Study on the vertical bearing characteristics and influencing factors of threaded piles

Abstract

This study investigated the mechanism by which thread height affects the load-bearing performance of threaded piles, as this is a critical factor influencing their vertical bearing capacity. Laboratory half-pile model tests combined with Digital Image Correlation (DIC) were used for this investigation. Concurrently, numerical simulation analysis was used to systematically examine the influence of thread height, thread pitch, thread shape and thread thickness on the load-bearing capacity of threaded piles. The findings suggest that the threaded parameters primarily influences the bearing capacity of individual threaded piles by increasing the contact area between the pile and the soil and enhancing the mechanical interlocking effects, compared to straight piles. As thread height increases, the pile’s bearing capacity increases, though at a gradually diminishing rate. Concurrently, the pile body’s material utilisation rate reaches a peak, with optimal performance observed when the thread height is between 8 and 10 mm. When the pitch ratio (i.e. the ratio of thread pitch to main pile diameter) is 1.0, the threaded pile demonstrates superior bearing capacity. In terms of thread geometry, trapezoidal threads correspond to the highest ultimate bearing capacity. Furthermore, under identical settlement values for threaded piles, trapezoidal threads maximise material utilisation efficiency. Additionally, thread thickness has a relatively minor influence on pile bearing performance.