Micropiles are small diameter bored piles. This type of deep foundation is increasingly being adopted in North America to retrofit existing structures, because of minimal installation vibration, excellent load capacity for seismic upgrades and low headroom and tight access applications. The main objective of this thesis is to investigate and analyze the results of full-scale load tests on micropiles to gain insight into factors affecting the development of axial load capacity. This thesis examines in detail the response of 9 micropiles in soil and 7 micropiles in rock during compressive axial load tests. The micropiles in soil are analyzed using the finite element software PLAXIS. The rock micropiles are analyzed using a closed form solution. Some of the micropiles were instrumented with a device called Contractometer, which permitted measurement of the distribution of axial compression along the pile at various axial loads. The internal contractometer measurements provide information on the structural performance of the pile. This study suggests that a significant portion of the axial capacity of micropiles comes from pile enlargement and post-yield dilatancy of the pile- to-soil interface
