NUMERICAL ANALYSIS OF ANCHORED GRANULAR PILE (AGP) UNDER COMPRESSIVE AND TENSILE LOADS

Abstract

To meet the demand and requirement for the construction of foundation of structures such as transmission line towers, bridges, radar-microwave and TV towers, Anchored Granular piles (AGP) project itself as one of the most innovative solutions to it as it can resist compressive as well as tensile forces and transmit it safely to the ground without posing any hann to the structure. In an AGP, the footing is anchored to an anchor plate at the bottom of the granular pile. This makes the granular pile tension resistant and enables it to absorb the tensile force caused on the foundation either by heaving of the swelling clay or by any external force or moment on the structure. It not only improves the properties of the soil but also safeguard it against swelling, shrinkage, liquefaction, overturning and uplift forces. Present study involves 3D modelling and analysis of Anchored Granular Pile Foundation (AGPF) system under compressive and tensile. The software used for the analysis is PLAXIS 3D. The study includes the parametric analysis of some important parameters like L/D ratio, swelling potential, number of piles and spacing between them and area ratio. The numerical study and analysis of AGPF confirms the fact that the strength of an AGP against uplift as well as compressive forces increases as the length to the diameter ratio increases. It also reveals that between L/D 6 and 8, the transition of mode failure from shaft failure to bulging failure happens. If the compaction of surrounding soil due to construction of granular pile is considered in the analysis, the average increase of strength of AGP (compared to its strength when the compaction of surrounding soil is ignored in the analysis) is 2.5% when L/D is less than 6 while it is 11.7% when it is more than 6. The resistance of an AGPF system to heaving is directly propoiiona1 to the extent of heaving irrespective of number of piles and spacing. The strength of AGP under compressive loading is more when the entire load is taken up by the pile alone than when it is taken up by both ground and pile.