Mechanical behavior of a volcanic ash soil (Typic Hapludand) under static and dynamic loading

Irrespective of the loading time interval, pore water pressure increased to even positive pore water pressure values when mechanical stresses of >300 kPa were applied, being more important in samples after pre-drying at −60 hPa than at −300 hPa. In the shear test the behavior was similar, but positive values of pore water pressure already occurred when the vertical stress exceeded 200 kPa. Thus, we can conclude, that hydraulic properties are specially important in soils showing thixotropic behavior and/or when shear stresses are applied resulting in a more pronounced weakening by increasing the destabilizing pore water pressure as a reason for an enhanced particle rearrangement and soil homogenization compared with the original soil structure.