Authors: Nizkous, I; Smith-Boughner, L; Shumila, V; de Beer, W; Angus, D

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This paper is hosted with the kind permission of the Universidad de Chile, Eighth International Conference & Exhibition on Mass Mining, 2020.


DOI https://doi.org/10.36487/ACG_repo/2063_94

Cite As:
Nizkous, I, Smith-Boughner, L, Shumila, V, de Beer, W & Angus, D 2020, 'Multi-attribute microseismic analysis to evaluate the evolution of in situ stress: imaging the complex relationship between stress and structure', in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining, University of Chile, Santiago, pp. 1268-1276, https://doi.org/10.36487/ACG_repo/2063_94

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Abstract:
Safe operations in the mining environment require mitigation of geomechanical risks through monitoring of production induced micro earthquakes. In this study we assess dynamic stress changes in an underground block caving mine in a tectonically active area during peak production activity and a following short period of relative inactivity. We analyse the collective behaviour of microseismic events (Dynamic Parameters Analysis or DPA) together with passive seismic tomography and stress inversion to get an integrated picture of the complex stress evolution processes occurring within the mine. These approaches provide complementary information for interpretation of the complex spatial and temporal stress evolution. DPA shows a cyclical process of loading and stress relaxation in the abutments of the cave during the period of study. Seismic tomography recovers compressional velocity variations correlating with the stress field behaviour observed in DPA. A region of high velocity within the rock mass is observed to undergo a loading process with local stress increase, while a region of low velocity rock mass undergoes stress relaxation with high intensity plastic deformation. Seismic moment tensor mechanisms show uniformity in the south abutment of the cave with predominantly tensile crack closure mechanism, which coincides with the region of low velocity. The high velocity region exhibits some tensile fracture opening with consistent tensile fracture closure failure type along the abutments of the cave. The principal stress directions vary around the mine abutment and display an additional level of complexity related to vertical distribution of the events. The maximum principal stress σ1 in the south abutment of the cave appears to be consistently vertical.

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