American Society of Civil Engineers


Compaction Grout: A Case History of Seismic Retrofit


by Kenneth Ivanetich, A.M.ASCE, (Field Engineer, Hayward Baker, Inc. 1780 Lemonwood Drive, Santa Paula, CA 93060), Francis Gularte, M.ASCE, (Senior Vice President, Hayward Baker, Inc. 1780 Lemonwood Drive, Santa Paula, CA 93060), and Becky Dees, A.M.ASCE, (Senior Engineer, Haro, Kasunich, and Associates, 116 East Lake Ave. Watsonville, CA 95076)

pp. 83-93, (doi:  http://dx.doi.org/10.1061/40516(292)6)

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Document type: Conference Proceeding Paper
Part of: Advances in Grouting and Ground Modification
Abstract: Along the San Lorenzo River, the Laurel Street Bridge in Santa Cruz, California was constructed in 1967. As was typical in design and construction of that time, seismic issues were not fully understood, analyzed or implemented. This became very apparent when the performance of the downtown area of Santa Cruz following the Loma Prieta Earthquake of 17 October 1989 (Magnitude 7.1) was investigated and documented by Kropp and Thomas. The study indicates substantial ground failure effects on the west side of the Laurel Street Bridge and both sand boils and ground cracking in the areas north and south of the eastern abutment. With the results of this study it was determined that a definite potential for liquefaction during a design level earthquake (Magnitude 8.0) existed. This could result in lateral spreading, differential settlement, and axial and lateral support failure of the existing pile foundation. In 1996 plans were in place to further research the potential for liquefaction and develop the necessary solutions. The original geotechnical explorations were analyzed, and additional studies were performed. The combination of these investigations along with California Department of Transportation (CalTrans) seismic design criteria led to the development of a geotechnical and structural retrofit program to overcome the now apparent seismic issues. A large portion of this seismic upgrade of the bridge was to treat the liquefiable soils underlying and surrounding the bridge piers. Insitu densification of the liquefiable soils by a ground modification program of compaction grouting was accomplished. This increased the density and cyclic shear strength of the soil, thus resisting liquefaction. In turn, the soil would continue to provide the lateral support and frictional resistance to the piles so that the bridge will maintain stability.


ASCE Subject Headings:
Bridges
Compaction grouting
Densification
Earthquakes
Soil liquefaction
Soil stabilization