An Unconfined Direct Tension Test for Compacted Clays

Abstract

Although problems associated with total stress tension arise in soil structures such as earth embankments and multilayer pavements, no standard tension test for soils exists. An unconfined direct tension test, either strain controlled or load controlled, is described, which can be used to determine the tensile (total) stress-strain characteristics of compacted clays. The overall tensile strains in the specimen are determined by observing the displacement of two surface markers spiked into the specimen with a displacement measuring optical device (DMOD) capable of measuring to one-micrometer displacement. An alternative radiographic technique of monitoring strains has shown that the distribution of average tensile strains in the specimens is substantially uniform. Moreover, the failure of the tension specimen occurs in midsection, indicating a uniaxial transmission of tensile force to the specimen. Comparison of standard triaxial unconfined compression tests with unconfined tension tests shows that elastic moduli are not equal in compression and tension for compacted clays at a given moisture content.

Development of semi-physically based model to predict erosion rate of kaolinite clay under different moisture content

“…1a) was designed and constructed to measure tensile-deformation characteristics of cylindrical soil samples. The design of the apparatus was based on Ajaz and Parry (1974), Ibarra et al (2005), Indraratna et al (2009), Munkholm et al (2002, and Tamrakar et al (2005). The apparatus applied a constant uniaxial load to a test specimen and was sensitive enough to measure the tensile-deformation forces of clay samples at very high precision as recommended by Ajaz and Parry (1974).…”

“…The design of the apparatus was based on Ajaz and Parry (1974), Ibarra et al (2005), Indraratna et al (2009), Munkholm et al (2002, and Tamrakar et al (2005). The apparatus applied a constant uniaxial load to a test specimen and was sensitive enough to measure the tensile-deformation forces of clay samples at very high precision as recommended by Ajaz and Parry (1974). The main components of this apparatus consisted of sample molds and holders, an S-type load cell, a linear variable displacement transducer (LVDT), and a motor-driven shear bench, which provided a constant uniaxial load.…”