Innovative Large-Scale Grout Research Simulating Karst and Hydraulic Conditions-Paper

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Alabama Power and Alden Research Laboratory developed a large-scale test chamber to evaluate grout mixes under conditions resembling pressure grouting in the karst foundation beneath Logan Martin Dam. The chamber measured 30 feet long and held simulated fractured rock, water, and a large cavity. Researchers monitored grout injection, discharge flow and specific gravity, pressure, and temperature to assess grout movement, mixing, filling, and efficiency.<br /><br />Five high-mobility grout mixes were tested, varying water-to-cement ratios and additives. Mix performance was judged by normalized grout take—the injected volume relative to available void volume—and by post-test observations of bleed water and unfilled areas.<br /><br />The 1:1 water-to-cement neat cement mix filled the rock effectively, with little bleed water. A thinner 1.5:1 mix without additives showed more bleed and was the least effective. Adding Diutan and Glenium to the 1.5:1 mix greatly reduced bleed, though its normalized grout take was relatively high. The 2.5:1 mix containing Bentonite, Diutan, and Glenium had the lowest normalized grout take and little bleed, but left a small ungrouted region where displaced water had no exit path. Its efficiency was attributed partly to limited mixing with water in the chamber.<br /><br />The tests showed that pressure and exposure time affect grout bleed, and that laboratory column tests alone may not predict performance during pressure grouting. The chamber offers a controlled, observable way to compare grout effectiveness and material use before field application, supporting more informed and cost-effective grouting decisions at Logan Martin Dam.

Keywords

grout mixes

pressure grouting

karst foundation

Logan Martin Dam

test chamber

grout performance

water-to-cement ratio

bleed water

bentonite additives

laboratory testing