This time, we worked with Ultra General Contracting to construct Mini Caissons in the West Chelsea district in New York City. The caissons were intended to be used as deep foundation support in a new elevator shaft. Project work occurred at night in order to not disrupt the tenants in the building.
Strategy and Action
We finalized a plan relying on construction of four 7.625″ O.D. Main Caissons drilled with water to rock at approximately 60′ from working grade. Afterwards we embedded the casing 2 feet into the rock and drilling of a 10 foot rock socket. We finished off the pile using a #18 centralizer bar and 8000 psi neat cement grout mix. The pile was designed to provide a minimum 200 kip of axial compression capacity.
At the start of the installation, our team experienced loss of water return from the internal flush of the pile due to unconsolidated soils. We coordinated with engineers in order to adjust the setup to use a 12″ solid plug. The adjustment lead to a better seal at the tip of the advancing pile.
At 50′, we began experiencing obstructions. in order to clear a path, we switched from water drilling to air drilling before reaching competent rock.