Evaluating the Effect of Footing Roughness on <i>N_&#x3b3;</i> Coefficient Using the Method of Stress Characteristics

Abstract

In this study, the bearing capacity coefficients Nγ were calculated for strip footings by considering different friction angles along the soil–footing interface (δ) using the numerical algorithm based on the method of stress characteristic lines. Changes in the geometric properties of plastic and nonplastic regions were also evaluated under the influence of footing roughness for different internal friction angles. The results revealed that the Nγ coefficient gradually increases with increasing roughness. At least 85% of the Nγ coefficient was achieved by mobilizing only 50% of the footing roughness. In addition, the magnitudes of Nγ under a full roughness state for φ &gt; 25° were obtained, which were almost twice that of the smooth footing case. It was found that increasing the values of φ and δ/φ resulted in the expansion of the width and depth of plastic and nonplastic domains. Similar to the observed trend for the Nγ coefficient, the major part of the maximum width and depth values of plastic and nonplastic regions obtained under complete roughness state were provided for φ ≥ 0.5. By increasing both φ and δ/φ, the curvature of the outer boundary of the nonplastic curved wedge increases and affects a deeper layer of the soil. Further, the emergence point of the curve tends toward the footing edge, therefore the wedge covering a wider part of the footing base.