The design and excavation of openings in kimberlite pipes and the surrounding country rocks has become a specialty of ours. We have probably conducted more mining rock mechanics designs for diamond mines in North America than any other consulting firm in the world.
Designing excavations for diamond mining, although similar to designing for other types of mining, is quite unique. Normally, the pipe is located on a craton. As such, the country rock is very old and and can be quite competent. The kimberlite's properties, on the other hand, can range from near soil-like composition to being as competent as the country rock.
For an open pit mining operation given the pipe geometry economics dictate that the pit walls must be kept as steep as possible. This requires excellent rock mass characterization prior to mining. A probability based slope design, based on the rock mass characterization, is also highly recommended. The result is a very neat, tidy, and economic pit. An example of such work is given as Improving Double Bench Performance at the Ekati Diamond Mine Site.
Bulk sampling of kimberlite from underground openings, as well as contemplated underground mining of kimberlites, requires a different strategy. Here, the excavation in the country rock is strictly for access. Most of the excavations of concern will be in the kimberlite. As kimberlite can be very weak, subject to air slacking,and be difficult to support due to potential reactions with shotcrete and poor bolt anchorage, rock mass characterization and design are critical to success. For examples of some of the concerns, read Drifting in Very Poor Rock - Experience and Analysis.
Our experience with kimberlites, both open pit and underground, is second to none. In addition, much of our work is done in sub-arctic to arctic conditions, providing a geotechnical experience base for the "polar" diamond pipes that is difficult to beat.