TEMPERATURE PREDICTIONS AND PREDICTIVE TEMPERATURES IN DEEP TUNNELS

Citation
L. Rybach et M. Pfister, TEMPERATURE PREDICTIONS AND PREDICTIVE TEMPERATURES IN DEEP TUNNELS, Rock mechanics and rock engineering, 27(2), 1994, pp. 77-88
Citations number
8
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary","Engineering, Civil
ISSN journal
0723-2632
Volume
27
Issue
2
Year of publication
1994
Pages
77 - 88
Database
ISI
SICI code
0723-2632(1994)27:2<77:TPAPTI>2.0.ZU;2-G
Abstract
Reliable assessments of the underground temperature are needed for con struction projects like deep tunnels, shafts and storage facilities. I n areas of pronounced topographic relief, special attention must be gi ven to the influence of three-dimensional topography on the subsurface temperature field. Further parameters for the prediction include grou nd surface temperature, local heat flow density, geological factors (s tructure/schistosity, thermal conductivity, erosion rate, water circul ation). A first prediction was attempted for the planned Gotthard rail road tunnel (NEAT). This tunnel will have a total length of 56 km with a maximum cover of 2500 m. The temperature predictions were calculate d, based on the RIMINI topography array, for points at 1-km-intervals along the planned axis. Maximum temperature (conservative upper limit) is about 45-degrees-C; the error of the predicted temperatures could be, in view of the uncertainties involved, in general ca. +/- 5-10-deg rees-C. Since little is known at present about the deep water circulat ion system in the realm of the planned Gotthard tunnel, the prediction calculations assume heat transport by pure conduction. Significant su bsurface water flow would mainly lead to the reduction of rock tempera tures by cold infiltrations from the surface, as demonstrated by obser vations in the Simplon and Mont Blanc tunnels. In fact, the deviation of actual measurements (performed right behind the advancing face) fro m ''conductive'' previsions should be used as a predictive tool of lar ge water flows which could be encountered during tunnel construction.