A scaling approach for the behaviour of different sand materials in cyclic direct simple shear tests

The foundations of offshore structures are subjected to cyclic loads from wind and waves. Cyclic loads can lead to an accumulation of deformations in the saturated soil as well as to an accumulation of excess pore water pressures with corresponding reductions in strength or bearing capacity. The latter is of particular importance under the conditions of a storm event. To assess excess pore water pressure accumulation, cyclic laboratory tests must usually be performed. From such tests, contour plots can be developed that describe excess pore pressure accumulation as a function of dimensionless amplitude and mean value of cyclic shear stress (cyclic stress ratio CSR and mean stress ratio MSR, respectively). Herein, the CSR value which leads to liquefaction after 10 cycles can be used as a parameter characterizing the cyclic soil response. Experimental results documented in the literature suggest that contour plots of different sandy soils can be transformed into each other if the experimental results are normalized to this value. In the presented work, different sandy soils at variable relative densities are investigated in a cyclic direct simple shear device to verify and quantify the above-mentioned assumption. Artificial soils consisting of glass beads are additionally used to investigate the influence of grain shape. A scaling approach to derive the cyclic response with a small number of cyclic laboratory tests is presented.