Guadarrama collapse

A ground collapse occurred early in the morning of 6 June 2003, affecting one of the two TBM-excavated tunnels in the north end of the Guadarrama tunnels, close to Segovia in Spain. No-one was injured.

The affected zone was immediately backfilled and ground stabilisation treatment began after the backfill completion.

The collapse was 8m diameter in its widest part (the upper part) and about 8m in depth. It developed from the excavation front, as the 9.5m diameter Herrenknecht Hard Rock TBM machine was performing a slight over-excavation in order to reduce convergence movements in a region where the tunnel crown is only 17m from the surface.

More details in August's T&TI