Compensation Grouting, Laboratory and Field Investigations

Compensation grouting has been attracting attention in recent years to control ground settlement caused by underground construction or deep excavation. A successful and effective application of compensation grouting depends not only on utilization of a sophisticated monitoring system in the field during grouting process but also on a fundamental understanding of grout soil interaction. Laboratory grout injection tests were performed on kaolin clay to investigate the effect of over-consolidation ratio and grout type on the effectiveness of compensation grouting. The experiments involved injection of various grouts into a clay specimen consolidated in a modified consolidometer, which has an injection needle installed from the base into the specimen. This paper also presents the results of two case histories where compensation grouting was used. The first case was carried out during shield tunneling work conducted in alluvial clay deposits in Koto-ku, Tokyo to investigate the effectiveness of compensation grouting to reduce surface settlements. In the second case history compensation grouting was used behind diaphragm wall to reduce the settlement of buildings during a deep excavation constructed in Shanghai soft clay. The variation of brace force and ground settlement with corresponding grouting pressure and construction sequences were recorded during the construction. Numerical simulations of these case histories are presented.