Modelled Base Roughness Effects on the Bearing Capacity and Settlement of Strip Footings

Strip footing tests were conducted on dune sand to examine the influence of base roughness on bearing capacity and settlement. Model footings, 50 mm wide and 150 mm long, were loaded on sand prepared at different shear-resistance angles. Base friction between the footing and the sand was controlled in 7 increments, ranging from a smooth interface at 8° to a rough interface at 38 °, matching the critical state friction angle. A numerical model was developed using finite element analysis to simulate the footing–sand interaction under the same base friction conditions. Bearing capacity increased by 200%, and the settlement reduction factor reached a 100% decrease as base friction increased from the smooth to the fully rough condition. Numerical predictions of load–settlement response agreed with experimental results within a 25% margin at angles of shearing resistance lower than 24°. The bearing capacity factor (Nγ) was found to increase from 26% to 166%, while the settlement reduction factor (SRF) ranged from 14% to 130% with increasing base roughness from 8° to 38°. An empirical equation was derived relating Nγ and SRF to the footing base friction angle and sand internal friction angle, applicable for dune sand from 8° to 38°.