Geotechnical Properties of Cemented Volcanic Soil

Abstract

A volcaniclastic formation, known as Cangahua, found in the Andes of Ecuador and Colombia is focused on. The deposit is composed of moderately cemented fine sand and silt‐sized particles. A pronounced linear correlation is shown between strengh, in terms of both uniaxial compressive and Brazil tensile strengths, and the dry unit weight of the deposit. The tensile strength is unusually high for soil, being between 18 and 29% of the uniaxial compressive strength. Brazil tensile, uniaxial compressive, and triaxial strength characteristics depend on the initial void ratio and degree of saturation. As the saturation declines from 90 to 40%, test results show a fourfold increase in tensile strength. Moreover, increasing degrees of saturation cause a shift from brittle to ductile failure. Slope failures in Cangahua develop from fractures which initiate at zones of high tensile stress. Material properties such as tensile strength and fracture toughness play an important role in explaining and evaluating slope failures in this material. The strong dependence of tensile strength on the degree of saturation indicates that local moisture conditions and exposure to rainfall should be considered in stability assessments.