A Laboratory Study into Fracture Grouting of Fissured Ankara Clay

Fracture grouting of fissured Ankara Clay with low viscosity cement grouts was investigated through laboratory injections. It was aimed to observe the effects of water/solid ratio of the grout and applied vertical stress on fracturing pressure, volume of grout taken up by the specimen and amount of heaving occurred at the top surface of the specimen due to grouting. For this purpose, undisturbed samples of fissured Ankara Clay of 14 cm diameter and 20 cm height were grouted through a cylindrical injection pipe placed horizontally at the mid height of the specimens. Water/solid ratios of 0.8, 1.0 and 1.2 were used with vertical stresses of 100 kPa and 40 kPa applied on the specimens. It is observed that both the fracturing pressure and the grout volume taken up by the specimen until fracturing occurs decreases as the water/solid ratio of the grout increases. The amount of heaving observed at the top surface of the specimen is almost zero until the soil is fractured. However, once the fracturing occurs and the grout starts to flow continuously through the planes of weakness formed within the specimen a certain amount of heaving, which shows an increasing tendency as the water/solid ratios of the grouts are increased, is captured at the time of fracturing. At a lower vertical stress (40 kPa) applied on the specimen, the fracturing pressures and the amount of grout taken up by the specimen until the soil is fractured decreases and a higher amount of heaving is observed.