WTC-2008

Directional core drilling in tunnel construction

Directional core drillingDevico ASBorehole survey systemsDirectional core drillingDeviDrill directional core barrelFirst version in 1988Present version in 2001ProjectsGeotechnical explorationMineral exploration

Geotechnical explorationChange direction of boreholesSteer towards targets or keep hole within limitsRetrive core from the most relevant areas

Coring along planned tunnel alignmentContinuous rock coreFault zonesFracturesGeological anomaliesRock mechanical propertiesHole for various analysisGeophysicalWater in-/outflowHydraulic fracturing

Directional coring in Hong Kong4 projects completed last five yearsTraffic tunnels (2)Drainage tunnels (4)Sewage tunnels (6)Guidance note from the HK Government4.1 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.

Eagles Nest2 boreholes580 and 1150 meters8 m radius toleranceBorehole between twin tunnelsFault zonesPressure grouting schedules

Harbor Treatment Scheme, Stage II6 boreholes600 to 1250 meters10 x 10m toleranceStart inclination from -33 to -45

ConclusionAccurate impression of the rock formations along the tunnel alignmentSecurity during constructionStabilization measuresPredict leakage and ground settingMaterial estimationsTime & cost estimationsAchieves reliable results, proven in mining and geotechnical exploration projects worldwide

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