EPB tunnelling in deltaic deposits: observations of ground movements

The Line 9 of Barcelona Metro is currently under construction. The southern part of the line connects the city to the airport and is completely excavated in soft deltaic deposits of Holocene age. In this part, tunnelling is performed by two EPB machines of 9.4 m diameter. The paper first describes the specific geology of the area. Information derived from the excavation of this part of Line 9 is presented and reviewed. In particular, the following issues are addressed: history of volume loss distribution along the line, magnitude and shape of subsidence troughs, influence of pressures used during tunnelling on observed movements, and contributing causes to observed instances of larger ground movements. The paper may constitute a useful case record for other EPB tunnelling projects in soft soil