2966 FRACTURING OF ROCK AHEAD OF THE FACE OF AN EXCAVATION AND ITS RELEVANCE TO MECHANISED EXCAVATION
DOI:
https://doi.org/10.17159/2411-9717/2024/v1234i07a2966Abstract
Boring of tunnels and shafts in hard rock under high stress conditions is becoming increasingly common as mines and tunnels are developed at greater depths. Under the high stress conditions, fracturing of the often-brittle rock occurs in the walls, and ahead of advancing faces, of excavations. Fracturing can have a significant impact on boring activities: sidewall spalling, affecting machine gripper capacity; fractures can also develop in the rock ahead of the face, leading to blocky rock conditions which may have a significant effect on machine excavation. Fracturing may develop dynamically, leading to strainbursts and rockbursts, which can be hazardous and destructive. In brittle rock, fracturing is commonly extensional in nature. The focus of this paper is on fracturing of the face of the bore. Examples of such fracturing behaviour are described briefly to place the approach to the problem in context. Numerical analyses were carried out to predict the initiation of extension fractures and their orientations ahead of excavation surfaces, and the resulting formation of rock slabs/plates, and the stability of these plates against buckling failure. The results should be beneficial in the evaluation of boring conditions prior to and during boring operations.
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Copyright (c) 2024 Matthews Mokgohloa, Thomas Dick Stacey
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