ABSTRACT:

Many tunnels were and are being built in the Swiss Jura Mountains. Consequently, much information is available on the performance of old tunnels, on modem experiments and analytical models used in the design of new tunnels, on new construction methods and on new project management methods. This paper summarizes this information and draws conclusions on what was learned between then and now.

INTRODUCTION

Many railroadand highway tunnels have been built through the Swiss Jura mountains (Figure 1). Some of the railroad tunnels are over 100 years old while new highwayand railroad tunnels are being built at present or will be built in the near future. This history and present state of tunnelling is ideal for making comparisons between past and present design and construction. The Jura mountains consist of two distinct parts, the "Chain Jura" and the "Plateau Jura" (Figure 1). Figure 2, a longitudinal geologic cross section along the Hauenstein Base Tunnel shows the clear difference between the "Chain Jura" and the "Plateau Jura" going from South to North. Several of the geologic formations associated with the Jura Mountains cause significant problems in tunneling mostly through swelling and softening or a combination of both during tunnel construction and runnel lifetime. Best known for causing problems are the clay sulfate rocks in the Keuper and the Opalinus Clayshale of the lower Dogger (lower Aalénien) of Jurassic Age. This paper deals with the latter. The existing tunnels in which Opalinus Clayshale was encountered were studied in a number of case histories, while on the other hand, significant state-of-the-art research was and is being conducted for the tunnels which are under construction or planned (EPFL, 1990; Bellwald, 1991, Aristorenas, 1992; NAGRA, 1988; Einstein et al., 1995, Bobet et al, 1999).

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