On the Eccentrically Loaded Strip Footing Resting Over a Circular Cavity in the Rock Mass: Adaptive Finite-Element Analysis, Observations, and Recommendations

Abstract

In this study, the effect of an eccentric load on the ultimate bearing capacity (UBC) of a strip footing of width B resting above a circular cavity in the rock mass is investigated using upper -and lower-bound finite-element limit analysis incorporating an adaptive meshing technique. The effect of governing independent variables, such as the diameter of the circular cavity, dc, load eccentricity, e, distance of the cavity from the footing (horizontal, P, and vertical, Q), and rock mass parameters based on the generalized Hoek–Brown (GHB) failure criterion on the reduction of the UBC, is studied using a reduction coefficient, Rc. This study reveals that the influence of the cavity on the UBC is minimal for a cavity beyond a depth of Q/B ≥ 2.5 when e/B ≥ 0.3; and that Q/B ≥ 3 when 0.1 ≤ e/B ≤ 0.2, irrespective of P/B. Similarly, a cavity situated at −2 ≤ P/B ≥ 2 and Q/B ≥ 2 when e/B = 0.3–0.4, and −3.5 ≤ P/B ≥ 3.5 and Q/B ≥ 2.5 when 0.1 ≤ e/B ≤ 0.2, does not show any significant impact on the reduction of the UBC. Dominant potential failure patterns that could cover at least all the representative cases are presented and discussed to strengthen the insight into the possible mechanism of such a footing failure.