Research Center for Geomechanics and Mining Practice Problems, Saint-Petersburg Mining University, Saint-Petersburg, Russia:

Yu. Yu. Kutepov, Senior Researcher, Research Center for Geomechanics and Mining Practice Problems, Candidate of Engineering Sciences, Kutepov_YuYu@pers.spmi.ru
M. A. Karasev, Professor of Department, Doctor of Engineering Sciences

Phosphoric acid production in apatite and phosphate rock processing involves by-production of phosphogypsum which is placed in dumps, landfills and gypsum storage facilities. Phosphogypsym has specific mineral and chemical composition, possesses peculiar physical and mechanical properties, and it is highly susceptible to compaction when piled in dumps. The lab-scale and in-situ deformation testing and monitoring of various phosphogypsum types made it possible to substantiate the deformation behavior model of the rock and to determine its mechanical properties. In view of the complex structure of phosphogypsum storage facilities and considering the deformation specifics of this manmade rock, prediction of phosphogypsum compaction should use 3D FEM-based modeling. Numerical modeling improves reliability of geomechanical behavior prediction in phosphogypsum dumps in terms of the volumetric deformation by taking into account nonlinear variations in physical and deformation parameters of the material in the range of compressive stresses. In a general case, the values of average stresses and bulk deformations are correlated via the laws of plastic compaction. A 3D model was constructed and compaction prediction was carried out as a case-study of a waste dump. The studies revealed possibility of increasing the phosphogypsum dump size by 15% of the project size with the height increase of the dump to 120 m. The significant economic effect comes from the land preservation, as well as from the reduction of cost of land reclamation and new dump construction.

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