Large Strain Consolidation

SASKATOON, May 13, 2013

SoilVision Systems Ltd. is pleased to announce the release of 1D, 2D (pseudo and quasi) and 3D (pseudo and quasi) large strain consolidation software packages. The ability to perform large strain consolidation has been integrated within the coupled solution of the existing SVFlux™ and SVSolid™ flow and stress deformation software packages. The release is the result of many years of work and collaboration with industry partners in the mining industry to provide an improved tool for modeling soft soils such as mine tailings. The tool represents the implementation of large strain consolidation technologies which are required for the excessive volume change encountered during the dewatering of mine tailings. The new software can be utilized by geotechnical consultants and mine planners in the planning of such facilities or in the analysis of existing tailings facilities.

The dewatering of mine tailings has become of particular importance and has received prominent attention in many industries due to pressures of reclamation experienced in recent years. Often there are standards requiring tailings to be dewatered within specific time periods. The planning activities related to dewatering of mine tailings have been difficult as the mathematics associated with the large strain consolidation of mine tailings are complex and current software tools are found to be lacking. This software release allows a more comprehensive tool for the analysis of the dewatering of mine tailings.

1D Analysis

1D analysis is implemented in the software based on the Somogyi formulation for 1D large strain consolidation of mine tailings. The software implementation allows quiescent consolidation to be modeled as well as dynamic filling scenarios to be analyzed based on volumes of tailings added per unit time. The software contains an easy-to-use interface and a comprehensive method of graphing the analysis. The results can be presented as profiles of void ratio, solids contents, pore-water pressures, as well as many other program variables versus elevation or time.

The process of sedimentation can also be modeled with the software package. Some mine tailing slurries have extremely high water contents and the process of sedimentation is dominant after first deposition. The software allows modeling of the process of sedimentation coupled with consolidation. The transition between the sedimentation and the consolidation processes can therefore be modeled in the software.

Pseudo 2D and 3D Analysis

In a pseudo 2D and 3D analysis the formulation of the 1D problem is extended to 2D and 3D for the flow portion of the analysis, however the stress-deformation portion of the equations remains vertical 1D only. There is no stress transference laterally and the effect of lateral strains is not considered in the numerical model. However, flow in 2 and 3 dimensions is considered in the numerical model. The 2D and 3D analysis allows quiescent consolidation to be modeled. The results of the analysis can be output in terms of dominant variables such as void ratio, pore-water pressures, solids content, and excess pore-water pressures to be graphed in the model as a function of space or time. The model has been fully benchmarked against existing numerical models and verified in actual field studies. The pseudo 2D and 3D formulation also implements coupled sedimentation with the numerical model.

Quasi 2D and 3D Numerical Modeling

In quasi 2D and 3D large strain consolidation, the problem is discretized as individual columns used to represent either a 2D or a 3D full model, therefore in a quasi 2D or 3D model there is no transference between columns of either water flow or of stress. This methodology was originally proposed by Coffin (2010) during research at the Colorado School of Mines. The analysis is useful in cases where the tailings facility is spread out and there is little chance of lateral stresses influencing the process.

The numerical model is set up in a manner similar to any other 3-dimensional numeric model in the SVOffice software. When the model is written to the solver, it is discretized into many 1D columns. Each 1D column is solved with the Somogyi coupled large strain consolidation and sedimentation formulation for its relative time period. Then the solver automatically assembles the results of all the 1D numeric models into a column based 2D or 3D representation of the results. The results may then be observed and dominant program variables such as void ratio, solids content, pore-water pressure, excess pore-water pressure, effective stress, and other major program variables can be plotted as a function of space or time in the sophisticated AcuMesh backend visualization engine.

If you are involved in the large strain analysis of tailings consolidation and have interest in these software tools please feel free to contact us. The analyses mentioned in this article have been released in the current version of the software and are currently available for consulting analysis. Documentation related to performing analysis and tutorials are also available.