Determining tunnel stability is a key issue during preliminary site investigation. In contrast, problems of excavatability have been largely ignored. While the choice of an economic tunnelling method is admittedly a clear priority in the planning stage, special investigations focussing on rock fragmentation (e.g. drilling or cutting performance, rock mass blastability or tool wear) are rarely carried out. This paper explores possibilities to quantify key parameters for rock mass excavatability in drilling, blasting and cutting by TBMs and roadheaders.


La determination de la stabilite du tunnel est une question cle lors des etudes preliminaires. En revanche, les problèmes d'excavabilite sont souvent en grande partie ignores. Tandis que le choix d'une methode de percement economique est evidemment une priorite claire dans l'etape de planification, des investigations speciales se concentrant sur la fragmentation de la roche (par exemple le comportement de la roche au forage, à l'excavation ou au dynamitage et l'usure des outil) sont rarement effectuees. Cet article explore les possibilites pour quantifier les paramètres cle de la roche lors d'excavation par forage, dynamitage, au tunnelier (TBMs) ou à l'excavatrice.


Beim Tunnelbau wir meist die Vorhersage der Stabilitat des ausgebrochenen Hohlraums als Schluesselfragestellung betrachtet. Im Gegensatz dazu werden Probleme der Gebirgslösung weitgehend ignoriert. Wahrend der Wahl einer wirtschaftlichen Vortriebsmethode wahrend der Planungsphase meist noch eine gewisse Prioritat beigemessen wird, werden spezielle Untersuchungen zur Gebirgslösung (Bohr- oder Schneidbarkeit, Sprengbarkeit oder Werkzeugverbrauch) nur sehr selten durchgefuehrt. Diese Publikation zeigt Möglichkeiten der Quantifizierung von Schluesselparametern fuer die Gebirgslösbarkeit auf, also der Bohr- und Sprengbarkeit, der Frasbarkeit mit Teilschnittmaschinen und der Schneidbarkeit mit TBMs.


Cutting and drilling performance as well as the wear of tools and equipment are decisive for the progress of excavation works. The estimation of these parameters in predicted rock conditions might bear an extensive risk of costs. Therefore an improved prediction of cutting performance and bit consumption would be desireable. For some years now basic rock drilling processes and bit wear have been studied in hard rock tunnelling1, 2. Extensive field studies and laboratory work has been carried out to record the connection between some geological features and geotechnical parameters on the one side and technical parameters such as cutting or drilling performance and disc or bit consumption on the other. For that reason 24 tunnel projects in Europe and overseas in different geological settings have been followed more or less extensively.

Excavatability is a term used in underground construction to describe the influence of a number of parameters on the drilling, blasting or cutting rate (excavation performance) and the tool wear of a drilling rig, roadheader or TBM (wear or usage criterion). The interaction of the main factors involved is illustrated in Figure 1:. These terms are used in underground as well as in surface construction. In this thesis, only the aspects relating to tunnelling are discussed.

(Figure in full paper)

In the first interaction, the excavation performance is influenced by the machine parameters of the chosen tunnelling rig: the installed power.

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