Load sharing and behavior of single pile embedded in unsaturated swelling soil

This study presents a series of model experiments conducted on single pile embedded in saturated and unsaturated expansive soil. A soil composed of 70% bentonite and 30% sand which represents a very high expansive soil is employed in this study. Soil suction (total and matric) was measured using the filter paper technique and calibrated electrical resistance gauges to study the behavior of the soil water retention curve (SWRC) and initial suction and their influence on the results. The results showed that the ultimate skin resistance is increased about 49% when the initial degree of saturation decreases from 90 to 70%. However, the adhesion factor (alpha, used in calculating the skin friction) increases as the unconsolidated undrained cohesion decreases and as the initial matric suction decreases. The adhesion factor reached a value of 1.3 when the undrained cohesion is 36 kPa, initial degree of saturation of 100% and initial matric suction of 10 kPa. The sharing ratio of the ultimate shaft capacity to the ultimate pile capacity of a single pile changes from 91 to 81% when the degree of saturation decreases from 100 to 70%.