Prestressed anchor construction technical disclosure
 Soil anchor location of this project is better, based mainly in the clayey soil. The west side of bolt length of not more than 14 meters, according to artificial Luoyang shovel into the hole experience in the area of the bolt can be used dry artificial Luoyang shovel operation into the hole, into the hole of artificial Luoyang shovel method can refer to a soil nail wall hole method; south and north sides of the north and east side of bolt length longer requires the use of dry-bolter into the hole.
First, dry-construction process
Cast anchor bolting machine seated position → → stable drill holes and adjust the angle correction → dry drilling operations designed to bolt into the hole over the length of the self-test and allied subject 500px → → → pull out the drill hole depth record decentralized Steel twisted beam and grouting pipe grout into the hole bottom → → → conservation → install secondary grouting steel beam waist (if any) and prestressed tension of anchor head → → → cutting strand tension lock with external allowance
Second, the construction preparation
1, anchor rod processing site
Located away from the working face nearer anchor construction area of 30m × 15m, and should cover the erection of shed.
2, slurry mixing station arrangement
Setting mobile slurry mixing plant 4, anchor construction changes with face move.
3. Rig: Rig approach to ensure equipment availability, and a corresponding inspection certificate.
4, the non-application of anchorage segment wrapped plastic sleeve, coupled with the anchor point with a lead wire fastened.
Third, the rod production
1, according to design requirements bolt body to ensure that the length of the rod.
2, reinforced plastic skeleton erection star locator, spacing 2.0m, the first one in the bottom of 0.5m from the anchor point.
3, the rod-type body with 1860 Strand, intermediate rod inserted Φ25 plastic grouting pipe.
4, anchor rod length: free section + + anchoring section tension lock segment. 3-4 people jumping from the hole when the bolt installation, removal and installation process should try to avoid dragging the rod, the rod to keep clean.
5, free grouting pipe at the bottom of 500px and anchor truss segment wrapped with plastic sheeting. Application of bolt and grouting pipe body fire wire lashing firmly.
Fourth, the dry work into the hole
1, bolting machine in place should be preceded by checking the elevation of the end portion of the drill pipe, bolt spacing meets the design requirements. Positive drill must be adjusted in place, consistent with the design of the level of inclination, and to ensure that drill horizontal projection perpendicular to the sides of the pit, after checking correct before drilling.
2, should be based on engineering geology drilling, drilling speed control, prevent limp drill. Obstacles encountered or unusual circumstances should promptly stop drilling, drilling or when the situation carefully before taking appropriate action.
3, after drilling to the desired depth design empty drill slowly unearthed, to reduce drag when pulling the drill pipe, and then pull out the drill pipe.
Fifth, transport and rod insertion hole
1, dowels should be checked before the anchor bar, including the length of the free part of the processing segment, whether grouting pipe leakage pulp.
2, the rod should not distort during transport, collision, strictly protect the rod from damage.
3, dowels should be lifted so that the rear and slowly inserted into the hole at an angle to prevent damage the hole wall. Tendon insertion hole should stay out of the length of the exposed portion of the tendon tension in order to meet the requirements.
4, the rod is inserted within the borehole depth should meet the design requirements, the rod does not reach the requirements if the insertion depth, pull rod should identify the cause and deal with it later inserted.
Sixth, grout
1, high-quality filling tube, filling tube outlet should be located away from the rod at the bottom of 200mm.
2, must be in strict accordance with the stirred slurry ratio, not free to change. It should be noted not use expired or damp cement.
3, the slurry from the bottom of the hole and began pouring out of the back, while slowly outward edge grouting extubation until after the slurry overflow aperture stop grouting. The slurry must continually end note once before the initial setting. After the first grouting is completed, half an hour to fix a pulp, such as severe bleeding pulp slurry can make two to three times.
4, if necessary, take the second high-pressure grouting, grout should first reach 5.0MPa compressive strength (about 12 to 24 hours) embodiment, the maximum injection pressure of not less than 2.5MPa.
Seven, processing and installation of the beam waist
1, based on the deviation field measurements pile shaped support plate processing, adjusted so that the beam waist bearing surfaces on the same plane, so that the beam waist force uniform.
2, H-beam welding assembly into the box beam waist, hoisting machinery installation.
3, the installation, according to the angle of the bolt, adjust the beam waist stress surface, ensure that the vertical direction with the bolt force.
Eight, tension lock
1, the bearing surface should be flat and perpendicular to the axis of the bolt.
2, bolt tension should be carried out when the grout strength of 20MPa.
3, tension major step design requirements should be.
4, in order to enable each unit Bolt even by force, for each unit should be graded bolt tensioning, bolt when compensated for each unit under the same load, displacement due to the free length difference caused by unequal, then overall tension.
5, according to design requirements to determine the load lock. If after locking bolt, prestressed value changes by more than 10%, you need to relax or repeated tension.
6, prestressed bolt tension before, to deal with the tension device calibration.
7, prestressed bolt tensioning procedure should be required, in the tensioning arrangement program, you should consider the interaction of adjacent drilling prestressed anchor tensioning.
8, prestressed anchor formal tension before, should go to 20% of the design tensile load, its pre-tensioned 1-2 times, so that all parts in close contact, so the strand completely flat.
9, at anchor in this project, each select three prestressed anchor test of tension, tension to 110% of design load, and then lock the lock 75% of the value of the design load. When each anchor construction should first test of tension, and then works bolt tensioning.
10, other parts of the Prestressed bolt tension, tension to the design load, and then lock the lock 75% of the value of the design load.
11, prestressed bolt lock within 48 hours, if found to have significant prestress loss should be compensated tension.
Nine, quality assurance measures
1, anchor the raw materials, steel cable, cement, etc. should be pre-qualified to prove, according to specifications retest qualified before use.
2, the horizontal bolt pitch error should not be greater than 100mm, the vertical pitch error should not be greater than 50mm. Inclination to allow deviation 3 °.
3, the strength of cement paste is not less than 20N / mm2, water-cement ratio 0.5. Test block of cement paste made every 30 two groups, one standard curing, a group of the same curing condition.
4, when the rod assembly, the spacing should be controlled carrier and spacer frame, strand should be straight smooth. Assembled rod placed in the designated storage yard, the next shot should check the ventilation performance grouting pipe precursors.
5, grout used with stir, stir, must be used before the initial setting of the slurry.
6, tensioning device before use must be approved prior to use.
7, the loading test of bolt tensioning grading and loading rate according to specifications.
8, anchor strand exposure amount, from the date of the pile skin is not less than 1.5m, for use Tension.