Underpinning with Chemical Grout

by W. C. Pete Parish, Geotechnical Coordinator; Pittsburgh LRT Project,
Wallace Hayward Baker, Pres.; Hayward Baker Co., Odenton, Md.,
Robert M. Rubright, Sr. Proj. Mgr.; Hayward Baker Co., Odenton, Md.,

Serial Information: Civil Engineering—ASCE, 1983, Vol. 53, Issue 8, Pg. 42-45

Document Type: Feature article


During construction of Pittsburgh's new subway, it became necessary to protect the foundations of six downtown buildings. A detailed study of building foundation support options by the designers resulted in the largest chemical grout underpinning job ever performed in the United States. The grouting contractor injected more than 1 million gallons of grout, transforming the noncohesive sand and gravel subsurface into a cohesive sandstone-like material. The grouting in effect extended the building foundations into the subgrade. This article documents the design options and how grouting was ultimately selected; contractual considerations; injection techniques; and the design of a customized excavation support system.

Subject Headings: Chemical grouting | Building design | Foundation design | Underpinning | Subways | Business districts | Personnel management | Contractors and subcontractors | United States

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