Performance of laterally loaded piles driven in collapsible soils

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Collapsible soils are known to experience significant volume decreases due to an increase in moisture content, regardless of a load increase. This in turn causes the design of foundations on collapsible soils to be highly problematic. Soils susceptible to collapse include loess, cemented sand and silts, and some residual soils. Collapsible soils are found in major parts of Eastern and Western Canada, USA, Eastern Europe, China, South East Asia, and both Northern and Southern Africa. As human activities continue to increase in these regions, the problems associated to foundation design increase accordingly (Brandon et al., 1990; Lim and Miller, 2004).The use of shallow foundations combined with soil replacement or soil treatment constitute economical designs for light structures on thin collapsible soil layer. However, for heavy structures and relatively thick layers of collapsible soil, pile foundations may be installed to a suitable bearing stratum overlying the collapsible soil layer. In this case, foundation designers should forecast the negative role of the collapsible layer within the lifespan of the structure. Piles driven in collapsible soil however may lose the existing shaft resistance upon wetting of the surrounding soil, and accordingly they will experience uncalculated drag load.The objective of this proposal is to study the performance of piles installed in collapsible soils subjected to vertical and lateral loads. Prototype model tests will be conducted in the Foundation Engineering Laboratory at Concordia University to simulate the stated problem. The model will be capable of measuring the volume change in the soil mass due to partial or full inundation. The experimental results will be used to validate a three dimensional finite element model, developed to examine the load-transfer mechanism and the sensitivities of the governing parameters. The results will be presented in terms of design theory to predict the capacity of these piles.