On quantifying inherent soil variability

Abstract

An important component of geotechnical variability is the inherent soil variability that results primarily from the natural geologic processes that produced and continually modify the soil mass in-situ. The usual probabilistic model for inherent soil variability is the random field, which can be described concisely by the coefficient of variation (COV) and the scale of fluctuation. This paper presents a critical review and summary of these two soil statistics using available data from a variety of common field measurements. For the range of field measurements evaluated, the results indicate that: (a) the COV of inherent variability for sand is larger than that for clay, (b) the largest COV typically is associated with measurements in the horizontal direction and measurements of soil modulus, (c) the vertical scale of fluctuation for most field measurements is between 1 and 5 m, and (d) the average horizontal scale of fluctuation is on the order of 50 m.