Comparison of Unit Skin Friction from Bi-Directional Static Load Test (Bdslt) with Theoretical Value for a River Front Structure in Assam
摘要
The capacity of any kind of pile is derived from skin friction developed between the pile surface and surrounding soil and from the end bearing offered at the pile toe. There are various approaches given in different codes like IS 2911, IRC 78, and CIRIA 143 to calculate the skin friction component and end-bearing component for different types of soil. In one of our projects in Assam State near to Brahmaputra River, the pile capacity for a 1200 mm diameter Bored Cast-In-Situ (BCIS) pile was calculated as per the IS 2911 approach. In pile capacity calculation the skin friction up to the scour level from the existing riverbed is neglected as the structure is near the river, and the riverbed is subjected to scour. Scour depth is estimated at 11 m from the existing riverbed. An instrumented initial pile load test using the Bi-Directional Static Load Test (BDSLT) method was carried out to confirm the design capacity of the pile. This paper describes the method adopted for the design of the pile, the method of load test adopted using double casing to avoid skin friction above the scour level, and a comparison of the unit skin friction obtained from the load test results with the theoretical value. The unit skin friction obtained from the BDSLT load test was found to be higher than the theoretical skin friction calculated as per the IS 2911 approach by 1.8 times.