Integration of field characterisation, mine production and InSAR monitoring data to constrain and calibrate 3-D numerical modelling of block caving-induced subsidence

Abstract

Block caving often leads to significant ground deformations that if not properly assessed and accounted for may threaten the integrity and safety of overlying mine infrastructure. To mitigate this risk, sophisticated 3-D numerical modelling has been turned to as a means of predicting the extent and magnitudes of caving-induced surface subsidence. However, the complexity of the rock mass interactions involved, coupled with the uncertainty associated with geological heterogeneity, rock mass properties and in-situ stresses results in the need for models to be constrained and calibrated. Results are first presented here from a detailed 3-D back analysis of a caving-induced open pit mine slope failure, used to constrain the rock mass properties and far-field in-situ stresses derived from field characterisation data, as well as to bring understanding to the problem with respect to the cave-pit interactions. The “best fit” set of input properties obtained was then used for forward modelling of caving-induced subsidence for the period 2009–2010. Further calibration of this model was performed using high-resolution InSAR monitoring data. The close fit achieved between the predictive 3-D numerical model and InSAR data demonstrates the promise of InSAR as a means to calibrate sophisticated numerical models, and thereby contribute to managing block caving associated subsidence hazards.