Geomechanical assessment of dilution potential for sublevel caving at Ekati Diamond Mine: Case study and generalized approach.

摘要

Sublevel caving is an applicable underground mining method for the exploitation of diamondiferous kimberlite pipes. The emplacement nature of kimberlite pipes creates a well defined carrot-shaped ore body. As mining progresses, the kimberlite ore caves and is drawn down, the host rock, which is left in situ, creates a deep, steep-sided pipe. Pipe wall sloughage allows waste rock to enter the cave; diluting the kimberlite ore. A methodology has been developed for the assessment of dilution potential, based on pipe wall stability. A case study of the Koala Kimberlite Pipe at the Ekati Diamond Mine, illustrates the dilution assessment process.; The analysis method involves the development of a structural geology model accounting for the distribution of joint sets and the geometric characteristics of discrete blocks within the rockmass of interest. A rigorous approach to developing a detailed structural geology model has been well documented to summarize the various phases of analysis; data amalgamation, macro-scale structural interpretation, and domain delineation, meso-scale structural interpretation, structural extrapolation, and geometric analysis.; The Block Shape Characterization Method has been developed to assess how variance in the structural fabric, defined throughout the structural geology model, contributes to variance in the geometric distribution of discrete blocks within the rockmass. Block shape is defined by three factors; beta; defining the elongation or flatness of a block, alpha; characterizing deviation from equidimensional geometry, and V, the block volume.; Pipe geometry was integrated with the structural model to numerically analyze pipe wall failure potential using a unit cell approach to simulate stability, within a large, complex pipe, as a series of small regions, defined by homogenous structural fabric and planar wall geometry, modeled independently. The-kinematic response of systems of discrete blocks, formed by intersecting discontinuities, to gravitational loading was simulated using a Discrete Element Method of numerical modeling.; Numerical results were summarized in a final dilution model which indicates spatial variations of the anticipated depth of failure and the geometric distribution of discrete dilution blocks. The complete dilution model is a valuable tool that can be utilized by mine planners and engineers to mitigate the hazards associated with dilution.