Elastoplastic analysis of pull-out resistance of soil nails in dilatant soils

Abstract

Soil dilation has significant effects on soil nail pull-out resistance. The dilation mechanism around a horizontal soil nail is analysed in this paper by treating the soil as a linear elastic-perfectly plastic material, using a non-associated Mohr-Coulomb yield criterion. Using this approach, closed-form solutions for calculation of the average compression stresses on the soil nail surface are obtained. This analysis theoretically explains a phenomenon commonly observed in experimental and field tests of dilation effects on soil nail pull-out resistance. It also explains why the apparent friction coefficient inclusive of the dilation effect is higher than the soil internal friction coefficient, but the apparent friction coefficient decreases with the increase of the soil overburden pressure and soil nail diameter. The conditions where the analytical approach can be applied are discussed. The theoretical predictions are compared with test results with good agreement, giving support to its validity.