Cementitious foundation cap with post-tensioned helical anchors

A concrete foundation for supporting on its upper surface a tall tower or other structure subject to heavy load and high upset forces, said foundation comprising:

• a concrete foundation cap for supporting a tall tower or other structure from an upper surface and having a lower surface, said concrete foundation cap including corrugated metal pipes positioned interior to and around the perimeter of the concrete foundation cap, said corrugated metal pipes providing vertical and circumferential steel reinforcing, and a perimeter form for precast or cast-in-place versions of the concrete foundation cap;
• and
• sleeved radial bolts extending horizontally through the concrete foundation cap, which are nutted against the interior of the inside corrugated metal pipe and the exterior of the perimeter corrugated metal pipe;
• and
• a plurality of helical anchors circumferentially spaced from one another which are connected to said foundation cap and include helical anchor pipes extending downwardly from said concrete foundation can lower surface into surrounding soil underneath said concrete foundation cap, said helical anchors further including a tensioning element coupled to an upper end of said helical anchor pipes and sleeved through the concrete foundation cap, an upper end of said tensioning elements terminating above said concrete foundation cap upper surface.

A concrete foundation for supporting on its upper surface a tower or other structure in clays, sands, and other soft ground surface which can be water-bearing and/or too weak to stand or maintain a formed excavation, said foundation comprising:

• a concrete foundation cap for supporting the tower or other structure from an upper surface and having a lower surface;
• and
• a plurality of helical anchors circumferentially spaced from one another around said concrete foundation cap, said helical anchors including a helical anchor pipe extending downwardly from said concrete foundation cap lower surface into surrounding soil underneath said concrete foundation cap, said helical anchors further including a tensioning element coupled to an upper end of said helical anchor pipes and sleeved through the concrete foundation cap, an upper end of said tensioning element terminating above said concrete foundation cap upper surface;
• and
• said helical anchor pipe including a plurality of grout holes along its length, said helical anchor pipe being pressure-grouted with cementitious material through its interior and around its perimeter to improve soil strength and increase the bond between the helical anchor pipes and the surrounding soil and thereby increase the foundation loading capacity and stiffness.