Analysis of effect of swelling clay in weakness zone on reinforced shotcrete rib

Numerical analysis with FLAC3D, a three dimensional finite difference program, is used in this paper to quantitatively estimate the effect of swelling on the reinforced shotcrete rib. As case for this study has been used the Finnfast subsea tunnel close to Stavanger in Southwest Norway where weakness zones containing swelling clay were encountered during excavation. NGI (Norwegian Geotechnical Institute) has instrumented one such zone. Laboratory tests of the gouge material from the zone based on NTNU (Norwegian University of Science and Technology) procedures indicate that the swelling pressure is moderate.