NING LU, PhD, is Professor of Engineering at the Colorado School of Mines, where he teaches courses in soil mechanics and geotechnical engineering. He is the author of more than thirty papers published in peer-reviewed journals and serves as an editorial board member for the Journal of Geotechnical and Geoenvironmental Engineering. He is a member of the American Society of Civil Engineers and a lifetime member of the American Geophysical Union. WILLIAM J. LIKOS, PhD, is Assistant Professor of Civil and Environmental Engineering at the University of Missouri—Columbia, where he teaches courses in soil mechanics and soil behavior. He is a former geotechnical engineer with the U.S. Geological Survey. He is the author of numerous papers regarding unsaturated and expansive soil behavior, an editorial board member for the Geotechnical Testing Journal, and a member of ASCE and the Clay Minerals Society.