Long-term Sediment Response Under Repetitive Mechanical and Environmental Loadings

• Main Author: Cha, Wonjun
• Other Authors: Santamarina, Carlos
• Language: en
• Published: 2021
• Subjects: Renewable energy; Sustainability; Repetitive loading; Shakedown / Ratcheting; Terminal density; Strain accumulation
• Online Access: Cha, W. (2021). Long-term Sediment Response Under Repetitive Mechanical and Environmental Loadings. KAUST Research Repository. https://doi.org/10.25781/KAUST-07L5T; http://hdl.handle.net/10754/673777

Geostructures experience repetitive load cycles, which gradually affect their long-term performance. This thesis explores the long-term response of soils subjected to mechanical load-unload, heat-cool, freeze-thaw, and atmospheric pressure oscillations. The research methodology involves new instrumented cells (oedometer, temperature-controlled triaxial chamber, and pressure-controlled drying chamber), various geophysical monitoring methods (X-ray micro-CT, NMR, S-wave, and EM-waves), and simulations using discrete element modeling. Results show that soils subjected to repetitive mechanical or environmental loading experience shear and volumetric strain accumulation and changes in saturation (during barometric pressure cycles). In all cases, soils evolve towards an asymptotic terminal void ratio; the change in void ratio is pronounced when the soil exhibits grain-displacive ice formation during freeze-thaw cycles. The initial stress obliquity defines the shear strain response, which may be either shakedown -at low stress obliquity-, or ceaseless shear strain accumulation in ratcheting mode when the maximum stress obliquity approaches failure conditions. Finally, we provide simple engineering guidelines to estimate the long-term behavior of soils subjected to repetitive mechanical or environmental loading.