Field Press–in Test of Tapered Steel Pipe and Timber Piles

Abstract

A relatively simple method was proposed in a previous study for predicting the vertical behavior of tapered piles penetrating from the ground surface. This method uses the radial cavity expansion theory to model the increase in side resistance due to the radial ground expansion as a tapered pile is being pressed, and applies the second theory of the ultimate point bearing capacity proposed by Takano N. for the point resistance. Field press–in tests were conducted on four steel sheet piles and nine timber piles at a site mainly composed of silty layers. This paper presents the test results of these four steel piles and three timber piles including one straight–sided steel pile and one straight–sided timber pile. Pile resistance obtained from field tests is compared with the predictions made by the proposed analytical method. As expected, the shaft resistance increased with the increase in taper angle and the tapered piles offered a larger resistance than the straight–sided piles. It was also found that, on sites consisting of extremely soft soil, the penetration force–displacement relationships are very sensitive to the internal frictional angle of the soil.