Modeling the Stiffening Behavior of Sand Subjected to Dynamic Loading

Abstract

In geotechnical engineering, dynamic soil models are used to predict soil behavior under different loading conditions. This is crucial for many dynamic geotechnical problems related to earthquakes, train loading and machine foundation design. Researchers agree that under dry or drained conditions, cohesionless soils increase in stiffness with each loading cycle. Soil models that simulate the dynamic behaviors of soils are often coupled with the Masing criteria. Such models neglect the impact of stiffening during cyclic loading, leading to an underestimation in the shear modulus (G). This study investigates the stiffening behavior by conducting laboratory tests on three types of Danube sands using the Resonant Column-Torsional Simple Shear device (RC-TOSS). The increase in the dynamic shear modulus with an increasing number of cycles is substantial, especially for samples with low density. Sometimes, the dynamic shear modulus doubles when loaded at high stress levels for more than 50 cycles. A new model is introduced to simulate the stiffening behavior of dry sand when subjected to cyclic torsional loading. Modifications are proposed for the Ramberg–Osgood and Hardin–Drnevich models and for the Masing criteria to overcome the limitations that accompany these models due to the influence of stiffening caused by repetitive loading being ignored. This model can be implemented in finite element and finite difference software to solve dynamic geotechnical problems.

Keywords

• resonant column
• torsional simple shear test
• Masing criteria
• stiffening of dry sand