Load Sharing Between Shaft and Tip of Pile Group in Saturated and Unsaturated Soil

This paper investigates and compares the mechanism and the amount of load to be carried by the shaft and tip for different pile group configurations tested in saturated soil prepared at two properties and unsaturated soil. The stresses under the center of pile group are measured by soil pressure transducer, and the stresses are converted to a load at shaft and tip. An attempt is made to investigate the load transfer in pile groups constructed in both soils using square aluminum model piles of 20 × 20 mm in cross section and 200 mm in length with 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 equal to 3 (60 mm). A series of laboratory tests were conducted on different pile groups embedded in soil with different properties: saturated soil with two dry densities and unsaturated soil. The results of single pile show a clear difference in load share mechanism, and this discrepancy seems to be eliminated as the number of piles increased and gave nearly a coincide behavior in the 3×3 group regardless of the soil consistency (block effect). It was concluded that the sharing of load between shaft and end resistance for a single pile in saturated soil is halved when the pile reaches its ultimate resistance, while this response is different for unsaturated soil where the load is transferred as a whole to the pile tip at approximately the intermediate stages of loading according to the analysis criteria adopted.