Prestress anti-floating anchor rod

Abstract

The prestressed anti-floating anchor rod comprises an anchoring pier sinking to the bottom of a pile hole, a prestressed steel strand connected to the anchoring pier and a concrete body formed by concrete poured in the pile hole. The anchoring pier comprises a concrete precast block and a reinforcement cage in the concrete precast block, an anchorage device cavity is formed in the lower end of the anchoring pier, the sheath steel pipe is fixedly connected to the concrete precast block, the lower end of the sheath steel pipe communicates with the anchorage device cavity, and the top end of the sheath steel pipe is located in a bottom plate of the underground structure. The lower end of the prestressed steel strand enters the anchorage device cavity through the sheath steel pipe and is locked through the lower anchorage device, the upper end of the prestressed steel strand is locked through the upper anchorage device, and cement slurry is poured in the sheath steel pipe. The anchoring piers are used as fixing sections of the anchor rods, so that stable connection of the prestressed steel strands and the anchoring piers is guaranteed, cracks of the anchoring piers are avoided, concrete bodies in the pile holes are used as counter-force supports for tensioning the steel strands, completeness of a bottom plate is guaranteed, and the risk that underground water enters a basement is avoided.

Description

Technical Field

[0001] The utility model relates to a prestressed anti-floating anchor rod. Background Art

[0002] As the burial depth of underground projects such as building basements, subways, underground transportation hubs, underground spaces, and hydraulic structures becomes deeper and deeper, the anti-floating problem of underground projects has become increasingly obvious.

[0003] Anti-floating issues in underground projects can be addressed using weighted concrete, anti-floating piles, or anti-floating anchors. The weighted concrete method increases the thickness of the concrete slab to counteract the buoyancy of water, but this method is significantly more expensive and less economical. Anti-floating piles are mostly cast-in-place piles, either manually dug or mechanically drilled. To accommodate cracks, these piles typically require a significant amount of reinforcement, resulting in significant waste of resources and high construction costs. However, the closely spaced anti-floating anchors allow for thinner basement slabs, reducing the cost of the anchors and significantly reducing the overall cost of the anti-floating structure.

[0004] The load of traditional tension-type anchor rods is transmitted from the top to the bottom end, relying on the bonding stress at the interface between the fixed section of the rod and the grouting body. When the anchor rod is working, tension cracks are prone to appear in the grouting body of the fixed section, which allows groundwater to enter the fixed section through the tension cracks, corroding the anchor rod, causing the anchor rod to break, and reducing the anti-buoyancy capacity of the pile body. Therefore, the existing tension-type anti-floating anchor rods can no longer meet the needs of underground projects that require high anti-buoyancy bearing capacity. At present, when constructing tension-type anchor rods, it is usually necessary to use the bottom plate as a reaction plate to tension the anchor rods after completing the bottom plate of the underground structure. Tensioning holes need to be reserved on the bottom plate. After the tensioning is completed, the reserved tensioning holes are repaired by grouting. This makes it easy for groundwater to seep into the underground structure from the edge of the tensioning hole, affecting the normal use of the underground structure. Utility Model Content

[0005] In order to solve the problem of using the bottom plate as a reaction plate to tension the anchor rod, it is necessary to reserve tensioning holes on the bottom plate. After the tensioning is completed, the reserved tensioning holes are grouting repaired, which makes it easy for groundwater to penetrate into the underground structure from the edge of the tensioning hole, affecting the normal use of the underground structure. The present application proposes a prestressed anti-floating anchor rod, which includes an anchor pier sunk at the bottom of the pile hole, a prestressed steel strand connected to the anchor pier, and a concrete body formed by concrete poured in the pile hole, wherein the prestressed steel strand is formed by tensioning the steel strand;

[0006] The anchor pier includes a concrete precast block and a steel cage cast in the concrete precast block, and an anchor cavity with an opening facing downward is provided at the lower end of the anchor pier, and a sheathed steel pipe is fixedly connected to the concrete precast block, the sheathed steel pipe is welded to the steel cage, and the lower end of the sheathed steel pipe is downwardly connected to the anchor cavity, and the top of the sheathed steel pipe is located in the bottom plate of the underground structure; the prestressed steel strand is passed through the sheathed steel pipe, and the lower end of the prestressed steel strand extends downward from the sheathed steel pipe and enters the anchor cavity and is locked by the lower anchor, and a casting body formed by cement grouting material is provided in the anchor cavity, and the lower end of the prestressed steel strand and the lower anchor are both wrapped in the casting body; the upper end of the prestressed steel strand extends upward from the sheathed steel pipe and is locked by the upper anchor, and cement slurry is poured in the sheathed steel pipe.

[0007] In the present application, an anchor pier is prefabricated separately, and the anchor pier is used as the fixed section of the anchor rod. Since the anchor pier is a prefabricated part, it can not only ensure the stable connection between the prestressed steel strand and the anchor pier, but also pre-test the quality of the anchor pier in advance to ensure the tensile strength of the anchor pier, thereby ensuring that when the anchor rod is working, its fixed section will not crack, avoiding the corrosion of the steel strand by groundwater, ensuring the integrity of the anchor rod, and thus ensuring the stability of the pile body's anti-floating ability. In the present application, the tensioning of the steel strand is supported by the concrete body in the pile hole as a reaction force. After the tensioning of the steel strand is completed, the construction of the base plate of the underground structure can be carried out. With the present application, there is no need to reserve tensioning holes on the base plate, which can ensure the integrity of the base plate and avoid the risk of groundwater entering the basement.

[0008] Furthermore, a lower end plate is fixedly mounted on the lower end surface of the precast concrete block. This lower end plate seals the opening of the anchor cavity and has a pouring hole connecting the inside and outside of the anchor cavity. Cement grout is poured into the anchor cavity through this pouring hole. The lower end plate forms a relatively sealed container in the anchor cavity, facilitating the pouring of cement grout and ensuring that the cement grout smoothly fills the anchor cavity.

[0009] Furthermore, to facilitate installation of the lower end plate, connecting ribs are provided on the precast concrete block, to which the lower end plate is fixed. These connecting ribs are not connected to either the steel cage or the sheathed steel pipe. Because the lower end plate can only be installed after the lower anchor has been installed, it cannot be pre-buried. Because the lower end plate is located at the lowest end of the precast concrete block, moisture in the soil could corrode the lower end plate and, consequently, the connecting ribs, leaving them disconnected from either the steel cage or the sheathed steel pipe. This prevents groundwater from seeping into the interior of the precast concrete block along the connecting ribs and corroding the steel cage and sheathed steel pipe.

[0010] Furthermore, anchoring bars are provided on the precast concrete block, and the anchoring bars extend upward from the upper end surface of the precast concrete block and then extend into the interior of the concrete body. Preferably, the length of the anchoring bars extending into the concrete body is 100-500mm. The use of anchoring bars can effectively improve the connection strength between the anchor pier and the concrete body, and improve the integrity of the prestressed anti-floating anchor rod. Since the anchor pier is a precast component, when pouring concrete in the pile hole, the connection strength between the anchor pier and the anchor pier is relatively weak. When the buoyancy of the groundwater is large, cracks are likely to appear on the bonding surface between the anchor pier and the concrete body, so that the groundwater penetrates into the anchor rod through the cracks, causing corrosion to the sheathed steel pipe and affecting the service life of the anchor rod. The use of anchoring bars can effectively improve the connection strength between the post-cast concrete body and the anchor pier, thereby improving the integrity of the prestressed anti-floating anchor rod to ensure the service life of the anchor rod.

[0011] Furthermore, a support steel plate is provided between the lower anchor and the sheathed steel pipe, and the anchor cavity is connected to the inner cavity of the sheathed steel pipe via the support steel plate. The support steel plate can provide a larger support area for the lower anchor, so as to facilitate the installation of the lower anchor.

[0012] Furthermore, in order to improve the protection of the prestressed steel strands, the cast body in the anchor cavity extends into the inner cavity of the sheathed steel pipe, and the cast body is bonded to the cement slurry in the inner cavity of the sheathed steel pipe.

[0013] Furthermore, the inner diameter of the pile hole is 50-100mm larger than the outer diameter of the anchor pier. This design allows the anchor pier to sink smoothly to the bottom of the pile hole and allows concrete to flow around the anchor pier when pouring into the pile hole, thereby improving the connection strength between the concrete body and the anchor pier. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural diagram of an embodiment of the present utility model.

[0015] Figure 2 is a schematic diagram of an anchor pier carrying a steel strand.

[0016] Figure 3 This is a schematic diagram of the anchor pier after the steel strands are removed.

[0017] Figure 4 yes Figure 3 Center AA view. DETAILED DESCRIPTION

[0018] See Figure 1 and Figure 2A prestressed anti-floating anchor rod includes an anchor pier 10 sunk at the bottom of a pile hole 30, a prestressed steel strand 22 connected to the anchor pier 10, and a concrete body 31 formed by concrete poured into the pile hole, wherein the prestressed steel strand 22 is formed by tensioning the steel strand. In this embodiment, the inner diameter of the pile hole is 500 mm, the anchor pier 10 is cylindrical, and the outer diameter of the anchor pier is 440 mm, that is, the inner diameter of the pile hole is 60 mm larger than the outer diameter of the anchor pier. It is understood that in other embodiments, the inner diameter of the pile hole can be 50 mm, 70 mm, 80 mm, 90 mm or 100 mm larger than the outer diameter of the anchor pier, or other data between 50-100 mm.

[0019] The anchor pier 10 includes a precast concrete block 11 and a steel cage 12 cast in the precast concrete block 11 . The steel cage 12 includes longitudinal bars 121 and spiral stirrups 122 surrounding the longitudinal bars.

[0020] The lower end of the anchor pier 10 has an anchor cavity 15 with a downward opening. A sheathed steel pipe 21 is fixedly connected to the precast concrete block 11. The upper end of the longitudinal reinforcement 121 is bent inward and welded to the sheathed steel pipe 21. The lower end of the sheathed steel pipe downwardly communicates with the anchor cavity 15. The upper end of the sheathed steel pipe 21 is located within the floor 43 of the underground structure. The prestressed steel strand is passed through the sheathed steel pipe 21. The lower end of the prestressed steel strand extends downward from the sheathed steel pipe and enters the anchor cavity 15, where it is locked by the lower anchor 23. The anchor cavity 15 has a cast body formed of cement grouting material. The lower end of the prestressed steel strand and the lower anchor are both encased in the cast body. For clarity, the cast body is not shown in the accompanying drawings. The upper end of the prestressed steel strand extends upwardly out of the sheathed steel pipe and is locked by the upper anchor 27. The upper end of the prestressed steel strand is poured into the bottom plate 43 of the underground structure, and cement slurry is poured into the sheathed steel pipe.

[0021] A waterstop steel plate 25 is welded to the top of the jacketed steel pipe, along with a backing plate 26 welded to the top surface. The backing plate has holes for steel strands. The prestressed steel strands freely pass through the backing plate 26 and are then secured by upper anchors 27, which are supported on the backing plate. The waterstop steel plate 25, backing plate, and upper anchors are all cast within the base plate 43.

[0022] A cushion layer 41 is laid below the bottom plate 43 , and a waterproof layer 42 is laid between the bottom plate 43 and the cushion layer 41 .

[0023] Connecting ribs 16 are provided at the lower end of the precast concrete block 11. These connecting ribs 16 are not connected to the steel cage 12 or the sheathed steel pipe 21. The connecting ribs extend downward from the lower end face of the precast concrete block 11, pass through the connecting holes in the lower end plate 17, and are welded to the lower end plate. In this embodiment, the connecting ribs 16 are connected to the precast concrete block 11 using embedded reinforcement. It will be appreciated that in another embodiment, the connecting ribs 16 may be connected to the precast concrete block 11 using a pre-embedded method, or the connecting ribs and the lower end plate may be pre-welded into a single integral component and then connected to the precast concrete block 11 using embedded reinforcement.

[0024] The lower end plate 17 rests on the lower end surface of the precast concrete block 11 , and blocks the opening of the anchor cavity 15 . The lower end plate 17 has a pouring hole 18 communicating with the inside and outside of the anchor cavity 15 , and cement grouting material is poured into the anchor cavity 15 through the pouring hole 18 .

[0025] Anchor bars 14 are provided on the precast concrete blocks. These bars extend upward and into the interior of the concrete body 31. In this embodiment, the anchor bars 14 are pre-welded to the reinforcement cage. In this embodiment, the length of the anchor bars extending into the concrete body is 150 mm. It is understood that in other embodiments, the length of the anchor bars extending into the concrete body may be 100 mm, 300 mm, 400 mm, or 500 mm, or any other length between 100 and 500 mm.

[0026] The cement grouting material enters the sheathed steel pipe upwards and bonds with the cement slurry in the sheathed steel pipe to form a whole.

[0027] In order to provide a stronger support for the lower anchor, a support steel plate 13 is provided between the lower anchor and the sheathed steel pipe. The support steel plate is pre-welded to the bottom of the steel cage and cast into the concrete prefabricated block 11. In this embodiment, each prestressed anti-floating anchor rod is provided with seven steel strands. Figure 4 Corresponding to each steel strand, a threading hole 131 is provided on the support steel plate 13, along with a grouting hole 132. Grouting hole 132 faces the sheathed steel pipe, and threading holes 131 surround grouting holes 132, connecting the anchor cavity to the inner cavity of the sheathed steel pipe through the grouting holes in the support steel plate. After passing through the corresponding threading hole 131, the steel strand enters the anchor cavity and is secured by the lower anchor. Cement grouting enters the sheathed steel pipe through grouting holes 132.

[0028] In this embodiment, the lower anchor is a single-hole anchor, so that the lower end of each steel strand is locked by a single-hole anchor. Each single-hole anchor cannot block the grouting hole 132. It is understood that in other embodiments, a multi-hole anchor with grouting holes can also be used, and the grouting holes can be connected to the grouting holes to allow cement grouting material to enter the jacketed steel pipe through the grouting holes and the grouting holes.

[0029] The following describes the construction method of the prestressed anti-floating anchor rod in this embodiment. Figure 3 and Figure 4 , Figure 3 The direction of the first axis X in the figure represents the direction of the first axis. The construction method includes the following steps:

[0030] (1) Making an anchor pier 10 with a steel strand:

[0031] A steel cage 12 is placed in the mold 50. A sheathed steel pipe 21 is welded to the steel cage. The sheathed steel pipe 21 extends along the first axis. The steel cage 12 includes longitudinal bars 121 and spiral stirrups 122 surrounding the longitudinal bars.

[0032] Concrete is poured into the mold 50, and after the concrete solidifies, a prefabricated concrete block 11 is formed. The mold is removed, and the two ends of the first axis direction of the prefabricated concrete block are formed as a lower end and an upper end respectively. Figure 3 In the figure, the first mark 111 indicates the upper end of the precast concrete block, and the second mark 112 indicates the lower end of the precast concrete block. The lower end of the precast concrete block 11 has an anchor cavity 15 with a depth of 100 mm. This cavity is formed by a depression in the lower end surface of the precast concrete block along the first axis. One end of the sheathed steel pipe 21 communicates with the anchor cavity, and the other end of the sheathed steel pipe extends beyond the upper end surface of the precast concrete block 11. The upper end surface of the precast concrete block 11 refers to the upper end surface of the precast concrete block 11.

[0033] A support steel plate 13 and anchor bars 14 are pre-welded to the reinforcement cage. The support steel plate is located within the lower end of the precast concrete block 11 and forms the roof of the anchor cavity 15. The anchor bars are located at the upper end of the precast concrete block 11, and the anchor bars 14 are long enough to extend beyond the upper end of the precast concrete block. The length of the anchor bars 14 extending beyond the upper end of the precast concrete block is set at 150 mm. After the concrete is poured into the pile hole, the anchor bars extend 150 mm into the concrete.

[0034] A reinforcement hole is drilled along the first axis at the lower end of the concrete precast block 11. The reinforcement hole passes through the lower end face of the concrete precast block 11. Rebar glue is poured into the reinforcement hole, and then the connecting bar 16 is inserted into the reinforcement hole. After the reinforcement glue is completely solidified, the lower end plate 17 is placed on the lower end face, and the connecting bar 16 is inserted into the connecting through hole on the lower end plate 17. The connecting bar is then welded to the lower end plate, and the lower end plate 17 is tightly pressed against the lower end face of the concrete precast block 11. The lower end plate blocks the opening of the anchor cavity. There is a pouring hole 18 on the lower end plate that connects the inside and outside of the anchor cavity. In the accompanying drawings, the connecting through hole on the lower end plate 17 is not marked. The lower end face of the concrete precast block 11 refers to the end face of the lower end of the concrete precast block 11.

[0035] When drilling the rebar holes, the steel cage and the embedded pipe must not be touched, so that the connecting bars 16 are not connected to the steel cage 12 and the sheathed steel pipe 21.

[0036] It is understandable that in another embodiment, the connecting ribs 16 can be connected to the precast concrete block 11 by pre-embedded means, or the connecting ribs and the lower end plate can be pre-welded into an integral component and then connected to the precast concrete block 11 by embedded ribs.

[0037] Insert the steel strand into the sheathed steel pipe 21, and one end of the steel strand passes through the wire hole 131 on the supporting steel plate and enters the anchor cavity. Use the lower anchor 23 to lock the end of the steel strand that enters the anchor cavity, so that the lower anchor 23 is accommodated in the anchor cavity, and the other end of the steel strand extends out of the sheathed steel pipe 21 away from the end of the anchor cavity.

[0038] Cement grout is poured into the anchor cavity 15 through the pouring hole 18 on the lower end plate and then into the end of the jacketed steel pipe facing the anchor cavity through the grouting hole 132. After the cement grout solidifies, it forms a cast body. The lower anchor and the end of the steel strand located in the anchor cavity are both enclosed in the cast body.

[0039] In this embodiment, to facilitate operation, the sheathed steel pipe 21 includes a pre-buried pipe 211 and a post-buried pipe 212. The pre-buried pipe 211 is pre-welded to the steel cage 12, with one end of the pre-buried pipe connected to the anchor cavity and the other end extending 200 mm from the upper end face of the precast concrete block. The steel strand is inserted into the pre-buried pipe 211, and one end of the steel strand is passed through the threading hole 131 on the supporting steel plate and then into the anchor cavity. The lower anchor 23 is used to lock the end of the steel strand that has entered the anchor cavity, so that the lower anchor 23 is accommodated in the anchor cavity, and the other end of the steel strand extends out of the pre-buried pipe 211 away from the anchor cavity.

[0040] Pour cement grouting material into the anchor cavity, and the cement grouting material enters the embedded pipe from the anchor cavity through the grouting hole 132 until the cement grouting material emerges from the end of the embedded pipe 211 away from the anchor cavity. Stop pouring the cement grouting material, and after the cement grouting material solidifies, put the rear connecting pipe 212 on the steel strand, and then weld the rear connecting pipe 212 to the end of the embedded pipe 211 away from the anchor cavity to form a complete sheathed steel pipe 21. Figure 3 In the figure, the third mark 213 represents the weld between the embedded pipe 211 and the rear pipe 212.

[0041] Use wire or other fixings to temporarily fix the end of the steel strand extending out of the sheathed steel pipe away from the anchor cavity to the end of the sheathed steel pipe away from the anchor cavity to prevent the end of the steel strand from falling into the sheathed steel pipe and affecting subsequent construction efficiency.

[0042] In this embodiment, when pouring cement grout, the cement grout emerges from the end of the embedded pipe away from the anchor cavity. Since the embedded pipe extends 200 mm from the upper end surface of the concrete precast block, when the anchor pier is sunk into the pile hole, the upper end surface of the cement grout extends upward by 200 mm from the upper end surface of the concrete precast block. It is understood that in other embodiments, the other end of the embedded pipe can extend 100 mm, 150 mm, 250 mm, or 300 mm from the upper end surface of the concrete precast block, and of course, other values ​​between 100 and 300 mm can also be used. Therefore, when the anchor pier is sunk into the pile hole, the upper end surface of the cement grout extends upward by 100 mm, 150 mm, 250 mm, or 300 mm, or other corresponding values, from the upper end surface of the concrete precast block.

[0043] (2) Drill a pile hole 30, sink the anchor pier carrying the steel strand into the pile hole, and make the lower end of the concrete prefabricated block face downward so that the first axis extends in the vertical direction and the top surface of the sheathed steel pipe is located within the height range of the bottom plate of the underground structure.

[0044] (3) Pour concrete into the pile hole until the set elevation is reached. After the concrete solidifies, it forms a concrete body. To prevent concrete from entering the sheathed steel pipe during pouring, plastic foam is used to plug the port at the top of the sheathed steel pipe. After the excavation of the foundation pit is completed, the plastic foam is removed when the steel strand is tensioned. Of course, other materials can also be used to temporarily plug the port at the top of the sheathed steel pipe.

[0045] (4) Excavating a foundation pit and completing it, pouring a foundation leveling cushion layer and a foundation waterproof cushion layer in sequence from bottom to top in the foundation pit, and the foundation leveling cushion layer and the foundation waterproof cushion layer together form a cushion layer 41.

[0046] (5) A water-stop steel plate 25 is welded on the outer wall of the top of the sheathed steel pipe 21, and then a pad 26 is welded on the top surface of the sheathed steel pipe 21. A steel strand hole is opened on the pad 26 so that the steel strand can freely pass through the pad 26 upward through the steel strand hole. The iron wire or other fixing parts that temporarily fix the steel strand are removed, and the steel strand is tensioned. After the tensioning is completed, the steel strand is anchored by the upper anchor 27 to form the steel strand into a prestressed steel strand 22; then the grouting pipe is inserted into the sheathed steel pipe, and cement slurry is injected into the sheathed steel pipe. The cement slurry is bonded to the cement grouting material at the bottom of the sheathed steel pipe.

[0047] (6) A waterproof layer 42 is constructed on the cushion layer, and then the base plate 43 of the underground structure is constructed. The water-stop steel plate, the base plate, the upper anchor and the upper end of the steel strand are all poured into the base plate 43 of the underground structure.

Claims

1. A prestressed anti-floating anchor, characterized in that: The concrete body comprises an anchor pier sunk at the bottom of the pile hole, a prestressed steel strand connected to the anchor pier, and a concrete body formed by concrete poured into the pile hole, wherein the prestressed steel strand is formed by tensioning the steel strand; The anchor pier includes a concrete precast block and a steel cage cast in the concrete precast block, and an anchor cavity with an opening facing downward is provided at the lower end of the anchor pier, and a sheathed steel pipe is fixedly connected to the concrete precast block, the sheathed steel pipe is welded to the steel cage, and the lower end of the sheathed steel pipe is downwardly connected to the anchor cavity, and the top of the sheathed steel pipe is located in the bottom plate of the underground structure; the prestressed steel strand is passed through the sheathed steel pipe, and the lower end of the prestressed steel strand extends downward from the sheathed steel pipe and enters the anchor cavity and is locked by the lower anchor, and a casting body formed by cement grouting material is provided in the anchor cavity, and the lower end of the prestressed steel strand and the lower anchor are both wrapped in the casting body; the upper end of the prestressed steel strand extends upward from the sheathed steel pipe and is locked by the upper anchor, and cement slurry is poured in the sheathed steel pipe.

2. The prestressed anti-floating anchor according to claim 1, characterized in that: A lower end plate is fixedly installed on the lower end surface of the concrete prefabricated block, which blocks the opening of the anchor cavity. The lower end plate is provided with a pouring hole communicating with the inside and outside of the anchor cavity, and cement grouting material is poured into the anchor cavity through the pouring hole.

3. The prestressed anti-floating anchor rod according to claim 2, characterized in that: A connecting rib is provided on the prefabricated concrete block, and the lower end plate is fixed on the connecting rib. The connecting rib is not connected to the steel cage and the sheathed steel pipe.

4. The prestressed anti-floating anchor according to claim 1, characterized in that: Anchoring bars are arranged on the prefabricated concrete block. The anchoring bars extend upward from the upper end surface of the prefabricated concrete block and then extend into the interior of the concrete body.

5. The prestressed anti-floating anchor rod according to claim 4, characterized in that: The length of the anchor bar extending into the concrete body is 100-500mm.

6. The prestressed anti-floating anchor according to claim 1, characterized in that: A supporting steel plate is provided between the lower anchor and the sheath steel pipe, and the anchor cavity is connected to the inner cavity of the sheath steel pipe through the supporting steel plate.

7. The prestressed anti-floating anchor according to claim 1, characterized in that: The cast body in the anchor cavity extends into the inner cavity of the sheath steel pipe, and the cast body is bonded to the cement slurry in the inner cavity of the sheath steel pipe.

8. The prestressed anti-floating anchor rod according to claim 1, characterized in that: The inner diameter of the pile hole is 50-100mm larger than the outer diameter of the anchor pier.

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