What is the function of the casing in mud wall drilled cast-in-place piles?

The function of the casing is to: fix the position of the pile hole, prevent surface water from entering, protect the hole opening, increase the water pressure inside the pile hole to avoid collapse of the hole, and guide the direction of the drill bit during hole formation. The casing is made of steel plates 4–8 mm thick, with an inner diameter that is 100–200 mm larger than the diameter of the drill bit; its top surface is 0.4–0.6 m above the ground level, and it has 1–2 holes for excess slurry to flow out. When burying the casing, first remove the topsoil from the pile hole and then embed the casing in the soil. Its burial depth should be no less than 1 meter in clay soil, and no less than 1.5 meters in sandy soil. Its height must meet the requirements regarding the level of the mud in the hole; the mud level in the hole should be kept at least 1 meter above the groundwater level. When using the pit burial method, the diameter of the pit should be 0.8–1.0 m larger than the outer diameter of the casing. The deviation between the center of the casing and the center line of the pile position should not exceed 50 mm; after alignment, clay should be filled outside the casing and compacted in layers. This post was last edited by 4507 on 2009-3-26 13:07]