Abstract

The behavior of allophanic soils is directly related to their fabric and structure. They are transformed according to their weathering degree through biogeochemical processes that may give rise to changes in the minerals. This paper investigated the influence of weathering degree on the susceptibility to dispersion in materials derived from volcanic ash soil in Armenia (Colombia). X-ray fluorescence (XRF) tests and scanning electron microscopy (SEM) tests were conducted to identify mineralogical composition and correlate it with the use of geochemical indices. Pinhole tests were developed on natural and compacted samples (with prior air and oven drying), to assess susceptibility to dispersion. It was found that the most weathered material exhibits lower susceptibility to internal erosion due to particle aggregation generated during the material alteration process. At similar dry density, natural materials present intermediate permeability values compared to compacted ones under both water content conditions. Samples dried in the air retain part of their structure and promote lower hydraulic conductivity values compared to samples dried in the oven, indicating that material alteration due to drying generates differences in porosity and hydraulic conductivity. The drying process at higher temperatures changes the material properties, eliminating the gel texture and hence the cementing bonds, inducing imminent changes in microporosity. The findings contribute to evaluating the application of allophanic soils for embankment construction, where the loss of cementation contributes to the degree of infiltration, reducing shear strength and affecting internal stability.