SOIL TEXTURE ANALYSIS FOR PREDICTING FRACTURES IN GLACIAL TILL

Predicting the occurrence and development of fractures in glacial tills is difficult because fracturing has been observed across many geographic areas, climates, land uses, soil types, and till units. A statistical investigation was performed on historic geologic and soil data to determine if fractures could be predicted based on soil texture analysis. Soil textures and fracture depths from 9 field sites and 45 soil pedons (140 points) in Ohio were analyzed using statistical and graphical methods. When plotted on the USDA soil texture ternary diagram, the data indicate that tills having less than 10% clay or greater than 52% sand are unlikely to support fracturing; conversely tills having greater than 10% clay or less than 52% sand are more likely to do so. Based on the 95% hexagonal confidence region for soil texture data, tills with less than 55% sand, 20-65% silt, and 5-53% clay would be more likely to form fractures. The texture classes of tills predicted to sustain fracturing were mainly clay, loam, clay loam, silty clay loam and silty clay. The depth of glacial tills having observed fractures ranged from 0.5 to 215 ft. These results are useful to explain and document how fractures are created in glacial tills and may be a useful tool for field geologists and engineers allowing them to anticipate fractures in glacial tills in Ohio and beyond.