SOIL DISTURBANCE AND PROPERTY CHANGES

Fieldwork was performed to evaluate changes in soil properties from an undisturbed to a disturbed state at five locations of differing geology using the US Army Rapid Soils Analysis and Rapid Quality Assurance Kits. Tested soil textures ranged from clay in Virginia, sand in Florida, silt in New Mexico and fine to coarse silty-sands in California and Arizona. Soils were tested at the ground surface and at a depth of 35 cm in both the in-situ condition and after being excavated and replaced. Properties measured included mineralogy, soil texture, Unified Soil Classification System (USCS) gradation, apparent soil gradation, moisture content, bulk density and thermal conductivity. Changes in these measured properties differed according to the geologic conditions of the sampled regions and the presence of gypsum and calcium carbonate deposits. Discussed are the magnitude of changes with soil type, correlations between measured properties and the influence of apparent soil gradation. Apparent soil gradation after disturbance differed from the USCS gradation in cases where partial cementation and duricrust development were present and was found to be the key indicator of soil property variability.