The many faces of Q: Rock mass characterisation, London

Overview

In civil engineering projects involving concrete, steel and foundations in soil, it is possible to fabricate, sample, or test representative elements of the media that will be involved in the foundation and construction. In the case of tunnel or cavern excavations, or foundations in jointed and perhaps faulted rock this ‘simplicity’ is absent. ‘Samples’ are too big. This is where a good rock mass classification comes into its own. Ratings for some principal components like relative block size, inter-block friction, stress/strength ratio and water, are combined to form quantitative guidance sometimes using simple equations.

The Q-system now addresses such widely ranging themes as core-logging, tunnel-logging, tunnel support, shotcrete thickness, bolt spacing, seismic velocity, deformation modulus, tunnel and cavern deformation, shear strength, over-break, permeability, TBM prognosis, tunnel delays in fault zones, construction cost and time, safe rock slope angles. The lecture will be liberally illustrated with the basics and with some good examples of application.