Screw piles are widely used in a variety engineering applications supplying stability against compression, overturning moment, uplift tension, and horizontal loads. Screw pile is a famous solution for support light structures, roads and rail signs which have relatively low-capacity foundation. In this study, the behavior of circular (10) mm solid screw pile models embedded in a bed of soft clay soil covering a layer of sandy soil has been studied. The 200 mm thick sand layer was compacted in a steel container with a diameter of 300 mm into four sublayers. The sandy soil layer was compacted at a relative density of 70%. The 300 mm thick soft clay soil bed with Cu (30) kPa was compacted in six sub-layers on the sandy bottom layer. Model tests are carried out with screw piles with a length of 300 mm, 350 mm and 400 mm and a helix diameter of 30 mm. Also, single and double helix and different S/Dh ratio were used for these piles and a comparative study between screw piles and ordinary piles (without helices) is accomplished. This study revealed that introducing screw pile of double helix increases its bearing capacity in soft clay soil by up to a (4-8) % as compared to a single helix screw pile. The results showed that the behavior of screw pile essentially depends on the geometric properties of the pile. According to the achievements, compressive load capacity of screw piles depends on embedded length, spacing ratio (S/Dh) and number of helical plates.

Despite the great development in the manufacture of the helical pile and the development of their use, especially in transmission towers and wind turbines, there is little research on their lateral behavior. In this laboratory study investigate the behavior of screw piles group (2×1) and (1×2) with the spacing to the diameter of helix ratio (S/Dh =1.5, 3, and 4.5) having a diameter (10 mm) and embedded length to diameter ratio (L/D = 40) by using single and double helix embedded in soft clay and extend to stiff clay under a cyclic lateral load of frequency (0.2 Hz). The results showed that increasing the distance between the piles had a great effect on increasing the lateral resistance. the increase of pile spacing in the groups from (1.5 Dh) to (3 and 4.5 Dh) increases the lateral resistance about 34-38% and 50% respectively. Also, from result showed that the group (2×1) gave a lateral resistance more than the group (1×2) about 11% for single helix and about 6% for a double helix, and for the same spacing and configuration the screw pile with double helix gives an increase in lateral resistance about 5-10 % from the single helix.

The screw piles application is constantly increasing due to their high efficiency and numerous advantages. Screw piles are supplying stability against compression, overturning moment, uplift tension, and horizontal loads. This investigation presents a set of model experiments performed on single screw pile embedded in soft clay soil over laying a sandy soil loaded in compression, at a constant strain rate. The sandy layer 20 cm thick was compacted in a test container of 30 cm diameter into four sublayers to attain a relative density of 70%. The 30 cm thick soft clay layer with Cu (undrained shear strength) 30 kPa was compacted in six sublayers on the sandy bottom layer. Three different pile length (30, 35 and 40 cm), single and double helix and pile without helix, (3D and 4D) helix diameter, (3 and 5) cm spacing between helix plate are used in this study. The experiment results showed that, the screw piles settlement for piles embedded in soft clay soil overlaying a sandy soil layer decreases (59-182)% with increasing depth of embedment in the sandy layer L/D from 35 to 40, number and diameter of helix those provide anchorage against settlement. The deeper screw piles with higher L/D ratios showed compressive capacity (24-55) times greater than the shallower piles (screw pile embedded in soft clay). In addition, screw piles demonstrated resistance to the applied compressive forces (9-16) times more than ordinary piles. The compressive force increases with rising number and diameters of helix plates.

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