Is face stability a problem in mechanised tunnelling through squeezing ground?

In the literature, a view can be found that the potential hazard of face instability is rather subordinate in mechanised tunnelling through squeezing ground; according to other works, unstable face conditions must be expected even in the case of minor squeezing. This paper contributes to a clarification of this question, by reviewing the expressed opinions; making a clear distinction between questions of stability and questions of deformation; explaining that a generally valid statement cannot be made; and showing that under certain conditions, the manifestations of face instability and squeezing may be similar in terms of excavation volume and cutterhead torque, although the underlying mechanisms are different from a mechanics viewpoint.