Rock Engineering Knowledge and Radical Uncertainty: From Empirical Methods to Professional Practice

It is important for the rock engineering practice to acknowledge the difference between uncertainty, which diminishes with adequate data access, and radical uncertainty, which persists because critical features and failure mechanisms may remain undetected, not because of inadequate sampling but because they represent conditions that cannot be expected. Radical uncertainty represents an ontological feature of complex geological systems rather than a limitation of our current state of knowledge. The paper’s central thesis is that current rock engineering practice has developed what we term the “epistemological three-body problem”: the interaction between (i) inherent geological uncertainty that includes radical uncertainty (unknown unknowns), (ii) empirical methods that lack field-scale validation yet have gained professional acceptance through historical precedent, and (iii) regulatory frameworks that demand apparent certainty. We demonstrate this thesis through three interconnected arguments. First, we expose the epistemological and validation challenges inherent in widely adopted design methods. Second, we analyze how operational definitions, validation processes, and numerical modelling approaches may generate misleading precision rather than meaningful understanding of rock engineering problems, and third, we propose a framework for acknowledging and working within the boundaries of radical uncertainty. On this basis, we must acknowledge that rock engineering practice necessarily operates under a standard of a “balance of probabilities”. Given the nature of radical uncertainty, professional practice should evaluate methods not by whether they eliminate uncertainty, but by whether they represent reasonable approaches to managing it.