Characteristics of prestressed anchor bolts and their applications

Description :

　　Construction method of prestressed anchor rod

　　(1) Special soil anchor drilling rig is selected for drilling, with an outer casing diameter of φ ХХ mm. The drill bit is hollow and directly installed on the outer casing, with an outer diameter of φ ХХ mm. After the completion of drilling, verify that there is no residual soil core inside the sleeve to ensure that the tie rod harness can be smoothly inserted into the hole.

　　(2) The treatment and removal of mud water generated during the pore forming process shall be promptly treated and removed. The mud shall be discharged through the drainage ditch to the collection well, and the clean water shall be pumped out by the water pump. The mud shall be transported away by tank trucks.

　　(3) Pull out the drill rod in a timely manner after completing the drilling, which is beneficial for the next step of pulling out the casing.

　　(4) After placing the anchor rods and transporting them to the site, conduct a comprehensive inspection to ensure that the injected plastic pipes are intact. After inserting the casing, expose the anchor rod to a length of no less than 2m outside the hole to ensure the required tension.

　　(5) After the installation of the anchor rod for pulling out the casing is completed, the process of pulling out the casing begins quickly and continuously, similar to pulling out the drill rod.

　　(6) The grouting operation starts from the bottom of the borehole and ensures smooth drainage and exhaust from the borehole during the grouting process until the end. The grouting operation is not interrupted, and the grouting pressure is 0.3-0.5Mpa.

　　(7) After the completion of anchor rod curing grouting, the anchor rod should be cured immediately, and the curing time should be determined based on the laboratory mix ratio test.

　　(8) Anchor rod tensioning is carried out when the anchor body reaches the design strength. Anchor rod tensioning is completed by a set of specialized equipment, consisting of a control box, a through steel cable jack, and an anchor.

　　The tension control stress value of the anchor rod is about 0.8 of the breaking stress of the steel cable. The tension is operated, observed, and recorded by a dedicated person, and a load displacement curve is drawn.

　　Process measures for prestressed anchor rod

　　(1) Before drilling the soil anchor, the hole position should be determined according to the design requirements and soil conditions, and marked to ensure that the hole position difference of the anchor rod does not exceed 100mm, and the hole depth is not less than 1% of the design length, nor more than 1% of the design length.

　　(2) Before installing the anchor rod, rinse the borehole with clean water until the hole overflows with clean water.

　　(3) Ensure that the anchor bundle is straight before assembly, and eliminate oil stains and rust.

　　(4) When installing anchor rods, set a centering bracket every 1-2 meters along the axis direction of the rod body.

　　(5) Coat the free section of the rod with butter and cover it with a plastic sleeve, and secure it with lead wire at the anchorage section. When placing the rod, avoid direct contact with the hole wall, especially for the rod located on the anchorage body.

　　(6) Mix the grouting slurry evenly and use it as it is mixed. Ensure that the slurry is used up before initial setting and strictly prevent the mixing of stones and debris. During grouting, the grouting pipe port should be kept 50-100mm away from the bottom of the hole.

　　(7) Before tensioning the anchor rod, the tensioning equipment should be regulated. When the strength of the anchor body and the pedestal concrete is greater than 15Mpa, tensioning should be carried out.

　　(8) Before tensioning the anchor rod, a design stress of 10% to 20% should be applied, and the anchor rod should be pre tensioned once to ensure that all parts are in close contact and the rod body is completely straight.

　　(9) During the locking process, the tension load usually needs to retract. Therefore, before locking, the tension should be increased to 1.1-1.2 times the design stress and held for 5 minutes (sand) or 10 minutes (clay) to ensure the stability of the anchor head displacement and prestress value.

　　Due to differences in production batches and specific models, the above pictures are for reference only. For details, please contact our sales personnel for specific verification. zmjt055

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