Centrifuge modelling of helical anchors

Abstract

Uplift and overturning forces occur due to natural processes such as temperature changes, wind and water action and fluctuating water tables. Ground anchors are commonly used instead of massive foundations to resist these forces. Various types of anchors are used in industry, such as plate, cone and helical anchors. This project deals with multi-helix anchors. Centrifuge modelling is a method used to simulate the behaviour of a prototype structure without conducting field tests. In this research, multi-helix anchors, a two and three-helix are modelled. The purpose of the project was to design and build the equipment used to install and pull-out model anchors along with establishing a systematic test procedure. The third and final objective of the project was to test the uplift capacity of model anchors and compare the results to theoretical values. Three tests were conducted on each type of anchor to determine if the uplift capacities of the anchors were reproducible. The theoretical capacities were based on Mitsch and Clemence's method (1985). Two essential parameters were discovered that significantly influence the uplift capacity of anchors; the location of the top helix and a variation in gravitational force. The study also helped in indicating the areas in design and procedures that need to be modified to improve the overall set-up.