What is the reason that the conduit floats after the first bucket of material is poured every time the perforated pile is poured?

The floating of the conduit may also be due to the following reasons: (1) cleaning hole is not complete, only the conduit part of the clear to the bottom of the hole, other parts of the slag is not completely clean, so only in the conduit around the formation of a "small hole", when filling concrete, concrete in the role of self-weight rapid decline, from the bottom of the conduit outflow, due to the small gap outside the conduit, resulting in a large upward force on the conduit, leading to the floating of the conduit. The conduit produces a large upward buoyancy force, resulting in the floating of the conduit. (2) Mud viscosity and specific gravity, or clear the hole for a long time, the mud wrapped in the conduit joints to make the conduit locally thick, resulting in increased buoyancy of the conduit, so that the conduit floats.