Dynamics of Pore Water and Air Distribution in Granite Residual Soil During Drying by X-Ray Computed Tomography

Abstract

This study investigates the dynamic distribution of pore water and air in granite residual soil (GRS) under varying drying conditions using advanced X-ray computed tomography (CT). The research focuses on microstructural changes during drying, particularly the interaction between pore water and air phases. Results reveal a transition from interconnected pore water networks to isolated water clusters as matric suction increases. Initially, air exists as isolated bubbles within the pore network, but as suction surpasses the air entry value, air pathways become connected, replacing water in the pores. An inverse relationship between pore water and air phases is observed, with increasing air volume and decreasing water content indicating a progressive displacement of water by air. Quantitative analysis shows reduced pore water porosity and increased pore air porosity across different suction levels. These changes modify the pore network structure, leading to decreased relative water permeability and increased relative air permeability, highlighting the critical role of matric suction in governing soil hydraulic behaviour.