Drilling and Grouting as a Versatile Tool at Boone Dam-Paper

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Boone Dam, built by the Tennessee Valley Authority between 1950 and 1953, has an embankment founded on soil and highly irregular karst limestone. In 2014, a sinkhole near the downstream toe and turbid seepage revealed active internal erosion, prompting a major remediation project.<br /><br />Drilling and grouting served several roles throughout the work: reducing immediate risk, treating groutable rock, assessing conditions for cutoff-wall construction, and verifying the completed barrier. The initial Drilling and Grouting Program used low-mobility grout to fill voids and displace soft infill, and high-mobility grout to treat defects in the epikarst and deeper rock. Grouting was modified as field observations improved understanding of the geology and construction effects. Although embankment movement led to suspension of this program before planned completion, the treatment improved conditions and helped limit slurry losses during subsequent work.<br /><br />A Slurry Cell Testing Program tested 34 boreholes along the proposed wall alignment. Results generally indicated low permeability and no slurry losses approaching the project’s threshold for concern. After upstream and downstream berms were built, an Additional Drilling and Grouting Program installed a two-line curtain beneath the planned wall to treat fractures and bedding features.<br /><br />The permanent barrier comprised 307 overlapping concrete secant piles extending through the embankment, foundation soils, and karst rock. A Cutoff Wall Verification Program used core drilling, imaging, and permeability testing to assess pile joints and concrete quality. It identified defects requiring remediation and informed improvements to construction procedures.<br /><br />Data from the original construction and each subsequent program were integrated into a three-dimensional subsurface model. The project demonstrates how adaptive drilling and grouting can support risk reduction, design, construction, and acceptance of a permanent seepage barrier in complex karst conditions.

Keywords

Boone Dam

Tennessee Valley Authority

karst limestone

sinkhole

internal erosion

drilling and grouting

cutoff wall

slurry cell testing

secant piles

seepage barrier