The authors monitored the dynamic response of the surrounding rock mass at the excavation face of Taru-toge tunnel at the prefectural border of Shizuoka and Yamanashi prefectures, Japan built in connection route between New Tomei and Chuo Expressways. This monitoring study in the immediate vicinity of the tunnel face is probably the first one in the world so far within the knowledge of the authors. In this paper, the authors describe the several monitoring studies and the results obtained so far. They also discuss the implications of this study within the integrated framework of tunnel construction.

1 Introduction

The monitoring of the real-time response of underground structures during excavation is of paramount importance for the safety evaluation and stability assessment. Drilling and blasting (DB) are commonly used for the excavation of rock engineering structures. The variation of stress state around the underground opening during excavation is a dynamic process and the stress state would be generally different from that under the static condition for the geometry particularly soon after blasting operation. One can not find any monitoring study on the dynamic response of underground excavations in literature except few studies by the authors. The authors have developed a multi-parameter monitoring system for monitoring the response and stability of the rock engineering structures.

Drilling-Blasting is the most commonly used excavation technique in mining and civil engineering applications. Blasting induces strong ground motions and fracturing of rock mass in rock excavations. The second author has developed a monitoring system for measuring blasting induced vibrations (Aydan et al. 2016, Imazu et al. 2014, 2015).

In this study, the authors attempted to monitor the blasting-induced vibrations and multi-parameter responses at the very close vicinity of the tunnel face in order to investigate if it is possible to evaluate its real time stability as well as the characteristics of surrounding rock masses in a Taru-Toge tunnel in Central Japan (Fig. 1). The multi-parameters measured involve electric potential variations, acoustic emissions, rock temperature, temperature and humidity of the tunnel during the face advance. The authors describe the outcomes of these unique monitoring studies in this paper and discuss the implications in tunneling.

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