A colleague recently contacted me to see if I had a copy of a paper published in New Zealand Engineering in 1964. At the time of publication, I was a high school student, but the paper did come to my attention a few years later when I started my professional career. The author, Tom Grant-Taylor, was a geologist who I got to know when we were both working for the New Zealand government Department of Scientific and Industrial Research.
After rummaging through some archive boxes, I turned up a copy. The title is “Grant-Taylor Stable Angles in Wellington Greywacke“.
This paper was written in an era before computers were available to solve engineering problems. It describes an empirical approach to slope stability that still has a place, but I suspect is rarely used. The only figure in the paper, giving the relationship between maximum stable angle and height of batter, is a useful check to use before undertaking more sophisticated analysis, such as TSLOPE provides.
I would be interested to know if there are any updated observational data that could be used to constrain or extend the applicability of the stable angle vs height figure, and in other rock types. With the availability of high precision topographic data, there should be an opportunity to use advanced GIS tools to develop such curves with a high degree of sophistication.