摘要
A cantilevered block is instable rock which results from a combination of several discontinuities, in interaction with an underground mining excavation giving a mass rocky under-gangway without natural support. Since the starting of the gold mine of Akka in 1998, 4 deaths and 26 grave accidents happened that are associated to the falling of the cantilevered blocks. However, this study analyzes the causes of apparition of this instability in the underground gold mine of Akka which is in the buttonhole of Tagragra （Anti-Atlas, Morocco） taking into account the geological and geotechnical aspects. The more utilized geotechnical approaches were used to evaluate the quality of rocky mass including RQD, RMR and Q System method besides laboratory tests and geomechanical stations. After development of some classical formulas and using of simulation software and analytical methods, a way of support by bolting is proposed to stabilize the risk of blocks collapse inherent to the mining operations. Also we discuss here other technical solutions and theirs application limits in these cases. Finally, we confirmed the reliability of our conclusions and the type of the support proposed during 2012 and 2013 because we did not register any accident associated to cantilevered block falling.
