Evaluating the Coefficient of Lateral Stress at Rest (K0) of Granular Materials under Repetitive Loading Conditions

Abstract

The coefficient of lateral stress at rest (K0) is a very important soil parameter determining the in-situ stress states of soils. While the K0 of soils under static loading conditions has been extensively studied, studies evaluating K0 under repetitive loading have been very limited. This study aims at investigating the characteristics of K0 of two granular materials with similar particle shapes but different particle shapes during repetitive loading. The modified oedometer cell equipped with bender elements and diaphragm transducer was developed to measure the variations of lateral stress and shear wave velocity during the manual repetitive load system. Additionally, the automatic repetitive loading system with pneumatic cylinder and diaphragm transducer was developed to explore the lateral stress change during a large number of repetitive loading cycles. The results of this study demonstrate that the K0 of tested materials in the repetitive loading during loading step increases with increasing cyclic loading number (i) though the void ratio of tested materials continuously decreases with cyclic loading number. However, the measured K0 during repetitive loading at unloading steps shows a little decrease or constant value as the number of repeated loads increases. The stiffness anisotropy based on shear wave velocity measurements also confirms the finding of this study. Finally, the results of this study demonstrate that rounded granular material shows a greater change in K0 during repetitive loading compared to angular sand.