Dynamic behavior of naturally desiccated clays via resonant column testing at constant water content conditions

Abstract

The surficial soil at a western region of Bogota (Colombia) is a sedimentary deposit of high compressibility lacustrine clays with lens of sand and peat and overconsolidation ratios (OCR) from 1 to 9 due to desiccation processes. This geomaterial is subjected to matric suctions up to 800 kPa that generate cracks above the groundwater level, in the vadose zone. Small-strain dynamic properties such as shear modulus, material damping, and shear wave velocity are key parameters for an adequate analysis and design of geotechnical structures like shallow foundations or pavements in this particularly condition. In order to characterize the dynamic behavior and its relationship with initial state and confinement level, fixed free resonant column tests at constant water content were performed in specimens of those desiccated, stiff, and overconsolidated materials. It was found that the influence of suction and confinement stress in shear modulus and damping ratio is more pronounced in lightly overconsolidated materials for similar water contents before the air entry value (AEV). Nonetheless, after the AEV, the stiffness response and the shear wave velocity take similar values in an independent way of the initial state. In highly overconsolidated conditions, the overall dynamic response is fairly similar before and after the AEV, despite the stress history.