For rock tunneling, it is important to ensure the safety of a working face, because the work concentrates at the unstable working face right after blasting. As the confirmation of safety in a working face depends on visual judgment at present, individual differences are likely to occur in judgment results. Therefore, in order to improve the safety of the face, it is important to quantitatively evaluate rock mass properties and to establish a judgment method based on the evaluation. The authors developed the method to quantitatively evaluate weathering and cracks density of a face using image analysis, and a category evaluation method to determine the probability of rock falling based on the results of quantitative evaluation by recording rock falling at a tunnel face during blast hall drilling. By constructing the system which can utilize this technique quickly and operating it at the actual construction sites, the danger of rock falling disaster can be greatly reduced. However, as data were continuously collected, there were some cases in which rock falling of a face could not be explained only by weathering and cracks density. Therefore, in order to improve the prediction accuracy, we are developing a new evaluation method by adding information such as collected image analysis results and information of wet condition of faces. In this paper, the result is reported.

1. Introduction

For rock tunneling, the work concentrates at the unstable working face right after blasting. Therefore, there is a danger that the rock falling from the face may lead to a serious disaster. Therefore, in order to ensure the safety of the face, it is necessary for the person in charge of the face worker to take appropriate measures after confirming the face status by face observation. However, because the current face observation depends on the visual judgment, individual differences are likely to occur in judgment results. Therefore, in order to improve the safety of the face, it is important to quantitatively evaluate rock mass properties and to establish a judgment method based on the evaluation.

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