Bearing capacity of piles in unsaturated soil from theoretical and experimental approaches

Abstract

Research in unsaturated soil mechanics has considerably developed in the past decades, through the simultaneous development of experimental investigations and theoretical analyses. A fundamental property of unsaturated soil is the ability to store and release water.In this study, an attempt was made to compare the results of bearing capacity of model pile groups constructed in saturated soil prepared at two dry densities and unsaturated soil, with results from theoretical approach (conventional and modified) α, β and λ methods. Square aluminum model piles of 20 x 20 mm in cross section and 200 mm in length were used. The piles were arranged in six group configurations, single, 2×1, 3×1, 2×2, 3×2, and 3×3, groups in addition to pull out test at which the pile is designed to verify this purpose. All groups have the same spacing, which is equal to 3 pile diameters (60 mm). The results showed that using the β method gives the value of ultimate capacity close to the experimental results for saturated and unsaturated tests, while the theoretical results showed overestimation when using other two methods. The results of load displacement curves for piles embedded in soil having three different properties indicate an increase in the ultimate pile load carrying capacity with increase in the number of piles for different soil properties. This increase however, is not linear and gives a high value when the soil becomes in unsaturated state compared to the soil in saturated state.