Analytical and Experimental Study of Pile Capacity in Unsaturated Sandy Clay

The design of pile foundation in technical practice is based on saturated soil mechanic or empirical procedure that ignores the influence of matric suction. Understanding the pile behavior and predicting the capacity of pile in unsaturated soil are important topics in foundation design. An experimental model test has been conducted on a single concrete pile model with a diameter of 16 mm and L/d ratios of 6, 10, 15 and 20. Model pile has been driven into sandy clay in the test box and is subjected to compression and uplift loading. The tensiometer instrument has been used to measure matric suction and the SoilVision has been used to get an estimate of the entire Soil Water Characteristic Curve (SWCC). The shear strength of sandy clay has been examined using a series of unconsolidated undrained triaxial tests to identify the relationship between cohesion, internal friction angle, and matric suction. The result has shown that end bearing pile capacity, skin friction capacity and total capacity of single piles are significantly influenced by the contribution of matric suction. Based on the experimental result, end bearing capacity and skin friction capacity of pile in saturated soil equation have been modified to calculate total capacity of pile in unsaturated soils by considering the influence of matric suction.