Influence of underground excavation on compensation grouting in clays; small-scale laboratory experiments

This study aims to improve tong-term compensation efficiency by grouting within the exclusion zone of underground excavation. The study proposes the existence of a neutral zone where the negative excess pore pressure generated during excavation can be used to significantly reduce the positive excess pore pressure generated during grout injection and hence counter consolidation. Small-scale laboratory testing is performed to verify the hypothesis. Results show that long-term compensation efficiency for normally consolidated and lightly overconsolidated clays can be improved by grouting closer to art excavation. The major concern on grouting closer to an underground excavation is the possibility of excavation face instability due to stresses exerted by grouting. Results indicate that no additional stresses are exerted on the excavation face if grouting is performed simultaneously with the excavation.