Causal Factors Associated with Hydraulic Fracturing During Foundation Grouting at TVA's Boone Dam-Video

Video Transcription

Video Summary

The presentation reviewed high-mobility grouting at an embankment dam from late 2015 to February 2017, focusing on work conducted after the reservoir pool had been lowered to reduce risk. Grouting targeted weathered Ordovician limestone beneath the dam, whose steeply dipping geological layers could provide pathways for grout to travel upward. During intensive grouting, instrumentation recorded downstream movement of up to about 1.1 inches. High injection pressures and volumes, sudden pressure drops, grout emerging at the surface, and visible seams in excavated trenches indicated that hydrofracturing had occurred. The presenters noted that earlier work may also have contributed, although the high-mobility grouting pressures were sufficient to cause fracturing. For later work, the team changed the grouting specifications: they prohibited higher-viscosity mixes, required packers to extend farther into rock, used instrumented packers, and capped gauge pressures near the soil-rock interface.

Keywords

high-mobility grouting

embankment dam

hydrofracturing

Ordovician limestone

grouting specifications