Appropriate Solution For Impervious Core Of Embankment Dams To Be Constructed Using Highly Plastic Soils

For a long time, highly plastic clays (CH soils) have been used extensively as impervious corernmaterial for many zoned embankment dams all over the world. In Ethiopia several dams arerncurrently under construction (e.g. Tendaho dam) and more are planned to be constructed (e.g.rnRibb, Megech, Meqa dams, etc.) using predominantly CH soils as the most availablernimpervious core material.rnNevertheless, several problems are associated with CH soils. The most common problemsrninclude high compressibility when saturated, potential for high swelling and cracking, slowrnrate of construction for safe dissipation of pore water pressure, large difference in stiffnessrnwith the surrounding shell materials leading to differential deformation, difficulty in moisturerncontrol during construction, and requiring extremely fine filters that can not be easily obtainedrnor produced on site.rnIn this thesis, a study has been conducted on the effects of blending the CH soils withrnnaturally available granular materials using several laboratory tests. The laboratory testsrninclude Atterberg limits, permeability, compaction, 1D-consolidation, and triaxialrncompression tests on samples collected from Tendaho dam site. The test results clearly revealrnthat blending with granular soils greatly improves the physical and mechanical behaviours ofrnthe CH soils. Based on the test results, an appropriate blending ratio has been recommendedrnfor the CH soils used in Tendaho dam.

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