“Difficult” Sites Derek H. Cornforth

siennatearfulUrban and Civil

Nov 25, 2013 (3 years and 6 months ago)

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Landslide Remediation

at Two “Difficult” Sites

Derek H. Cornforth

Past CEO, Landslide Technology,

Portland, Oregon

Faraday Canal
Slide

Estacada, Oregon

Faraday Canal, Upper Slide

“Difficult” remediation because:


Landslide is active (FS slightly below 1.00)


Poor Access


Emptying the canal for reconstruction decreases
slope stability


Excavation into the toe of the landslide decrease
slope stability

What to do?

Selected Remediation

Restore the original canal profile by a three
-
step

earthworks procedure that keeps FS always
above 1.00

Summary of Faraday Canal
Slide Remediation

“Difficult” Site Conditions


Active landslide


Difficult access


Removal of landslide debris from toe area and
dewatering the canal both decrease

stability




Remedial Treatment


Simple earthwork procedures (3
-
steps) to keep
FS above 1.00 at all times

Goat Lick Slide

Glacier National Park, Montana

Goat Lick Slide

“Difficult” remediation because:


Reinforced earth wall disturbed by movements


Steep slope


Environmentally sensitive:


No access to slope


No treatment permitted at toe of landslide

What to do?

Selected Remediation


Installed vertical
and sloping

inclinometers
from the road to define the slip

surface


Used

heavily reinforced concrete piles,
tied back into bedrock,

to stabilize the
road at the head of the landslide


Built

the concrete pile

wall

behind the
existing R.E. wall to reduce pile

loads and
lengths

Summary of Goat Lick


Slide Remediation


Difficult” Site Conditions


Slope at angle of repose


No work permitted below road for environmental
reasons




Ongoing erosion at toe of slide

Remedial Treatment


Used tied back reinforced concrete shear piles to
stabilize

road (selective stabilization)