Earth anchors are becoming a very useful technique for securing temporary and permanent foundation systems subjected to uplift loads. In recent years, helical anchors have become more widely used because of their ease of installation and low cost. Past research has concentrated on static loading. Recent investigations into the cyclic capacity of anchors have increased rapidly due to increased construction in the ocean and the importance of anchors in advancing offshore technology. Laboratory tests were performed with one-quarter scale single-helix model anchors in dry sand at a constant relative density and embedment depth. The two parameters investigated were the displacement amplitude and prestress load. Appropriate equipment and instrumentation were used to monitor anchor deflection, dynamic load, and horizontal soil stresses during the cycle tests. Static tests were performed to determine the ultimate pullout capacity of dead anchors and the post-cyclic failure capacity of anchors. It was concluded that screw-in anchor installation technique and the application of a prestress load both produced an increase in horizontal soil stresses and soil densification in the vicinity of the single-helix anchor. Cyclic loading caused a reduction in horizontal stress and an upward cyclic creep of the anchor. Reduction of horizontal stress occurred until the active failure stress was approached. At this point, the sand had loosened and the anchor began to pullout rapidly. The post-cyclic static capacity was found to be lower than the ultimate static capacity of a dead anchor.
|Original language||English (US)|
|Number of pages||23|
|Journal||Civil Engineering for Practicing and Design Engineers|
|State||Published - May 1 1983|
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