The construction of the pile drilling machine can be roughly divided into three stages: the buried casing, the centering of the pile drilling machine, and drilling into holes.
(I) Buried protective tube
Buried protection tube is a necessary process for bored cast-in-situ piles, including digging, placing protection tube and surrounding backfill. The protective tube adopts the method of open digging and burying: the pile center is led out of the excavation area before excavation. When the protective cylinder is buried, its plane position and inclination should be carefully checked. The clay filled at the bottom and surrounding of the protective cylinder must be compacted in layers and drainage measures should be taken. The protective cylinder can be sunk by hammering, low pressure or vibration, etc. Bury securely. Finally, cross the pile position to the center of the protective tube for verification.
Burying of the protective cylinder shall also meet the following requirements:
1. The plane position of the protective cylinder is embedded accurately (the deviation is not greater than 50mm);
2. The top surface of the protective cylinder should be 2m higher than the construction water level or groundwater level, and the height of the mud surface in the hole should also be met.
3. In dry land, it should be 0.5m higher than the construction ground; the bottom of the protective tube should be 0.1-0.3m below the lowest water level of the construction;
4. The digging of the buried protective tube only needs to be 0.5-1.Om larger than the diameter of the protective tube;
5. The surrounding of the protective cylinder is compacted with clay, and the bottom of the protective cylinder must be in the clay layer, otherwise the clay should be filled and compacted with a thickness of not less than 50cm.
(B) rig alignment
After the protection tube is buried, the centering operation of the center of the pile position must be performed again before the pile rig is officially constructed. After the pile drilling machine is moved to a position close to the protective cylinder, the luffing device is adjusted by micro-movement, so that the center point of the pile drill is aligned with the center of the protective cylinder.
(Three) drilling construction
After the centering of the pile drilling machine, the drilling construction can be started. During the construction, the construction process of the pile drilling machine should be strictly observed. During the drilling process, the following matters should be noted:
1. According to the geological conditions of the site, select the appropriate construction technology and equipment, and configure the optimal drilling tool combination;
2. Control mud performance when drilling in unstable formations;
3. It is not easy to increase the pressure during drilling of the soil layer, so as to avoid the excessive amount of single footage;
4. During the drilling of rock formations, the equipment shall be maintained at irregular intervals to ensure that the drilling is in the best working condition and the rotary drilling rig bit shall be repaired in time;
5. When drilling large-diameter rock formations, step drilling can be used to improve construction efficiency;
6. When a drilling accident occurs during drilling, it should be handled in a timely manner. Do not leave it for a long time to avoid engineering accidents.