[Process Introduction]

This technology adopts the inner and outer double tube construction method, with an inner tube inside the outer tube, an open bottom of the outer tube, and a closed bottom of the inner tube. The outer tube is 15 centimeters longer than the inner tube. Using a diesel hammer as power, the inner and outer sleeves are simultaneously driven into the ground to a certain depth. The inner tube is extracted, and a certain amount of dry and hard concrete is poured into the outer tube. Then, the inner tube is placed into the outer tube, and the dry and hard concrete inside the outer tube is pushed out by the inner tube. This process is repeated multiple times to form an enlarged head with a diameter of 600-1000mm at the pile end. Simultaneously ram the outer and inner pipes into the bottom of the enlarged head, extract the inner pipe, place the steel cage inside the outer pipe to the bottom of the enlarged head, pour concrete to the top of the pile, press the concrete surface with the inner pipe, slowly lift the outer pipe, and finally use a vibrating rod to compact the area 3-5 meters below the pile top. The single pile construction is completed.

[Process Characteristics]

1. Suitable for various types of fill, silt, cohesive soil, sand layer, pebble layer or strongly weathered rock.

2. Squeezing soil into holes greatly improves the compactness of the foundation soil, enhances the restraining force of the soil around the pile, increases the compactness and end resistance of the soil at the pile end, spreads the stress at the pile end, and significantly increases the bearing capacity of a single pile.

3. Based on the protective effect of the outer pipe, there is no need for mud wall protection, and there is no sediment at the pile end. The pile does not shrink in diameter.

4. Using penetration as a quality control indicator, the bearing capacity of a single pile is uniform and has small dispersion, and the settlement deformation at the pile end is small.

5. In the same geological structure, compared with conventional pile types, this pile type has a bearing capacity of more than 4 times that of single concrete, and does not require mud or soil transportation on site, with outstanding comprehensive economic indicators. Compared with ordinary cast-in-place piles, the construction cost is saved by more than 40% and the construction period is shortened by more than 50%.