Laboratory Study of Plug Length Development and Bearing Capacity of Pipe Pile Models Embedded Within Partially Saturated Cohesionless Soils

摘要

This research presents an experimental study to investigate the development of plug length and load capacity of the pipe piles foundation embedded within unsaturated cohesionless soil. The influence of matric suction (i.e., capillary stresses) in unsaturated zone is typically considered on load capacity investigation and plug length development within the pipe piles. The experimental work consist of twenty models of open pipe piles, these models are divided into four different configurations; single pipe pile, group of double pipe piles, group of triple pipe piles and group of six pipe piles. All these models are loaded and tested under three different states of saturation; dry, fully saturated (i.e., matric suction 0 kPa) and unsaturated conditions with three different matric suction values of (6.0, 8.0 and 10.0) kPa, which are achieved by predetermined lowering of water table. The relationship between matric suction and depth of ground water table was measured in suction profile set by using three Tensiometers (IRROMETER). The soil, water characteristic curve (SWCC) estimated by applying fitting methods through the program (Soil Vision). The results of experimental work demonstrate that the matric suction has great influence on the ultimate load capacity of all the pipe pile models and the variations of load capacity with respect to matric suction are similar to that of shear strength of unsaturated soils. The increasing value of the ultimate load capacity for different configuration of pipe pile models under unsaturated conditions is approximately (1.3 to 2.7) times than that of saturated condition. Also it shows that the plug length decrease with increasing the value of matric suction for the same configuration of pipe piles, and with increasing the number of pipe piles.