Evaluation of Bearing Capacity of a Small-Diameter Spiral Pile Subjected to Combined Load Using Model Tests

Abstract

A spiral pile is a useful pile because it has high resistance against vertical load such as push-in and pull-out loading, but it also has a problem that its horizontal resistance is relatively small, comparing to a steel pipe pile with the same diameter. In addition, the conventional design has the following problems; 1) unifying effect of the surrounding ground by the revolving press-in has not been considered for safety design, 2) evaluation method for bearing capacity against combined load is not established, and 3) inclination effect of loading has not been clarified. In the previous research (Isobe and Yamauchi, 2017), a simple method is proposed to consider the unifying effect of the surrounding ground due to the revolving press-in, based on the various loading test results such as push-in, pull-out and lateral loading tests for the spiral piles in soft clay ground. Then, the bearing capacity of the spiral pile subjected to combined load was investigated with the numerical analysis method. In this paper, in order to verify this analysis, model tests have been carried out in which model piles were revolving press-in a dry silica sandy ground and then loaded at some arbitrary angles.