Parameters Affecting Screw Pile Capacity Embedded in Soft Clay Overlaying Dense Sandy Soil

Abstract

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.

Bearing Characteristics of Helical Pile Foundations for Offshore Wind Turbines in Sandy Soil

“…Interestingly, scholars have shown that simply increasing the size of the blade is not the most reasonable way to increase the bearing capacity of the spiral pile. Based on model tests of helical pile foundations in a soft clay layer overlying a sandy soil layer, Hassan [27] concluded that the spacing between blades is the main factor affecting the bearing capacity of double-blade helical piles, whereas increasing the blade size has no obvious effect on bearing capacity.…”

Influence of Spacing and Cross-Sectional Shaft of Screw Piles Group on Lateral Capacity

“…There are also some local studies about screw piles in Iraqi soils [11,15]. This study was conducted on soft clay and stiff clay multilayer because this soil covers large parts of central and southern of Iraq and this soil becomes hard when dry and weak when mixed with water [12,16]. Soft clay also distinguished by low undrained shear strength 20 to 40kPa and high in compressive Cc 0.19 to 0.44 and stiff clay distinguished by the range of undrained shear strength between 100 to 150 kPa [17].…”