There are several factors that affect the formation of localized rockfalls in self-supporting underground mines. Between these factors we can point out the type of material, the environmental conditions, the process of exploitation or the redistribution of stresses. All of them contribute to the alteration of the rock and the formation of cracks, and their spreading produces rockfalls and increase in the temperature of the surrounding material. The measure, all through the time, of the temperature of the rock with thermic images allows us to identify variations in it. These changes in the thermic conditions of the rock mass identify areas with a high probability of rockfalls. Following this principle, researchers of the University of Oviedo have developed a methodology for the prevention of localized rock falls in self-supporting underground mines using infrared thermography techniques. To test its goodness, they have applied it in an underground mine of limestone located in the north of Spain. This work has been realized in the last year and it has realized that the infrared thermography technique is a quantitative way to know the risk of rockfalls, that lets to prepare the adequate proceedings in order to avoid accidents or situations of risk within the exploitation. In this paper the methodology developed and its application on a real mine, as well as the results of the job are described.

1 Introduction

The purpose of this article is to develop and validate a procedure for quantitatively determining the location and probability of localised detachments of material in self-supporting underground excavations through the evaluation of thermal alterations to reduce the risk of accidents in such situations.

When an excavation is made inside a fractured rock mass and the spacing of joints is considerable, large blocks of rock may appear. If these blocks are unstable, may come loose inside the excavated cavity, causing significant personal and material damages. For this reason it is important to have analytical tools for identifying such blocks before or during the execution of work.

For straight galleries with a constant cross-section and tetrahedral blocks made up of three families of joints and the surface of the gallery itself, the problem of identifying blocks has been widely studied and solved (Goodman & Shi 1985, González et al. 2005). For pentahedral blocks made up of four families of joints and the surface of the gallery, both the problems of identification and support have also been studied in considerable depth and solutions found (González et al. 2005).

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