Permeability calculation based on grain size analysis for hydrogeological-geotechnical investigation of Van Cao-Hoa Lac metro line

Abstract

Permeability (K) is a fundamental parameter governing the design, construction, and operation of underground projects. Various methods have been developed to determine K; among them, estimation from grain size distribution is widely regarded as a simple and cost-effective approach. This study aims to estimate K from grain-size data using several empirical formulas applied to 14 samples collected during the hydrogeological-geotechnical investigations of the Van Cao-Hoa Lac metro project. The estimated K values were subsequently validated through two field pumping tests conducted at the corresponding boreholes with the purpose of identifying the most appropriate method for determining K. The mean K values obtained from different empirical methods varied by several orders of magnitude, with the Hazen method showing the closest agreement with those derived from pumping tests. The results indicate that grain-size-based formulas provide a reliable approach for evaluating aquifer permeability and offer valuable support during the preliminary design stage of the metro project. Keywords: Permeability, grain size distribution, pumping test, hydrogeological-geotechnical investigation, Van Cao - Hoa Lac metro.