Influence of grout rheology and placement technique on integrity of soil nails

This paper documents the findings from a research study that investigated the effects of grout mix design and grout placement method on the integrity of soil nails. The experimental plan included two separate series of tests. The first test series involved installation of fifteen soil nails, each 6.1m (20ft) in length, under simulated conditions. In these tests, steel tendons were placed inside six inch diameter PVC tubes that were split along the length, inside surface roughened and reassembled. The PVC tubes were then grouted using different grout placement methods and grout mixtures with varying consistency. The second test series involved thirty two actual soil nails that were installed on a 2.0m (6.5ft) tall vertical cut at approximate spacing of 1.2m (4 ft). The actual condition of the soil nails were observed at the conclusion of the study by exhuming the soil nails. The findings from this research found that proper installation of grout material can only be achieved when the grout is placed using a grout tube that extends the full length of the soil nail. Additionally, this study showed that grout consistency is an important variable that require careful control.