SPECTROMETRY TECHNIQUES FOR IDENTIFICATION OF EXPANSIVE CLAY SOILS AND DETERMINATION OF SWELLING POTENTIAL

Sabine Chabrillat [1], Alexander F.H. Goetz[1,2], Harold W. Olsen [3], Lisa Krosley [3], David C. Noe [4] [1] Center for the Study of Earth from Space/CIRES, Campus Box 216, University of Colorado, Boulder, CO 80309-0449 USA
[2] Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0449 USA
[3] Colorado School of Mines, Golden, CO USA
[4] Colorado Geological Survey, Denver, CO USA



Swelling soils are a major geologic hazard, and expansive clays and clay-shales cause extensive damage world-wide every year. The cost of post-construction mitigation is prohibitive, and the costs of standard engineering soil tests and creation of regional maps is also very high. One example of this problem is the current situation in the Front Range Urban Corridor in Colorado which is underlain by Cretaceous clay-shales, furthermore with steeply-dipping bedrock strata. Smectite is the clay mineral group that has the greatest swelling potential and is responsible for most swelling soil damage in Colorado. We are developing a field spectroscopic technique for in-sity determination of swelling soil potential. Near-infrared (NIR) reflectance spectroscopy of swelling soils samples shows that it is possible to discriminate among pure smectite and mixed smectite/illite layers samples, and to detect high water content by spectroscopic means. Spectroscopic identifications are well correlated with mineralogical x-ray diffraction analyses and geotechnical engineering tests.