The pre-investigation of geological conditions for a tunnel boring machine project is of great importance as difficult conditions, either very hard rock or too soft and decomposed rock can result in a slow down of the performance and an increase of the cost. This can be difficult to accept both for the contractor and the owner of the tunnel. It is described how the pre-investigations have been made on a project in Karnten, Austria, and how the follow-up has been made in cooperation between the owner, contractor and the supplier of the TBM. Different new ideas have been tried to improve the testing of the rock and the information of the rock mass.
Die geologischen Voruntersuchungen sind von grosser Bedeutung fur eine Tunnelfrasmaschine. Entweder sehr harte Gesteinspartien oder schlechte gebrache Verhaltnisse können zur Verminderung der Maschinenvortreibsleistung fuehren und dadurch zu erhöhten Baukosten. Dies kann zu vertraglichen Schwierigkeiten zwischen Bauherr und Unternehmer fuehren. Es wird beschieben, wie die Voruntersuchungen fuer ein Projekt in Karnten, Oesterreich ausgefuehrt wurden und wie die eigentliche Projektverfolgung verlief, in enger Zusammenarbeit mit Bauherr, Unternehmer und dem Maschinenhersteller. Verschiedene neue Methoden wurden untersucht um die Aussagekraft einzelner Testverfahren zu verifizieren.
Les analyses geologiques precedentes sont de très grande importance pour un tunnelier. D''une part les zônes extrèmement dures ou d''autre part des zones mylonitisees avec très peu de resistence conduisent à une diminuation de la performance de la machine et y inclus une augmentation des frais. Cela provoque souvent des problèmes entre le proprietaire et l''entrepreneur. Les analyses precedentes sont descrites pour un projet à Karnten, Autriche. Et puis on decrit les travaux et les tests qui sont faits pendant et après le travail du tunnelier en collaboration avec Ie proprietaire, l''entrepreneur et le constructeur de la machine. Plusieurs nouvelles methodes ont ete testees concernant leur valeur pour des predictions de la performance et les frais d''un tunnelier.
The Woellabach is a part of an extension of the hydropower plant Innerfragant in the Fragant Power Project Group belonging to Karntner Elektrizitats-Aktiengesellschaft (Kelag) with headoffice in Klagenfurt, Austria.
The tunnel is 6770 m long with a diameter of 3.5 m and will bring the water from the Woella stream to the plants in the valley. Two smaller streams will also be taken in by short diversion tunnels. One of them is also made by TBM why the total length driven will be 7200 m. The contractor responsible for the tunnelling project is Ilbau in Spittal/- Drau, Austria, see Fig. 1
(Figure in full paper)
A general geological report for this project was prepared by a consulting geologist for the owner company Kelag including a geological map 1:10''000, a geological profile for the tunnel line, a detailed mapping for a main shear zone and a description for the petrographic and the tectonic situation in this area, see Fig. 2. Later on, three variants of tunnel lines with further geological descriptions were available. At the beginning all descriptions were based to a conventional method. After a decision to use a TBM (it was the first project for Kelag and for Ilbau to operate with a TBM) for the contract a classification in 7 classes was prepared. It is including different rock qualities and their influence on the tunnelling with a TBM and the corresponding need for rock support, similar to DETZELHOFER, (1979).
The tunnel passes through the rocks of the "zentralalpinen Altkristallins", mainly composed of paragneissis, chlorite- mica-schists, with amphibolitic pegmatite and amphibolitic lenses. The whole complex is modified by intensive tectonic and diaphthoretic events.
For the predictions of the TBM performance (advance rate and cutter consumption) the Atlas Copco Jarva company tested 12 rock samples for calculations with the prediction formula of the Colorado School of Mines (FUN DEN WANG OZDEMIR, SNYDER, 1978) in combination with experiences in similar rock conditions (uniaxial Compressive Strength, Point Load Test, Cerchar Abrasivity Index, petrographic thin section analysis).
Later on, in collaboration with the University of Luela (S) a further prediction for the advance rate for the whole project was given, based on indentation tests, (HANDEWITH 1972).
(Figure in full paper)
