1、 General requirements
1. For broken and uneven slope, loose pumice and rock slag must be removed, mortar rubble shall be used to fill the hole, and the slope gap shall be Closed treatment. The slope shall be leveled and compacted after trimming
2. In the process of slope excavation and drilling, the lithology and structure shall be recorded and comprehensively analyzed. If there is a large discrepancy with the design, it shall be reported to the supervising engineer for approval.
3. The waste slag from slope trimming shall be stacked according to relevant regulations and shall not pollute the environment.
4. When pouring concrete, the formwork shall be supported and fixed.
2、 Anchor rod frame construction
1. See the drawing for construction process of anchor bolt frame
Construction process of anchor bolt frame
2. Key points of construction
(1) The position of anchor hole and frame shall be accurately positioned, and the profile of vertical beam and beam rib shall be excavated. The slope surface must be grooved, and the depth shall meet the design requirements.
(2) The anchor hole shall be drilled without water to prevent the geological conditions of the slope from deteriorating due to the drilling construction.
(3) The drilling process shall be in the charge of a specially assigned person, who shall record the geological conditions and drilling conditions in detail. If it is inconsistent with the design, the drilling shall be stopped immediately, and feedback and measures shall be taken in time.
(4) Clean the hole with high-pressure air after drilling, and there shall be no clay or silt on the hole wall.
(5) The assembly of frame formwork shall be flat and tight, and the clearance size shall be accurate and meet the design requirements. The formwork surface shall be brushed with isolating agent to facilitate demoulding. When pouring concrete, the formwork shall be supported and fixed.
(6) The frame shall be constructed in pieces, and each piece shall be composed of 2? It is composed of three columns, their beams and top beams. An expansion joint of 2cm wide shall be reserved at the contact of adjacent frames and filled with asphalt soaked wood boards with the same size as the end of the frame.
3. Key points of quality control and supervision
(1) The hole location, hole diameter and inclination angle meet the design requirements. The allowable deviation of hole spacing is ± 50mm, and the elevation of the hole orifice is 100mm.
(2) The anchor bolt frame shall be straight, beautiful and free from pitted surface, and the concrete strength shall meet the design requirements.
(3) The fabrication and installation of reinforcement shall comply with the Technical Code for Construction of Highway Bridges and Culverts (JTJ041-2000).
(4) Check the construction record, and check the axis error of anchor rod ± 3 °.
(5) Check the pulling force and length of anchor cable (rod).
3、 Prestressed anchor cable (anchor rod)
1. Construction process is shown in the figure
Prestressed anchor cable (anchor rod)
2. Key points of construction
(1) The slope surface of the designed anchoring works is excavated and formed, and has passed the acceptance.
(2) Before construction, the basic test of prestressed anchor cable (rod) shall be carried out, and the construction can be carried out only after the anchoring parameters are determined.
(3) Surveying and setting out, the anchor hole position shall be accurately measured on the slope and clearly marked.
(4) Hole making.
① The drilling equipment shall be selected according to the anchoring stratum type, hole diameter, depth, construction site and other conditions. It is strictly prohibited to use geological drilling rig to form holes; Pipe following drilling technology shall be adopted in the stratum prone to collapse, sticking and burying.
② Drilling rig in place: the vertical and horizontal error of drilling rig in place is ≤± 50mm, the elevation error is ≤± 100mm, the drilling inclination error is ≤ 0.5 °, and the azimuth error is ≤± 1.0 °.
③ Water free dry holes shall be used for drilling to prevent the geological conditions of slope from deteriorating due to drilling construction.
④ During drilling, the geological changes, drilling status (weight on bit, drilling speed), groundwater, etc. shall be recorded on site.
⑤ After the drilling reaches the design depth, the drilling must be stable for 1? 2 minutes. After drilling, it is required to use high-pressure air (0 2a~0. 4Mpa) Remove all rock powder and water in the hole outside the hole.
⑥ The borehole inclinometer can be used to control and detect the borehole inclination, etc.
(5) Fabrication and installation of anchor cable (rod).
① An assembly platform with a height of no less than 50cm must be erected for the assembly of anchor bars.
② The bolt joint shall be a special bolt joint, and welding technology shall not be used. The reinforcement of anchor bolt body shall be straight and free of oil stain and rust. The free section shall be sleeved with plastic casing according to the design requirements. The connection with the anchor section shall be firmly bound with lead wire and treated with anti-corrosion.
③ The anchor cable shall be bundled, and the steel strand shall be mechanically cut. Arc cutting is strictly prohibited. The surface shall be free of oil stain, rust and bending, and the anti-corrosion treatment shall be strictly carried out.
④ After the assembly of the isolation frame and the fastening ring, the anchor cable body shall be connected with the guide cap at its bottom end. The size error of the guide cap is ≤± 5mm, and the error of the connection and positioning is ≤± 20mm. The guide cap is bound firmly with iron wire, and the welding method is not suitable
⑤ When the anchor bar assembly with secondary supplementary grouting is adopted, the secondary grouting pipe and grout stop sealing device shall be installed at the same time; When high-pressure splitting grouting is adopted, the time of starting splitting grouting shall be controlled by the slurry strength (the primary slurry strength is 5Mpa), and the anchor section of the secondary grouting pipe shall be provided with flower holes and plugs.
⑥ The split bolt connection is required between the steel bearing plate and the extrusion sleeve of the pressure dispersed (tension compression composite) anchor cable anchorage section, and the surface of all exposed steel materials shall be painted with anti rust paint for protection. The extrusion sleeve shall be subject to on-site extrusion sampling test, and the sampling frequency is generally 3%? 5%。 For pressure dispersion type (tension compression composite type) anchor cables, each unit anchor cable shall be clearly and firmly marked, so as to use differential tension step by step.
⑦ The anti-corrosion and isolation of the free section of the anchor bar body shall be carried out in strict accordance with the design requirements. The technology of unbonded prestressed reinforcement and pressure dispersion anchor head should be used for anti-corrosion to improve the anti-corrosion level of the free section and the working condition of the anchor section.
⑧ Length of anchor bar body: the allowable error of length fabrication of anchor section is ± 50mm. The length of free section should not only meet the design requirements, but also fully consider the requirements of tensioning equipment and construction technology. Generally, an extra length of 1.0? Should be reserved? 1.5m。
(6) Grouting.
① After the completion of anchor hole drilling, the anchor solid shall be installed in time and grouting shall be carried out, which shall not exceed 24 hours in principle.
② The corresponding grouting equipment shall be comprehensively selected according to the grouting material, grouting method and grouting pressure and the actual anchoring stratum conditions.
③ Ordinary Portland cement should be used instead of high alumina cement. The fine aggregate shall be medium sand with particle size less than 2mm; The mud content shall not be more than 3%. Except for secondary high-pressure grouting (splitting grouting) and secondary grouting in free section (supplementary grouting), expansion agent should not be used generally.
④ During grouting, the grout shall be mixed evenly and used immediately, and shall be completed before the initial setting of grout. The strength of grouting body shall not be less than 20Mpa.
⑤ Generally, grouting should be carried out by means of grouting at the bottom of the hole until grout overflows from the anchor hole orifice or the exhaust pipe stops venting.
⑥ Grouting records shall be made during grouting.
⑦ One time normal pressure grouting generally adopts one-time grouting in the whole section; The secondary supplementary grouting is applicable to the grouting of the primary normal pressure anchor section, that is, after the completion of the prestress tensioning and locking process, the free section of the anchor solid is supplemented with filling grouting; According to the design requirements, secondary high-pressure grouting (splitting grouting) should be adopted to improve the uplift resistance of the anchorage section.
(7) Tension locking and anchor sealing.
① When the anchor bar is tensioned, the bearing surface of the anchor bracket shall be flat and perpendicular to the axis direction of the anchor bar.
② The installation of anchorage shall be closely aligned with the anchor pad and the jack. The axis of the jack is in the same line with the axis of the anchor hole and the anchor bar body. It is not allowed to bend or deflect the anchor head to ensure that the load is uniform and coaxial. If necessary, steel shims can be used to adjust.
③ Tensioning can be carried out only when the strength of anchor solid and abutment concrete reaches more than 80% of the design strength.
④ Before the anchor bar is formally tensioned, 10% of the design tension value shall be taken? 20% of anchor bars? Pre tensioning shall be conducted twice to ensure that all parts of the anchor body are in close contact and the anchor reinforcement body is straight.
⑤ The tension control stress of permanent anchor bar shall not exceed 60% of its limit stress value, and the tension control stress of temporary anchor bar shall not exceed 65% of its limit stress value.
⑥ The tensioning operation shall be carried out in strict accordance with the design requirements. After the anchor bar is tensioned to the set maximum tension load value, the load shall be 10? 15 minutes, then unload and lock. If obvious prestress loss is found, compensation tensioning shall be carried out in time.
⑦ After the anchor bars are locked, the remaining exposed anchor bars shall be cut mechanically. Arc cutting is strictly prohibited, and the length of 5? 10cm exposed anchor bars to prevent dragging and sliding. Fill the gap between the anchor base plate and the anchor head with cement paste, paint with antirust paint, and seal the anchor according to the design requirements. The strength of the anchor sealing concrete shall not be less than 20Mpa.
3. Key points of quality control and supervision
① Inspect various materials, anchoring components, etc.
② Hole location (longitudinal and transverse slope ± 50mm, hole elevation), drilling inclination, horizontal angle (hole axis inclination, hole axis orientation, hole bottom deflection is 3% of the drilling depth), hole diameter (+5%, 0 of the design hole diameter), hole depth (200? 500mm greater than the design depth), anchor hole cleaning.
③ Appearance quality, connection firmness and anti-corrosion treatment of anchor rod.
④ Appearance quality, fabrication size, anti-corrosion treatment and number of anchor cable; Manufacturing size, assembly positioning and binding of guide cap.
⑤ Grouting condition and grouting body strength.
⑥ The strength of anchor solid and abutment concrete, and the tensioning condition before tensioning. Anticorrosion treatment and anchor sealing of exposed parts.
⑦ Grouting and tensioning shall be carried out in accordance with the supervision site system.
