ABSTRACT
Quantitative measurement of soil properties differentiated the new discipline of soil mechanics in the early 1900s from the engineering of earth works practiced since antiquity. These measurements, however, uncovered a great deal of variability in soil properties, not only from site to site and stratum to stratum, but even within what seemed to be homogeneous deposits. We continue to grapple with this variability in current practice, although new tools of both measurement and analysis are available for doing so. This chapter summarizes some of the things we know about the variability of natural soils and how that variability can be described and incorporated in reliability analysis.
