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Helical PiersThe earliest patent anchor was a screw foundation designed in 1833 by a blind English brick maker, Alexander Mitchell. Mitchell's screw foundations were used in the construction of lighthouses and beacons throughout the world. There were few improvements in patent anchoring until February 1876 when the Picket Stake was assigned patent number 172915. While these were the earliest of the patent screw anchors, it was not until the late 1950s when the A. B. Chance Company introduced the Power-Installed Screw Anchor (PISA®) that screw anchoring found favorable, wide-spread acceptance. These PISA® anchors, as they are popularly called, were originally restricted to plastic soils. With improvements in anchors, wrenches and power equipment, successful installations in packed sand and gravel can be in minutes as compared to hours for other anchors and methods. The addition of multiple-helix designs results in holding capacities of 60,000 pounds in swamp country – a load unheard of even in firm soils years ago. The Chance Helical Pier® System offers a technically superior and extremely cost effective alternative to other remedial pier systems. It is backed by almost ninety (90) years of structural engineering experience. This concept focuses upon screwing steel piers with single and multiple helixes into stable subsoil until the torque applied indicates that the necessary load capacity has been achieved. Once the necessary load capacity has been accomplished, adjustable brackets are attached to the base of foundation walls where the problem exists. They are then hydraulically jacked and locked into position with the weight of the wall now shifted to the installed piers. The Chance Helical Pier System®, barely disturbs the landscape. The average residential structure problems usually are completed in less than two working days. The Chance Helical Pier® System is listed with major building codes including I.C.B.O and SBCCI. Gibson’s Pressure Grouting Service uses only A. B. Chance helical anchoring systems for your underpinning and foundation support needs. |
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