SEDL / STP / STP1089-EB / STP25054S

Use of Stone Columns to Support I-90 Cut and Cover Tunnel

Allen, TM
geotechnical engineersState Materials Engineerthe Chief Geotechnical Engineer, Washington State Department of Transportation (WSDOT)WSDOTWSDOT, Olympia, WA

Harrison, TL
geotechnical engineersState Materials Engineerthe Chief Geotechnical Engineer, Washington State Department of Transportation (WSDOT)WSDOTWSDOT, Olympia, WA

Strada, JR
geotechnical engineersState Materials Engineerthe Chief Geotechnical Engineer, Washington State Department of Transportation (WSDOT)WSDOTWSDOT, Olympia, WA

Kilian, AP
geotechnical engineersState Materials Engineerthe Chief Geotechnical Engineer, Washington State Department of Transportation (WSDOT)WSDOTWSDOT, Olympia, WA

Pages: 15    Published: Jan 1991

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Abstract

A case history is presented describing the use of stone columns to support a portion of a cut and cover tunnel. The tunnel was intended to be supported on spread footings founded on dense granular glacial soil. Inspection and testing of the bottom of the footing excavation revealed the presence of soil below the footing level inadequate for the design loads. A number of alternatives were evaluated. Stone columns were chosen, resulting in a savings of over $350,000 when compared to the next lowest cost alternative. Performance measures were used to ensure that the stone columns improved ground performance sufficiently to result in less than 5.1 cm (2.0 in.) of footing settlement under a maximum load of 290 kN/m² (6 ksf). Two plate load tests were performed on the stone columns, and instrumentation was placed in the ground and on the structure. Data are presented indicating structure induced pressures in the foundation soil, settlement at four depths below footing level, and rotation of the footing.