No abstract

No abstract

In the course of designing the Gotthard Base Tunnel, extensive questions were considered about the tunnelling conditions to be expected and the resulting requirements for the TBM. Naturally this mainly concentrated on the achievable advance rates and the associated costs. The tunnelling works have now been completed and the essential assumptions and decisions from the design phase could be confirmed. Experience does however also show that the behaviour of the rock mass could not always be correctly predicted in its entireness and a corresponding flexibility in the use of support measures is unavoidable, which is only possible with suitable tunnelling equipment and machinery. The present article collects the essential data and facts from the TBM drives and described the areas where significant deviations arose. Particular attention is paid to the following subjects and the corresponding effects: wear to the cutterhead, heavy water ingress, rockburst, reciprocal influencing of the two tunnel drives under poor geological conditions and the collapse in the Tenelin Zone. The stated matters are described with a comparison against the assumptions made in the design phase and a complemented with few of the lessons learnt.

No abstract