Abschätzung der dynamischen Kenngrößen nichtbindiger Böden anhand der Korngrößenverteilungskurve

Estimating dynamic properties of granular soils under consideration of the grain size distribution curve.

The common empirical formulas for dynamic soil parameters were developed for uniform sands and do not consider the influence of the grain size distribution curve. The application of these formulas can lead to a considerable overestimation of the shear modulus of well-graded granular soils. 650 resonant column tests on 65 specially mixed grain size distribution curves of a quartz sand have been performed in order to extend various empirical equations by the influence of the grain size distribution curve. For each sand mixture different initial densities, pressures and shear strain amplitudes have been tested. Amongst others, a considerable decrease of the small-strain shear modulus Gmax with increasing coefficient of uniformity Cu = d60/d10 and increasing fines content was measured. In contrast, mean grain size has nearly no influence on dynamic soil parameters. A good prediction of the extended empirical equations can be demonstrated not only for linear, but also for stepwise linear, gap-graded and S-shaped grain size distribution curves. In comparison to the empirical formulas applied so far, the new extended empirical equations should deliver a more reliable estimation of dynamic soil properties.