Stiffness of pyroclastic scoriae under different degrees of saturation

¹ Universidad Politécnica de Madrid, Madrid, Spain
² Purdue University, Lyles School of Civil Engineering, West Lafayette, IN, USA

^* Corresponding author: fausto.molina@upm.es

Abstract

Pyroclasts are natural materials formed during volcanic eruptions, characterised by low densities due to their high porosity, which results in reticular, vesicular or mixed internal structures. These unique structures give rise to singular geomechanical behaviour that varies with the stress level, allowing pyroclasts to behave as either rock-like or soil-like material. Despite their importance, the small-strain stiffness of these materials under different degrees of saturation remains unexplored. To accurately characterise the response of pyroclastic materials under different water content conditions, precise measurement of the degree of saturation is essential. This study assesses the small-strain stiffness under various degrees of saturation of pyroclastic scoria sourced from Tenerife, Spain. For this purpose, an experimental program was conducted using a Resonant-Column apparatus to investigate these relationships. The program involved real-time Sr monitoring during element testing. The degree of saturation is contrasted against a theoretical curve describing its evolution with the B-value. Shear modulus degradation curves were obtained to assess the influence of water content on the small-strain stiffness in these geomaterials. The results offer experimental evidence regarding the effect of Sr on the small-strain stiffness of reticular pyroclastic materials, contributing valuable insights into its geomechanical behaviour under different water contents.