Assessment of liquefaction potential of unsaturated oil sand tailings subjected to future saturation

油砂尾矿是油砂提取沥青过程的副产品，包括水、砂、细颗粒、残余沥青或其他碳氢化合物。加拿大采矿业生产了大量的油砂尾矿，这些尾矿被永久地储存在大型尾矿坝后面。尾矿坝液化流破坏和尾矿失控释放将对生产、环境、公众认知和生命损失造成灾难性影响。对这些尾矿进行安全和负责任的管理需要正确理解它们的抗剪强度和抗液化能力。然而，油砂尾矿的液化行为和强度损失，无论是通过地震荷载还是其他触发机制，如降雨、饱和、施工荷载或坝坡过陡，都不是很清楚。特别是，局部饱和度对原位试验测量和尾矿不排水抗剪强度解释的影响尚不清楚。本研究将利用饱和和非饱和油砂尾砂的强度、刚度、单位重量和细粒含量，对一种广泛使用的原位测试工具——锥贯入测试（CPT）进行校准。将对油砂样品进行综合的实验室CPT模型实验、剪切波速测量和直接简单剪切试验。研究结果将对油砂尾矿的剪切响应和液化特性产生新的认识。建立一种可靠的方法来预测油砂尾矿在动、静载荷作用下的原位强度和液化敏感性。然后，采矿工程师可以在非饱和油砂尾矿中使用该方法来评估尾矿坝饱和后的液化潜力和稳定性。这将使矿山经营者和工程师能够设计更安全的尾矿处理水坝，并更好地了解现有水坝的风险。这将进一步有利于加拿大，特别是阿尔伯塔省，通过确保矿床最终与周边地区融为一体，并将其改造成一个环保和安全的生态系统，从而最大限度地降低采矿的环境风险。

Oil sand tailings are by-products of the bitumen extraction process from oil sands, which include water, sand, fine particles, residual bitumen or other hydrocarbons. Large amounts of oil sand tailings are produced by the Canadian mining industry which are stored permanently behind large tailings dams. Liquefaction flow failure of a mine tailings dam and uncontrolled release of tailings would have a catastrophic impact on production, the environment, public perception, and loss of life. Safe and responsible management of these tailings requires proper understanding of their shear strength and resistance to liquefaction. However, liquefaction behavior and strength loss of oil sand tailings, either through earthquake loading or other triggering mechanisms such as rainfall, saturation, construction loads, or oversteepening of dam slopes are not well understood. In particular, the effect of partial saturation on in-situ test measurements and interpreting undrained shear strength of tailings is unknown. The proposed research will calibrate a widely used in-situ testing tool, the Cone Penetration Test (CPT), with strength, stiffness, unit weight, and fines content of saturated and unsaturated oil sand tailings. A comprehensive program of laboratory CPT model experiments, shear wave velocity measurements, and direct simple shear tests will be carried out on oil sand samples. The results will produce new knowledge in shear response and liquefaction behavior of oil sand tailings. A robust method will be established to predict in-situ strength, and liquefaction susceptibility of oil sand tailings under dynamic and static loads from CPT measurements. Mining engineers can then use this method in unsaturated oil sand tailings to assess the liquefaction potential and stability of tailings dams if they become saturated. This will allow mine operators and engineers to design safer tailings disposal dams and have a better understanding of the risks to existing dams. It will further benefit Canada, and particularly Alberta to minimize environmental risks of mining by ensuring that the mine deposit is ultimately integrated with the surrounding area and reclaimed into an environmentally-friendly and safe ecosystem.