Dry snow slab avalanche release is preceded by a shear failure in a weak layer or an interface of the snowpack, followed by a fracture in tension. Both these processes can be described by fracture mechanics. For a better understanding of the slab release process, measurements of the relevant snow mechanical properties, such as the fracture toughness, are essential. Knowledge of these properties is necessary for a snow slope stability analysis that includes fracture propagation. The purpose of this work was to measure the snow fracture toughness in mode I (tension), and to determine whether or not snow fracture toughness is affected by a size effect for the used specimen size. The latter is limited because of practical difficulties in handling big specimens. Edge-cracked beam-shaped snow specimens cut from a homogeneous layer of naturally deposited snow were loaded in three point bending. All experiments were performed in a cold laboratory. In order to quantify the size effect, specimens of the same shape but of four different sizes were used. Preliminary results indicate that fracture toughness is affected by the specimen size. The reason for this behaviour is the size of the fracture process zone, which for snow is within the range of the ligament widths of the used specimens. Actually, these specimens showed a non-linear, quasi-brittle behaviour. In order to be used in slope stability models, the measured fracture toughness values require a corresponding size correction.
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