The expression ''squeezing rock'' is a concept too vague to be used by
practicing engineers. In this paper, it is assumed to mean large conv
ergences of the tunnel walls. Two case histories are briefly presented
. The Frejus tunnel was driven with a large overburden; on the contrar
y, the Sidi Mezghiche tunnel was shallow. Different techniques were us
ed to control the convergences. In both cases, the tunnels were locate
d in ''complex formations''; the complexity stems from the heterogenei
ty and anisotropy of the rock masses, and no efficient technique is av
ailable to determine the geotechnical characteristics and the natural
state of stress in the formations.