Foundation Design and Construction Challenges with Marsh Deposits in a High Seismic Risk Zone-Article

Article

Pdf Summary

The case study describes the foundation design and construction for a biosolids-processing and energy-recovery plant on a 4.5-acre marsh site in Irvine, California, within a high seismic risk zone. The plant included three large, closely spaced digesters and other heavy structures.<br /><br />Site investigations found up to 45 feet of highly compressible peat and organic clay over dense sand and gravel, with shallow groundwater. Because the peat and organic soils exceeded code thresholds, the site was classified as Site Class F. Site-specific seismic response analyses were therefore performed. Although localized layers had liquefaction potential, estimated earthquake-induced ground settlement was about one inch, and the risk of lateral spreading was low.<br /><br />Shallow foundations were unsuitable because of settlement, while ground improvement and drilled piers were judged impractical. The team selected 14-inch-square precast prestressed concrete driven piles. More than 3,000 piles were installed, with pile design requiring close coordination between geotechnical and structural engineers to address high seismic lateral loads, tight spacing, and reinforcement constraints.<br /><br />A 24-pile instrumented indicator program confirmed that design capacities were generally reached at shallower depths than initially estimated. The resulting pile-length revisions reduced planned lengths by more than 52,000 linear feet, saving manufacturing costs and installation time. However, some production piles encountered unexpected refusal or needed full-depth predrilling to achieve required lateral resistance. The authors suggest that a larger indicator-pile program might have better predicted these conditions.<br /><br />The project highlights the importance of thorough site characterization, site-specific seismic analysis, collaboration across the project team, and well-designed indicator pile testing. It also shows that local subsurface variability and pile-driving effects can complicate predictions, even on a small site.

Keywords

biosolids processing

energy recovery plant

foundation design

high seismic risk

Site Class F

peat and organic clay

liquefaction potential

driven piles

indicator pile testing

seismic ground settlement