Element Nail Pullout Tests for Prediction of Soil Nail Pullout Resistance in Expansive Clays

The performance of soil nail systems relies primarily on soil-nail interaction, which is especially complex for nails embedded in clay materials. Soil-nail interaction is difficult to predict in these soils because of the effect of moisture-induced stress and swelling along the interface between soil and nail. As part of this investigation, tests were conducted to characterize the soil-nail interface shearing mechanisms using a novel element nail pullout device that involves comparatively short nails embedded in soils under varying degrees of saturation. Additionally, a large-scale pullout test, involving inundation and loading phases, was conducted using soil nails embedded in expansive clays. The soil-nail interface shearing mechanisms identified with the element nail pullout device and the vertical rise measurements of the clay from the inundation test were used within a load transfer theoretical framework aimed at predicting the response of soil nails in expansive clays. This load transfer framework provided a very good prediction of the large-scale pullout test results using the data collected from the element nail pullout tests.