Abstract: Tensile strength is an important mechanical index of clay. A set of tensile strength apparatus is developed to test the tensile strength of clay and the specimen-preparing methods on tensile strength are studied. Tensile strength tests for two types of swell-shrink soils are respectively designed to discuss the influences of water content, dry density and drying-wetting cycles. Analysis of the data shows that there is an exponential relationship between tensile strength and water content; and the tensile strength reaches the peak value at optimum water content, saturation degree of 66%. And the change rule of tensile strength with water content is impacted by the forms of water in soils. It is also found that tensile strength linearly increases with dry density and the increase rate is significant. As experienced three dry-wetting cycles, the tensile strength sharply decreases to 20% of the initial value and its impact is especially obvious during the first and second cycles. Through theoretic and contrast analysis, it is found that the decrease of tensile strength of swell-shrink soils with drying-wetting cycles is due to the deterioration of microstructures.

Key words: swell-shrink soil, tensile strength, uniaxial tension test, drying-wetting cycle