The Evolution of the Hydraulic Conductivity of Fly Ash-Treated Sand as a Liquefaction Countermeasure

Abstract

A soil improvement method that utilizes fly ash as a cementing material for liquefaction countermeasures has been examined. This study investigates the changes in the hydraulic conductivity of sand treated with fly ash, which has prospects for use as a liquefaction countermeasure. By tracking the development of hydraulic conductivity over time, the study seeks to determine how well fly ash mitigates liquefaction. The hydraulic conductivities were investigated through a series of constant head laboratory tests on sand specimens treated at varying proportions of fly ash, degree of saturation during curing, and curing time. The hydraulic conductivity results on treated sand were compared to that on untreated sand to assess the impact of fly ash on permeability reduction. The research findings indicate that adding fly ash to sand significantly reduces hydraulic conductivity compared to untreated sand. Furthermore, the study also shows that fly ash-treated sand’s hydraulic conductivity, k, decreases over time. This evolution is attributed to the pozzolanic reaction over time and the cementitious properties of the fly ash, leading to the formation of a cementitious gel, gradual densification, and a soil structure with reduced permeability. The results of this study provide valuable insights into the long-term behavior of sand treated with 5–10% fly ash as a liquefaction countermeasure. The evolution of hydraulic conductivity highlights the potential for sustained improvement in soil properties, making fly ash an effective solution for mitigating liquefaction hazards in geotechnical engineering and earthquake-prone regions.