Page 99 - Geotechnical Engineering Soil and Foundation Principles and Practice

Soils That Are Sediments
94 Geotechnical Engineering

Figure 4.15
Approximate
extents of
glaciation and of
loess deposition in
Eurasia. Loess
map is from
Russian sources,
reprinted in Loess
Letter 48,
Nottingham Trent
University, Ian
Smalley, ed.

Figure 4.16
Intrepid student
engineer
suspended on a
bosun’s chair in
order to collect
samples of loess in
western Iowa.Here
the soil is so
porous that it will
collapse if it
becomes
saturated with
water. A vertical
tension crack and
landslide are at the
left.

soil grains together, but this is not borne out by microscopic examination or
by the fact that loess close to a source can collapse under its own weight if wet
with water. The cohesive mechanism therefore appears to involve capillary
forces or ‘‘suction’’ of water enhanced by clay surface activity and that is reduced
by wetting.

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