The Southern African Institute of Mining and Metallurgy (SAIMM) has published a new rock mechanics textbook, which is titled Theoretical Rock Mechanics for Professional Practice.
Speaking at an event hosted by the SAIMM’s Johannesburg branch last month, author Matthew Handley elaborated that the textbook was a synthesis of 22 classic texts on rock mechanics, solid mechanics, his 15 years’ experience in rock mechanics in the gold mining industry and ten years as a professor of rock mechanics at the University of Pretoria’s (UP’s) Department of Mining Engineering.
Handley said that, throughout his involvement in the rock mechanics sector, he found that all the introductory texts on stress and strain were incomplete “in one way or another” and that this, together with the “watered-down” introductions to stress and strain currently accepted in the mining rock mechanics fraternity, effectively placed a barrier between students and readers and their fuller understanding of rock mechanics.
He stressed that this incompleteness in the texts was not as a result of the omission of important material by any of the authors of these texts, but rather the result of the assumed level of learning of readers.
“Readers with an advanced tertiary engineering qualification would understand the work, while almost all others would struggle. Most texts require, in differing proportions, a grounding in solid statics and dynamics, prior knowledge of the calculus, including partial differential equations, linear algebra and tensor calculus when introducing fundamental concepts, such as stress and strain.”
Handley remarked that such high-level introductions to stress and strain can never be informative to the uninitiated, which he believes is part of the reason why so many flounder in the rock mechanics certificate examinations, even when asked to perform simple calculations and interpretations.
Therefore, to make the rock mechanics theory accessible to all, these complete dissertations on stress and strain were stripped to the essentials of their content and reintroduced in simplified form as found in earlier rock mechanics textbooks.
He reiterated that previous textbooks were not wrong in any of their essentials, explaining that the theory of stress and strain are, however, reduced to the notion that stress is a vector, defined by force divided by area, while strain is a ratio of change in length of a body through deformation with respect to some original length.
“These notions, while not essentially wrong, are so reduced with respect to the reality that no candidate can actually develop from them a proper understanding of what the quantities of stress and strain actually are. This is unless if they are prepared to make the leap from those texts and grapple with more advanced (and complete) texts on the subject,” said Handley.
Further, he noted that stresses and strains had been treated as scalar quantities in two- dimensional (2D) views, whereas a three- dimensional (3D) view was “essential” for any proper understanding of rock mass behaviour in a mine. Therefore, Handley said that the practice of rock mechanics had stagnated for the past 30 to 40 years within a reduced 2D view of what is “at the least” a 3D problem.
He said it was for these reasons that he had spent the past decade developing more accessible texts on the fundamentals of rock mechanics, which he had presented as lectures on rock mechanics to undergraduate mining engineering and geology students at UP.
Handley said that the litmus test for these texts was that the geology students progressed equally well to the engineering students, even though they had lesser mathematical backgrounds.
“This encouraged me to believe that the content of the book would be equally understandable to the uninitiated,” he enthused.
Further, Handley stated that the advantage this textbook would provide candidates was that it would build “a clearer and deeper understanding” of what is actually happening in a rock mass and therefore they would be “far better equipped” to understand the output of numerical models, which were at least 3D (static) and sometimes four-dimensional (dynamic).
He emphasised that candidates with this background would therefore be able to make the right interpretations of the model outputs and would ultimately draw the correct conclusions. “This will result in the advancement of the practice of rock engineering in the future, with the concomitant improvement in rock-related safety in shallow and deep-level mines.”
Handley highlighted that the textbook was not intended to supplant the learning material for the rock mechanics certificate that would be written for sector education and training authority the Mining Qualifications Authority in the short to medium term.
However, he also said that, in accordance with the ninth Engineering Council of South Africa exit level outcome of independent learning ability, the learning texts for the rock mechanics certificate should provide a basis for life-long learning and should therefore include a description of the fundamental theory.
“Otherwise, the transition to more advanced texts will be too difficult,” Handley warned.
The textbook is available for purchase through the SAIMM in hardcopy or as an e-book.