Practical Advice on Foundation Design - Micropiles






Abstract

Certain details of micropile design remain unresolved between various practitioners and such disagreements have limited the acceptability of micropiles in certain quarters. Detailed micropile design is an extremely lengthy and often complex subject, especially when micropile groups are concerned or seismic issues must be addressed. The paper provides a simplified step-by-step design approach discussing initial evaluation of feasibility, review of data, loading combinations and general considerations. Thereafter the final design steps are discussed. These include geotechnical strength limit states, other structural considerations, service limit states, corrosion protection, and some seismic considerations.


Introduction

Through the efforts of many authors it is now well established that micropiles have been used throughout the world since their development in Italy in 1952 (FHWA, 1997). In North America, the use is somewhat more recent, and as is typical with a relatively new specialty geoconstruction technique, most of the technical knowledge has resided with the contractors. Not surprisingly therefore, and even given that such contractors have displayed admirable skill, knowledge, and zeal in their developments, there still tends to be more certainty and consensus within the industry with respect to issues relating to construction and testing than to design.


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