Stope dilution can be influenced by a number of parameters, most notably by mining-induced stress regime, the strength and structural characteristics of the host rock, and the type of stope: primary or secondary. A case study from the Bousquet mine operation is presented. Adjacent primary and secondary stopes, situated at 1100 meter depth, were studied to assess stress-induced yield of ore zone and hanging-wall rock, using brittle Hoek-Brown parameters, compared against measured stope blast vibration attenuation and
mined stope profiles.
In a global competitive market, there is pressure on mines to reduce costs. One approach to reducing mine costs is in ore dilution reduction. Dilution has a direct and large influence on the cost of a stope, and ultimately on the profitability of a mining operation. Consequently, methods of controlling factors in the design process, which result in dilution reduction should go a long way to increase the overall profitability of a mine.
The Bousquet deposit is a lens of massive sulphide and associated disseminated breccia and stringer sulphides, located approximately 50 km east of Rouyn-Noranda, Qutbec. The orebody is hosted within a series of volcanic rocks, primarily schists of varying quality. The main massive pyrite lens extends from 180 meters below surface and is open at depth. The orebody strikes east-west and dips steeply (80 degrees) to the south.
The Bousquet property is situated in the Abitibi region of northwest Quebec, in the southern part of the Abitibi Greenstone Belt in the Superior Province of the Canadian Shield. The orebody follows an east-west regional structural trend, dipping steeply south in a tabular form, shown in Figures 1 and 2 and is accessed by a shaft, driven to a depth of 1245 meters on the footwall side of the orebody.
Rock mass conditions are controlled extensively by the geological history, with the dominant schistose fabric controlling the behaviour of wall rocks in all underground excavations. The host rock mass is strongly schistose, quartz-mica schist.
The schistocity contains sericite and acts as a dominant low friction angle weakness plane in the rock mass. Schistocity planes form platy blocks up
[Figure 1 is available in the full paper]
to approximately 50 mm in thickness. The lenticular shaped massive pyrite orebody, ranges in thickness from 4 to 19 meters, and has lateral and vertical dimensions of 300 m and 1500 m respectively.
