Prestressed anti-corrosion and anti-floating anchor rod and construction method

Abstract

The present invention discloses a prestressed anti-corrosion and anti-floating anchor and a construction method, wherein a plurality of slow-bonding prestressed steel strands, the lower end of the slow-bonding prestressed steel strands, a first water stop plate and a lower pressure plate are integrally formed by pre-grouting and pouring to form a first column, a portion of the first water stop plate is exposed from the first column, and a second column is formed after continued pouring outside the exposed portion of the first water stop plate to form a prefabricated anchor, the second column wraps the exposed portion of the first water stop plate, the upper portion of the slow-bonding prestressed steel strand is sleeved with a second water stop plate, and a supplementary pouring is formed between the inside of the second water stop plate and the slow-bonding prestressed steel strand to form a supplementary pouring column, so that the supplementary pouring column is connected to the second column. In the above manner, the prestressed anti-corrosion and anti-floating anchor and a construction method of the present invention adopt slow-bonding prestressed steel strands, and a new waterproof structure and construction method are used to prevent the anchor from being corroded by water as a whole, and to avoid the problem of failure of the anti-floating anchor.

Description

Technical Field

[0001] The invention relates to the field of prestressed anti-floating anchor rods, and in particular to a prestressed anti-corrosion anti-floating anchor rod and a construction method. Background Art

[0002] Anti-floating anchor rods are an anti-floating technology used by underground structures to resist water buoyancy. They are widely used both at home and abroad, especially in China in recent years. As the burial depth of underground projects such as building basements, subways, underground transportation hubs, underground spaces, and hydraulic structures becomes deeper and deeper, anti-floating anchor rods are increasingly playing an irreplaceable and important role.

[0003] Anti-floating anchor rods are generally permanent structures, which are divided into two categories: prestressed anchor rods and fully bonded anchor rods (non-prestressed anchor rods). The construction process of prestressed anchor rods is relatively complicated, the construction management is inconvenient, and a casing needs to be set when the anchor head passes through the underground structure. Waterproof measures need to be taken inside and outside the casing, and waterproofing is difficult. Therefore, the steel strands in the anti-floating anchor rods will be eroded by groundwater and gradually corroded, and the tensile bearing capacity will be reduced. In severe cases, the stressed steel bars may be broken, causing the anti-floating components to fail. Summary of the invention

[0004] The main technical problem solved by the present invention is to provide a prestressed anti-corrosion and anti-floating anchor rod and its construction method, adopt slow-bonding prestressed steel strands, and use a new waterproof structure and construction method to prevent the entire anchor rod from being corroded by water, thereby avoiding the problem of failure of the anti-floating anchor rod.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a prestressed anti-corrosion and anti-floating anchor rod, comprising a plurality of slow-bonding prestressed steel strands, the slow-bonding prestressed steel strands are supported in the vertical direction by installing a centering isolation frame, the lower end passes through the lower pressure plate and is connected to the extrusion anchor, the upper end of the slow-bonding prestressed steel strand is inclined and bent to the vertical direction, the lower end of the slow-bonding prestressed steel strand is sleeved with a first waterstop plate, the first waterstop plate, the lower pressure plate and the lower end of the slow-bonding prestressed steel strand are integrally formed by pre-grouting and pouring to form a first column, part of the first waterstop plate is exposed from the first column, and a second column is formed after continuing to pour outside the exposed part of the first waterstop plate to form a prefabricated anchor rod, the second column wraps the exposed part of the first waterstop plate, and the first column and the second column are integrally connected through the first waterstop plate, the upper part of the slow-bonding prestressed steel strand is sleeved with a second waterstop plate, and a supplementary pouring is formed between the inside of the second waterstop plate and the slow-bonding prestressed steel strand.

[0006] In a preferred embodiment of the present invention, the second column is directly cast outside the borehole and then the prefabricated anchor rod is placed in the borehole, or the first column is cast and the above part is placed in the borehole and then the second column is cast in the borehole, and the first column and the second column are cylindrical structures.

[0007] In a preferred embodiment of the present invention, the first water stop plate is an annular water stop plate, and its upper and lower ends are funnel-shaped openings.

[0008] In a preferred embodiment of the present invention, the slow-bonding prestressed steel strands are evenly arranged at center intervals below the lower pressure plate, the upper ends of the slow-bonding prestressed steel strands are sleeved with a water-stop ring that expands when exposed to water, the upper ends of the slow-bonding prestressed steel strands pass through the upper pressure plate and are connected to the finished anchor, a first elastic member is installed between the lower end of the slow-bonding prestressed steel strand and the lower pressure plate, a second elastic member is installed between the upper end and the upper pressure plate, the upper ends of the slow-bonding prestressed steel strands are bent, and the bending radius of curvature is 5000 mm.

[0009] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide a construction method of the above prestressed anti-corrosion and anti-floating anchor rod, comprising the following steps: a. Prefabricated anchor rod: at least three slow-bonding prestressed steel strands are evenly distributed along the circumference, and supported and fixed by a plurality of centering spacers arranged at intervals in the vertical direction, and the lower end passes through the first water stop plate and is connected with the lower pressure plate, the first elastic member and the extrusion anchor, and the mold is set on the outside of the lower end of the steel strand, and the upper half of the first water stop plate is exposed from the mold, and then grouting is performed to form a first column, and after the pouring is completed, the mold is removed and maintained, and the outside of the first column is treated with anti-seepage to form a prefabricated anchor rod; b. Drilling: before drilling, the hole position is determined according to the design requirements, and marking is made, and wet drilling is adopted. After drilling, the hole is cleaned with water until clear water flows out of the hole mouth; c. Grouting: Place the pouring conduit and the prefabricated anchor rod made in step a into the drilled hole together, and complete the grouting in one go using the grouting material. Stop grouting when the hole overflows. Replenish the grout in time before the final setting until the slurry is full. Determine the grouting pressure based on the engineering conditions and design requirements to ensure the slurry grouting density. After grouting, the second column and the first column are connected as a whole through the first water stop ring so that water can only penetrate upwards; d. End treatment: excavate along the periphery of the precast anchor to form a construction pit, break the casting part of the upper end of the precast anchor, and then put on the second water stop plate. The inside of the second water stop plate is cast to form a supplementary cast column and the second column are connected. Then pour the cushion layer. The pouring height of the cushion layer must be lower than the second water stop plate, and the upper end of the second water stop plate must be exposed. Then tie the steel bars longitudinally and transversely on the cushion layer. After the steel bars are tied, install the water stop ring, upper pressure plate, second elastic member and anchor on each slow-bonding prestressed steel strand and reserve the tensioning groove, and then pour the bottom plate and surface layer; e. Tensioning and anchor sealing: Tensioning can only be carried out after the concrete strength of the bottom plate reaches 100% of the design strength. After the prestressed tendons are tensioned, the end treatment is done well.

[0010] In a preferred embodiment of the present invention, in step a, a portion of the PE jacket is stripped off the lower end of the slow-bonding prestressed steel strand for extrusion, and the steel strand is exposed 1 to 5 mm from the extrusion anchor, stains on the surface of the slow-bonding steel strand are removed, and an isolation frame is installed every 1000 mm for centering and fixed by binding. After the mold is removed, two coats of waterproofing agent are applied for anti-penetration treatment, and C40 concrete is used for grouting and pouring to form the first column.

[0011] In a preferred embodiment of the present invention, before drilling in step b, the hole position is determined according to the design requirements and marked. The anchor hole positioning deviation should not be greater than 20 mm, the anchor hole deflection should not be greater than 1%, and the drilling depth should not be less than the designed length of the anchor rod, nor greater than the designed length.

[0012] In a preferred embodiment of the present invention, when inserting the anchor rod in step c, the prestressed tendons should be prevented from twisting, compression and bending, the rod body is inserted at an angle consistent with the drilling angle, and the second column is formed by underwater pouring of C35 fine stone concrete.

[0013] In a preferred embodiment of the present invention, in step d, the bottom plate steel bars should actively avoid or bypass the steel strands. After the bottom plate steel bars are tied, rubber water stop rings and welded tensioning end pads are installed one by one. Each steel strand is protected from two water stop rings within the bottom plate range, and tensioning grooves are reserved with polystyrene foam boards.

[0014] In a preferred embodiment of the present invention, in the end sealing treatment in step e, the excess steel strands are first cut off with a grinding wheel, and the length of the remaining exposed steel strands is not less than 30 mm. Then the tensioning end and its surroundings are cleaned, two coats of waterproofing agent are applied, and finally the tensioning end is sealed with micro-expanded fine stone concrete and vibrated to make it dense.

[0015] The beneficial effects of the present invention are as follows: the prestressed anti-corrosion and anti-floating anchor rod and its construction method of the present invention adopt slow-bonding prestressed steel strands, and through a new waterproof structure and construction method, prevent the entire anchor rod from being corroded by water, avoid the problem of failure of the anti-floating anchor rod, and have a service life of more than 50 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0017] Figure 1 It is a structural schematic diagram of a preferred embodiment of the prestressed anti-corrosion and anti-floating anchor rod and the construction method of the present invention;

[0018] Figure 2 yes Figure 1 Schematic diagram of the local structure;

[0019] Figure 3 yes Figure 1 Schematic diagram of the local structure;

[0020] Figure 4 yes Figure 1 Schematic diagram of the local structure (the slow-bonding prestressed steel strands are not drawn in the figure);

[0021] The markings of the components in the accompanying drawings are as follows: 1. Slow-bonding prestressed steel strand, 2. Centering isolation frame, 3. Lower pressure plate, 4. Extrusion anchor, 5. First waterstop plate, 6. First column, 7. Second column, 8. Second waterstop plate, 9. Supplementary pouring column, 10. First elastic part, 11. Second elastic part, 12. Waterstop ring, 13. Finished anchor, 14. Upper pressure plate, 15. Pad layer, 16. Base layer, 17. Surface layer. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] See also Figures 1 to 4 A prestressed anti-corrosion and anti-floating anchor rod comprises a plurality of slow-bonding prestressed steel strands 1, the slow-bonding prestressed steel strands 1 are supported in the vertical direction by installing a centering isolation frame 2, the lower end of the slow-bonding prestressed steel strands 1 passes through a lower pressure plate 3 and is connected to an extrusion anchor 4, the upper end of the slow-bonding prestressed steel strands 1 is inclined and bent with respect to the vertical direction, the lower end of the slow-bonding prestressed steel strands 1 is sleeved with a first water stop plate 5, the first water stop plate 5, the lower pressure plate 3 and the lower end of the slow-bonding prestressed steel strands 1 are integrally formed by pre-grouting and pouring to form a prefabricated Anchor rods, part of the first water stop plate 5 is exposed from the first column 6, prefabricated anchor rods and grouting pipes are put into the drilled hole and then grouting is performed to form the second column 7, the second column 7 wraps the exposed part of the first water stop plate 5, the first column 6 and the second column 7 are connected as a whole through the first water stop plate 5, the second water stop plate 8 is sleeved on the upper part of the slow-bonding prestressed steel strand 1, and a supplementary pouring column 9 is formed between the inside of the second water stop plate 8 and the slow-bonding prestressed steel strand 1, so that the supplementary pouring column 9 and the second column 7 are connected.

[0024] In addition, the first water stop plate 5 is an annular water stop plate, and its upper and lower ends are funnel-shaped openings.

[0025] In addition, the slow-bonding prestressed steel strands 1 are evenly arranged at center intervals below the pressure plate 3, the upper end of the slow-bonding prestressed steel strand 1 is sleeved with a water stop ring 12 that expands when exposed to water, the upper end of the slow-bonding prestressed steel strand 1 passes through the upper pressure plate 14 and is connected to the finished anchor 13, a first elastic member 10 is installed between the lower end of the slow-bonding prestressed steel strand 1 and the lower pressure plate 3, a second elastic member 11 is installed between the upper end and the upper pressure plate 14, the upper end of the slow-bonding prestressed steel strand 1 is bent, and the bending curvature radius is 5000 mm.

[0026] In addition, the first column 6 and the second column 7 are cylindrical structures.

[0027] A construction method for a prestressed anti-corrosion and anti-floating anchor rod comprises the following steps:

[0028] a. Prefabricated anchor rods: Use 17.8mm slow-bonding prestressed steel strands, whose performance should meet the requirements of "Steel Strands for Prestressed Concrete" (GB / T5224-2014). The standard tensioning application period of the slow-setting adhesive is 180 days, and the standard curing time is 540 days. The slow-bonding prestressed steel strands must be tensioned within the tensioning application period. The PE jacket of the lower end of the slow-bonding prestressed steel strand is peeled off for extrusion. The steel strand is exposed 1 to 5 mm from the extrusion anchor. The stains on the surface of the slow-bonding steel strand are removed. An isolation frame is installed every 1000 mm for centering and fixed with binding. Three slow-bonding prestressed steel strands are evenly distributed along the circumference and supported and fixed by three centering isolation frames arranged at intervals in the vertical direction. The lower end passes through the first water stop plate and is connected with the lower pressure plate, the first elastic member and the extrusion anchor. The mold is set on the outside of the lower end of the steel strand. The upper half of the first water stop plate is exposed from the mold. Then, C40 concrete is grouted to form the first column. After the pouring is completed, the mold is removed and maintained. Two coats of waterproofing agent are applied to the outside of the first column for anti-seepage treatment to make a prefabricated anchor rod.

[0029] b. Drilling: Before drilling, the hole position should be determined and marked according to the design requirements. The hole positioning deviation should not be greater than 20mm, and the anchor hole deflection should not be greater than 1%. Wet drilling should be adopted. After drilling, the hole should be cleaned with water until clear water flows out of the hole. The hole diameter should be greater than 200mm, and the drilling depth should not be less than the design length of the anchor rod, nor greater than 500mm of the design length;

[0030] c. Pouring: Place the casting conduit and the prefabricated anchor rod made in step a into the borehole together. Prevent the prestressed tendons from twisting, compression and bending. The angle of the rod body should be consistent with the drilling angle. The distance from the end of the casting conduit to the fixed end surface layer should not be less than 100mm. The casting conduit is poured with cement-based grouting material or M40 cement composite mortar. Grouting is completed in one go with the grouting material. The conduit is buried in the grouting material for not less than 1000mm. It is strictly forbidden to produce mud-entrained necking. When pouring, stop grouting when the hole overflows. The slurry should be replenished in time before final setting until it is full. The pouring pressure is determined according to the engineering conditions and design requirements to ensure the slurry pouring density. The test blocks for slurry strength test should not be less than one group for every 30 anchor rods, and each group should be no less than 6 test blocks. The strength of the test blocks meets the design requirements and the strength is not less than 30Mpa. After grouting, the second column and the first column are connected as a whole through the first water stop ring so that water can only penetrate upward;

[0031] d. End treatment: excavate along the periphery of the precast anchor to form a construction pit, break the casting part of the upper end of the precast anchor, and then put on the second water stop plate. The inside of the second water stop plate is cast to form a supplementary cast column and the second column are connected. Then pour the cushion layer. The pouring height of the cushion layer must be lower than the second water stop plate, and at least 1 / 3 of the second water stop plate is exposed. Then tie the steel bars longitudinally and transversely on the cushion layer. After the steel bars are tied, install the water stop ring, upper bearing plate, second elastic member and anchor on each slow-bonding prestressed steel strand, and reserve the tensioning groove with polystyrene foam board, and then pour the bottom plate and surface layer;

[0032] e. Tensioning and anchoring: Tensioning can be carried out only after the concrete strength of the bottom slab reaches 100% of the design strength. The pull-out bearing capacity characteristic value Nka is 400KN. The tensioning force F1 of the test pile anchor is controlled at 2 times the pull-out bearing capacity characteristic value 800KN; the construction anchor locking tensioning force F2 is controlled at 650KN. During tensioning, the stress control method should be adopted as the main method and the strain verification method should be adopted. The actual elongation value force record should be within the range of -6% to +6% from the calculated value. During construction, the prestressing record should be kept on site. Tensioning should be uniform and orderly to avoid the adverse effects of concentrated tensioning in local areas on adjacent anchors. It is forbidden to disturb the tendons, jacks or other anchor clamps during tensioning. After the prestressed tendons are tensioned, the ends are sealed. First, the excess steel strands are cut off with a grinding wheel. The remaining exposed steel strands are not less than 30 mm long. Then the tensioned ends and their surroundings are cleaned and two coats of waterproofing agent are applied. Finally, the pit wall is coated with cement-based penetrating crystallization waterproofing material and then the tensioned ends are sealed with micro-expanded fine stone concrete and vibrated to make them dense. Figure 2 As shown, since the first water stop plate connects the first column and the second column as a whole, the bottom water will not enter the slow-bonding prestressed steel strand laterally, but will flow in the vertical direction, and will not cause corrosion to the slow-bonding prestressed steel strand. Figure 3 As shown, similarly, the upper water also flows in the vertical direction and will not cause corrosion to the slow-bonding prestressed steel strands.

[0033] In Example 2, in step c, the second column is cast on the first column cast in step a outside the borehole, the second column and the first column are integrally connected via the first water stop ring, and then the above parts are inserted into the borehole again, and step d is continued after additional casting. The rest is the same as in Example 1.

[0034] Different from the prior art, the prestressed anti-corrosion and anti-floating anchor rod and its construction method of the present invention adopt slow-bonding prestressed steel strands, and prevent the entire anchor rod from being corroded by water through a new waterproof structure and construction method, thereby avoiding the problem of failure of the anti-floating anchor rod, and the service life is as long as more than 50 years.

[0035] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A construction method for a prestressed anti-corrosion and anti-floating anchor rod, characterized in that: The prestressed anti-corrosion and anti-floating anchor comprises a plurality of slow-bonding prestressed steel strands, the slow-bonding prestressed steel strands are supported in the vertical direction by installing a centering isolation frame, the lower end of the slow-bonding prestressed steel strands passes through the lower pressure plate and is connected to the extrusion anchor, the upper end of the slow-bonding prestressed steel strands is inclined and bent to the vertical direction, the lower end of the slow-bonding prestressed steel strands is sleeved with a first waterstop plate, the first waterstop plate, the lower pressure plate and the lower end of the slow-bonding prestressed steel strands are integrally formed by pre-grouting and pouring to form a first column, a portion of the first waterstop plate is exposed from the first column, and a second column is formed by continuing to pour outside the exposed portion of the first waterstop plate to form an anchor, the second column wraps the exposed portion of the first waterstop plate, and the first column and the second column are integrally connected through the first waterstop plate, the upper part of the slow-bonding prestressed steel strand is sleeved with a second waterstop plate, A supplementary pouring column is formed between the interior of the second water stop plate and the slow-bonding prestressed steel strands by additional pouring, the slow-bonding prestressed steel strands are evenly arranged at the center interval of the lower pressure plate, the upper end of the slow-bonding prestressed steel strand is sleeved with a water stop ring that expands when exposed to water, the upper end of the slow-bonding prestressed steel strand passes through the upper pressure plate and is connected to the finished anchor, a first elastic member is installed between the lower end of the slow-bonding prestressed steel strand and the lower pressure plate, a second elastic member is installed between the upper end and the upper pressure plate, the upper end of the slow-bonding prestressed steel strand is bent, and its bending curvature radius is 5000mm; The construction method includes the following steps: a. Prefabricated anchor rod: at least three slow-bonding prestressed steel strands are evenly distributed along the circumference and supported and fixed by multiple centering spacers arranged at intervals in the vertical direction. The lower end passes through the first water stop plate and is connected to the lower pressure plate, the first water stop plate and the extrusion anchor. The mold is set on the outside of the lower end of the steel strand, and the upper half of the first water stop plate is exposed from the mold. Then grouting is performed to form the first column. After the pouring is completed, the mold is removed and maintained, and the outside of the first column is treated with anti-seepage; b. Drilling: Before drilling, determine the hole position and mark it according to the design requirements. Use wet drilling. After drilling, clean the hole with water until clear water flows out of the hole. c. Grouting: Place the pouring conduit and the anchor rod made in step a into the borehole together, and use the grouting material to complete the grouting in one go. When the hole overflows during grouting, the grouting can be stopped. The grouting should be replenished in time before the final setting until the slurry is full. The grouting pressure is determined according to the engineering conditions and design requirements to ensure the grouting density. After grouting, the second column and the first column are connected as a whole through the first water stop ring so that water can only penetrate upwards; d. End treatment: excavate along the outer periphery of the anchor rod to form a construction pit, break the cast part of the upper end of the anchor rod, and then put on the second water stop plate. The inside of the second water stop plate is cast and formed to connect the supplementary cast column and the second column, and then cast the cushion layer. The pouring height of the cushion layer must be lower than the second water stop plate, and the upper end of the second water stop plate must be exposed. Then, tie the steel bars longitudinally and transversely on the cushion layer. After the steel bars are tied, install the water stop ring, upper bearing plate, second elastic member and anchor on each slow-bonding prestressed steel strand and reserve the tensioning groove, and then cast the bottom plate and surface layer; e. Tensioning and anchoring: Tensioning can be carried out only after the concrete strength of the bottom slab reaches 100% of the design strength. The end of the prestressed tendons should be capped after tensioning.

2. The construction method according to claim 1, characterized in that: After the first column is cast, the above part is placed in the drilled hole and then the second column is cast in the drilled hole. The first column and the second column are cylindrical structures.

3. The construction method according to claim 1, characterized in that: The first water stop plate is an annular water stop plate, and its upper and lower ends are funnel-shaped openings.

4. The construction method according to claim 1, characterized in that: In the step a, a portion of the PE jacket is stripped off the lower end of the slow-bonding prestressed steel strand for extrusion, and the steel strand is exposed 1 to 5 mm from the extrusion anchor, stains on the surface of the slow-bonding steel strand are removed, and an isolation frame is installed every 1000 mm to align the center and fix it with binding. After removing the mold, two coats of waterproofing agent are applied for anti-penetration treatment, and C40 concrete is used for grouting and pouring to form the first column.

5. The construction method according to claim 1, characterized in that: Before drilling in step b, the hole position is determined according to the design requirements and marked. The anchor hole positioning deviation should not be greater than 20 mm, the anchor hole deflection should not be greater than 1%, and the drilling depth should not be less than the designed length of the anchor rod, nor greater than the designed length.

6. The construction method according to claim 1, characterized in that: The step c or continues to cast the second column on the first column cast in step a outside the drilled hole, the second column and the first column are integrally connected by a first water stop ring, and then the above parts are inserted into the drilled hole again, and step d is continued after additional casting.

7. The construction method according to claim 1, characterized in that: In the step d, the bottom plate reinforcement should actively avoid or bypass the steel strands. After the bottom plate reinforcement is tied, rubber water stop rings and welded tensioning end pads are installed one by one. Each steel strand is protected from two water stop rings within the bottom plate range, and tensioning grooves are reserved with polystyrene foam boards.

8. The construction method according to claim 1, characterized in that: In the end sealing treatment in step e, the excess steel strands are first cut off with a grinding wheel, and the remaining exposed steel strands are not less than 30 mm in length. Then the tensioning end and its surroundings are cleaned, and two coats of waterproofing agent are applied. Finally, the pit wall is coated with cement-based penetrating crystallization waterproof material, and then the tensioning end is sealed with micro-expanded fine stone concrete and vibrated to make it dense.

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