1 Workshop of the Committee on Geological and Workshop of the Committee on Geological and Geotechnical Engineering Geotechnical Engineering LIFECYCLE COSTS LIFECYCLE COSTS ROCK SLOPE STABILIZATION AND ROCK SLOPE STABILIZATION AND PROTECTION MEASURES PROTECTION MEASURES November 28, 2007 November 28, 2007 Duncan C. Wyllie Duncan C. Wyllie Wyllie & Norrish Rock Engineers Wyllie & Norrish Rock Engineers Vancouver, Canada Vancouver, Canada
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Workshop of the Committee on Geological and Workshop of the Committee on Geological and Geotechnical EngineeringGeotechnical Engineering
LIFECYCLE COSTS LIFECYCLE COSTS ROCK SLOPE STABILIZATION AND ROCK SLOPE STABILIZATION AND
Wyllie & Norrish Rock EngineersWyllie & Norrish Rock EngineersVancouver, CanadaVancouver, Canada
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Rock FallsRock Falls
3Rock fall bounced on asphalt and then into windshield
4Rock fall in strong, blocky granite during heavy rainfall
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Trains can survive larger impacts than cars, but cannot swerve or brake to avoid hazard.
Rock fall modeling programs tend to calculate trajectories that are higher than reality.
This results in nets and fences being larger than required.
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Rock falls can be managed by one of Rock falls can be managed by one of three approaches:three approaches:
1.1. Design and construction of rock fall Design and construction of rock fall protection for new facilitiesprotection for new facilities
2.2. Slope maintenance during operationsSlope maintenance during operations3.3. Reactive Reactive –– clean slides after they happenclean slides after they happen
Decision analysis can be used to evaluate strategy to
minimize lifecycle costs
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Design and construction of rock fall Design and construction of rock fall protection for new facilities:protection for new facilities:
1.1. Uniform face with no benchesUniform face with no benches2.2. Rock fall containment ditchesRock fall containment ditches3.3. Controlled blasting on final facesControlled blasting on final faces
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Drill offset~2 to 3 ft.
Uniform face with no benches
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Serious accident due to rock bouncing off
remnant bench and landing on car
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Benched cuts in horizontally
bedded sedimentary
rock
Intermediate benches on weaker rock
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Design and construction of rock fall Design and construction of rock fall protection for new facilities:protection for new facilities:
1.1. Uniform face with no benchesUniform face with no benches
2.2. Rock fall containment ditchesRock fall containment ditches3.3. Controlled blasting on final facesControlled blasting on final faces
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Rock fall containment
system
Sloped ditch with loose gravel
cushioning layer
Posts to support Ringnet
fence
Planting between walls
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Ditch design chart –
depth/width related to slope
height and angle.
Also, Oregon ditch design
charts.
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Design and construction of rock fall Design and construction of rock fall protection for new facilities:protection for new facilities:
1.1. Uniform face with no benchesUniform face with no benches2.2. Rock fall containment ditchesRock fall containment ditches3.3. Controlled blasting on final facesControlled blasting on final faces