Safe Rapid Drifting – Drift Stability

2004

Reddy C Damodara, Peter K. Kaiser, Fidelis T. Suorineni,

Stability of underground excavations is of utmost concern in both mining and civil engineering projects. Rocks vary greatly in terms of texture (grain size), mineralogy, porosity, and foliation/schistocity depending on the genesis of the rock. In the Canadian Mining Industry Research Organization (CAMIRO) funded rapid drift development project, it was established that understanding the role of these factors in rock behaviour had a significant impact in rockwall support demand determination. Observations at the Underground Research Laboratory (URL) and some underground mines show that rocks with similar characteristics in the same stress environment respond differently to stress-induced damage. The brittle rock parameter concept (m=0) for assessing damage in rock excavations, often over estimates the depth of failure in some rock types. This limitation is attributed to the difference in brittleness of rocks and implies that the value of the cohesion component “s” in the m-zero concept is not the same for all rocks as previously postulated. This paper presents a procedure for rating rock brittleness for use in adjusting the brittle parameter “s” in assessing potential damage and support levels in underground excavations in brittle rocks at depth. The URL La du Bonnet Granite and granodirorite and South African and Thompson Mine quartzite are used to illustrate the importance of the concept in assessing drift stability. Preliminary results show that the procedure has promise in more reliably assessing potential damage in excavations in other rock types, where the conventional value of s=0.11 overestimate damage.

Keywords: Drift stability, Stress, Brittleness, Rapid drifting, Safe