Micropiles are slight in diameter (typically less than 12 inches) drill and grouted foundation fundamentals with outline loads ranging from 50 to 400 tons. The structural burden is primarily carried in steel fortification and shifted by friction into surrounding ground. Micropiles reinforce both tension and compression loading and are cast into pile caps for load relocation to above grade structure. The piles normally include a substantial reinforcing bar (up to 3.5 inch diameter) grouted in place with steel casing increasing from pile cap to top of load bearing soils. Specific drill rigs allow construction in limited access circumstances. The equipment can pass through structural doorways and function in headroom of 9 feet, making Micropiles ultimately suited for structural improvements, underpinning of present structures, and seismic retrofit.
Tiedown anchors are undersized diameter friction elements designed and created for only tensile loading. Structural capability is provided by high strength strands or support bars, which are grouted for load relocation to load bearing formations. Tiedowns are usually pre-loaded alongside structures and locked off to continue resistance against uplift loads.
Tiedowns and Micropiles are built using comparable equipment. Rotary hydraulic drills move on the bored hole using segmental lengths of drill steel. Rush thread jointed steel casing can be progressed concurrently as needed to uphold the hole stability. The core reinforcing is positioned into the drill hole and tremie grouted. The casing is usually removed to top of bond zone for Micropiles, and completely removed for Tiedown methods. The construction application permits installation in most any ground conditions, which include cohesive and caving granular soils underneath ground water as well as rock. Downhole percussion hammers are used for drilling through high strength formations. Tiedowns and Micropiles can offer a money saving alternative to conventional drilled piers, hand mined underpinning, or augercast piling methods in complicated geotechnical conditions.
Our design-build knowledge allows us to supply owners with the most effective foundation solution, even in the most challenging ground conditions.