Model Tests to Determine Uplift Capacity of Combined Vertical and Batter Pile Groups Embedded in Sandy Soil

Foundations of some structures like transmission line towers, tall chimneys and many offshore structures are subjected to overturning moments due to wind load, seismic effect, wave load, ship impacts, etc. For foundations in such structures, generally a combination of vertical and batter piles are used. Batter piles provide a much stiffer resistance to horizontal and inclined loads than would be possible with vertical piles. Experimental model tests have been conducted on pile groups embedded in sandy soil and subjected to pure axial uplift loading. In the present study an attempt has been made to estimate the uplift capacity of combined vertical and batter pile groups embedded in sandy soil of uniform relative density of 63%. The model piles used in this investigation are mild steel solid shaft. The pile groups consisting of 2x2 piles (2 vertical and 2 batter piles), c/c spacing is 3d (d is diameter of pile) and slenderness ratio (L/d) of 8, 12 and 16. In pile groups the angle of batter piles is varied as 10Ëš, 20Ëš and 30Ëš. The influences of pile embedment depth, batter angle on the uplift capacity of piles are investigated. Results indicate that the pull out capacity of these pile groups increases with increasing the batter angle. The uplift capacity of pile group also increases with increase of slenderness ratio.