Short fiber-reinforced earth construction methods in which non-continuous geosynthetic filaments are mixed uniformly with soil aggregates are being developed recently for the purposes of improving the mechanical properties of shear strength and strain-dependent toughness of the reinforced soils. In addition this method has some beneficial functions in wide-range environmental applications such as the re-use of poor surplus soils produced in the construction sites and stabilizing the steep slopes providing the vegetation base. At present insufficient knowledge is available regarding to effects of material, shape, size, flexibility, surface fiction and other fundamental properties of short fiber on the mechanical behavior. A newly developed short fibers with several side branches (so called ribbed-type fiber) is employed in order to not only improve their reinforcement effects but also to be able to exclude the fibers without great effort in case of reuse of the soils. In this study effects of the mixing rate of the fibers on the reinforcing mechanism are investigated using an unconfined compression test and a large box shear test (box size:

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Geotextile or goecomposite drain sheets are used commonly for collecting and draining the seepage water in an embankment or the pore water in a cohesive soil with high moisture content. In these cases the combined hydraulic characteristics of the multi-layered structure depend on both the permeability of soil and the transmissivity in plane direction and the permittivity in cross-plane direction of a geodrain sheet. In this study a laboratory two dimensional model test is conducted for a cohesive soil embankment in which a geotextile is placed. The effects of thickness of geotextile, overburden pressure and degree of compaction (i.e. soil density and permeability) on the hydraulic properties of the models are investigated and the results of tests and the interaction between the geotextile and the soil conditions are discussed.

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