Variable cross-section anti-floating anchor rod and construction method

Abstract

The invention discloses a variable cross-section anti-floating anchor rod and a construction method. The anti-floating anchor rod comprises an anchoring device, an anchor rod body and a variable cross-section anchoring structure. The anchoring device comprises a sealing device, a fastening device and a pressure device, the sealing device is connected with the upper end of the anchor rod, the pressure device is arranged at the top of the sealing device, and the fastening device is connected with the upper end of the anchor rod and used for enabling the pressure device to enable the sealing device to seal a drill hole; the variable cross-section anchoring structure comprises a capsule and a one-way grouting hole; the capsule is fixed to the lower end of the anchor rod in a sealed mode, and the one-way grouting hole is formed in the anchor rod, located in the capsule and used for injecting a pressure medium into the capsule to enable the capsule to deform. The variable-cross-section anti-floating anchor rod is matched with the gradually-changed circular-truncated-cone-shaped reaming hole, so that the potential hole collapse problem existing in reaming construction can be effectively relieved.

Description

Technical Field

[0001] The invention relates to the technical field of support for building structures and foundations and reinforcement and stabilization of soil and rock structures, and in particular to a variable-section anti-floating anchor rod and a construction method. Background Art

[0002] With the acceleration of urbanization and the shortage of land resources, the development and utilization of underground space has become particularly important. However, some potential problems caused by high groundwater levels will have a serious impact on building structures. Its existence will generate huge buoyancy on buildings, causing the foundation of the building to become unstable. If the building does not take effective anti-floating measures, it may cause cracking, leakage and even overall damage to the foundation, seriously affecting the safety of the building. In addition, the settlement and deformation of the building structure caused by the high groundwater level will affect its integrity and functionality. The use of anti-floating anchors can effectively alleviate this problem. By penetrating the anchor into the solid layer of the foundation and connecting it to the building foundation, the building foundation is provided with pull-out resistance to offset the buoyancy, thereby preventing the building from floating.

[0003] When the uniform cross-section anti-floating anchor is subjected to tension, the peripheral frictional resistance of the surrounding soil to the anti-floating anchor is not evenly distributed, but decays nonlinearly with the increase of the buried depth of the rod body. Generally, the force variation of the upper steel bars is large, while the force variation of the lower steel bars is very small, and its tensile bearing capacity cannot be fully exerted. Summary of the invention

[0004] In order to overcome the problems of hole collapse and insufficient filling of the bladder in traditional variable-section and bladder-type anchor rods, the present invention provides a variable-section anti-floating anchor rod and a construction method, which optimizes its force transmission mechanism to alleviate the potential hole collapse problem in the hole expansion section, while ensuring the normal expansion of the bladder to a certain extent, so as to achieve the requirement of enhancing the anti-floating ability of the anchor rod and promote the rapid development of the anti-floating anchor rod structure.

[0005] The present invention is achieved through the following technical solutions: In a first aspect, the present application proposes a variable-section anti-floating anchor rod, including an anchoring device, an anchor rod, and a variable-section anchoring structure; The anchoring device comprises a sealing device, a fastening device and a pressure device, wherein the sealing device is connected to the upper end of the anchor rod, the pressure device is arranged on the top of the sealing device, and the fastening device is connected to the upper end of the anchor rod, and is used to make the pressure device generate the sealing device to seal the borehole; The variable cross-section anchoring structure includes a capsule and a one-way grouting hole; the capsule is sealed and fixed to the lower end of the anchor rod, and the one-way grouting hole is arranged on the anchor rod and located in the capsule, which is used to inject pressure medium into the capsule to deform the capsule.

[0006] Preferably, a grouting pipe is sleeved on the corresponding anchor rod in the capsule, and a plurality of one-way grouting holes are arranged on the grouting pipe and are arranged at intervals along the axial direction of the anchor rod. The one-way grouting holes are connected to the grouting pipe, and the upper end of the grouting pipe is connected to the grouting pipeline, and the inlet of the grouting pipeline extends to the outside.

[0007] Preferably, the one-way grouting hole comprises a grouting hole and a one-way medium-pressure grouting valve, the grouting hole is arranged on the side wall of the grouting pipe, and the one-way medium-pressure grouting valve is installed on the grouting pipe.

[0008] Preferably, a plurality of conical bearing bodies are arranged at intervals on the anchor rod.

[0009] Preferably, an epoxy anti-corrosion coating is sprayed on the anchor rod.

[0010] In the second aspect, the present application proposes a construction method of a variable-section anti-floating anchor rod, comprising the following steps: Step 1, expanding the preformed anchor hole by high-pressure rotary jet expansion. When expanding the hole, a constant pressure is used to expand the hole expansion section. After reaching a preset position, the airflow of the high-pressure rotary jet is gradually reduced to form a variable-section hole expansion section between the hole expansion section and the anchor section, thereby forming a variable-section anchor hole; Step 2: installing a variable-section anti-floating anchor in the variable-section anchor hole, with the capsule located in the expansion section, and injecting a pressure medium into the capsule; Step 3: Install the anchoring device on the upper end of the anchor rod.

[0011] Preferably, in step 1, the hole is enlarged from bottom to top; The expansion section is expanded first, and then the variable cross-section section is expanded. Preferably, high-pressure jet hole expansion is performed in rock at a lifting speed of 15 cm / min and a rotation speed of 15 r / min, and high-pressure jet hole expansion is performed in silty clay at a lifting speed of 20 cm / min and a rotation speed of 15 r / min.

[0012] Preferably, cement slurry is used for hole expansion.

[0013] Preferably, waterproof nodes are installed at the positions of the anchor rods and the anchor rod holes and a concrete cushion layer is laid, and polymer cement waterproof mortar and cement-based penetrating crystallization waterproofing, as well as an SBS additional layer, are laid around the waterproof nodes.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The present application provides a variable-section anti-floating anchor rod, in which a capsule is arranged at the lower end of the anchor rod, and a pressure medium is injected into the capsule, thereby improving the bonding strength of the soil, which can effectively solve the problems existing in anchor rods with equal cross-sections. As the stress increases, the surrounding soil is subjected to the expansion and compaction effect of the anchor expansion section, which significantly increases the side friction and end resistance of the anchor rod, thereby improving the pull-out bearing capacity of the anchor rod. The use of variable-section anti-floating anchor rods in areas with anti-floating requirements can effectively ensure the stability of the building structure, reduce potential safety hazards, and increase the life cycle of the building structure. Obviously, the application of the optimized variable-section anti-floating anchor rod can provide effective technical support for geotechnical engineering and anti-floating of building structures.

[0015] The construction method of the present application, the variable cross-section anti-floating anchor rod and the gradually changing truncated cone-shaped expansion hole can effectively alleviate the potential hole collapse problem existing in the expansion hole construction. To a certain extent, it reduces the problem that the bag cannot be normally unfolded or the bag is not poured in an ideal state, reduces the number of secondary rework, and improves the yield rate; secondly, the truncated cone-shaped hole can reasonably disperse the soil pressure transmitted from the upper soil, optimizes the force transmission structure, and changes the soil from the original shear force to the pressure, thereby improving the bearing capacity of the soil, making the overall structure more reasonably stressed, and reducing the possibility of local damage in the early stage of pile formation. Compared with the traditional anti-floating anchor rod, the invention can effectively increase the contact area between the slurry of the expansion section and the soil during the tension stage of the anchor rod, increase the frictional resistance between the two, and enhance the overall strength of the anti-floating anchor rod. At the same time, with the increase of tensile stress, the gradually changing part reaches the limit state first and is destroyed, which to a certain extent ensures that the strength of the core area of ​​the anchor rod is not greatly affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the variable cross-section anti-floating anchor structure of the present invention.

[0017] Figure 2 It is a schematic diagram of the waterproof node structure of the present invention.

[0018] Figure 3 It is a cross-sectional view of the non-expanded section of the anchor rod of the present invention.

[0019] Figure 4 It is a schematic diagram of the structure of the conical carrier of the present invention.

[0020] Figure 5 It is a schematic diagram of the anchor plate structure of the present invention.

[0021] In the figure: grouting pipeline 1, anchoring device 2, pad 3, concrete cushion 4, bent steel bar 5, nut 6, spring 7, waterproof node 8, water-swelling water-stop rubber ring 9, non-expanded opening 10, anti-corrosion coating 11, anchor rod 12, conical bearing body 13, truncated cone opening 14, cylindrical opening 15, capsule 16, rubber gasket 17, exhaust pipe 18, variable cross-section anchoring structure 19, one-way medium pressure grouting valve 20, anchor plate 21, drill bit 22, polymer cement waterproof mortar 23, cement-based penetrating crystallization waterproof 24, SBS additional layer 25. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0023] See also Figure 1-5 , a variable-section anti-floating anchor rod, comprising an anchoring device 2, an anchor rod 12 and a variable-section anchoring structure 19; The anchoring device 2 includes a sealing device, a fastening device and a pressure device. The sealing device is connected to the upper end of the anchor rod 12. The pressure device is arranged on the top of the sealing device. The fastening device is connected to the upper end of the anchor rod and is used to make the pressure device generate the sealing device to seal the borehole. The variable cross-section anchoring structure 19 includes a capsule 16 and a one-way grouting hole; the capsule 16 is sealed and fixed to the lower end of the anchor rod, and the one-way grouting hole is arranged on the anchor rod and located in the capsule 16, which is used to inject pressure medium into the capsule to deform the capsule.

[0024] In some embodiments, the capsule 16 is sleeved on the lower part of the anchor rod, and the lower end of the anchor rod passes through the capsule, and an anchor plate 21 is provided at the lower end of the anchor rod. A grouting pipe is sleeved on the anchor rod in the capsule 16, and a plurality of one-way grouting holes are provided on the grouting pipe, which are arranged at intervals along the axial direction of the anchor rod. The one-way grouting holes are connected to the grouting pipe, and the upper end of the grouting pipe is connected to the grouting pipeline 1. The inlet of the grouting pipeline 1 extends to the outside, and the pressure medium enters the grouting pipe through the grouting pipeline, and then enters the capsule through the one-way grouting hole to cause it to deform.

[0025] The one-way grouting hole comprises a grouting hole and a one-way medium-pressure grouting valve 20 installed on the anchor rod. The grouting hole is arranged on the side wall of the grouting pipe. The one-way medium-pressure grouting valve is installed on the grouting pipe and communicated with the grouting pipe through the grouting hole.

[0026] A rubber gasket 17 is provided at the contact position between the capsule and the anchor rod to ensure the sealing of the capsule; at the same time, an exhaust pipe 18 is also provided on the capsule, and a drill bit 22 is provided at the lower end of the anchor rod.

[0027] During the grouting process, the slurry enters the grouting pipe through the grouting pipeline 1 and then enters the capsule. The grouting hole is located at the lower end of the capsule, so that the slurry is injected from top to bottom in the capsule, thereby improving the density of the slurry and solving the problem that the slurry in the capsule cannot be vibrated to form foam and density inside. At the same time, an exhaust pipe is arranged in the capsule to discharge the gas in the capsule during the grouting process.

[0028] In some embodiments, the fastening device includes a pad 3, which is sleeved on the upper end of the anchor rod and used to be laid on the concrete cushion layer 4. The pressure device is a spring 7, which is sleeved on the anchor rod and displaced on the pad. A pad is provided on the top of the spring, and a bent steel bar 5 is provided between the two pads. Water-swellable water-stopping rubber rings 9 are provided on both sides of the lower pad to prevent the slurry from overflowing during the grouting stage and affecting the anchoring. The upper end of the anchor rod is connected by a nut. In other embodiments, a plurality of conical bearing bodies 13 are arranged at intervals on the anchor rod. The conical bearing bodies 13 are made of 40cr steel and matched with fine-rolled threaded matching threads to achieve the purpose of fixing the position. The conical centering bearing body 13 is used to fix the downward direction of the anchor rod to ensure that the anchor rod will not deviate from the predetermined hole 15 position.

[0029] In other embodiments, a waterproof node 8 is provided on the anchor rod and is located at the mouth of the drill hole and at the bottom of the concrete cushion layer 4 , so as to achieve preliminary waterproofing and reduce the corrosion of the anchor rod 12 .

[0030] In other embodiments, an epoxy anti-corrosion coating 11 is sprayed on the anchor rod.

[0031] Correspondingly, the present application also provides a construction method of a variable-section anti-floating anchor rod, comprising the following steps: Step 1: Determine the installation hole position of the anchor rod.

[0032] When measuring and laying out the hole positions, fixed points are set outside and clearly marked with red paint for use in measurement, laying out and inspection. This ensures that re-measurements can be carried out frequently during the construction process to ensure the accuracy of the hole positions. After the hole position measurement is completed, the deviation is guaranteed to be less than 20mm.

[0033] Step 2: Drill holes for anchor rods.

[0034] During the drilling stage, before drilling, the verticality of the drill rod is adjusted by the hanging line method. Long spiral drilling rigs are used for anchor holes, and the position of the drilling rig is appropriately adjusted to align the drill bit with the anchor hole to be constructed. The allowable deviation of the anchor inclination is ±1°, and the vertical and horizontal deviations of the drilling position shall not exceed ±150mm. After the hole reaches the designed depth, the drilling shall not be stopped immediately, and the loose soil in the hole shall be cleared after steady drilling for 1 minute.

[0035] Step 3, then use high-pressure rotary jet expansion method to expand the anchor hole. When expanding the hole, it is expanded from bottom to top. First, a constant pressure is used to expand the expansion section. After reaching the preset height, the airflow of the high-pressure rotary jet is gradually reduced to form a variable-section expansion section between the expansion section and the anchor section, forming a variable-section anchor hole.

[0036] High-pressure rotary jet hole expansion uses plain cement slurry for diameter expansion, and the cement strength is not less than 42.5 ordinary Portland cement; the amount of cement is carried out according to the design drawings; the water-cement ratio of the cement slurry is 0.5, the rotary jet pressure is 25MP~30MPa, and the slurry volume is 75L / min.

[0037] When the drilling depth reaches the design requirement, the lifting speed is adjusted according to different types of rocks. In rock, the high-pressure jet hole expansion is carried out at a lifting speed of about 15cm / min and a rotation speed of 15r / min, and in silty clay, the high-pressure jet hole expansion is carried out at a lifting speed of about 20cm / min and a rotation speed of 15r / min.

[0038] Hole expansion is calculated by measuring the length of the drill rod outside the hole. Hole expansion is divided into two stages: In the first stage, the hole expansion section is expanded, and the hole expansion section is a cylindrical opening 15. The lifting speed is reduced to 10 cm / min, and the rotary spraying pressure is linearly adjusted according to the lifting height.

[0039] In the second stage, the variable cross-section section is expanded, and the variable cross-section section is a truncated cone-shaped opening 14. During the expansion process, the injection pressure is gradually reduced to form the truncated cone-shaped opening 14.

[0040] When the expansion length reaches the design requirements, in order to ensure that the diameter of the expansion section meets the design requirements, the expansion section is re-sprayed, and cement slurry is used for spraying mud. The grouting can be detected by observing the back slurry at the hole opening to see whether it meets the requirements.

[0041] After the jet hole expansion is completed, the drill rod is taken out of the hole, and the drilling rig, high-pressure mud pump and pipeline are immediately cleaned with a large amount of clean water. The construction time of a single anchor rod is about 2 hours, and the specific time is determined according to the site conditions and the difficulty of the construction.

[0042] Step 4: Install the anchor in the variable cross-section anchor hole, and the capsule 16 is located in the expansion section.

[0043] During the anchor installation phase, after checking that the rod assembly quality meets the requirements, the capsule 16 medium-pressure grouting pipeline 1 and the anchor 12 are lowered together, and manual assistance is used to avoid twisting, pressing, and bending of the rod. The rod is inserted into the hole no more than 100 mm from the bottom of the hole, and it cannot be lifted at will after placement.

[0044] Step 5: Inject pressure medium into the capsule 16 to make it expand and deform.

[0045] During the grouting stage, the grouting pipeline is first cleaned with clean water, and then the plain cement slurry with a water-cement ratio of 0.5 is replaced. When the color of the slurry flowing out of the slurry pipeline becomes obviously darker, grouting can be performed into the slurry pipeline. A conspicuous mark is set on the slurry bucket to control the grouting amount. The grouting pressure in the capsule 16 is controlled at 1~2MPa. When the grouting volume reaches the specified injection capacity, it can be determined that the capsule is full. Even if there is an overfilling problem, the excess mortar will be discharged due to the exhaust pipe 18 installed in the capsule 16. After the grouting is completed, the grouting pipeline is temporarily blocked, and the secondary grouting treatment is carried out after the cement slurry is initially set for about 4 hours. The slurry is used as soon as it is mixed. After grouting, the rod body must not be knocked or heavy objects hung at will.

[0046] Step 6: Install the anchoring device on the upper end of the anchor rod.

[0047] First, waterproof nodes 8 are installed in the anchor holes and concrete is poured to form a concrete cushion layer connected to the anchor 12. The concrete cushion layer 5 is poured with concrete, with an average thickness of 100 mm. The part close to the anchor is thickened to a thickness of 150 mm, which helps to disperse and transfer the structural load, prevent foundation settlement or uneven settlement, and thus ensure the stability of the anti-floating system. The specific parameters of the steel bars and stirrups used in the anchoring section should be selected according to the specific design requirements.

[0048] Springs and fasteners are installed on the upper surface of the pad 200*200*20 at the waterproof node, the gap between the water-swelling water-stop rubber ring 9 and the anchor rod is filled with paste, the polymer cement waterproof mortar 23 is covered within 300mm around the anchor rod, and the cement-based penetrating crystallization waterproof 24 is brushed within 150mm, plus a 300 wide and 3mm thick SBS additional layer 25.

[0049] The working principle of the variable cross-section anti-floating anchor is as follows: Most of the components of the variable cross-section anti-floating anchor rod play a role in fixing the anchor rod as a whole, such as the bending steel bar 5, the spring 7, and the conical centering bearing body. The anchor rod 12 and the mortar injected into the variable cross-section anchor rod hole play a key role in the tensile strength of the anchor rod.

[0050] The force of the variable cross-section anti-floating anchor is divided into several parts. The stage with small tensile stress can be regarded as the initial stage of the force of the anti-floating anchor. In this stage, the anchor 12 still mainly bears the load, and the deformation is mainly the elongation of the anchor 12 in the non-expanded section, and the anchor 12 shows obvious elastic deformation characteristics.

[0051] As stress increases, the friction between the anchor rod 12 and the slurry filled in the non-expanded opening 10 and the soil decreases, and shear failure begins to occur, resulting in a significant decrease in the bearing capacity of the non-expanded anchoring section. The truncated cone opening 14 and the cylindrical opening 15 begin to bear the main part of the bearing capacity. The expansion section is tensile, resulting in a slight displacement of the structure, so that the surrounding soil of the truncated cone opening 14 and the cylindrical opening 15 is subjected to the expansion and compaction of the anchor body, resulting in additional lateral stress, which increases the lateral friction. In addition, the truncated cone opening 14 and the cylindrical opening 15 produce corresponding end resistance with the squeezed upper soil, so the pull-out bearing capacity continues to increase, which greatly solves the problem of insufficient force on the lower part of the equal-section anchor rod.

[0052] As the stress continues to increase, the plastic zone of the soil around the truncated cone opening 14 and the cylindrical opening 15 continues to expand, and large-scale shear failure occurs in the surrounding soil. The deformation corresponding to the increase in load increases sharply, and the soil at the front end of the truncated cone expansion section is fully compressed and compacted, so that the end bearing capacity of the expansion anchor section increases with the increase in the compression degree of the end soil, and the tensile strength further increases until it is completely destroyed.

[0053] Expanded anchor rods can effectively solve the problems existing in equal-section anchor rods. As stress increases, the surrounding soil is expanded and compacted by the anchor expansion section, which significantly increases the side friction and end resistance of the anchor rod, thereby improving the pull-out bearing capacity of the anchor rod. The use of variable-section anti-floating anchor rods in areas with anti-floating requirements can effectively ensure the stability of the building structure, reduce potential safety hazards, and increase the life cycle of the building structure. Obviously, the application of optimized variable-section anti-floating anchor rods can provide effective technical support for geotechnical engineering and anti-floating of building structures.

[0054] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A variable cross-section anti-floating anchor, characterized in that: It includes an anchoring device, an anchor rod and a variable-section anchoring structure; The anchoring device comprises a sealing device, a fastening device and a pressure device, wherein the sealing device is connected to the upper end of the anchor rod, the pressure device is arranged on the top of the sealing device, and the fastening device is connected to the upper end of the anchor rod, and is used to make the pressure device generate the sealing device to seal the borehole; The variable cross-section anchoring structure includes a capsule and a one-way grouting hole; the capsule is sealed and fixed to the lower end of the anchor rod, and the one-way grouting hole is arranged on the anchor rod and located in the capsule, which is used to inject pressure medium into the capsule to deform the capsule.

2. The variable cross-section anti-floating anchor rod according to claim 1, characterized in that: A grouting pipe is sleeved on the corresponding anchor rod in the capsule, and a plurality of one-way grouting holes are arranged on the grouting pipe and spaced apart along the axial direction of the anchor rod. The one-way grouting holes are connected to the grouting pipe, and the upper end of the grouting pipe is connected to the grouting pipeline, and the inlet of the grouting pipeline extends to the outside.

3. The variable cross-section anti-floating anchor according to claim 1, characterized in that: The one-way grouting hole comprises a grouting hole and a one-way medium-pressure grouting valve. The grouting hole is arranged on the side wall of the grouting pipe, and the one-way medium-pressure grouting valve is installed on the grouting pipe.

4. The variable cross-section anti-floating anchor according to claim 1, characterized in that: A plurality of conical bearing bodies are arranged at intervals on the anchor rod.

5. The variable cross-section anti-floating anchor according to claim 1, characterized in that: An epoxy anti-corrosion coating is sprayed on the anchor rod.

6. A construction method for a variable cross-section anti-floating anchor as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, expanding the preformed anchor hole by high-pressure rotary jet expansion. When expanding the hole, a constant pressure is used to expand the hole expansion section. After reaching a preset position, the airflow of the high-pressure rotary jet is gradually reduced to form a variable-section hole expansion section between the hole expansion section and the anchor section, thereby forming a variable-section anchor hole; Step 2: installing a variable-section anti-floating anchor in the variable-section anchor hole, with the capsule located in the expansion section, and injecting a pressure medium into the capsule; Step 3: Install the anchoring device on the upper end of the anchor rod.

7. The construction method of a variable cross-section anti-floating anchor rod according to claim 6, characterized in that: When expanding the hole in step 1, the hole is expanded from bottom to top; The expansion section is expanded first, and then the variable cross-section section is expanded.

8. The construction method of a variable cross-section anti-floating anchor rod according to claim 6, characterized in that: High-pressure jet hole expansion was performed in rock at a lifting speed of 15 cm / min and a rotation speed of 15 r / min, and in silty clay at a lifting speed of 20 cm / min and a rotation speed of 15 r / min.

9. The construction method of a variable cross-section anti-floating anchor rod according to claim 6, characterized in that: Use cement slurry to expand the hole.

10. The construction method of a variable cross-section anti-floating anchor rod according to claim 6, characterized in that: Waterproof nodes are installed at the positions of the anchor rods and the anchor rod holes and a concrete cushion layer is laid. Polymer cement waterproof mortar and cement-based penetrating crystallization waterproofing, as well as an SBS additional layer, are laid around the waterproof nodes.

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