Static Liquefaction of Mine Tailings under Non-Standard Stress Paths

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Static liquefaction of mine tailings has caused numerous recent failures in the United States and around the world. Failure of tailings storage facilities lead to devastating consequences for the environment and civil infrastructure, and lead to loss of human lives. The 2008 Kingston fossil plant failure in Tennessee, an environmental disaster with associated losses on the order of 1.2 billion dollars, is a prime example of the tremendous impact that a tailings storage facility failure can cause. Future failures could have similar devastating consequences for the local and state economies, populations, and industries. Therefore, evaluating the safety of tailings storage facilities is vitally important in any region where mining is active, such as in Colorado, Nevada, Utah, Arizona, and others. Mine tailings are intermediate soil materials often classified as sandy silt to almost pure silt. Conditions for static liquefaction (sudden loss of stability even in the absence of extreme events such as earthquakes) on these materials cannot be evaluated using known engineering procedures. This research will create new knowledge for improving resilient design of tailings storage facilities against static liquefaction and provide insights into creating new design protocols to mitigate potential disasters in the United States and worldwide that are induced by the static liquefaction of mine tailings. The research will also establish an educational and outreach program focused on curriculum development on intermediate soil materials for K-12 students, through STEM centers at Georgia Tech.Through an integrated experimentally and numerically-based program inspired by recent failures in tailings storage facilities, this research advances liquefaction engineering by investigating (1) the mechanical response of mine tailings under standard and non-standard stress paths, while considering a range of boundary conditions; (2) the conditions for static liquefaction under drained loading conditions, where recent failure events point to a lack of thorough understanding despite the opposite perception among geotechnical engineers; (3) the micromechanics of mine tailings under shearing through image-based experimental techniques; and (4) the effects of micromechanical configurations (i.e. fabric) and induced anisotropy on triggering static liquefaction by using the novel anisotropic critical state theory. Gaining insights into the key parameters that govern the triggering of static liquefaction in mine tailings and developing well-calibrated numerical procedures using the anisotropic critical state theory will transform the ability of geotechnical engineering profession to more effectively evaluate and mitigate the risk of static liquefaction in mine tailings.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.