Why Is The Hole Drilled by Rotary Drilling Rig Filled with Mud?

1. Mud wall protection against hole collapse

When drilling the loose soil layer is easy to collapse by the horizontal soil pressure, the mud balances the soil pressure by the outward pressure, forming a stable ‘mud skin’ to protect the hole wall.

2.Characteristics of non-circulating mud process

The rotary drilling rig adopts intermittent slag discharge, the slag is lifted to the ground directly from the drilling bucket, the mud is not discharged with the circulation, so it always remains in the hole.

3. Geological conditions

In loose, fluid-plastic formations (e.g. sand or silt), the mud needs to maintain high viscosity and specific gravity to support the hole wall and prevent collapsing or slag accumulation.

4. Adjustment of mud properties

Adjust the mud properties (e.g. toughness, specific gravity) according to the water table or fissures during construction, and increase the viscosity of the mud to form an effective wall protection layer when there is a slight leakage of mud, which will lead to the retention of mud in the hole.

5. Remaining in the hole cleaning process

When clearing the hole, it is necessary to replace the old mud with new mud (replacement method), or wait for the slag to settle and then clean up (sedimentation method), mud as a medium is difficult to remove completely.

6. Conclusion

Mud in the hole is the key of rotary drilling rig process, not only to ensure the stability of the hole wall, but also to assist the slag removal and hole cleaning, although it seems redundant, it is the core link to ensure the quality of the pile.