Interpreting the Initial Growth Process of Surface Peeling: Microstructural Evolutions of Soil Deterioration on Archaeological Sites

Abstract

ABSTRACT Few previous studies have investigated the mechanism of surface peeling from the perspective of soil microstructure. This study investigated surface peeling patterns and their growth feature in a large-size archaeological site, and SEM-EDS observed microstructure characteristics towards soil samples collected at different stages. Muddy Peeling (MP) irregular crusts with curling edges and Peeling with Salt Efflorescence (PSE) triggered by salt accumulation and formation of flakes in different shapes and thicknesses were the two main surface peeling patterns on the site. The average particle size of MP and PSE decreased from 6.0 μm to about 3.1 μm and 2.5 μm, respectively. Average pore size (4.5 μm) in unweathered soil decreased to 2.21 μm (MP) and 2.36 μm (PSE), and then rose to 4.86 μm (MP) and 5.74 μm (PSE), respectively. Micro-observation showed that the formation of flocculated calcium secondary minerals in MP and CaSO4 in PSE triggered by different water impacts caused different surface peeling patterns. This is the first study to reveal the differences lying in the initial growth process of archaeological site’s surface peeling in depth.