Liquefaction assessment and flume modelling of the Merriespruit gold and Bafokeng platinum tailings

[摘要] The thesis describes the determination of the steady state line for the Merriespruit gold and Bafokengplatinum tailings by means of triaxial undrained compression tests. It shows that there are numerous steadystate lines for the above mentioned tailings products and thatthe location oftheirsteady state lines in voidratio- mean confining effective stress space is influenced by the percentage fines (particles smaller than0.075mm) present in the tailings, among other factors. As the percentage fines increases so the steadystate line for the particular material shifts downwards in void ratio- mean confining effective stress space.The difficulty of defining a unique steady state line for a particular fines content tailings, due to errors inmeasurement of initial size, mass, etc. and changes in void ratio due to flooding, saturation andconsolidation of the moist tamped triaxial test samples is illustrated and it is recommended that error bandsbe assigned to the steady state lines.The steady state lines determined for the Merriespruit gold tailings and the concepts of liquefaction arecombined with evidence obtained from the post failure investigation into the Merriespruit flow slide failureto prove the premise that the flow slide was as a result of static liquefaction failure of the tailings. It is alsoillustrated that the notion of using a single steady state line to evaluate the liquefaction susceptibility of atailings dam is insufficient due to the particle size distribution of the tailings varying along the beach lengthof the tailings dam and the location of the steady state line being influenced by the percentage finescontent.Flume modelling using the Merriespruit gold tailings were carried to obtain a qualitative understanding ofthe behaviour of flow slides. Comparisons between the flume model tests and the Merriespruit flow slide(prototype) showed that it is difficult to obtain a correlation between the two due to the influence of scale,different dominating forces in the model and prototype and the inherent variability associated with suchgeotechnical phenomena- particularly in the preparation and deposition of the tailings in the flume model.Keywords: liquefaction, steady state line, flow slide, failure, flume modelling, Merriespruit, Bafokeng,gold, platinum, tailings

[发布机构] University of the Witwatersrand