Reduction of Liquefaction Potential by Compaction Grouting at Pinopolis West Dam, SC

Baez, Juan I.; Henry, James F.; ,

Reduction of Liquefaction Potential by Compaction Grouting at Pinopolis West Dam, SC

by Juan I. Baez, Hayward Baker, Inc, Ventura, United States,
James F. Henry, Hayward Baker, Inc, Ventura, United States,

Document Type: Proceeding Paper

Part of: Geotechnical Practice in Dam Rehabilitation

Abstract:

A previous 1984 field study and subsequently published paper (Salley et.al., 1987) described the seismic design background and evaluated the potential success of compaction grouting to mitigate the liquefaction risk of a sand to silty sand layer underlying the 70 ft (21.3 m) high Pinopolis West Dam in Moncks Corner, SC. This paper emphasizes a description of 1989 construction procedures and the evaluation of observations of the different monitoring criteria. Evaluated criteria were limited to grout volumes, grout pressures, and ground heave. In order to closely evaluate these criteria, 4 of the 42 sectors grouted in 1989 were selected as representative of the overall grouting operations. The usefulness of a strip chart recorder attached to the grout line is also highlighted. Observations indicated that volume displacement ratios averaged around 18%. The target volume per foot (0.3 m) was generally achieved in the primary injections, and grout pressures or volume quantities usually controlled the grouting in the secondary injections. The tertiary grout phase was usually governed by pressures or ground heave. Grout pressure development showed a general pattern of gradual rise to 250 psi (1,725 KPa) followed by a rapid increase to the limiting criterion. Corrected SPT results obtained following the completion of the grouting program ranged between 11 and 38 bpf compared to an average of 4 bpf before treatment. Revised specifications required that SPT values range from 12 to 17 bpf depending on the amount of fines present in the soil. Where post grouting SPTs were found to be lower than required, a quaternary injection phase was applied.

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