Peak Friction Angle of Sand at a Wide Range of Effective Stresses from Drained Direct Shear, Triaxial, and Plane-Strain Tests for the Design of Retaining Structures

ABSTRACT A uniformly graded clean sand from a backfill of a sloped reinforced soil wall, located in Skedsmo, Norway, was tested in direct shear, triaxial, and plane-strain modes of shear. The tests were performed at a range of effective stress ranging between 4 kPa to 300 kPa. The goal of the laboratory testing program was to assess the credibility of typical empirical correlations to estimate friction angles used in the design practice of retaining walls. Additionally, the experimental results obtained were compared with the very few exclusive literature studies in which all three devices have been used at comparable effective stresses. The discussion addresses the extent previous empirical correlations are applicable and the selection of the peak friction angle in design practice. The stress levels were chosen to represent in situ conditions for a variety of geotechnical problems, like sloped reinforced walls or sloped dam faces, but also offshore for cables, suction buckets, or shallow template foundations.