TUNNELING IN SQUEEZING ROCKS - CASE-HISTORIES

Authors
Citation
W. Steiner, TUNNELING IN SQUEEZING ROCKS - CASE-HISTORIES, Rock mechanics and rock engineering, 29(4), 1996, pp. 211-246
Citations number
55
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary","Engineering, Civil
ISSN journal
0723-2632
Volume
29
Issue
4
Year of publication
1996
Pages
211 - 246
Database
ISI
SICI code
0723-2632(1996)29:4<211:TISR-C>2.0.ZU;2-#
Abstract
Squeezing rock conditions have posed and continue to pose a major obst acle to the construction of tunnels through mountains, as experience d ating back more than a century shows. The paper deals with the study o f past experiences in the light of present geotechnical engineering kn owledge. Many of the transalpine tunnels were constructed before geote chnical engineering had been developed, and the principles underlying squeezing were not yet understood. Also construction techniques have c hanged with time. By studying past experience in the light of our pres ent knowledge in geotechnical engineering (rock and soil mechanics), o ne may gain more insight into the nature and causes of squeezing groun d behaviour. Here, a number of older and newer case histories are summ arised, providing substantial insight into the phenomenon of squeezing rock. Squeezing rock behaviour is influenced by rock type and structu re. Usually, in squeezing zones the rock is strongly jointed and fract ured and has low strength. Overburden has also a significant effect an d squeezing behaviour may occur abruptly in a tunnel once a limiting o verburden has been exceeded. Water pressures in strongly jointed and o ften crushed rock are important and so are the adopted construction pr ocedures and sequences. A support of substantial structural strength m ay be necessary to prevent long-term deformations and to withstand inc reased loading on the tunnel liner from the rock mass surrounding the tunnel.