Tailings Management Facilities (TMFs) require the numerical modeling of large-strain consolidation to represent the release of water with time. Such numerical modeling in the state of practice has traditionally involved running a single 1D large-strain consolidation numerical model at the center of the deposit and inferring long-term performance of the entire deposit from the results. The difficulty with such a methodology is that the 3D effects of depositing in a TMF are not fully considered. Full 3D numerical modeling of the large-strain consolidation process has been performed; however, it remains technically challenging to model the deposition process in a 3D model.
The pseudo-3D methodology couples a 3D slurried tailings deposition scenario with the effects of saturated 1D large-strain consolidation in order to model the volume of tailings in a TMF over time. The deposition process is represented by a 3D methodology that determines the shape and elevation of the tailings surface prior to consolidation. The consolidation process is modeled through a discretization of the 3D model into a grid of independent 1D models. The settlement of the 1D models provides an approximation of the 3D consolidation model vs. time as well as the tailings volume over time. Each “cell” of the grid represents a full 1D large-strain consolidation numerical model and is solved based on the tailings deposition scenario. The advantage of this method is that it is robust — each 1D numerical model is relatively easy to solve with the solution being simply a function of time. This methodology does not consider lateral seepage or deformations and is ideally suited for facilities with a high horizontal to vertical ratio in their geometry.
Advantages of the pseudo-3D approach to consolidation modeling:
Figure 1: Elevation and volume results of a pseudo-3D consolidation analysis.