Penetration tests at the Koralm Tunnel (KAT2) – The right tool to improve penetration prediction in TBM tunneling? / Penetrationsversuche am Beispiel des Koralmtunnels (KAT2) – Ein Werkzeug zur Verbesserung von Penetrationsprognosen im maschinellen Tunnelbau?

Abstract

Performance prediction is one of the crucial issues for estimating excavation costs and construction time of tunnel projects. In mechanized tunneling, TBM performance highly depends on achieved penetration rate and cutter wear. The aim of the research group ABROCK and the topic of this paper is the improvement of penetration prediction by performing on-site penetration tests. Therefore estimated parameters by two existing prediction models (Gehring model, Colorado School of Mines model) are compared with the results of penetration tests at Austrians large infrastructure project of the OeBB Koralm tunnel construction lot KAT2. Penetration tests are a common tool to determine the performance of a TBM in certain geological environments. During a test, the TBM is operated under defined conditions that allow the comparison of different tunnel projects and machine types in analogous geological conditions. Results show that only for a narrow scope, considered prediction models reveal appropriate fitting. Once the rock mass is fractured or the stress level within the rock mass changes, existing models are not applicable. This fact emphasizes the need of an update for penetration prediction models by implementing a correction factor for discontinuities and the stress state in a rock mass. This may result in a new prognosis model called Alpine model.