without being excessively restricted by the steel sleeve, which helps to reduce prestress loss and improve the efficiency of prestressing transfer. There is no need to reserve channels, which simplifies the construction steps of the steel strand 2 cast-in-place pile and is conducive to improving the construction efficiency of the steel strand 2 cast-in-place pile.

[0039] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

[0040] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A steel strand bored pile, characterized by: The invention comprises a concrete pile body, a steel cage (1) and a plurality of steel strands (2) embedded in the concrete pile body. A sleeve (3) is provided on the outer periphery of the steel strand (2). A blocking piece (4) is provided at the lower end of the sleeve (3). The blocking piece (4) is provided with a through hole (41) for the sleeve (3) to pass through.

2. The steel strand bored pile according to claim 1, characterized in that: The blocking member (4) is a circular steel plate, and the circular steel plate is fixed to the end of the sleeve (3) by welding.

3. The steel strand bored pile according to claim 1, characterized in that: The outer peripheral surface of the steel strand (2) is covered with an epoxy resin layer.

4. The steel strand bored pile according to claim 2, characterized in that: The lower end of the sleeve (3) is filled with grouting material.

5. The steel strand bored pile according to claim 4, characterized in that: A hole (31) is provided on the peripheral wall of the lower end of the sleeve (3).

6. A method for constructing a steel strand bored pile according to claim 5, characterized in that: The following steps are involved: S1: completing the assembly steps of the casing (3), the steel strand (2) and the plugging member (4), then transporting the steel strand (2) to the construction site, completing the steel cage (1) binding step at the construction site, and binding and fixing a plurality of steel strands (2) to the inner side of the steel cage (1), and fixing the lower ends of the steel strands (2) to the anchors; S2: Drilling is performed on the construction ground of the cast-in-place pile to form a construction hole on the construction ground; S3: Hanging the steel cage (1) into the construction hole; S4: Concrete is poured into the construction hole until the concrete fills the construction hole to form a concrete pile body. The steel strand (2) is buried in the concrete pile body. The lower end of the steel strand (2) is anchored in the concrete through an anchor, and the upper end of the steel strand (2) extends out of the construction hole. After the concrete reaches the designed strength, the prestressing step of the steel strand (2) is finally performed.

7. The method for constructing a steel strand bored pile according to claim 6, characterized in that: In the assembly steps of the sleeve (3), the steel strand (2) and the plugging member (4) of the S1, a circular steel plate is used as the plugging member (4). The sleeve (3) is first sleeved on the outer periphery of the steel strand (2), and then a through hole (41) is opened in the circular steel plate. Then, the end of the steel strand (2) and the through hole (41) are penetrated, and finally the circular steel plate is welded and fixed to the end of the sleeve (3).

8. The method for constructing a steel strand bored pile according to claim 7, characterized in that: After completing the assembly steps of the sleeve (3), steel strand (2) and the plugging member (4) of S1, a hole (31) is opened on the peripheral wall of the lower end of the pipe, and the distance between the hole (31) and the plugging member (4) at the lower end of the sleeve (3) is 200 mm. Then, the steel strand (2) is kept in an inclined state, and the inclination angle is not less than 45°. Then, grouting material is injected into the lower end of the through pipe through the hole (31) until the grouting material overflows from the hole (31) and the injection action is stopped. After the grouting material solidifies and forms, the binding steps of the steel strand (2) and the steel cage (1) are completed.

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