Effect of moisture content on tensile strength and fracture toughness of a silty soil

Determination of fracture parameters (tensile strength, fracture toughness) is essential in determining the cracking behaviour of soils. In drying soils, a crack initiates when the tensile stresses exceed the soil strength. Crack propagation is considered to be governed by the stress state in the crack front and subsequent dissipation of fracture energy, for which Fracture Mechanics Theory can be used. In this context characterizing the soil for these two parameters require two different testing equipments. The tensile strength was determined using existing equipment (direct method) at the Soil Mechanics Laboratory of UPC whereas new equipment was designed for the fracture toughness determination. The results of tensile strength tests are consistent with published literature. Fracture toughness decreases as the moisture content increases; an attempt is made to explain this using the concept of Rate Process Theory and Activation Energy of soils.