The model piles with an open end and hollow circular section were fabricated from aluminum alloy tubes () of 15.88 mm out diameter, 1 mm wall thickness and an embedded depth of 500 mm. It is worth noting that, for the pile properties and the selected soil, pile behaves as flexible pile.
Three plates made of steel were used as pile cap for different spacing. To satisfy fixed head conditions, the piles were passed through exiting holes in the cap and then screwed to angle profiles (length = 50 mm) welded on these holes. Lateral loads were applied to the model piles using a 650 N capacity electric motor through a pulley supported by a loading platform with flexible wire attached to the cap.
The horizontal deflection of the pile group was measured by means of two Linear Variable Differential Transducers (LVDT) to the angle profiles of the two corner piles. The rotation of cap was determined from axial displacement measured by other two LVDTs fixed on front and behind of the cap in load direction. A load cell was placed between the flexible wire and electric motor to monitor the total loads applied to the pile cap.