A Micropile Solution for Lifting and Repairing the SR-67 Bridge in Elizabethton TN after Hurricane Helene-PPT Presentation

PPT Presentation

Pdf Summary

Hurricane Helene severely damaged the SR-67 Broad Street Bridge in Elizabethton, Tennessee, on September 28, 2024. The 306-foot bridge, built in 1929 and carrying about 22,650 vehicles daily, sustained major scour at Pier 3: footings beneath columns E, F, and G were completely undermined. The bridge deck and railing also showed visible deflection, with a survey measuring roughly 4–5 inches of settlement.<br /><br />The repair stabilized the footings with grout bags, installed a sheet-pile cofferdam, and dewatered the work area. Crews then installed micropiles using both through-deck and low-clearance drilling methods, built shoring frames, and demolished the damaged footing. A prefabricated column-support frame transferred loads while the bridge was lifted approximately 4.5 inches. Workers subsequently constructed a permanent pile cap and repaired existing cracks.<br /><br />Micropiles were designed for axial and lateral forces using AASHTO load combinations. Design considerations included bridge dead and live loads, stream pressure, and potential scour. The analysis used a 500-year flood event, with a modeled maximum stream velocity of 13.3 feet per second. Calculated scour depth was 16.5 feet, compared with six feet of observed scour and deposition over 2005–2024. The presentation also highlights the importance of engineering judgment: measured jack loads exceeded the estimated column dead load during lifting.

Keywords

Hurricane Helene

SR-67 Broad Street Bridge

Elizabethton Tennessee

bridge scour

micropile repair

pier footing failure

cofferdam dewatering

column lifting

AASHTO design

500-year flood