Investigation of lateral cyclic load capacity of screw pile group in multi clay layer

A laboratory study for screw pile group driven in two clay layers soft and stiff under the influence of lateral cyclic load. The aim of this research is to investigate how screw piles behave laterally under peridic load because these types of piles increased their use in previous years, especially in wind turbines and energy towers, the scarcity of studies on their lateral behavior, and the spread of this soil profile in central and southern Iraq. This study investigated the behavior of screw pile group 2 × 2 with three spacing equal to 1.5, 3, and 4.5 D h where D h is the helix diameter, two embedded lengths of 400 and 330 mm, shaft diameter equal to 10 mm by using single, double helix, and ordinary pile (straight shaft without helix) under the effect of cyclic lateral load with frequency 0.2 Hz. Through the results it was found the increasing lateral resistance was significantly impacted by the increment spacing between the piles. For pile group with an embedded length of 400 mm, increasing the distance between the screw piles from 1.5 D h to 3 and 4, 5 D h leads to an increase in the side resistance at rates ranging between 25–39% and 49–64% respectively and also found that the embedded length of the pile has an influent effect on the side resistance, the decrease in the embedded length from 400 to 330 mm leads to an increase in lateral deflection by a rate ranging between 27 and 150% depending on the strength and amount of the cyclic lateral load. It was also found that for the same distance between piles, the screw piles gave better lateral resistance than the ordinary piles, as well as the double helix piles gave a higher side resistance than the single piles.