directional core drilling in tunnel construction

Directional core drilling in tunnel

construction

Directional core drilling

• Devico AS• Borehole survey systems• Directional core drilling

• DeviDrill directional core barrel• First version in 1988• Present version in 2001

• Projects• Geotechnical exploration• Mineral exploration

Geotechnical exploration

• Change direction of boreholes• Steer towards targets or keep hole within limits• Retrive core from the most relevant areas

Coring along planned tunnel alignment

• Continuous rock core• Fault zones• Fractures• Geological anomalies• Rock mechanical properties

• Hole for various analysis• Geophysical• Water in-/outflow• Hydraulic fracturing

Directional coring in Hong Kong

• 4 projects completed last five years• Traffic tunnels (2)• Drainage tunnels (4)• Sewage tunnels (6)

• Guidance note from the HK Government• “4.1 Directional drilling techniques are now available to drill from

ground level to great depth and then along a horizontal alignment. This method does not require provision of working space at the tunnel level and can be very useful in GI for deep tunnels.”

Eagle’s Nest

• 2 boreholes• 580 and 1150 meters• 8 m radius tolerance• Borehole between twin

tunnels• Fault zones

Pressure grouting schedules

Harbor Treatment Scheme, Stage II

• 6 boreholes• 600 to 1250 meters• 10 x 10m tolerance• Start inclination from -33° to -45°

Conclusion

• Accurate impression of the rock formations along the tunnel alignment

• Security during construction• Stabilization measures• Predict leakage and ground setting• Material estimations• Time & cost estimations

• Achieves reliable results, proven in mining and geotechnical exploration projects worldwide

Thank you for your attention!

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