A Laboratory Investigation into Time-Pressure Curves for Stable versus Unstable Grouts

Permeation grouting has been used as a cost-effective low disturbance ground improvement technology, which allowed geotechnical engineers to help improving soil properties to be suitable for different engineering activities. While permeation grouting can be a very useful fix to problematic soils, its success is dependent on the quality of the grout propagation, particularly the uniformity and extent of grout coverage. One quality control measure that has been adapted for years is the pressure versus time curve for constant flow grouting. An experimental study using 2 ft (61 cm) sand columns was performed using different grout mixes to assess the ability of pressure-time curves to predict the effectiveness of permeation grouting. Monitoring of grout front propagation in the sand column, and measurement of the grouted soil strength allowed a direct evaluation of the grouting process and the grouted soil. The results showed that although the pressure-time curves can capture filtration in most cases, they can be misleading for some grout mixes.