Use of Corrective Grouting in Cityringen Copenhagen Metro 

The new Cityringen Metro is located in the central Copenhagen area and will underpass a variety of buildings built in different ages, spanning from the medieval times to present; it’s envisaged the construction of 17 underground stations and twin tunnels 15.5 Km long. The contract requirements on Cityringen Project are tight and only minor aesthetic damages are allowed in terms of building damage (damage category 1 according to BRE Digest 251 classification). During the execution of the retaining walls of the metro stations, some settlements occurred on the surrounding structures. Even if the structures were not at risk, to avoid any kind of problems related to additional expected settlements coming from the next excavation of the metro stations, the General Contractor decided to execute a grouting campaign to heave the structures and to restore the original situation. The Corrective Grouting campaigns were performed in two worksite having a different geology; the structures lifted were a railway bridge, an apartment building and a public library and the grouting interventions have been done without suspending their exercise. After the completion of the grouting campaigns the structures reached a safer condition, the soil underneath them reacquired the needed bearing capacity and the construction works proceeded without any further problem. Moreover, it was possible to apply further grouting to correct additional movements related to an incident which happened after the first grouting campaigns. The successful application of the Corrective Grouting technique depends on several factors, mainly related to operative and construction aspects; the experiences gained on site are described in the paper