American Rock Salt Company, LLC
The objective of this work was to calibrate the in situ properties of the overburden and mining horizon salt to reasonably reproduce measured subsidence and room closure and to simulate ground response to planned mining through 2011. A 2D numerical model was developed to predict mine-scale subsidence profiles along a section through the mine assuming a simplified mining sequence. A simple, 3D pillar-scale model was developed to calibrate the salt creep and room closure. A 3D model was then developed to more accurately predict subsidence given a more accurate mining sequence.
The FLAC and FLAC3D explicit finite-difference programs were used for this analysis because of their ability to simulate time-dependent creep behavior for the salt and in-elastic strength behavior for the overburden materials. Calibration of stratigraphic properties was performed using the 2D model by estimating in situ values from empirical methods for adjusting laboratory properties and by comparing subsidence predicted from the model to measurements. The calibrated properties were then used in the 3D model to predict surface subsidence.