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What if shrinkage occurs during drilling?

November 2, 2023

1. Quality problems and phenomena

When using a borehole probe to check for holes, the hole probe is blocked when lowered to a certain part, and the bottom of the hole cannot be inspected smoothly. The diameter of a part of the drilling is less than the design requirements, or from a certain part, the aperture is gradually reduced.


2. Cause analysis

1) There is a weak layer in the geological structure. When drilling through the layer, the weak layer is squeezed into the hole to form a shrinkage hole under the action of earth pressure.

2) The plastic soil layer in the geological structure expands when it meets water, forming shrinkage holes.

3) The drill wears too fast and is not repaired welding in time, resulting in shrinkage holes.


3. Preventive measures

1) According to geological drilling data and soil quality changes in drilling, if it is found to contain weak layers or plastic soil, pay attention to often sweep the hole.

2) Check the drill frequently, and repair welding in time when there is wear. After repairing welding, the drill with more wear, reaming the drill to the design pile diameter.


4. Treatment measures

When shrinkage holes appear, the drill can be used to sweep the holes repeatedly until the design pile diameter is met.

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