ABSTRACT

Squeezing refers to the phenomenon of large timedependent deformations during tunnel excavation. It occurs mostly in weak rocks with a high deformability and a low strength, often in combination with a high overburden (Kovári 1998). It is also known that a high pore water pressure promotes the development of squeezing. If suitable preventive measures are not implemented, squeezing may even lead to complete closure of the tunnel cross section. In the presence of a lining, the ground exerts a gradually increasing pressure which can lead to it becoming damaged or even completely destroyed.