Dynamic mechanical analysis for sands using a shear rheometer

Abstract

Dynamic mechanical properties such as shear modulus (G) and damping ratio (ξ) are key parameters governing soil response under cyclic loading. However, evaluating these properties in loose dry sands under low confining pressures over a wide strain range (γ = 10−6–10−2) remains challenging using a single testing method. Dynamic Mechanical Analysis (DMA) addresses this limitation by enabling measurements across both small- and large-strain ranges within a single test. Although DMA is widely used in asphalt engineering, its application to geotechnical materials is relatively recent. Previous studies have adapted shear rheometers to perform DMA on loose sands. Nevertheless, the benchmarking with traditional methods remains limited. This study presents a detailed DMA procedure for loose sands and benchmarks its results against conventional dynamic testing methods, including Resonant Column (RC) and Bender Element (BE) tests. The material tested is TP-Lisbon sand, a natural alluvial sand with subangular particles; it was tested under different confining pressures σ3 = [10-50]kPa. The results demonstrate that DMA successfully captures shear modulus degradation and damping ratio evolution over the investigated strain range, showing good agreement with conventional laboratory techniques and confirming the method's reliability for dynamic soil characterization.