Rainfall-Induced Failure of Unsaturated Volcanic Slope Subjected to Freeze-Thaw Action and Its Mechanism

Stability of Volcanic Slopes in Cold Regions

“…In a series of model tests, negative pore water pressure due to suction exhibited small values. On account of this, the influence of the dissipation of suction on slope instability was ignored (Kawamura et al, 2010a). This fact has also been confirmed by triaxial compression tests which revealed the effect of the decrease in suction on the shear strength of volcanic soils (Ishikawa, Miura, & Ito, 2010).…”

“…In previous studies, the relative relations between saturation degree, pore water pressure, and deformation prior to failure were also demonstrated on the basis of the preliminary test data on Toyoura sand and volcanic slopes (Kawamura et al, 2010a;. As a result, slope failure characterized by large deformation developed rapidly after a shear strain of 4-6%.…”

“…6, No. 3; For all model testing, the difference in failure mechanism due to around 5% of variation in the initial degree of saturation for each position was not observed (Kawamura et al, 2010a). As a result, the variation in initial saturation was set within 5%.…”

“…The model test results (Kawamura et al, 2010a; demonstrate that slope failures of volcanic soils depend strongly on both the angle of the slope and the friction of its impermeable layer; however, slope density was not shown to be a significant factor. It was also shown that the softening of the slope by freeze-thaw action is important for evaluating the stability of volcanic slopes; in particular, its effect is attributed to the reduction of the shearing resistance due to particle breakage and cannot be ignored for the evaluation of slope stability, and that slope failure can be predicted if the depth of frozen area and the water retention capacity in the slope are estimated by monitoring an index property such as water content.…”

“…In the case of lower water content, seepage water due to rainfall can be retained in voids in the slope because its velocity becomes slower. As a result, surface slope failure rapidly occurs due to the increase of self-weight around shallower areas in Kashiwabara volcanic slopes (Kawamura et al, 2010a). Ishikawa, Miura and Tokoro (2009) have revealed the unsaturated mechanical behavior of Kashiwabara volcanic soil using element test devices.…”