Chief engineervisiting professor, Ground Engineering Ltd.Queens University, Borehamwood, HertsBelfast,
The governing criteria for internal stability of reinforced soil require that the soil reinforcement should have adequate factors of safety against tensile fracture and pullout. In terms of total stress the pull-out resistance will be some function of the area of reinforcement embedded in the restraint zone and the soil-reinforcement adhesion that may be related to the undrained shear strength of the soil by an adhesion factor. This factor has been assessed for several types of reinforcement using a direct shear box with the reinforcement inclined across the two halves of the box. These tests showed grid reinforcement to be the most efficient, consequently, subsequent testing, in the form of pull-out and shear box tests with horizontal reinforcement, was restricted to grids. The adhesion factors were found to be markedly dependent on test method with the pull-out test giving the lowest values. An analytical assessment of the results suggests that grid pull-out resistance is a function of the area of grid members normal and parallel to the direction of applied load rather than embedded plan area.
Paper ID: GTJ10839J