Jet Grouting and Safety of Tuttle Creek Dam-Article

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The paper examines the safety risks of jet grouting beneath Tuttle Creek Dam, an operating reservoir dam in Kansas. Jet grouting was selected as part of a seismic retrofit to strengthen liquefiable foundation soils and construct an upstream seepage cutoff wall without lowering the reservoir.<br /><br />Downstream test columns showed substantial variability: many contained large inclusions of untreated native soil, and actual column diameters often exceeded targets. Such inclusions could obstruct the narrow spoil-return annulus. Blocked or inadequate spoil return, combined with high injection pressures, can raise underground pressures and fracture surrounding soils.<br /><br />During upstream trials, air bubbled into the reservoir during several columns. Investigations also found grout fractures in the fine-grained foundation blanket, including downstream of the proposed cutoff alignment. The authors concluded that jet-grouting pressures and disrupted spoil return likely caused ground fracturing, although more than one pathway may have contributed to the observed air releases. Fractures could create new seepage routes, increase hydraulic gradients, and promote erosion or piping. Because their effects could not be reliably controlled or assessed, the U.S. Army Corps of Engineers stopped upstream jet grouting and used a non-jet-assisted method for downstream stabilization.<br /><br />The paper recommends improving spoil return through larger annuli, effective soil disaggregation, and adjusted grouting procedures; establishing early-response plans for blockages; and developing equipment to measure downhole pressure and detect fracture onset. It also calls for monitoring the condition of existing seepage-control features before, during, and after construction. The authors stress that jet grouting beneath an operating dam requires particular caution because damage may remain undetected until reservoir levels rise.

Keywords

jet grouting

Tuttle Creek Dam

seismic retrofit

liquefiable soils

seepage cutoff wall

ground fracturing

spoil return

reservoir dam safety

hydraulic gradients

piping erosion