Abstract: In order to research the tensile properties of compacted clay, a conventional triaxial test apparatus was modified to a uniaxial tensile apparatus for clays, by which clay samples can be extended and the stress and corresponding strain of the samples can be measured directly. A series of laboratory tests were conducted to investigate the tensile properties of compacted clay. The tested clay samples have various moisture contents (from 16% to 24%) and various dry densities (from 1.29 g/cm3 to 1.65 g/cm3), which have impacts not only on the tensile strength of samples, but also on the pattern of tensile stress-strain curves. It is found that there are three patterns of stress-strain curves for the tension of clay soil, i. e. strain-softening, strain-hardening, and strain-strengthening, corresponding to the increasing tensile strength and failure strain. The tensile strength of compacted clay approximately increases with its dry density and decreases with its moisture content linearly. With the increasing dry density and decreasing moisture content, the pattern of stress-strain curves of the clay samples changes from strain-softening to strain-hardening, then to strain-strengthening pattern. The tensile rate has obvious effect on the measured tensile strength and the pattern of stress-strain curves. For the samples with identical dry density and moisture content, lower tensile rate results in smaller measured tensile strength and strain-softening stress-strain curves; and higher tensile rate causes greater measured tensile strength and strain-strengthening stress-strain curves.

Key words: uniaxial direct tensile test, compacted clay, stress-strain curve, tensile strength