Dubai Creek Harbour — 280 Bored Piles Through Mixed Strata

Location: Dubai Creek Harbour, Dubai, UAE

Scope: 280 bored piles, φ900mm–φ1500mm diameter, 25–45 meter depth

Rig Fleet: Bauer BG36 (×2), Bauer BG40 (×1), Soilmec SR-70 (×1)

Xuanwa Tools Supplied: Rock Drilling Buckets (φ900, φ1200, φ1500mm), Core Barrels with Bullet Teeth (φ1200, φ1500mm), Cleaning Buckets (φ900, φ1200, φ1500mm), Replacement Bullet Teeth Sets

The Challenge

Dubai Creek Harbour sits on the edge of Dubai Creek — a geotechnical transition zone where the "typical" Dubai profile of sand-over-sandstone gets significantly more complicated.

The soil investigation revealed a four-layer profile:

1. 0–8 meters: Loose to medium-dense marine sand. Highly permeable. High water table at approximately 3 meters below ground level.
2. 8–22 meters: The problem zone. Alternating bands of calcarenite (cemented carbonate sand) and dense silty sand. Calcarenite UCS ranged from 8–18 MPa — hard enough to destroy standard soil bucket teeth, but not a uniform layer where you could simply switch to a core barrel.
3. 22–38 meters: Highly weathered to moderately weathered mudstone and siltstone. UCS 5–15 MPa. Highly abrasive due to silt content.
4. 38–45+ meters: Competent mudstone. Pile toe required minimum 3 meters penetration into competent strata.

The alternating calcarenite-sand-calcarenite pattern in the middle zone was the main challenge. Switching tools mid-pile for each calcarenite band would kill cycle time. Using a soil bucket through calcarenite would destroy teeth within 2-3 piles. Using a core barrel through the sand layers would be slow and unnecessary.

Our Solution

After reviewing the soil report with the contractor's project engineer, we recommended:

Primary tool per pile: Rock Drilling Bucket with staggered bullet teeth, configured for the full depth range. The rock bucket's reinforced bottom plate (Hardox 500) and arc-guide tooth arrangement could handle both the calcarenite bands and the underlying mudstone, while still penetrating the sand layers efficiently.

Tool configuration per diameter:

Backup strategy: Core barrels with bullet teeth (φ1200mm and φ1500mm) were kept on standby. If any pile encountered a calcarenite band exceeding 2 meters in continuous thickness with UCS above 12 MPa, the operator would switch to core barrel for that section. In practice, this happened on approximately 15% of piles — mainly on the eastern side of the site closer to the Creek channel where calcarenite was thicker and more competent.

Cleaning: φ900mm, φ1200mm, and φ1500mm cleaning buckets for borehole base cleaning after reaching competent strata.

Consumables plan: We supplied 12 complete tooth sets for the φ1200mm buckets (the highest-use diameter) and 8 sets each for φ900mm and φ1500mm. Tooth replacement was scheduled every 350 linear meters, with mid-pile inspection if the operator noted increased torque or decreased penetration.

The Results

Production rate: Average 3.5 piles per rig per day across the four-rig fleet. This met the contractor's program requirement of 3 piles per rig per day with comfortable margin.

Tool performance:

• Rock drilling buckets completed an average of 18 piles between tooth changes in the φ1200mm size
• Actual tooth life averaged 380-420 linear meters in the calcarenite-mudstone mix — slightly better than the conservative 350m estimate
• No bucket body failures. Hardox 500 bottom plates showed minimal erosion (<2mm material loss after 280 piles)
• One core barrel was deployed on 42 piles (15% of total) and completed the project with its original roller bits still serviceable

Cost comparison: The contractor previously used OEM drilling tools for similar projects. For this project, the tooling cost (buckets + core barrels + consumable teeth) was approximately 45% lower than their previous OEM spend, with no measurable difference in penetration rate or downtime.

Downtime: Zero rig-hours lost to tool failure. The only downtime related to tools was scheduled tooth changes, which were factored into the daily program.

Client Feedback

"The calcarenite bands at Creek Harbour caused us problems on previous phases. The Xuanwa rock buckets handled them without the constant tool-switching we used to do. And having a warehouse in Abu Dhabi meant we could get extra tooth sets delivered same-day when we ran low."
— [Project Manager Name], [Contractor Company]

Key Takeaways

1. Rock buckets in mixed ground: When the soil report shows alternating hard and soft layers, a properly configured rock drilling bucket often outperforms a tool-switching strategy. The reinforced bucket handles the hard bands while the staggered tooth arrangement doesn't over-penalize penetration in soft ground.
2. Tooth life matters more than bucket price: The cost of a bucket is amortized over hundreds of piles. The variable cost is teeth. Optimizing tooth life through correct configuration (staggered pattern, arc-guide layout, correct pick grade) has a bigger impact on project tooling cost than the bucket purchase price.
3. Local stock eliminates program risk: Running out of consumables mid-project is a program-level risk. The contractor's ability to get same-day tooth delivery from KIZAD meant they could run leaner on-site consumable inventory without increasing risk.

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