(1) Anchoring engineering construction
Anchor construction process flow chart (see next page)
Because the main part of the anchoring project is underground concealed engineering, the quality of the project is closely related to the construction technology. It is required to strictly follow the technical specifications and quality inspection and evaluation standards for the construction and acceptance of the anchoring project to ensure the slope stability and structural safety.
Anchor construction mainly includes construction preparation, anchor hole measurement and setting-out, anchor hole drilling, anchor rod preparation, anchor hole grouting, concrete structure reinforcement preparation and concrete pouring. There are two main links: one is anchor hole forming, the other is anchor hole grouting, and the key technology of anchor hole forming is how to prevent the hole wall from collapsing and blocking; The key technology of grouting is how to discharge the air, rock (soil) sediment and groundwater at the bottom of the hole to ensure the grouting is full and dense.
(1) construction preparation
Before anchor construction, do a good job in personnel organization, construction equipment, materials and testing. Before construction, do a good job in reinforcement, slurry test, mixture ratio test and related mechanical equipment inspection.
Before installing the anchor rod, check the drilling depth, drilling inclination and anchor rod length; Then install the anchor rod that has passed the on-site supervision and inspection and grouting; After the anchor construction is completed, the anchor acceptance and length inspection shall be carried out according to the specification requirements.
(2) Measurement and release of anchor hole
According to the elevation of each project and the design requirements, accurately measure the anchor hole position on the slope, and the hole position error shall not exceed 50 mm In case of uneven slope brushing or special difficult sites, it is necessary to obtain the consent of the design supervision unit, and relax the positioning accuracy or adjust the anchor hole positioning appropriately on the premise of ensuring the slope stability and structural safety.
(3) Erecting scaffold working platform
Starting from the platform, the steel pipe scaffold is erected on the anchoring slope in stages, and the platform position of the scaffold corresponds to the drilling position. The cross bar and longitudinal bar of the scaffold are reinforced with diagonal bars, and then wooden boards are laid to form the operating platform of the drilling rig. Scaffolding is required to be driven into the stratum where the stress point on the platform and slope is not less than 20cm, and all fasteners are firmly connected.
(4) Anchor hole drilling
① The drilling rig is in place.
Before drilling anchor holes, scaffolding shall be erected to meet the corresponding bearing capacity and stability conditions. According to the hole position on the slope, accurately install the fixed drilling rig, carefully adjust the position of the aircraft, and ensure that the vertical and horizontal errors of anchor hole drilling are not more than 50mm, the elevation error is not more than 100mm, the inclination and direction of drilling meet the design requirements, the allowable error of drilling rig guide rail inclination is 1.0, and the allowable error of azimuth angle is.
② Drilling equipment
The selection of drilling equipment depends on the type of anchoring stratum, the diameter of anchor hole, the depth of anchor hole and the construction site conditions. Downhole impact pore-forming is adopted in the rock stratum; In the stratum prone to hole collapse, sticking and buried drilling, such as broken or soft and saturated rock, casing drilling technology is adopted.
③ Drilling method
Dry drilling is required when drilling, and it is forbidden to use rhinestones and wash the hole wall to ensure that the anchor construction will not damage the engineering geological conditions of the slope rock mass and ensure the bonding performance of the hole wall. According to the performance of the drilling rig and the anchoring stratum, the drilling speed is controlled to prevent drilling deviation, distortion and diameter shrinkage, resulting in anchoring difficulties or other accidents.
④ Drilling process
During drilling, site construction records should be made, and the formation change, drilling state (WOB, ROP), formation and groundwater of each hole and some special conditions should be recorded. If unfavorable drilling phenomena such as hole collapse and necking are found, drilling should be stopped immediately, and solid wall grouting should be carried out in time after notifying the supervision engineer (grouting pressure is 0. 1 ~ 0.2 MPa). After the initial setting of cement mortar (after 24 hours), hole sweeping and drilling should be carried out again or the following drilling technology should be adopted.
⑤ Aperture and depth
Borehole diameter and hole depth shall not be less than the design value. In order to ensure the diameter of the anchor hole, the actual diameter of the drill bit is required to be not less than the design aperture. In order to ensure the depth of anchor hole, the actual drilling depth is required to be not less than the design value and more than 20cm.
⑥ anchor hole cleaning
After drilling reaches the design depth, it is not allowed to stop drilling immediately. It is required to stabilize drilling for 1 ~ 2 minutes to prevent the bottom tip of the hole from failing to reach the design aperture. There must be no sediment and water attached to the borehole wall, and it must be cleaned up. After the completion of drilling, the rock powder and water body in the hole are all excluded from the hole with high-pressure air (wind pressure is 0.2 ~ 0.4 MPa), so as not to reduce the bond strength between cement mortar and rock and soil on the hole wall. Except for the hard and complete rock anchor hole, high-pressure water flushing is not allowed. If there is confined water flowing out of the anchor hole, the anchor rod and grouting can only be installed after the water pressure and water volume become smaller, and drainage holes are set at appropriate positions around if necessary.
(5) Anchoring steel bar
1. material of anchor rod: in the anchoring project of this bid section, the material of anchor rod adopts secondary reinforcement with a diameter of 28mm; The horizontal hole adopts φ 100mmPVC pipe;
2. Assembly of anchor rod body: φ28 anchor rod adopts φ6 steel bar with a spacing of 2m;
3. Storage, transportation and hoisting of anchor rod: The assembled anchor rod should be placed in a ventilated and dry place. When stored or manufactured in the open air, it should not be in direct contact with the ground, and covering measures should be taken. During horizontal transportation, the distance between the fulcrums shall not be greater than 2m, and the bending radius of the anchor rod body shall not be too small, so as not to change or damage the structure of the reinforced rod body. During vertical transportation, except the main lifting point, other lifting points should make the bolt body unhook quickly and safely. During transportation and hoisting, be careful not to damage the anchor rod and its protective media and components.
4. Installation of anchor rod body: Before the anchor rod body is put into the anchor hole, the production quality of the anchor rod body must be checked to ensure that the assembly of the anchor rod body meets the design requirements and is approved by the supervision engineer. Debris in and around the anchor hole should be removed. The length of the anchor rod body should be consistent with the design depth of the anchor hole. The bolt body has no obvious bending and torsion, and the protective medium of the bolt has no damage. Any damage must be repaired. The length of the anchor rod extending into the hole should meet the design requirements. After the anchor rod body is installed, it is not allowed to knock or hang heavy objects at will.
(6) Grouting of anchor holes
After the completion of anchor hole drilling, anchor body should be installed in time and anchor hole grouting should be carried out, in principle, it should not exceed 24 hours.
(1) Equipment and grouting materials: BW- 150 grouting machine is adopted according to the design requirements of anchorage protection in this bid section; M20 cement mortar shall be used for anchor grouting, and ordinary portland cement shall be used for cement, and high alumina cement shall not be used.
⑵ Preparation: In the preparation of grouting, raw materials should be carefully prepared in strict accordance with the mixture ratio. When the grouting operation is started and stopped for a long time, water or cement slurry should be used to lubricate the grouting pump and the grouting pipeline.
(3) Grouting slurry: the grouting slurry is mixed evenly in strict accordance with the mixture ratio, and can be taken as needed. Cement slurry should be completed before initial setting, and it is forbidden to mix stones and sundries into the cement slurry. The strength of anchor grouting liquid is not less than 20Mpa.
(4) End of grouting: After grouting, clean the grouting pipe, grouting gun and grouting sleeve.
5] Grouting record and test: record the grouting operation process, and at the same time conduct slurry strength test for each batch of grouting, with no less than 2 groups of specimens. When the cement slurry does not reach 70% of the design strength, it is not allowed to hang heavy objects and tie and collide at the end of the anchor rod.