Uplift precast pile structure

Abstract

The utility model relates to the field of pile foundations, in particular to an uplift precast pile structure which comprises a precast hollow pile and an anchoring device, the anchoring device is connected with the precast hollow pile, a plurality of unbonded prestressed steel strands are arranged in the precast hollow pile, and the anchoring device comprises a pile bottom anchoring part and a pile top anchoring part. The anti-pulling precast pile solves the problem that an anti-pulling precast pile in the prior art cannot be used as a long pile or an ultra-long pile, improves the anti-pulling bearing capacity of a single pile, improves the stress performance of the anti-pulling pile, and enables the anti-pulling pile to have better integrity and anti-pulling ductility.

Description

Technical Field

[0001] The utility model relates to the field of pile foundations, in particular to a pull-out resistant prefabricated pile structure. Background Art

[0002] With the increasing demand for urban underground space development, the anti-floating problem of deep and large underground structures has become more and more prominent. The use of pull-out piles to resist floating is a common form in engineering. According to the pile foundation process, pull-out piles can be divided into cast-in-place piles and prefabricated piles. The existing commonly used pull-out cast-in-place piles have defects such as long construction period, large amount of steel, high cost, and large environmental pollution. Some new technologies have also been gradually applied, such as post-tensioned partially bonded prestressed pull-out cast-in-place piles, slow-bonded prestressed pull-out cast-in-place piles, etc. Although these pile types improve the bearing capacity of the pile foundation through prestressing technology and reduce the amount of steel used in the pile foundation, the application of prestressing needs to wait until the concrete strength of the cast-in-place pile reaches the design requirements (at least 28d) before it can be carried out, which prolongs the construction period to a certain extent. At the same time, the mud discharge problem and environmental pollution problem of cast-in-place piles have not been well solved.

[0003] Compared with cast-in-place piles, precast piles have the advantages of fast construction, less environmental pollution, and a high degree of industrialization. However, since the maximum length of a single section of a precast pile is usually limited to about 15m, multiple sections of the pile need to be spliced ​​on site, and the reliability of the connection nodes is often questioned by the engineering community. When precast piles are used for pull-out resistance, their pull-out bearing capacity can generally only be calculated based on the upper two sections of the pile. Some conservative regions even stipulate that the pull-out bearing capacity can only be calculated based on the uppermost single section of the pile, resulting in a small pull-out bearing capacity of precast pull-out piles, a low utilization rate, and they cannot be used in deep soft soil areas.

[0004] Publication (announcement) number: CN 212452597 U, Publication (announcement) date: 2021-02-02 It relates to a prefabricated building structure, including a pile body and a pile hoop, the pile body includes a hollow part, a solid part and a first cage, the hollow part is connected to the solid part, a core groove is opened inside the hollow part, and the first cage is arranged in the solid part and the hollow part; the pile hoop is arranged on the outer peripheral wall of the end of the pile body, and the pile hoop includes at least one first hoop section recessed in the axial direction of the pile body, and at least one second hoop section convex relative to the first hoop section, and the first hoop section and the second hoop section are arranged at intervals. This solution requires bonding and has low reliability. Utility Model Content

[0005] The purpose of the utility model is to solve the problem that the pull-out prefabricated piles in the prior art cannot be used as long piles or super-long piles, and to provide a post-tensioned unbonded prestressed pull-out prefabricated pile structure that improves the pull-out bearing capacity of a single pile, improves the force performance of the pull-out pile, and makes the pull-out pile have better integrity and pull-out ductility.

[0006] In order to achieve the above-mentioned purpose, the solution provided by the utility model is: a pull-out resistant prefabricated pile structure, comprising: a prefabricated hollow pile and an anchoring device, the anchoring device is connected to the prefabricated hollow pile, a plurality of unbonded prestressed steel strands are arranged in the prefabricated hollow pile, and the anchoring device comprises a pile bottom anchor and a pile top anchor.

[0007] Preferably, the pile bottom anchor comprises a fixed end anchor and a plurality of bearing steel plates, wherein the bearing steel plate is fixed at one end of the fixed end anchor and a concrete pile tip is installed at the other end of the bearing steel plate.

[0008] Preferably, the unbonded prestressed steel strands include a strand body and a coating, wherein the coating covers the strand body, a sheath tube is provided outside the strand body, and the coaxially arranged unbonded prestressed steel strands are connected via a connector.

[0009] Preferably, the pile bottom anchor is arranged at the bottom of the precast hollow pile, the pile top anchor is arranged at the top of the precast hollow pile, and a prefilled core is installed in the top of the precast hollow pile.

[0010] Preferably, a plurality of through holes are axially provided in the prefilled core, and the unbonded prestressed steel strands are arranged in the through holes of the prefilled core.

[0011] Preferably, the pile top anchor comprises a load-bearing steel plate and a tension end anchor.

[0012] Preferably, the prefabricated hollow pile comprises a lowermost pile section and an uppermost pile section, and the lowermost pile section and the uppermost pile section are fixed by a connecting joint.

[0013] Preferably, the pile top anchor is fixed on the cap.

[0014] The beneficial effects of the utility model are as follows: the application utilizes the post-tensioning non-bonded prestressing technology to transfer the anchoring force of the pile top anchor end to the pile bottom of the precast pile, so that the force bearing point is mainly at the pile bottom, and the pile side resistance is first exerted at the lower pile side and then transferred to the pile top, which can give full play to the pile side friction resistance. At the same time, the application of prestressing forces always keeps the pile body and the connection nodes under pressure, which can not only avoid the generation of cracks and ensure the reliability of the connection nodes, but also give full play to the material properties of the high-strength concrete of the precast pile and improve the bearing capacity of the pile body. In addition, the application designs the pile head concrete core filling into a pre-filled core, which ensures the pile head force performance and speeds up the construction progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the front view of the utility model.

[0016] Figure 2 It is a schematic diagram of a pile bottom anchoring piece of the utility model.

[0017] Figure 3 It is a schematic diagram of a pile top anchoring piece of the utility model.

[0018] Figure 4 It is a cross-sectional schematic diagram of the pre-filled core of the pile head of the uppermost section of the utility model.

[0019] Explanation of numbers in the figure: 1-prefabricated hollow pile, 1.1-lowest pile section, 1.2-upper pile section, 2-unbonded prestressed steel strand, 2.1-strand body, 2.2-coating, 2.3-casing pipe, 3-pile bottom anchor, 3.1-fixed end anchor, 4-pile top anchor, 4.1-tensioning end anchor, 5-bearing steel plate, 6-concrete pile tip, 7-connector, 8-prefilled core, 7-pile top anchor, 9-connecting joint, 10-cap. DETAILED DESCRIPTION

[0020] The specific embodiments of the utility model will be described in detail below. It should be noted that the embodiments described here are only part of the embodiments of the utility model, not all of them. Based on the following embodiments, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0021] The utility model provides the following technical solutions:

[0022] Embodiment 1:

[0023] like Figure 1 As shown, a pull-out resistant prefabricated pile structure comprises: a prefabricated hollow pile 1 and an anchoring device, wherein the anchoring device is installed at both ends of the prefabricated hollow pile 1, wherein a plurality of unbonded prestressed steel strands 2 are evenly arranged axially in the prefabricated hollow pile 1, and the anchoring device comprises a pile bottom anchor 3 and a pile top anchor 4. By utilizing the post-tensioning unbonded prestressing technology, the anchoring force of the pile top anchoring end is transferred to the pile bottom of the prefabricated pile, so that the bearing point is mainly at the pile bottom, and the pile side resistance is first exerted at the lower pile side and then transferred to the pile top, which can give full play to the pile side friction resistance; at the same time, the application of prestress makes the pile body and the connection node always in a compressed state, which can not only avoid the generation of cracks and ensure the reliability of the connection node, but also give full play to the material properties of the high-strength concrete of the prefabricated pile and improve the bearing capacity of the pile body.

[0024] The prefabricated hollow pile 1 is composed of at least two pile sections. The cavity diameter of the prefabricated hollow pile 1 is not less than 300 mm. The adjacent piles are fixed by connecting joints 9. The pile at the bottom is the lowest pile section 1.1, and the pile at the top is the highest pile section 1.2. The prefabricated hollow pile 1 can be a hollow pipe pile or a hollow square pile. The bottom of the lowest pile section 1.1 is installed with a pile bottom anchor 3, and the top of the highest pile section 1.2 is installed with a pile top anchor 4. The prefilled core 8 is installed in the pile top anchor 4 and the top of the highest pile section 1.2. When the traditional prefabricated pile is used as an anti-pulling pile, due to the unreliable connection joint of the pile, the anti-pulling bearing capacity of the pile foundation is only allowed to be calculated according to the upper 1 to 2 pile sections. For soft soil foundations, the pile side resistance of the shallow soil is very small, and the pile side resistance of the deep soil is relatively large. However, due to the connection structure of the prefabricated pile, the side friction resistance of the deep soil cannot be used, and the anti-pulling efficiency of the pile foundation is low. At the same time, traditional pull-out piles are generally tension-type piles, which are subjected to tension at the pile top and connection nodes and are prone to cracking and failure; and the side resistance of the pile is first exerted on the upper pile side and then transmitted to the lower pile side. The force transmission efficiency is low, and the tension on the upper pile body is too large.

[0025] like Figure 2 As shown, the pile bottom anchor 3 includes a fixed end anchor 3.1, and multiple fixed end anchors 3 are evenly arranged on the bearing steel plate 5. The other end of the bearing steel plate 5 at the pile bottom is installed with a concrete pile tip 6. The concrete pile tip 6 is sealed with epoxy resin when connected to the pile end of the prefabricated hollow pile 1.

[0026] The unbonded prestressed steel strand 2 is composed of a strand body 2.1, a coating 2.2, and a sheath tube 2.3. The strand body 2.1 is a prestressed steel strand, the coating 2.2 covers the surface of the strand body 2.1, the coating 2.2 is an anti-corrosion lubricating coating, and the sheath tube 2.3 protects the anti-corrosion lubricating coating when the unbonded prestressed steel strand 2 is installed. The coaxial unbonded prestressed steel strand 2 is connected and extended by a connector 7.

[0027] like Figure 3 As shown, the pile top anchor 4 includes a tensioning end anchor 4.1 and a bearing steel plate 5. A plurality of tensioning end anchors 4.1 are evenly arranged on one side of the bearing steel plate 5 at the bottom of the prefabricated hollow pile 1. The pile top anchor 4 is disposed in a cap 10, which may also be a bottom plate.

[0028] like Figure 4As shown, a through hole is provided in the uppermost pile section 1.2, a prefilled core 8 is arranged in the uppermost pile section 1.2, a plurality of through holes are axially provided in the prefilled core 8, an equal number of through holes are provided at the corresponding position of the bearing steel plate 5 at the pile bottom of the precast hollow pile 1, and the unbonded prestressed steel strand 2 is arranged in the through hole, and the unbonded prestressed steel strand 2 is tensioned at the pile top of the uppermost pile section 1.2 and locked on the pile top anchor 4. Before pouring the cap and the bottom plate, the traditional precast pile needs to use micro-expansion concrete to fill the pile head. Since the hole needs to be cleaned on site before pouring concrete, it is difficult to ensure that the core filling is reliably bonded to the precast pile hole wall, and after pouring the concrete, it is necessary to wait until the concrete reaches the design strength before the next step of construction can be carried out, which prolongs the construction period.

[0029] The bearing steel plate 5, the fixed end anchor 3.1 and the concrete pile tip 6 are cast together. On the one hand, the concrete pile tip has good rigidity and is easy to deliver the pile; on the other hand, it is beneficial to protect the anchor end from corrosion and improve durability. The advantage of pre-filled core concrete is that it can ensure the compactness of concrete casting, improve the bearing capacity of the pile head, and there is no need to wait until the concrete reaches the strength before tensioning the prestressed tendons, which speeds up the construction progress.

[0030] In actual use, the following steps can be taken:

[0031] Step 1: The lowest pile section 1.1 and the pile bottom anchor 3, as well as the remaining hollow pile sections are prefabricated in the factory;

[0032] Step 2: Sink the lowest pile 1.1 at the designed pile position;

[0033] Step 3: Insert the unbonded prestressed steel strand 2 into the second pile cavity and temporarily fix it;

[0034] Step 4: hoist the second pile section and connect the unbonded prestressed steel strands 2 in the two pile sections on site;

[0035] Step 5: Align the second pile section with the bottom pile section 1.1 and weld them together;

[0036] Step 6: Sink the piles section by section according to Step 3 and Step 4, until all the piles are sunk to the required elevation;

[0037] Step 7: After excavating the foundation pit and exposing the pile head of the last pile section, the pile top anchor 4 is placed on the pile top, and the unbonded prestressed steel strand 2 is tensioned and anchored.

[0038] Step 8: After anchoring, the length of the steel strand above the anchor device should meet the anchoring length requirement, and it should be anchored into the cap 10 and cast integrally with the cap 10.

[0039] In addition to improving the mechanical properties of the pile foundation, the structure of this application also has the following advantages in terms of construction and construction measures:

[0040] (1) The bearing steel plate 5 of the pile bottom anchor 3, the unbonded prestressed tendon fixed end anchor 3.1 and the concrete pile tip 6 are integrally cast together to effectively protect the anchor end from corrosion and improve durability;

[0041] (2) Unbonded prestressed tendons have a simple structure, good corrosion resistance, and are easy to construct, avoiding the complicated grouting process and speeding up the construction progress;

[0042] (3) The pre-tension of the prestressed steel strand is locked at the top of the pile, and there is no need to extend it to the cap surface for tensioning and locking, which avoids leakage problems in the basement. At the same time, there is no need to wait until the basement floor is poured before tensioning, which speeds up the construction progress.

[0043] (4) The steel strands are directly anchored into the cap 10, and the connection is reliable, thus avoiding the problem of easy failure of the connection between the conventional prefabricated pile top reinforcement and the cap 10;

[0044] (5) The concrete core at the top of the pile is poured in the factory, which ensures the load-bearing performance of the pile head and speeds up the construction period.

[0045] Embodiment 2:

[0046] A pull-out resistant prefabricated pile structure comprises: a prefabricated hollow pile 1 and an anchoring device, wherein the anchoring device is installed at both ends of the prefabricated hollow pile 1, and four unbonded prestressed steel strands 2 are evenly arranged in the axial direction in the prefabricated hollow pile 1, and the anchoring device comprises a pile bottom anchor 3 and a pile top anchor 4. The post-tensioning unbonded prestressing technology is used to transfer the anchoring force of the pile top anchor end to the pile bottom of the prefabricated pile, so that the bearing point is mainly at the bottom of the pile, and the pile side resistance is first exerted at the lower pile side and then transmitted to the pile top, which can give full play to the pile side friction resistance; at the same time, the application of prestress makes the pile body and the connection node always in a compressed state, which can not only avoid the generation of cracks and ensure the reliability of the connection node, but also give full play to the material properties of the high-strength concrete of the prefabricated pile and improve the bearing capacity of the pile body. Traditional pull-out piles are generally tension-type piles, which bear tension at the pile top and connection nodes, and are prone to cracking and failure; and the side resistance of the pile is first exerted on the upper pile side and then transmitted to the lower pile side. The force transmission efficiency is low, and the tension on the upper pile body is too large. The present application utilizes post-tensioning non-bonded prestressing technology to transfer the anchoring force of the pile top anchor end to the pile bottom of the precast pile, so that the bearing point is mainly at the bottom of the pile, and the pile side resistance is first exerted on the lower pile side and then transmitted to the pile top, which can give full play to the pile side friction resistance.

[0047] The prefabricated hollow pile 1 is composed of a lowermost pile section 1.1 and an uppermost pile section 1.2, which are fixed by a connecting joint 9. The prefabricated hollow pile 1 can be a hollow pipe pile or a hollow square pile. A pile bottom anchor 3 is installed at the bottom of the lowermost pile section 1.1, and a pile top anchor 4 is installed at the top of the uppermost pile section 1.2. A prefilled core 8 is installed in the pile top anchor 4 and the top of the uppermost pile section 1.2. The prefabricated hollow pile 1 adopts a prestressed pipe pile with a pile diameter of 500 mm and an inner diameter of 300 mm.

[0048] The unbonded prestressed steel strand 2 is composed of a strand body 2.1, a coating 2.2, and a sheath tube 2.3. The strand body 2.1 is a prestressed steel strand, the coating 2.2 covers the surface of the strand body 2.1, the coating 2.2 is an anti-corrosion lubricating coating, and the sheath tube 2.3 protects the anti-corrosion lubricating coating when the unbonded prestressed steel strand 2 is installed. The coaxial unbonded prestressed steel strand 2 is connected and extended by a connector 7.

[0049] The pile bottom anchor 3 includes a fixed end anchor 3.1, and four fixed end anchors 3 are evenly arranged on the bearing steel plate 5. The other end of the bearing steel plate 5 at the pile bottom is installed with a concrete pile tip 6. The concrete pile tip 6 is sealed with epoxy resin when connected to the pile end of the prefabricated hollow pile 1. The concrete pile tip 6 adopts a multi-faceted design, mainly to improve its bearing capacity and stability. The multi-faceted design can increase the contact area between the pile tip and the soil, thereby better dispersing pressure and stress. In addition, the multi-faceted concrete pile tip 6 can also better cut the soil when the pile foundation sinks, reduce the resistance of the pile foundation sinking, and make it easier to insert into the soil. During the construction process, in order to ensure the integrity and stability of the concrete pile tip 6, it is usually necessary to conduct quality inspection and maintenance on it. .

[0050] The pile top anchor 4 includes a tension end anchor 4.1 and a bearing steel plate 5. Four tension end anchors 4.1 are evenly arranged on one side of the bearing steel plate 5 at the bottom of the prefabricated hollow pile 1. The pile top anchor 4 is arranged in the cap 10, and the cap 10 can also be a bottom plate. The traditional pull-out pile is generally a tension pile. The pile top and the connection node are subjected to tension, which is easy to crack and fail; and the pile side resistance is first exerted on the upper pile side and then transmitted to the lower pile side. The force transmission efficiency is low, and the tension on the upper pile body is The present application utilizes the post-tensioning non-bonded prestressing technology to transfer the anchoring force of the pile top anchor end to the pile bottom of the precast pile, so that the bearing point is mainly at the pile bottom, and the pile side resistance is first exerted at the lower pile side and then transmitted to the pile top, which can give full play to the pile side friction resistance. In the present application, the anchoring force of the pile top anchor end is transferred to the pile bottom of the precast pile, so that the bearing point is mainly at the pile bottom, and the pile side resistance is first exerted at the lower pile side and then transmitted to the pile top, which can give full play to the pile side friction resistance.

[0051] A through hole is provided in the uppermost pile section 1.2, and a prefilled core 8 is arranged in the uppermost pile section 1.2. The prefilled core 8 at the pile top is processed in the factory, and the core filling depth is 1.5m. Four axial through holes are provided in the prefilled core 8, and the same number of through holes are provided at the corresponding positions of the bearing steel plate 5 at the bottom of the prefabricated hollow pile 1. The unbonded prestressed steel strand 2 is arranged in the through holes, and the unbonded prestressed steel strand 2 is tensioned at the pile top of the uppermost pile section 1.2 and locked on the pile top anchor 4.

[0052] The bearing steel plate 5, the fixed end anchor 3.1 and the concrete pile tip 6 are cast together. On the one hand, the concrete pile tip has good rigidity and is easy to deliver the pile; on the other hand, it is beneficial to protect the anchor end from corrosion and improve durability. The advantage of pre-filled core concrete is that it can ensure the compactness of concrete casting, improve the bearing capacity of the pile head, and there is no need to wait until the concrete reaches the strength before tensioning the prestressed tendons, which speeds up the construction progress.

[0053] Based on the above embodiments, the present application proposes a pull-out resistant prefabricated pile structure to solve the problem that the pull-out resistant prefabricated pile in the prior art cannot be used as a long pile or an extra-long pile, comprising: a prefabricated hollow pile 1 and an anchoring device, the anchoring device is installed at both ends of the prefabricated hollow pile 1, a plurality of unbonded prestressed steel strands 2 are evenly arranged axially in the prefabricated hollow pile 1, the anchoring device comprises a pile bottom anchor 3 and a pile top anchor 4, and the post-tensioning unbonded prestressing technology is used to transfer the anchoring force of the pile top anchor end to the pile bottom of the prefabricated pile, so that the bearing point is mainly at the bottom of the pile, and the pile side resistance is first exerted at the lower pile side, and then transmitted to the pile top, which can give full play to the pile side friction resistance. At the same time, the application of prestress makes the pile body and the connection node always in a compressed state, which can not only avoid the generation of cracks and ensure the reliability of the connection node, but also give full play to the material properties of the high-strength concrete of the prefabricated pile and improve the bearing capacity of the pile body.

[0054] The above shows and describes the basic features, principles and advantages of the utility model. It should be noted that the utility model is not limited to the above embodiments, which are only partial embodiments. Under the premise of not departing from the spirit and scope of the utility model, several improvements and supplements made are deemed to be within the protection scope of the utility model.

Claims

1. A pull-out resistant prefabricated pile structure, characterized in that: include: A prefabricated hollow pile (1) and an anchoring device, wherein the anchoring device is connected to the prefabricated hollow pile (1), a plurality of unbonded prestressed steel strands (2) are arranged in the prefabricated hollow pile (1), and the anchoring device comprises a pile bottom anchor (3) and a pile top anchor (4).

2. According to the pull-out resistant prefabricated pile structure described in claim 1, the pile bottom anchor (3) includes a fixed end anchor (3.1) and a plurality of bearing steel plates (5), the bearing steel plate (5) is fixed at one end of the fixed end anchor (3.1), and a concrete pile tip (6) is installed at the other end of the bearing steel plate (5).

3. According to the pull-out resistant prefabricated pile structure described in claim 1, the unbonded prestressed steel strand (2) comprises a strand body (2.1) and a coating (2.2), the coating (2.2) covers the strand body (2.1), a sheath tube (2.3) is provided outside the strand body (2.1), and the coaxially arranged unbonded prestressed steel strands (2) are connected via a connector (7).

4. According to the pull-out resistant prefabricated pile structure described in claim 1, the pile bottom anchor (3) is arranged at the bottom of the prefabricated hollow pile (1), the pile top anchor (4) is arranged at the top of the prefabricated hollow pile (1), and a prefilled core (8) is installed in the top of the prefabricated hollow pile (1).

5. According to the pull-out resistant prefabricated pile structure of claim 4, a plurality of through holes are axially arranged in the prefilled core (8), and the unbonded prestressed steel strands (2) are arranged in the through holes of the prefilled core (8).

6. According to the pull-out resistant prefabricated pile structure of claim 4, the pile top anchor (4) comprises a bearing steel plate (5) and a tension end anchor (4.1).

7. An anti-pulling prefabricated pile structure according to any one of claims 1 to 6, wherein the prefabricated hollow pile (1) comprises a lowermost pile section (1.1) and an uppermost pile section (1.2), and the lowermost pile section (1.1) and the uppermost pile section (1.2) are fixed by a connecting joint (9).

8. According to the pull-out resistant prefabricated pile structure according to any one of claims 1 to 6, the pile top anchor (4) is fixed on the cap (10).

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