engleski

Preliminary results on the undrained cyclic behavior of uniform sand at low confining stress

Earthquakes are one of the main landslide triggering factors. Earthquake induced cyclic shear strain and stress generate the rise in the pore water pressure and soil strength degradation which tends toward soil failure. Slopes in which shallow landslide can be formed due to geological conditions are most susceptible to such kind of loading mainly because of soil low confining stress. Confining effective stress has a significant role on the soil response during static and cyclic load. Tests performed on soil samples under monotonic shear indicate that the shear strength properties increase with decreasing effective stress due to dilatancy. This paper presents preliminary results of an undrained cyclic triaxial test on sand material used for modelling small scale shallow landslides under 1g conditions. Based on the scaling rules for 1g conditions, frequencies of straining amplitudes for undrained strain- controlled cyclic triaxial tests were defined. Undrained cyclic triaxial tests on the type of sand used in a small-scale landslide model were performed. Samples were consolidated on low confining stress which corresponds to an assumption of a shallow landslide used as prototype. All tests were conducted in the Laboratory for geotechnics at the Faculty of Civil Engineering in Rijeka, Croatia. The influence of loading frequency and low confining stress was investigated and a simple model for pore pressure build-up was proposed which can be used to estimate the increase in pore water pressure due to cyclic loading at low confining stress for frequencies of loading less than 1 Hz.

uniform sand ; low confining stress ; strain controlled ; cyclic triaxial test

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