École Nationale Supérieure de
Techniques Avancées

Abstract

This report aims to clearly and concisely present the main results and challenges encountered during my Research Project (Pre) internship. The focus of this project is the analysis of soil liquefaction occurrences following the Petrinja earthquake in December 2020 (Mw = 6.4) in the alluvial terrains along the Kupa, Sava, and Glina rivers. In 2022, liquefied sand samples (sand dykes) were collected at depth for physical and mechanical characterization. In 2023, an initial phase of cyclic triaxial tests was conducted to define the cyclic resistance ratio (CRR) curves and pore water pressure ratios (ru) as a function of the number of cycles to liquefaction for various density indices. These preliminary tests showed that beyond a threshold (ru ~ 0.6 to 0.8), the sample will systematically reach liquefaction, defined as ru = 1, and that between these two stages, there is a transitional phase where the sample can be described as "solid liquid." The internship aims to explore this solid-liquid phase, particularly through the apparent viscosity criterion defined by Mele (2019), by reinterpreting the already conducted tests and then performing additional complementary tests. The student will first familiarize themselves with the concepts and experimental equipment before interpreting the test results.