At present, the commonly used technical methods to improve the vertical bearing capacity of a single cast-in-place pile include the expansion method and the grouting method after drilling the cast-in-place pile.
In the same stratum, the pile end resistance is directly proportional to the pile end bottom area using the expansion method.
On the premise of keeping the diameter of the pile constant, increasing the bottom area of the pile end can significantly improve the end bearing capacity of the pile.
Therefore, using a bottom expanding drill bit to enlarge the bottom size of the pile hole, forming a bottom expanding pile with a small top and a large bottom, is an effective technical method to improve the vertical bearing capacity and pull-out resistance of a single pile.
Most Japanese rotary drilling machines are equipped with oil pipe trays related to the expansion drill bit under the power head. Using expansion piles can save 50% of concrete, so 95% of pile holes in Japan are expansion piles.
The post grouting method effectively eliminates the hidden danger of sediment at the bottom of the pile, strengthens the pile body, densifies the soil around the pile, and improves the bonding force between the pile and the soil around the pile, thereby increasing the bearing capacity of a single pile by generally 30-90%.
The effect produced by the post grouting process is that the cement slurry injected is combined with the pile bottom sediment to form concrete, eliminating the influence of pile bottom sediment. The injected cement slurry is used to fill the “virtual tips” and “dry slag stones” formed due to segregation, thereby improving the strength of the concrete at the pile tip. The grouting at the bottom of the pile causes the soil at the bottom of the pile to be compacted, and the cement slurry infiltrates into the soil at the bottom of the pile to form a consolidated body, thereby improving the strength of the soil at the bottom of the pile and increasing the bearing capacity of the pile end of the drilled pile. Injecting high-pressure slurry can create upward prestress at the bottom of the pile, which is beneficial for end bearing piles. The high-pressure grouting fluid on the pile side has a squeezing and compacting effect on the soil around the pile, and infiltrates into the soil around the pile, forming bamboo like slurry bubbles with bamboo like pile effect, improving the pile side friction resistance. After drilling the pile hole, when placing the steel cage, a grouting pipeline is pre-set, the pile body concrete is poured, and grouting is carried out after solidification. Before grouting, conduct a water injection test to confirm that the pipeline is unobstructed before grouting. First pile side, then pile bottom, group grouting first, and then group grouting.
Post time: Dec-26-2024