Cementitious foundation cap with post-tensioned helical anchors and method of making the same

A method for forming a post-tensioned concrete foundation with helical anchors for supporting on its upper surface a tower or a structure subject to high upset and dynamic forces comprising the steps of:

• a) Excavating a hole into the ground or leveling the existing ground surface if no excavation is required for the concrete foundation cap;
• b) Spin drilling a plurality of helical anchors to depth, each helical anchor having a helical anchor pipe and helical discs that is drilled into the ground;
• c) Connecting the helical anchor pipes to tensioning elements to enable post-tensioning of said helical anchors;
• d) Setting sleeves over the tensioning elements;
• e) Positioning corrugated pipes interior to and around a perimeter of said concrete foundation cap;
• f) Placing sleeved radial bolts or tendons horizontally across the foundation and securing the radial bolts to the corrugated pipes;
• g) Pouring a concrete/slurry leveling course encasing electrical, communication, and grounding trench with conduits if conduits are routed under the foundation and the discs;
• h) After slurry cures, pouring the concrete foundation cap and casting in place in situ all bolts, conduits, wires, embedment plates, corrugated pipes and any other foundation cap appurtenances previously positioned and secured;
• i) Allowing said cementitious material in said concrete foundation cap to cure and solidify around, without bonding to, said tensioning elements;
• j) Tensioning the sleeved horizontally extending radial bolts or tendons from outside the perimeter corrugated metal pipe;
• and
• k) Post tensioning the helical anchors from above the concrete foundation cap using the tensioning elements.