Evaluation and reduction of liquefaction potential at a site in St. Louis, Missouri

This paper presents results of seismic ground response and liquefaction analyses performed for a site located in the floodplain of the Missouri River in St. Louis, Missouri. Synthetic earthquake time histories and recorded ground motions from two earthquakes in Canada were used to perform the analyses. Synthetic time histories were generated using attenuation relationships for Central United States. The ground response analyses indicated that the ground motions at the site are likely to amplify by a factor between 1.4 and 2.25. From the liquefaction analysis it was concluded that the site had significant liquefaction potential. The site was remediated to reduce liquefaction potential using deep dynamic compaction. Modifications, in the form of construction of stone columns, were made to the conventional method of deep dynamic compaction to densify the soils to required depths. Results presented show that site remediation procedure used at the site successfully densified the site soils to desired densities. Construction of stone columns not only densified the in-place soils to deeper depths, but also helped to support relatively heavily loaded columns on spread footings. The project was completed on schedule with significant cost savings.