This paper describes the tunnel seismic reflective survey, which has been developed by the authors in order to detect the geological condition ahead of the tunnel face three-dimensionally using reflected seismic waves. In addition, the applicability and the accuracy of the result of this system has been validated by comparing with the geological observation results at the tunnel face and the result of the drill logging system, which was conducted simultaneously with this survey in order to predict the rock properties using the data acquired during drilling from the tunnel face by rotary percussion drilling.

In dieser Arbeit werden Reflektionsseismische Tunneluntersuchtungen beschrieben, die von den Autoren entwickelt wurde, um die geologischen Eigenschaften am Tunnelstirnende dreidimensional an Hand reflektierter seismischer Wellen bei minimaler Unterbrechung der Arbeit zu untersuchen. Darueber hinaus wurde die Anwendbarkeit und Genauigkeit der mit diesem System erhaltenen Ergebnisse durch Vergleiche mit den Ergebnissen geologischer Beobachtungen am Tunnelstirnende sowie den Ergebnissen des Bohrlogsystems bewiesen. Das letztgenannte System wurde gleichzeitig mit dem hier genannten System eingesetzt, um die Gesteinseigenschaften mit Hilfe der Daten vorherzusagen, die beim Bohren von Probelöchern im Tunnelstirnende mit einer Drehschlagbohrmaschine erhalten wurden.

Cet article decrit une methode de prospection sismique de tunnel, developpee par les auteurs, pour determiner en 3 dimensions les conditions geologiques existant derrière le front de taille, au moyen d'etude et de mesure des ondes sismiques reflechies dans le sous sol, et ce, avec un minimum d'arrêt des travaux d'excavation. En outre, l'applicabilite et l'exactitude des resultats de ce système ont ete verifiees, en comparant les resultats des observations geologiques effectuees au front de taille, avec ceux du log de forage qui a ete effectue parallèlement à ce système, en vue de prevoir les proprietes de la roche, grace aux donnees collectees au cours du forage d'un trou de sonde depuis le front de taille à l'aide d'une foreuse rotative à percussion.

Introduction

To the excavation of tunnels, precise prediction of the geological conditions ahead of the tunnel face is important for the economy, safety and efficiency of the project. In particular, sections of poor ground, such as faults and fracture zones, are likely to require changes in construction methods as well as tunnel support patterns, and could thus impede the progress of construction. Therefore, it is desirable to obtain high quality data on geology and properties of rock masses in advance. Thus, a new seismic reflective survey has been developed by the authors in order to detect the geological conditions ahead of the tunnel face three-dimensionally using reflected seismic waves with minimal suspension of the excavation work (Neil et al. 2001, Yamamoto et al. 2001, Yamamoto et al. 2002).

This paper describes a theory of the seismic reflective survey. In addition, the applicability and the accuracy of the result of this system has been validated by comparing with the geological observation results at the tunnel face and the result of the drill logging system, which was conducted simultaneously with this survey in order to predict the rock properties using the data acquired during drilling from the tunnel face.

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