Kishorn Dock, Wester Ross, Scotland Presented by Mark Day & Richard Collumbine.
-
Upload
ethel-clark -
Category
Documents
-
view
213 -
download
0
Transcript of Kishorn Dock, Wester Ross, Scotland Presented by Mark Day & Richard Collumbine.
Kishorn Dock, Wester Ross, Kishorn Dock, Wester Ross, ScotlandScotland
Presented by Mark Day & Richard CollumbinePresented by Mark Day & Richard Collumbine
Geological ContextGeological Context Torridonian sedimentary Torridonian sedimentary
rocksrocks 20 – 170 MNm20 – 170 MNm-2-2
Arkose bands (gritstone Arkose bands (gritstone group) unalteredgroup) unaltered
Shaly layers contain Shaly layers contain chlorite produced by chlorite produced by thermal metamorphismthermal metamorphism
Geological ContextGeological Context
Discontinuity dataDiscontinuity data
1. Bedding planes (131. Bedding planes (13°° – 21 – 21° SW° SW))- Spacing variable- Spacing variable- Tight discontinuity, rough irregular surface/no water - Tight discontinuity, rough irregular surface/no water
flowflow2. Set of parallel faults (602. Set of parallel faults (60°° – 80 – 80°° NW) NW)
- Spaced at 18m- Spaced at 18m- Open discontinuity 10mm, smooth with - Open discontinuity 10mm, smooth with
slickenside's/no water flowslickenside's/no water flow3. Joint set discontinuities (403. Joint set discontinuities (40°° S) S)
- Spaced at 18m- Spaced at 18m- Open discontinuity, smooth surface/no water flow- Open discontinuity, smooth surface/no water flow
Plan view of Kishorn DockPlan view of Kishorn Dock
ProblemProblem
Rock mass inhomogeneousRock mass inhomogeneous Potentially unstable in vertical cutsPotentially unstable in vertical cuts Awkward to excavateAwkward to excavate Difficult to blast clean angled benches on Difficult to blast clean angled benches on
excavated faceexcavated face
ProblemProblem
When blasting took place When blasting took place • Nearest fault plane to face openedNearest fault plane to face opened• Wedge of rock between plane and faceWedge of rock between plane and face• SpallingSpalling• Dock face left with dangerous overhangDock face left with dangerous overhang
Cross Section BlastingCross Section Blasting
Cross Section BlastiingCross Section Blastiing
Cross Section BlastingCross Section Blasting
Question raised: what angle Question raised: what angle of slope was needed to of slope was needed to
make it safe?make it safe?
Possible SolutionPossible Solution
• A slope at right angles to the angle of dip A slope at right angles to the angle of dip of the reverse faults (~30of the reverse faults (~30°) °)
• Angle would fit well with friction angle of Angle would fit well with friction angle of sandstone (25° - 35°)sandstone (25° - 35°)
- not feasible because of cost- not feasible because of cost
- insufficient free ground at end of - insufficient free ground at end of excavationexcavation
Actual SolutionActual Solution
Slope angle of main bench reduced from vertical to Slope angle of main bench reduced from vertical to 7575°°
Chain mesh was hung on face to minimise risk from Chain mesh was hung on face to minimise risk from rock fallrock fall
Solution proved to be adequate and in the first 2 year Solution proved to be adequate and in the first 2 year period no rock fellperiod no rock fell
THE ENDTHE END