• Ground Improvement
• Illinois DOT
• Hazelwood Schools
• Wentzville
• West Memphis
• St. Peters Rec Plex
• Sheboygan Police Station
• Lange-Stegman
• Kennett
• Bluffton Ethanol
• Wheeler Center
• Earth Retention
• Metrolink
• Warrenton Copper
• MoDot
• Centrum Properties
• Pinnacle Tunnel
• Metropolitan Sewer
• Drilled Shafts
• Pinnacle Casino
• Eads Bridge
• Driven Pile
• MCI WorldCom
• Ameren UE
• Augercast
• Proctor & Gamble
• Micropile
• St. Louis Zoo
• Cupples Station

Service: Drilled Shafts
When the Eads bridge was built in 1874, it was the first bridge to span the Mississippi River. Still in use today, the bridge deck was removed in the early 1990's for the construction of a light rail system. In 1999 work began to rebuild the deck to once again allow vehicular traffic to flow in addition to the light rail system. In order to reopen the historic Eads Bridge to automobile traffic, the City of St. Louis needed to retro fit the bridge with approach ramp structures on the Illinois side of the river. The original bridge span foundations were driven pile, but due to vibration and settlement concerns the approaches were designed on 6' and 7' diameter caissons. In this particular case, the caissons were to be drilled through sand and silt to a depth of 45-60 ft using a polymer drilling slurry. To verify the design, an Osterburg cell was installed in one of the piers to thoroughly test its capacity.

After difficulties were encountered on the initial caisson site, a second location was selected and the Osterburg cell was installed. At the initial site a large diameter auger became lodged on an obstruction while making a final clean out pass. We finally had to abandon the tool in the bottom and back-filled the shaft with sand until we could design around the problem. The caisson was redrilled at a later date, grout tubes were affixed to the reinforcing cage, shaft concrete poured in place and the pier bottom was injected with high pressure grout to ensure a good end-bearing despite the abandoned auger.

The Osterburg cell consisted of a load cell mounted near the bottom of the drilled shaft with instrumentation rigged throughout the reinforcing cage. After the concrete is poured and cured, a series of loads were imposed on the caisson by the load cell. Technicians from the test company measured the results in a computer model and produced an in depth analysis of the caissons performance. The Osterburg test verified the design was sound and the installation of the 15 remaining caissons proceeded. By using high capacity storage tanks and air driven pumps we were able to recycle the polymer slurry and then remove it from the site for disposal. Drilling these large diameter shafts so deep into the river sand wasn't our only challenge. Maintaining the integrity of the existing foundations of the 110 year old bridge, staying clear of the light rail system that was in operation overhead, and dynamic groundwater conditions due to the Mississippi River, were just some of the difficulties that were present during construction. The project went smoothly, despite these challenges, and the foundations were completed ahead of schedule.

• Owner: City of St. Louis
• General Contractor: St. Louis Bridge
• Soils Engineer: Sverdrup
• Drilling Equipment: Watson 3100