Abstract
Mechanical properties of geosynthetics required for improving bearing capacity and increasing stability of slope of soft cohesive soils are summarized as: (1) high strength and stiffness to follow the large deformation due to applied loads, (2) adequate frictional resistance at the interface of geosynthetics and soil, (3) long-term permeability and transmissibity. As one of the geosynthetics which may suit the above-stated requirements, the authors have recommended the use of composite unwoven geosynthetics. It consists of high strength woven geosynthetics pasted within unwoven varieties. This composite geotextile can act as reinforcement as well as drainage media when used within soft soil. The advantageous features of this geo-composite material have been proved in laboratory small-scaled model tests. Test results of the improvement of bearing capacity of soft clay and increase in slope stability of embankment made with volcanic ash cohesive soils (called Kanto Loam) are reported. It is emphasized that placement of thin sand mat in-between geo-composites and soft cohesive soil is more effective for attaining those requirements, particularly for maintaining permeability and transmissibity of the materials when it is used for increasing stability of embankment by Kanto Loam.
