Is rotary drilling bored pile a dry job?

Rotary bored piles are also divided into rotary bored piles with dry holes and rotary bored piles with positive and negative circulation.

Dry rotary drilling cast-in-place pile is to use that kind of crawler rotary excavator (there are many in Sany Heavy Industry) to directly drill down on the hole to borrow soil, and there should be a loader next to it to push the dry soil away in time.

This kind of crawler rotary drill is suitable for friction piles in loess plateau. The water level is low, and there is basically no rock layer in the pile-length stratum. The rotary excavation speed is fast, there is no water, the hole is not big, and there is no need to protect the wall. But it is more troublesome to encounter water and rock layers.

Extended information:

The basic information of matters needing attention in bored pile construction is as follows:

1. Hole-forming equipment: after the hole-forming equipment is in place, it must be level and stable to ensure that it does not tilt or move during construction; In order to accurately control the hole-forming depth, a scale for controlling the depth is set on the wire rope of the pile driver and the pile hammer for observation and recording in construction.

2. The pile casing shall be buried accurately and stably. The deviation between the center of the pile casing and the center of the pile position shall not be greater than 2mm, and the inner diameter shall be greater than 1mm of the drill bit diameter. In order to ensure that the hole wall does not collapse, the water level in the pile casing shall be 2m higher than the natural groundwater level.

3. During drilling, according to different geological conditions, the main indexes such as mud specific gravity, viscosity, sand content and colloid rate are often measured.

4. In case of inclined hole, hole collapse, slurry leakage and ground subsidence during drilling, stop drilling immediately and take the following effective measures before drilling. When the drill hammer tilts, it can be cleaned; When the deflection is large, fill in the pebble clay to the upper part of the eccentric hole for .5m, and then re-drill. During or after hole formation, the hole wall collapses, and slight hole collapse increases mud density and water level; In case of serious hole collapse, put in clay mud paste, and use low-speed drilling after the hole wall is stable.

5. In case of slurry leakage from drilling, thick mud or clay can be properly added and rotated slowly; The joints around the liners and at the bottom shall be backfilled and compacted with soil, and the head height in the hole shall be properly controlled to avoid excessive pressure.

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