Environmental Engineering Reference
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done immediately the foundation is exposed, but may be done after a second cleanup
immediately before placing the earthfill core. If cement-sand grout is used, it may crack
under the trafficking of equipment placing the earthfill and it may have to be removed
immediately prior to placing the earthfill.
-Remove from the surface all loose soil and rock, and debris from grouting (using light
equipment and with an air or air-water jet). Hand cleanup may be necessary. The sur-
face may need to be moistened immediately before placing earthfill to maintain the
earthfill moisture content.
- If the rock in the floor or the sides of the cutoff trench displays open joints or other fea-
tures which would allow erosion of the earthfill into them, it should be cleaned of loose
material and covered by a cement-sand grout, pneumatically applied mortar or con-
crete. This is particularly critical on the downstream side of the cutoff trench. If there
are only a few such features they might be treated dentally.
Under no circumstances should the surface of the cutoff foundation be rolled, even if it
is a weathered rock. Rolling will only disturb the rock leading to a higher permeability
material.
Figures 17.3 to 17.8 show cutoff foundation cleanup, treatment of seams and open
joints for Dartmouth, Kenyir and Blowering Dams.
Figure 17.3.
Abutment of Dartmouth Dam showing cleanup in cutoff foundation, and construction of
the grout cap (Courtesy of Murray-Darling Basin Commission and Goulburn-Murray
Water).
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