Rectangular Foundations on a Sand Embankment over Mine Tailings

Abstract

This paper reports results from centrifuge model tests that provide insight into the behavior of rectangular foundations (representing earthmoving equipment) during penetration, with freedom in rotation, adjacent to a sand embankment (cover layer), into a weaker clay layer (representing mine tailings). A parametric study was used to explore the relevant range of the setback ratio, slope height ratio, normalized clay strength and its nonhomogeneity, and foundation base geometry. The effect of these nondimensional parameters on the penetration resistance profile is discussed in the context of the likelihood and severity of failure. The failure of a flat-based rectangular foundation was less severe than that associated with a strip foundation, and the corresponding measures reduced with the increasing setback ratio (λ) and slope height ratio (η). No rotational failure occurred for λ/(su,av/γcB)cr>8 (where su,av/γcB is the average normalized strength of the lower clay layer) or η≥0.604, regardless of strength nonhomogeneity and the normalized strength of the bottom clay layer. The addition of small skirts to the base of the rectangular foundation assisted in reducing the likelihood and severity of failure significantly, with the exception of λ=0.19 and η=0.264. Expressions were proposed for calculating the modified bearing capacity factors.