Introduction
The full rotary drilling rig with casing is an advanced piling technology that utilizes steel casing for wall protection during bored pile construction. This method ensures high-quality pile formation, eliminates slurry pollution, offers environmental benefits, and reduces the concrete bulb coefficient. It effectively addresses common issues such as hole collapse, necking, and excessive bulb coefficient encountered in urban high-fill areas and karst landscapes. Widely applied in bridge construction, building foundations, and petrochemical projects, this technique enhances efficiency and reliability in challenging ground conditions.
Key Equipment and Components
Main Equipment
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Full Rotary Drilling Rig – Forms the borehole.
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Power Station – Supplies power to the rotary host.
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Casing Pipe – Provides wall protection.
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Reaction Fork – Prevents host displacement during rotation.
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Control Cabin – Operator platform for drilling control.
Auxiliary Equipment
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Rotary Drilling Rig or Grab Bucket – Excavates soil, penetrates rock, and cleans the hole.
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Pipe Jacking Machine – Extracts casing for continuous workflow.
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Crawler Crane – Lifts and positions the host, power station, and reaction fork; supports reaction fork; handles rebar cage installation, concrete conduit placement, and grab bucket operations.
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Excavator – Levels the site and removes spoil.
Construction Process
1. Site Preparation
The construction area must be leveled to accommodate large drilling equipment and auxiliary machinery. Adequate access for rebar cage fabrication, spoil removal, cage lifting, and concrete pouring must be ensured.
2. Surveying and Marking
After verifying design coordinates and elevations, the pile center is marked using a total station. A cross-line is extended 1.5m from the center, with reference points for future checks.
3. Host Positioning
The rotary base is aligned with the pile center, followed by host installation and reaction fork setup.
4. Casing Installation
The steel casing is lowered and secured after the host is in position.
5. Verticality Adjustment
During rotary drilling, the casing is driven into the ground while maintaining vertical alignment using plumb bobs in the XY directions.
6. Soil Excavation
As the casing advances, a grab bucket or rotary drill removes soil from inside the casing.
7. Rebar Cage Installation
Upon reaching the design depth, the hole is cleaned and inspected before placing the rebar cage.
8. Concrete Pouring and Casing Extraction
Concrete is poured, and once sufficient height is achieved, the casing is extracted using a pipe jacking machine or the rotary host.
Advantages of Full Rotary Drilling
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Versatility – Suitable for special sites, complex strata, and challenging conditions with low noise and vibration.
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Slurry-Free Operation – Eliminates mud contamination, enhances concrete bonding, reduces sediment, and minimizes hole wall damage.
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Real-Time Stratum Analysis – Enables visual assessment of soil and rock properties during drilling.
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High Speed – Achieves up to 14m/h in standard soil conditions.
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Deep Drilling Capability – Maximum depth of 80m, depending on ground conditions.
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Precise Verticality Control – Accuracy up to 1/1000.
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Stable Borehole – Minimizes collapse risks, ensures a clean base, and reduces sediment to 30mm.
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Optimal Diameter & Low Bulb Coefficient – Saves concrete compared to conventional methods.
Comparison with Rotary Drilling
In thick backfill layers with large boulders, traditional rotary drilling often causes severe hole collapse, whereas full rotary casing ensures stability and efficiency.
Additional Applications
Beyond handling quicksand, karst terrain, and ultra-high backfill, this technology is also used for:
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Secant pile walls
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Subway steel column installation
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Pile extraction and obstacle removal
Conclusion
The full rotary drilling rig with casing offers a reliable, eco-friendly, and efficient solution for complex foundation projects, ensuring superior quality and cost-effectiveness.
