Micropiles: the state of practice Part 1: Characteristics, definitions and classifications

Abstract

A major study of micropiles has recently been funded by the Federal Highway Authority (FHWA) in the United States. The subject is limited to drilled and grouted, cast-in-place, reinforced piles of nominal diameter less than 300 mm. Such piles are used for direct structural underpinning, and, when installed closely spaced in groups or networks, are used for in-situ soil reinforcement. They have become increasingly popular throughout the world since their inception in Italy in 1952, and are widely used in association with urban and industrial development and redevelopment projects. In the series of five papers, the major findings of the FHWA study are presented. Part 1 in the current paper, deals with the background to the FHWA study, characteristics and definitions, classification, historical development and types of application. Part 2 summarizes design, with distinctions drawn between single piles, and groups and networks of piles. Part 3 describes construction techniques, with reference to various national practices. Part 4 discusses testing procedures, while Part 5 provides summaries of well documented case histories which illustrate the application of the principles introduced in the first four parts. As an integral feature of Parts 2, 3 and 4, the gaps in current knowledge are highlighted, as a possible guide to future research.