Helical Tieback Anchors - Blount Island Naval Station

LRE Foundation Repair was hired by RUSH Marine to install (61) 2.0\" square bar helical piers. The piers were designed by the Engineer of Record (EOR) to tieback the new sheet pile seawall. The design loading was 30 kips in tension and required load testing to verify the design and lengths of the piers. One challenge was to build a large test frame capable of spanning several sections of sheet pile. Additionally the soils behind the sheet piles were very weak, consisting mainly of loose back fill.

Per the design professionals, original helix configuration 3) 14\" helix blades were ordered on the 10 foot lead sections. Load testing was performed and found that an additional 14\" blade and deeper, longer piers would be required. The pier lengths were increased from 30 feet to 58 feet to achieve the desired loading. The Pier installation was performed using the torque correlation method. 2,000 psi was the targeted hydraulic torque required for each pier to achieve the pre-determined loading. The final pressure for each pier was recorded. Upon completion of the piers and the waler system installation, each pier was individually proof-tested and seated using hydraulic rams to remove any slack. Finally each pier was manually locked off, using a specified torque.