Environmental Engineering Reference
In-Depth Information
(a)
Longitudinal section (exaggerated vertical scale)
(b)
Cross section original design
(c)
Cross section showing failure surface
Figure 3.20.
Longitudinal and cross sections, Waco Dam (Stroman et al., 1984).
condition that can be related to a material that has been broken prior to construction and
to the condition of the Pepper Shale after the slide”.
Londe (1982) considers that the sliding at Waco Dam occurred by progressive shear
failure (e.g. as described by Bjerrum, 1967, Terzaghi and Peck, 1967, Skempton and
Hutchinson, 1969 and subsequently by Skempton and Coates, 1985, to explain the fail-
ure of Carsington Dam).
It seems equally possible to the present authors that very thin but continuous bedding
surface faults with 7° to 9° residual strength may have existed in the Pepper Shale before
the slide and contributed to the movement. Such bedding surface features require very
small movements for their development and these could easily have occurred during the
formation of the normal faults which bound the slide area. As described in Section 3.5.2,
such minor bedding faults can be difficult to recover and recognize in drill cores.
3.5.7
Suitability of mudrocks for use as construction materials
Most mudrocks are not suitable for the production of materials for use in concrete, filters
or pavements due to their generally low strengths and their slaking properties. However,
