Summary:
During and after construction of tunnels in swelling rock extensive heaving of the invert and failures of the lining of reinforced concrete occured rather frequently in the past. The swelling potential of unleached Gypsum Keuper containing anhydrite has been found to be especially high.
Up to now, there is no unique opinion among experts about the de-sign and construction of tunnels situated in the unleached Gypsum Keuper. The concurring design principles are the “Ausweichprinzip” (“principle of yielding support”) and the “Widerstandsprinzip” (“principle of resisting support”). Following the “Ausweich-prinzip”, a yielding zone is placed underneath the invert in order to considerably reduce the swelling pressures acting on the in-vert. Using the “Widerstandsprinzip”, the swelling pressure is met by a stiff lining. At the moment, there is no reliable information available, neither on the maximum possible swelling pressures and strains nor on their development with time
The given thesis is a contribution to the improvement of the theo-retical basis for the design of tunnels in swelling rock and for the bearing behaviour of rock and lining subjected to swelling pressures.
A constitutive model that has often been used for the design of tunnels in swelling rock is developed further with regard to the description of time dependency of the swelling and the interaction between tunnel lining and rock.
Using the results of extensive monitoring carried out in the experimental gallery of the tunnel “Freudenstein”, the constitu-tive model is calibrated. The experimental gallery had been arti-ficially watered and various principles of support had been con-structed in the same rock conditions.
The constitutive model, implemented in a numerical computation program according to the finite element method, is used for the design of a tunnel that has been constructed according to the “Widerstandsprinzip”. It is shown that such a tunnel can be designed with a thickness of the lining of 1 metre. Using this example, the consequences of a variation of the characteristic parameters are investigated by means of a sensitivity study. The results show which parameters have a considerable influence on the design of tunnels according to the “Widerstandsprinzip”.
