ABSTRACT:

The tunnel boring machine (TBM) mining technique is capable of outperforming all other tunneling methods, in terms of advance rate under favorable tunneling conditions, but often fails to deliver such performance due to unanticipated rock mass conditions. Work has been undertaken at The University of Texas at Austin to identify and better characterize the salient features of the tunneled rock mass that impact TBM performance in order to better predict the performance of TBM mining techniques in a given rock mass, and to support the selection the most appropriate equipment and operating techniques.

RESUME:

Sous des conditions favorables un tunnelier peut creuser un tunnel plus rapidement que toutes autres methodes. Malgre ceci, la performance du tunnelier est souvent decevant, dans Ie cadre du planning du projet global, car la definition des characteristiques du massif rocheux sont insuffisamment definies au moment du lancement du projet. A l'Universite de Austin, Texas an système utilisant une base de donnees a ete develope pour aider à la characterisation d'un massif rocheux. L'objectif de cette recherche est de prevoir plus precisement la performance d'un tunnelier en tenant compte des divers effets que la roche peut avoir sur les fonctionnements de la machine.

ZUSAMMENFASSUNG:

Unter guenstigen Bohrbedingungen vollbringt die Tunnelbohrmaschine (TBM) bessere Leistungen hinsichtlich der Schnelligkeit des Bohrens als andere vergleichbare Maschinen. Ihr Nachteil liegt aber darin, dass Sie aufgrund unvorhergesehener Felsstrukturbedingungen oftmals nicht in der Lage ist, solche herausragenden Leistungen zu erbringen. Die Universitat in Austin, Texas, hat es sich deshalb zur Aufgabe gemacht, spezeill diejenigen Eigenschaften der Felsstruktur, die die Leistung der Tunnelbohrmsschine beintrachtigen, zu identifizieren und besser zu charakterisieren, um die Leistung der TBM in einer gegebenen Felsstruktur besser vorhersagen und eine bessere Auswahl der Ausruestung und Arbeitsweise treffen zu können.

1 INTRODUCTION

The increased use of tunnel boring machines (TBMS) may seem an attractive proposition to the potential users of underground space given the high rates of advance, greater intrinsic stability of the excavated profile, relatively low labor requirements and safer construction environment afforded by the adoption of such equipment. However, cases are common in which the traversal of unexpected rock conditions can reduce mining rates or, in extreme cases, bring activities to a standstill, partially or completely nullifying the anticipated financial and technical benefits of TBM adoption. Some recent headlines taken from engineering magazines yield some insight into the common place occurrence of these "below par" performances: "Boston Tunnels Slip Behind" (Angelo, 1994), "Excavators rescue TBM job" (Anon, 1993), "Bad rock stalls boring machine" (Rosenbaum, 1991) and "Battling Portland's blocky basalt" (Green, 1995). In fact, the cases of TBM performance attaining or exceeding expectations are relatively infrequent and usually occur only in the excavation of the more homogeneous rock masses. Significant improvements in the capacity and reliability of underground equipment have been made since the initial use of the present generation of TBMs some thirty years ago, and these machines have now been applied economically in ever harder, more massive rock masses such as granites and quartzites (Jordal and Hartwig, 1991). However, the overall performance achieved by TBMs is still commonly limited by the presence of unexpected rock mass conditions traversed along any given tunnel alignment.

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