| dc.description.abstract | This thesis presents the results of geological investigations
carried out at the Kiserian damsite, Kajiado district. The
study was undertaken with the aim of obtaining information that
could help in the design and construction of the proposed dam.
The ma in parameters to be determi ned were, the structure,
lithostratigraphical sequence, hydrogeological conditions and
the depth to the bedrock.
Field investigations were conducted by
approach. The methods used included
geological mapping, seismic refraction,
electrical profiling and core-logging.
way of an integrated
photo-interpretation,
electrical sounding,
The dam site is underlain by the Ngong Basalts. Seismic
refraction results suggest a highly irregular bedrock surface.
There "is a substantial variation in velocity within the
overburden as well as in the sound rock. These variations are
explained in terms of fracturing and weathering of the rocks.
Geoelectrical sections revealed a low resistive zone below the
foundation bed. This is attributed to a weathered zone. Corelogs
show that the overburden materials are underlain by fresh
basalts,weathered basalts, agglomeratic zone and residual soils
resulting from weathering.
The seismic and resistivity results allowed interpolation of
the bedrock surface between drill holes with much more
confidence than would otherwise have been possible. On the
bas is of the resu 1ts obtained, it is recommended that the
overburden be excavated to depths of 1.5 m to 2 m. Grout cap
should be used to seal off the fractures. This will strengthen
the fractured foundation. A deep cut-off or grout curtain is
recommended at the heel of the dam to provide a better
anchorage which will increase resistance to sliding | en |
