Extended Use of Spring Hammer Rapid Load Testing

Abstract

Instruction As one of rapid load test methods, Spring Hammer test (SH test) method has been developed (Matsumoto et al., 2004) and used in practice. A simplified interpretation method of dynamic signals called Non-Linear Damping interpretation (NLD) is basically used for the SH rapid pile load test to derive a static response of the tested pile. In this paper, details of the Spring Hammer test method including NLD interpretation method is mentioned first. Second, validation of the SH test method is demonstrated through comparisons of static and the SH rapid load tests on relatively short piles and on circular rigid plates. Three case studies of the SH rapid load tests are then presented. The SH tests were conducted on perfect end-bearing piles (H-steel pile having end plate) in cases 1. In this SH tests, the NLD interpretation method did not work well to obtain the static behaviours of the piles due to the influence of wave propagation phenomena even though the pile lengths were relatively short compared to the loading durations. Hence, an extended NLD interpretation method is proposed for perfect end-bearing piles in case 1. In case 2, the SH test was carried out for estimating bearing characteristics of a pile group supporting a small bridge in service which was planned to be renewed, in order to make a decision whether existing pile foundations also were to be re-constructed or not. In case 3, the results of the SH plate load tests are compared with the static plate load tests on a saturated loam layer and on an improved soil. This paper discusses the applicability and limitation of the SH rapid load test methods through the case studies.