Gloggnitz contract after completion of the intermediate access at Göstritz

Abstract

AbstractThe intermediate construction access at Göstritz was planned based on the results of a comprehensive geological investigation programme. The intermediate access minimises the risk of the excavation of the Semmering Base Tunnel through the Grassberg‐Schlagl fault system, which is located in the Otterstock area in Lower Austria. The site consists of an approx. 1000 m long access tunnel, a complex system of shaft head caverns, two shafts with a depth of about 250 m down to the level of the tunnel as well as a system of shaft bottom caverns for the four tunnel drives in the directions of Gloggnitz and Mürzzuschlag. During the construction of the access tunnel, a new shaft head layout was proposed by the contractor in form of value engineering to optimize further construction operation, and the optimized layout was adopted to the contract. At the end of the access tunnel, it turned out that the shaft head cavern system could neither be constructed in the original layout as tendered nor in the newly revised layout due to a geological fault zone, which had not been predicted despite extensive geological investigation in advance. Consequently, ÖBB, designer and contractor worked intensively to find a new feasible design to enable further construction of the cavern system, avoid a standstill of tunnelling works and comply with all approvals.