Wind Turbine Foundation
The P&H rock or pile anchor foundation is a proprietary (patent pending) foundation used to support large wind turbines. The P&H anchor foundations consist of a 5-foot thick, 24-foot diameter, reinforced concrete mat (cap) supported by commonly 12 to 20, 35 to 50-feet long anchors aligned within a typical 20-foot diameter circle. Large wind turbines greater than 2 MW may require more anchors and a double row.
Large 2-½ inch diameter rods are used as the anchors. The number and length of anchors are based on the magnitude of applied loads at the top of the foundation as well as the soil and rock conditions. The pile or rock anchors are installed by drilling a shaft and the anchor rod is inserted and grouted. Post-tensioning is used to develop an internal tension force in each anchor. The intention is to have enough tension in the rod to reduce foundation deflections from normal wind loading.