Environmental Engineering Reference
In-Depth Information
FIGURE 9.40
Soil “breccia” of fragments of indurated clayey silt in a crushed uplifted zone at Portuguese Bend.
In the Seattle Freeway slides
(Figure 9.41),
failure occurred along old bedding plane
shears associated with lateral expansion of the mass toward the slopes when the glacial ice
in the valley against the slopes disappeared (Palladino and Peck, 1972). Similar conditions
probably existed at the site of the slide occurring at Kingston, New York, in the Hudson
River valley in August 1915 (Terzaghi, 1950). The Kingston slide was preceded by a period
of unusually heavy rainfall. Factors contributing to failure, as postulated by Terzaghi,
were the accumulation of stockpiles of crushed rock along the upper edge of the slope and
perhaps the deforestation of outcrops of the aquifer underlying the varved clays which
permitted an increase in pore-water pressures along the failure surface.
Glaciomarine Soils: South Nation River Slide
Event
: The South Nation River slide in Casselman, Ontario, of May 16, 1971, is typical of
many slides occurring in the sensitive Champlain clays of glaciomarine origin, in Quebec
province, Canada (Eden et al., 1971). These clays are distributed in a broad belt along the
St. Lawrence River and up the reaches of the Saguenay River. Most of the slides occur
along riverbanks, commencing as either a slump or block glide and retrogressing through
either slumping or lateral spreading. At times, the frontal lobes of the slides liquefy and
become flows
(Figure 9.4f)
(see
Section 9.2.11).
