Site investigation and performance of radial deep consolidation grouting in soft soil

This paper presents the site investigation and ground stiffening carried out in an 8 m thick, soft soil deposit located in the western zone of Rio de Janeiro, Brazil. The stiffening was achieved through the use of pre-fabricated vertical drains and radial deep consolidation grouting, a form of compaction grouting. In this study, the results of the site investigation, comprising laboratory and in situ tests, are presented and discussed. Soft soil parameters were used to compute the settlement–time curve considering vertical drains without grout injection. This was compared with the settlement–time field curve after grouting, obtained using data from settlement plates monitored for a period of 147 d. Comparison of the two sets of data enabled an improvement factor to be determined, thus quantifying the efficiency of the grouting. Field measurements, provided by settlement plates, were extrapolated to a long-term condition. Also, the final settlement after grouting treatment was evaluated.