Laboratory Study on Load Carrying Capacity of Pile Group in Unsaturated Clay

Abstract

In this study, an attempt is made to investigate the load transfer in pile groups constructed in saturated and unsaturated soil using aluminum model piles of $$20\times 20$$ mm in cross section and 200 mm in length with six group configurations, single, $$2\times 1$$ , $$3\times 1$$ , $$2\times 2$$ , $$3\times 2$$ , and $$3\times 3$$ , groups in addition to pull-out test. The samples are prepared at three different soil properties: two models with the same degree of saturation and two with different dry unit weights and the third is unsaturated soil model with. A relationship between the soil suction and water content is introduced using a digital monitor, accompanied by eight suction probes planted in CBR molds. This relationship is used to predict the value of suction when conducting tests on models of the unsaturated soil. Further, the soil suction is measured using a filter paper method. Results of ultimate load capacity obtained from the load–displacement curves reveal an increase in the ultimate load with increasing the number of piles in the group for the same soil properties, and also an increase in the soil dry unit weight. Further, the results indicate an increase in pile capacity when the soil becomes in unsaturated state compared with saturated soil for the same pile group tested. On the other hand, the pull-out test gives a maximum load carrying capacity when the single pile tested was in saturated soil with high dry density, and minimum results are obtained when tested in unsaturated condition with the percentage of increase being about 463 and 34% for two saturated soils, compared with that for unsaturated soil.