Abstract:
Infrastructure development in Kenya has led to the need for alternative material in slopes and embankments construction.
Sourcing of recommended cohesionless material often leads to the destruction of the environmental features such as rivers
and involves high extraction and transportation costs. The need for alternative material is the motivation behind this study.
The study aims to evaluate the potential of Red coffee soils of Kenya as a backfill material in the construction of slopes
and embankments. Provision of sand cushion layers to sandwich non-woven geotextile material has been suggested to
overcome the water drainage and stability problems that have been associated with these soils. The study first involved
identifying the properties of both the Red coffee soils (RCS) and the river sand that is to aid in drainage. Numerical model
SEEP/W was used in evaluating the effect of geotextile inclination on the performance of RCS embankments before the
effect of introducing sand cushions of different thickness evaluated. The numerical results revealed that the stability of
reinforced RCS decreased with increase in pore water pressure in the embankments due to rainfall infiltration. Provision
of sand cushion layers helped improve both the local and global stabilities of the RCS subjected to rainfall infiltration. The
results showed that 150mm sand cushion layer was adequate to improve the performance of RCS embankments and
reduced the sand consumption in the construction of embankments to 15%.
