ABSTRACT:

A method for estimating rock strength using TBM cutting force is proposed based on experimental findings. The cal- culated rock strength coincides well with those obtained using other methods, such as bedrock survey, Schmidt-hammer rebound hardness, etc. The proposed. method is relatively simple and requires the determination of only three values: thrust, torque, and cutting depth. The proposed method appears to be promising for real-time in-situ estimation of rock strength.

RESUME:

Cet article presente une methode de calcul de la resistance des roches par application, de l'effort de coupe TBM basee sur des donnees experirnentales. Le resultat des calculs obtenu par cette methode correspond à celui obtenu à l'aide de methodes comme, entre autres, l'analyse des roches de fond et la durete de rebondissement au marteau de Schmidt. La methode proposee est relative-ment simple et ne demande que la deterrnination de trois valeurs: poussee, cople et profondeur de coupe. Cette methode semble appelee à un brillant avenir pour le calcul in-situ et en temps reel de la reistance des roches.

ZUSAMMENFASSUNG:

Auf Versuchsergebnissen basierender Vorschlag einer Methode zur Beurteilung von Felsstarke unter Anwendung von TBM Schneidkraft., Die derart errechneten Felsstarken decken sich mit Resultaten aus anderen Kalkulationsmethoden wie z, B. Felsschichtuntersuchung, Schmidt-Hammer Rueckschlagsharte-Test usw. Die vorgeschlagene Methode ist relativ einfach und erfordert die Bestimmung von nur drei Werten: Druck, Drehmoment und Schnitttiefe. Die Methode erscheint vielversprechend fuer in sitll Echtzeit-Beurteilungen von Felsstarke.

1
INTRODUCTION

At present, various types of tunneling boring machines (TBMs) are widely, used as a substitute for conventional tunneling methods, i.e.; drilling, blasting; and mucking. The performance of TBM is potentially far better than that of conventional methods. If TBM, is properly applied, a mean penetration rate several times greater than, those of conventional methods can be ex- pected. However, TBM performance is very poor when applied under conditions that are adverse to TBM. Since TBM is a full- face machine, the face cannot actually be observed. This is dis- advantageous when excavating rock which has rapidly changing characteristics, as is commonly the case for rock in Japan. Therefore, measuring geological characteristics forward of the face is essential. This measurement is generally performed using the wave reflection method. However, the relationship between wave velocity and the mechanical properties of rock is very complicated. Therefore, comprehensive estimation of the mechanical properties of rock is difficult using the wave reflection method.

In the present study, a method for estimating the rock strength of face using TBM cutting force, such as thrust, torque and cutting depth, is proposed. The response of rock to indentation by disc cutter has been the subject of several investigations. The thrust-force of the disc cutter was found to be roughly pro- portional to the compressive strength of the rock. Moreover, the relationships between rock mass classification and TBM mechanical data, such as thrust, torque and penetration rate have been reported. The results obtained in previous studies indicate that the higher the rock mass classification, the lower the penetration rate and the higher the thrust.

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