Load Displacement Behaviour of Granular Anchor Pile (GAP) and Group Piles Under Oblique Pullout Loads

摘要

This paper presents the experimental investigations on load displacement behaviour of granular anchor pile (GAP) and Group piles under oblique pullout loads. The foundation of various structures such as bridges, transmission lines, chimneys, jetty structures, mooring system for surface and submerged platforms, oil storage tanks, tall buildings etc. are required to transmit compressive forces safely to the subsoil at certain occasions, these forces may be accompanied with moment in addition to sustained compressive and lateral forces acting on the top, thereby causing overturning or uplifting of foundation. The problem become difficult when foundations are required to be laid in subsoil deposits. This necessitates the adoption of suitable ground improvement foundation technique. Out of various foundation technique for improvement, a granular anchor pile system that may serve as a better alternative solution to conventional methodologies that are in vogue. Experimental investigation on single GAP system, 2 GAP and 4 GAP system with length to diameter ratio varying as 6.9, 9, 10, 12 and 15 for 50 mm dia GAP system and 3.45, 4.5, 5, and 7.5 for 100 mm dia of 2 GAP and 4 GAP system were conducted in different type of cohesionless soil (loose to medium dense) at different relative density. The spacing of piles in the groups varied from 200 to 400 mm and expressed as spacing and depth (S/D) ratio of 2, 2.5, 3, and 4. The single pile and group piles were subjected to oblique pullout loads at angles Q = 30°, 45°, 60° and 90° with vertical central axis. Ultimate pullout loads and efficiency were found to be a function of length to diameter ratio of the piles and angle of inclination of the pullout loads. It was observed that ultimate pullout capacity decreases as angle of load inclination increases with pile axis. The ultimate load of pile under oblique pull for Q = 30° was found to increase at a high rate with increase in L/D length to diameter ratio of piles. Where as