Industrial Tank

Woodward, Oklahoma

Geopier Densipact® system provides cost-effective solution for support of 5,000 psf tank pressures

  • Tank Designer/Contractor: CB&I
  • General Contractor: T.D. Farrell Construction, Inc.
  • Geotechnical Engineer: Terracon
Client's Challenge

The project involved support of a new, 174-foot diameter storage tank for chemical storage. The tank design incorporated a flexible-bottom steel tank with perimeter ring wall support. The tank pressure for design was 5,000 psf. A total settlement tolerance of 4-inches was required. The site grades generally required 4-feet of cut to reach the finished grades.

Subsurface Conditions

Borings revealed the presence of loose to medium dense, fine-grained sand with less than 10% fines in the tank location. The sand is medium-dense with depth and extends to 34 to 42 feet where very hard clay was encountered. Groundwater was observed at a depth of 36 feet below grade.

Geotechnical Challenges and Options

The geotechnical engineer raised concerns about settlement and bearing capacity of the loose sand under the large tank design pressures. Ground improvement options including a Rammed Aggregate Pier® solution and vibro stone columns were considered to treat the loose sand conditions to meet the performance requirements of the tank.

Geopier® Solution

Geopier® developed and offered two solutions: a Rammed Aggregate Pier® solution using the Geopier Impact® system and a Rammed Compaction® solution using the Geopier Densipact® system. The Densipact® solution was selected as the most cost-effective option for the project compared with the other ground improvement options. The Densipact solution involved densification of the loose sand and was accomplished by installing a grid of closely-spaced Rammed Compaction Points uniformly beneath the entire footprint of the tank and the ringwall foundation. The densification system was designed to reinforce the upper 10 to 13-feet of the profile.