The prediction of tunnel stability usually is the main subject in geotechnical site investigations prior to tunnelling projects. During the last few years in mechanical excavation, problems have occured also connected with the accurate prediction of excavation performance and tool wear in soft and hard rock. Every now and again problems have been encountered leading to high bit consumption and low cutting performance of roadheaders. In this paper the connection between some geological features, cutting performance and bit wear is presented. Further, some major correlations of specific rock properties as well as geological factors with measured bit wear and excavation rates are shown.
D ordinaire lors d'etudes prelirninaires aux grands projets de percement de tunnel, les pronostics sur la stabilite de L'excavation se trouvent au premier plein d'interêt. Ce pendant ces dernières annees les difficultes de prevoir correctement la resistence des roches lors de percement mechaniques, Encore des problèms revenaient en connexion avec la consommation des ciseaux et avec le progrès de couper de bas avec des machines de percement. Dans cet, bulletin, sont exposees les correlations fondamentales entre quelques proprietes geologiques, le progrès de couper et l'usage des ciseaux, utiliser l'assistance des etudes allemandes en differentes entourages geologiques.
Bei den geotechnischen Voruntersuchungen zu großen Tunnelprojekten steht ueblicherweiee die Vorhersage der Stabilitat des auszubrechenden Hohlraums im Vordergrund. In den letzten Jahren haben sich beim Vortrieb mit Teilschnittmaschinen in Fels alIerdings auch vermehrt Probleme bei der Prognose der Fras- bzw. Schneidleistungen in den verschiedenen Gesteinen ergeben. Hierbei sind vor allem niedrige Vortriebsleistungen und hoher Werkzeugverschleiß zu nennen. In den folgenden Ausfuehrungen soll auf die geologischen Verhaltnisse und die Zusammenhange zwischen geomechanischen Gesteins-und Gebirgseigenschaften und den vortriebsrelevanten Parametem eingegangen werden.
Excavation performance is a' term used in underground construction to describe the influence of a number of parameters on the cutting rate and the tool wear of a roadheader. The interaction of the main factors is illustrated in Figure 1.
(Figure in full paper)
First of all, the excavation performance is influenced by the machine parameters of the chosen tunnelling rig - the installed power, the type of cutter head and the rock cutting tools mounted.
Apart from technical parameters, especially the geological parameters will basically influence the cutting performance and the tool wear (Figure 2). The specific characteristics of rock material and rock m/ass may be at least partly put into figures with the help of mechanical rock properties. But rock mass conditions also highly depend on the geological history, weathering conditions., hydrothermal decomposition and the structure of discontinuities. Therefore, one has to go through three levels of investigation: mineral- rock type - and rock mass - meaning also three levels of dimension!
(Figure in full paper)
The last important factor influencing rock excavation performance is the working process itself.' Firstly, smooth operation and permanent maintenance of the tunnelling rig contributes to a successful cutting performance. Secondly, a high penetration rate at, the tunnel face does not automatically lead to a high performance of the tunnel heading (Thuro & Spaun 1996a). Therefore, it is a matter of understanding the entire excavation system - before applying, expertise to the investigation of excavation performance.
