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Keywords: numerical simulation, wet disposal, upstream, residue areas.

Summary

The deposition of industrial waste is a major challenge in geotechnical engineering, since these materials exhibit a distinct materials' behaviour usually found in natural deposits [1].

The overall decrease in the number of waste disposal areas and the implementation of strict environmental legislation has created the need for maximum utilization of the existing deposition areas. The objective is to operate and handle the reservoirs so as to maximize the volume stored and, consequently, the useful life of these deposits.

Generally, the technique of waste processing bauxite operation deposition provides an initial operation of release waste (wet disposal), in artificial reservoirs. The reservoir life depends fundamentally on the geotechnical behavior of the residues, whose properties vary over time and depth in the light of simultaneous processes of consolidation and sedimentation [2,3].

After the exhaustion of the reservoir and drying the residue, the upstream method starts, increasing the useful life of reservoirs. In this method, the pulp is thrown on the waste pre-existing, which is in the process of consolidation, resulting in significant settlements in the residue foundation. The analysis of the settlements is complex, considering that the waste consolidation requires large strains. So, the use of classic theories of consolidation is not applicable.

The above clearly shows the complexity of the problem and the importance of numerical analysis in the study areas for waste disposal, and the search for a representative model of this material. Predicting the behaviour of waste areas have been studied from simplifying assumptions, which generally lead to conservative estimates.

The present paper concerns the simulation of a bauxite residue area in different stages of operation: wet disposal and upstream, using a finite element program Plaxis [4]. The waste area is located in the state of Maranhão, Brazil, and has a storage capacity of approximately 4,000,000m³. The geotechnical parameters were defined according field and laboratory tests executed in the area. The numerical prediction was compared with the instrumentation field, located in different phases of operation.

The results show the applicability of the numerical program in predicting the behaviour of waste areas. In the filling phase, the response of the program proved to be consistent with the results of the field bathymetry, with a difference of fifty days between numerical prediction and the actual filling. Additionally, numerical settlements were also consistent with those measured in the field.

References

1: L.H.A. Villar, "Study of Density and Drying of Waste Bauxite Mining & Processing", PhD Thesis, Pontifical Catholic University of Rio de Janeiro, 2002. (in Portuguese)
2: J. de Lima, "Numerical Simulation of Residues Areas During the Upstream Operation", Dissertation, State University of Rio de Janeiro, 2008. (in Portuguese).
3: L.M. Costa Filho, S.B.M. Pedrosa, A.C.C.F. Sieira, M.R.P. Silva, "Behaviour of an upstream stack formed with geotextile wrapped dikes", 8th International Conference on Geosynthetics, Yokohama, 1, 2006.
4: R.B.J. Brinkgreve, "Finite Element Code for Soil an Rock Analyses. PLAXIS-2D user's manual", Balkema, Rotterdam, Netherlands, 2002.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 96 PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping and Y. Tsompanakis Paper 214 Numerical Simulation of Residue Areas A.C.C.F. Sieira and D.B.D. Araújo Structural Engineering Department, State University of Rio de Janeiro - UERJ, Brazil doi:10.4203/ccp.96.214 purchase the full-text of this paper Full Bibliographic Reference for this paper , "Numerical Simulation of Residue Areas", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 214, 2011. doi:10.4203/ccp.96.214 Keywords: numerical simulation, wet disposal, upstream, residue areas. Summary The deposition of industrial waste is a major challenge in geotechnical engineering, since these materials exhibit a distinct materials' behaviour usually found in natural deposits [1]. The overall decrease in the number of waste disposal areas and the implementation of strict environmental legislation has created the need for maximum utilization of the existing deposition areas. The objective is to operate and handle the reservoirs so as to maximize the volume stored and, consequently, the useful life of these deposits. Generally, the technique of waste processing bauxite operation deposition provides an initial operation of release waste (wet disposal), in artificial reservoirs. The reservoir life depends fundamentally on the geotechnical behavior of the residues, whose properties vary over time and depth in the light of simultaneous processes of consolidation and sedimentation [2,3]. After the exhaustion of the reservoir and drying the residue, the upstream method starts, increasing the useful life of reservoirs. In this method, the pulp is thrown on the waste pre-existing, which is in the process of consolidation, resulting in significant settlements in the residue foundation. The analysis of the settlements is complex, considering that the waste consolidation requires large strains. So, the use of classic theories of consolidation is not applicable. The above clearly shows the complexity of the problem and the importance of numerical analysis in the study areas for waste disposal, and the search for a representative model of this material. Predicting the behaviour of waste areas have been studied from simplifying assumptions, which generally lead to conservative estimates. The present paper concerns the simulation of a bauxite residue area in different stages of operation: wet disposal and upstream, using a finite element program Plaxis [4]. The waste area is located in the state of Maranhão, Brazil, and has a storage capacity of approximately 4,000,000m³. The geotechnical parameters were defined according field and laboratory tests executed in the area. The numerical prediction was compared with the instrumentation field, located in different phases of operation. The results show the applicability of the numerical program in predicting the behaviour of waste areas. In the filling phase, the response of the program proved to be consistent with the results of the field bathymetry, with a difference of fifty days between numerical prediction and the actual filling. Additionally, numerical settlements were also consistent with those measured in the field. References 1 L.H.A. Villar, "Study of Density and Drying of Waste Bauxite Mining & Processing", PhD Thesis, Pontifical Catholic University of Rio de Janeiro, 2002. (in Portuguese) 2 J. de Lima, "Numerical Simulation of Residues Areas During the Upstream Operation", Dissertation, State University of Rio de Janeiro, 2008. (in Portuguese). 3 L.M. Costa Filho, S.B.M. Pedrosa, A.C.C.F. Sieira, M.R.P. Silva, "Behaviour of an upstream stack formed with geotextile wrapped dikes", 8th International Conference on Geosynthetics, Yokohama, 1, 2006. 4 R.B.J. Brinkgreve, "Finite Element Code for Soil an Rock Analyses. PLAXIS-2D user's manual", Balkema, Rotterdam, Netherlands, 2002. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £130 +P&P)
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