Appropriate Solution for Impervious Core of Embankment Dams to be Constructed Using Highly Plastic Soils
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Date
2007-10
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Addis Ababa University
Abstract
For a long time, highly plastic clays (CH soils) have been used extensively as impervious core
material for many zoned embankment dams all over the world. In Ethiopia several dams are
currently under construction (e.g. Tendaho dam) and more are planned to be constructed (e.g.
Ribb, Megech, Meqa dams, etc.) using predominantly CH soils as the most available
impervious core material.
Nevertheless, several problems are associated with CH soils. The most common problems
include high compressibility when saturated, potential for high swelling and cracking, slow
rate of construction for safe dissipation of pore water pressure, large difference in stiffness
with the surrounding shell materials leading to differential deformation, difficulty in moisture
control during construction, and requiring extremely fine filters that can not be easily obtained
or produced on site.
In this thesis, a study has been conducted on the effects of blending the CH soils with
naturally available granular materials using several laboratory tests. The laboratory tests
include Atterberg limits, permeability, compaction, 1D-consolidation, and triaxial
compression tests on samples collected from Tendaho dam site. The test results clearly reveal
that blending with granular soils greatly improves the physical and mechanical behaviours of
the CH soils. Based on the test results, an appropriate blending ratio has been recommended
for the CH soils used in Tendaho dam.
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Keywords
Tendaho; Dam