Commercial Services

Foundation Settlement » Pressure Grouted Piles/Rock Anchoring

High capacity pressure injected steel micropiles are small diameter piles w/ diameters ranging from 2 ½" (63mm) to under 12" (300 mm), with a typical or common range of 3 ½" to 6".
Pressure grouted micropiles are a one step process. The bore hole is drilled using a drill bit connected to high strength hollow bar drill stem, through which a cementitious grout is injected under pressure through the hollow bar and out the drill bit through a series of holes in the drill bit. The drill bits, percussion of the drill bit from the drill motor, and displacement of the soil or rock via water, grout or air injection allow for the penetration through varying and mixed soil strata, I.e. clay, sand, rock, or combination.
Because the diameters of the piles are generally small the end value is generally ignored. Capacities are derived through the high strength hollow bar that is left in place and reinforces the surrounding grout body and from the high grout to ground bond values (friction) along grout to ground interface from the pile length. "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 ground anchors. "(1). The high pressure injection (300-1,200 psi) displaces soil along the pile shaft length, often creating a series of irregular bulges and irregular hole diameter, thereby significantly increasing the surface or bond area of the grout to ground interface.
"Since the installation procedure causes minimal vibration and noise and can be used in conditions of low headroom, micropiles are often used to underpin existing structures. Specialized drilling equipment is often required to install the micropiles from within existing basement facilities." (1). KCMC/ Pier Masters specializes in such applications and has specialty equipment specifically design for confined space, limited access, or low head room applications along with multiple, specialized engineered brackets to transfer loads from the structures to the pile.