Directional core drilling in tunnel construction Directional core

Directional core drilling in tunnel construction

Directional core drilling • Devico AS • Borehole survey systems • Directional core drilling • Devi. Drill 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 10 m 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

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