Comparing the Axial Performance of Screw Pile with Ordinary Piles in Soft Clay Layer Overlaying Sandy Soil

Abstract

Soft soil covers large parts of central and southern Iraq. As many locations in these regions can be used for important projects; many types of research had been carried out to find a suitable technique to solve the problem of this soil which is characteristic with a low bearing capacity, problems of settlements, and stability. An appropriate, fast, efficient, and economical solution has been proposed to solve the problems of this soil using a screw pile. The present study is concerned with screw piles utilized in the foundations of structures exposed to compressive loads. The behavior of 10 mm2 circular shaft screw pile models, embedded 300 mm in soft clay layer overlaying 200 mm thickness of well compacted sandy soil were studied and compared with pile without helix (conventional steel pile). Model tests are carried out with screw lengths of 300, 350, and 400 mm and helical plate diameters of 15 and 30 mm. Single and double helical screw pile have been considered (30 and 50) mm spacing between helix is used in this study. This study revealed that the screw pile has a higher compressive capacity on soft clay soil than a conventional pile (steel pile without helix). The augment in compressive strength can reach 2–8 times larger than the value obtained using the ordinary steel pile. The results showed that the screw piles with single and double helix can resist pile settlement 45–700% more than ordinary piles when screw piles are embedded to dense sandy soil through soft clay soil.KeywordsScrew pileCompressive capacityOrdinary pileSoft clayDeep foundation