Improvements in Grouting of Large Ground Anchors

Better grouts have become necessary with increases in the size and complexity of ground anchors. This is because large anchors, such as those now used for stressing dams to their foundations, have closely packed hardware that makes it difficult to slide the grout tubes out as the grouting proceeds, as was previous practice. Because the tubes are stationary, the grout emerging from them has to travel considerable distances, and as the grouting progresses, fresh grout is compelled to either push through earlier‐placed grout, or to push that earlier grout bodily upward before it. The mechanisms of these alternatives were investigated in large scale tests. To ensure void‐free grouting, grouts have been developed with an unusually low water content. The testing for these quite unexpectedly found that large voids can result from some commonly used expansive additives, which evidently should be regarded with caution for this type of anchor.