Open Cut » Environment
Post mining landforms are constructed of unconsolidated material which can be highly erodible. In such structures of loosely bonded material, rill erosion and gully erosion are major issues. To ensure long term stability and sustainability, these landforms need to be designed to minimise rilling and gullying. Over the years various landform evolution models have been used to predict the evolution of such landforms and identify areas at risk of erosion.
In this project, a new set of tools that can be used to assess the long term sustainability of post mining landforms were created by enhancement of the State Space Soil Production and Assessment Model (SSSPAM). SSSPAM is a coupled landform-soilscape evolution model capable of simulating fluvial erosion and armouring, diffusive erosion (surface), sediment deposition, and weathering within the soil profile. SSSPAM was specifically developed to incorporate the evolution of the soil profile in combination with landform evolution and for this reason it is more suitable for simulating unconsolidated structures such as post-mining landforms. In addition to the new landform evolution model (SSSPAM), a data analysis tool set specifically designed to analyse and visualize SSSPAM results were also developed.
For evaluation, the evolution of a proposed post-mining landform, SIBERIA and SSSPAM model outputs were compared. Results demonstrate that SSSPAM predictions compare well with the results from the more established landform evolution model SIBERIA. The results demonstrate that SSSPAM produces similar erosion rates to SIBERIA both of which compare well to field measured erosion rate and type.
A further evaluation used a LiDAR survey of a working mine to represent the initial landform. Site specific erosion parameters were developed for input to SSSPAM. The results demonstrate that SSSPAM is able to predict the position and geomorphic characteristics of the observed gullies at an active mine site. Further, the results demonstrate how the surface properties (particle size distribution) change over time due to the process of armouring which is known to reduce the rates of erosion.
The results highlight the versatility and reliability of SSSPAM as a coupled soilscape-landform evolution model for simulating unconsolidated structures such as waste rock dumps. It also demonstrates that the SSSPAM parameter calibration methodologies are reliable for the sites examined. The accuracy of SSSPAM simulations gained through correct parameterisation establishes SSSPAM as a viable tool to analyse future stability of post mining landforms.