Sixth, pile foundation construction
1. Classification of pile foundation
1.1. According to the construction method: prefabricated piles, cast-in-place piles
1.2. According to the pile sinking method: hammer sinking pile, static pile pressing, vibrating pile sinking, water sinking pile, drilling hammer sinking pile
2. Definition of prefabricated pile construction
2.1. Hammer sinking pile: use drop hammer, diesel hammer and other pile hammers, and use the impact of the hammer to overcome the pile resistance to the pile, so that the pile sinks to a predetermined depth.
2.2. Static pile pressing: With the help of the total weight of the pile driver, the pile is pressed into the soil, so that the pile sinks to a predetermined depth, which is suitable for soft soil layers
2.3. Vibrating pile sinking: The vibrating pile hammer of the high-power electric vibrator is used to make the pile sink into the soil quickly, which is suitable for the sand layer.
3. The construction process of the prefabricated pipe pile static pile: hoisting the pile (nozzle welding) and pressing into a section of continuous pile pressing
4. The process of sinking the pile by the prefabricated pile hammer: drive into the first section of the pile, drive the electric welded pile, and drive into the last section of the pile
5. Mechanical hole forming construction technology
5.1. Process flow
Pile positioning measurement, digging and burying the casing, drilling rig in place, aligning and leveling, percussion into holes (making reinforcement cages), placing reinforcement cages, lower conduits, secondary hole cleaning, underwater pouring of concrete
2.2. Main construction technology
Pile foundation positioning measurement: According to the measurement and positioning points handed over on site, the coordinates and elevation of the pile foundation are measured, and marked and numbered after review and confirmation
Excavation and burial casing: Before drilling, in order to ensure the stability of the facility and the hole is not deflected, the circular steel casing is buried in the ground, the embedding depth is not less than 1 meter, and the deviation between the center of the casing and the center of the pile position is 5cm. The steel casing is made of steel plate with a thickness of more than 8 mm, and a slurry hole is opened in the upper part.
6. Definition of manual digging pile: reinforced concrete pile excavated by manpower and poured on site.
7. Static load detection of single pile: the age of the concrete cast-in-place pile reaches 28 days or the test block with the same conditions is reserved to reach the design strength. The number of sampling piles is 1% of the total number of construction piles, and there are no less than 3
8. The second large excavation: the soil excavation between the piles should pay attention to the protection of the pile body, and follow the principle of "slotted support, first support and then digging, layered excavation, and it is strictly forbidden to over-excavate", reserve 20-30cm for manual excavation, and guide the positioning pile to check whether the excavation size and elevation of the foundation pit are correct
9. Mechanical pile cutting head: the elevation requirement after pile cutting is 50mm higher than that of the foundation cushion
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