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Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1983. / Includes bibliographical references (leaves 98-99).

The mining industry is an important component of the Canadian economy. The principal waste material from this industry is tailings. Numerous failures of tailings dams have caused loss of life and serious pollution problems. This thesis relates to the broad scale investigation and development of improved methods for tailings disposal. A systematic morphology has been developed which provides an effective approach to the overall problem for long-term planning and design. Improved design and construction techniques are advanced for the hydraulic construction of tailings dams with mobile hydrocyclones. The new design incorporates a sealed structure to improve the structural quality and safety of the dam by reducing and maintaining the porewater pressure at zero or negative values over the long-term period. Significant economic benefits are also attainable with the new design techniques. Economic advantages and structural considerations are presented for the system to decant effluent from the tailings basin. Special instrumentation has been designed, developed, and tested which will facilitate the evaluation of the material shear strength for this specific type of tailings dam.

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The stress-strain and volume (or pore pressure) change characteristics of a Southern Arizona copper mine tailings material were investigated in the laboratory by conducting static loading triaxial compression tests. The tailings material is silty sand with highly angular grain shapes, rough grain surface texture and approximately 37% by weight passing No. 200 sieve. Isotropically consolidated drained (CID) and isotropically consolidated undrained (CIU) tests were performed on laboratory compacted samples. The test samples were loaded to relatively large axial strains (20-35%) to study the residual shear strength and the shear stress induced pore pressure change or volume change at steady state. Test sample densities and effective confining stresses were systematically varied in these tests. The definition of critical void ratio and "lower" critical void ratio were reviewed and their values for different effective confining stresses were obtained from the CID tests. Stress-strain and volume (or pore pressure) change curves and strength parameters obtained by using conventional and lubricated loading end platens were compared and discussed. Steady state lines and undrained brittleness indices were obtained from the CIU tests with strain-controlled and load-controlled loading methods. The liquefaction potential of the tailings material was then evaluated. These results were compared with others reported in the literature. The significance of the results was discussed with respect to tailings material behavior.

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Extremely huge quantities of mined ore materials are processed annually to obtain the various types of minerals being the barebones of industry. Impounding the waste materials (tailings) of the mined minerals behind a raised embankment is the major and most common method used for the disposal of theses materials. Due to its execution simplicity and low cost, the upstream raising method has been the most common method used for retaining the disposed tailings in spite of being the most failure-vulnerable one. The sophisticated hydromechanocal behavior of the upstream tailings disposal facilities (UTDFs) during the staged construction makes the traditional approaches of consolidation, stability, and seepage analyses inefficient for producing accurate and, in many situations, correct design and evaluation of the UTDFs. The major objective of this thesis is to propose a thorough procedure for realistically evaluating the hydromechanical response of the UTDFs during their staged construction. The procedure incorporates a numerical model that reflects the combination of important realistic features of the UTDFs, namely (i) the partially saturated flow characteristics under the transient state dominating the facility throughout its operation/construction life; (ii) the two dimensional consolidation response of the facility components under both the partially and fully saturated cases considering (a) the full coupled response between the fluid and the solid phases and (b) the large deformation-nature of the tailings; as well as (iii) the appropriate mechanical behavior of the facility materials including a model that can detect the inception of liquefaction in the liquefaction-susceptible zones of the facility. The influences of a number of operational/construction measures that have been reportedly critical for the stability of the UTDFs are investigated in the light of the proposed model. Moreover, the inappropriateness of the traditional approaches for realistically evaluating the UTDF hydromechanical response during its staged construction is substantiated in the analyses carried out in this work. / The conclusions and recommendations drawn from this thesis are paramount not only for the feasibility, preliminary design and risk assessment studies of the UTDF during its operation/construction life but also for the on going analytical investigations and monitoring/instrumentations plans carried out throughout such life.