Deep Foundation

Micropile

A micropile is a small-diameter (typically less than 12 inches), drilled and grouted pile that is typically steel reinforced.  A micropile is constructed by drilling a borehole, placing steel casing and bar reinforcement, and grouting the hole.  Micropiles can withstand axial and/or lateral loads, and may be considered a substitute for conventional piles or as one component in a composite soil/pile mass, depending upon the design concept employed.  Micropiles are installed by methods that cause minimal disturbance to adjacent structures, soil, and the environment.  They can be installed in access - restrictive environments and in all soil types and ground conditions. Micropiles can be installed at any angle below horizontal using the same type of equipment used for ground anchor and grouting projects.  Since the installation procedure causes minimal vibration and noise and can used in conditions of low headroom, micropiles are often used to underpin existing structures.

Most of the applied load on conventional cast-in-place concrete piles is structurally resisted by the reinforced concrete; increased structural capacity is achieved by increased concrete cross sectional and surface areas.  Micropiles structural capacities, by comparison, rely on high capacity steel elements to resist most or all of the applied load.  The grout transfers the load through friction from the reinforcement to the ground in the micropile bond zone in a manner similar to that of high capacity soil and rock anchors.