Pile drilling through pebble strata: 100% hole acceptance
Main-pier piles of a major bridge in Southwest China crossed deep pebble beds with stones over 800 mm. Φ1500 holes shrank to Φ1380, blocking cage installation, and bottom sediment ran thick — more than 4 clean-out passes per pile.
Project overview
- Region
- Southwest
- Project type
- Bridge piles
- Project scale
- Main-pier piles at Φ1500 mm through pebbles over 800 mm
Construction challenges
The main construction challenges encountered on this project.
Challenge 1Undercut
A weak protective layer let the hole shrink after drilling, hampering cage installation.
Challenge 2Thick sediment
Large pebble cuttings settled fast, leaving bottom sediment beyond specification.
Challenge 3Repeated clean-out
Over 4 clean-out passes per pile tied up crews and rigs.
Solution & materials
Materials and mix ratios used step by step on this project, for reference by similar works.
| Stage | Material | Function | Ratio / dosage |
|---|---|---|---|
| Make-up | PAM-P | High-carry main material | 1:250 |
| Base slurry | BENT-N | Base make-up | 8% |
| Thickening | CMC-N | Raises yield point | 0.3% |
| Purify | Pond flocculation | Fast cutting separation | 80 g/m³ |
Implementation notes
Switching to the PAM-P high-carry system with CMC-N to raise yield point built a cemented ring on the wall and eliminated undercut. Adding pond flocculation separated cuttings quickly. Clean-out dropped to within 2 passes per pile, hole acceptance hit 100% and piling sped up 22% per pile.
Delivered results
Site photos
Related products
NPT-PAM-P- Good film encapsulation
- Strong scour resistance
- Low fluid loss keeps hole diameter
NPT-BENT-N- Yield ≥ 18 times its mass
- Low iron and sulphur
- Consistent batch to batch
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