CAREER: Understanding and Predicting the Dynamic Behavior of Mine Tailings Dam Materials

在美国的1,555个尾矿结构中，大约有三分之一是高危险的潜在结构，如果发生故障将导致生命损失。在过去的40年里，全球约有15座尾矿库因地震震动导致细粒垃圾液化而坍塌。分析土的抗液化能力的方法有很多，但矿山尾矿，包括粗、细两种，与土有本质的区别。人们在了解和预测尾矿材料的循环行为、抗液化能力和抗剪强度方面做了一些努力，但缺乏一种全面了解和统一的方法来评估尾矿的动态行为，部分原因是尾矿库结构的测试和取样涉及的困难。这项工作将集中在实验室和现场试验，以了解和预测尾矿坝材料的动态行为。实验室共振柱试验将用来测量剪切模数、材料阻尼和剪切应变之间的关系。室内循环三轴试验将用循环阻力比(CRR)来确定液化抗力。研究了孔隙率、细粉含量、龄期、含水率、孔压和围压等参数对材料动力性能的影响。将采取特别措施回收样品进行实验室测试，包括固定活塞取样和在蓄水池内建造工作垫，以降低现场设备的表面压力。将进行现场标准贯入试验(SPT)、圆锥贯入仪(CPT)和地震试验，并将开发使用覆盖校正的SPT击数((N1)60)、圆锥尖端阻力(Qc1)和剪切波速(Vs1)来评估现场液化抗力的方法。现场叶片剪切数据将与静力触探数据相关联，以开发一种用于稳定性分析的估计细粒垃圾峰值和剩余不排水抗剪强度的方法。通过测量这些材料的动态特性，将采用用于土壤的方法，包括现场方法。地质学家将能够更好地预测尾矿坝对动态激励的反应，这将导致在循环应力比(CSR)方面改进对地震诱发荷载的估计。他们将能够更好地预测地震引起的过度孔压和液化导致的有效应力减少和强度降低，这将使他们能够更准确地评估地震期间和地震后条件下大坝的稳定性。

Approximately one-third of the 1,555 tailings structures in the United States are high-hazard potential, where failure would result in loss of human life. Over the past 40 years, approximately 15 tailings dams have failed worldwide as a result of liquefaction of fine refuse due to earthquake shaking. Methods to analyze liquefaction resistance exist for soil, but mine tailings, including coarse and fine refuse, are inherently different than soil. Some efforts have been made towards understanding and predicting the cyclic behavior, liquefaction resistance, and shear strength of tailings materials, but a comprehensive understanding and unified approach towards the assessment of the dynamic behavior of mine tailings is lacking, partly due to the difficulties involved with testing and sampling of tailings dam structures. This work will focus on laboratory and field testing to understand and predict the dynamic behavior of mine tailings dam materials. Laboratory resonant column testing will be used to measure the relationship between shear modulus, material damping, and shear strain. Laboratory cyclic triaxial testing will be used to determine liquefaction resistance in terms of the cyclic resistance ratio (CRR). The effect of parameters such as void ratio, fines content, age, water content, pore pressure and confining stress on the dynamic behavior of the materials will be investigated. Special measures will be taken to recover specimens for laboratory testing, including fixed piston sampling, and construction of work pads in the impoundments to reduce surface pressures of field equipment. Field standard penetration testing (SPT), cone penetrometer testing (CPT), and seismic testing will be performed, and methods will be developed to use overburden-corrected SPT blow count ((N1)60), CPT cone tip resistance (qc1), and shear wave velocity (vs1), to assess in situ liquefaction resistance. In situ vane shear data will be correlated with CPT data to develop a method to estimate peak and residual undrained shear strength of fine refuse for stability analyses.By measuring the dynamic behavior of these materials, methods used for soils will be adapted, including in situ methods. Geoscientists will be able to better predict the response of tailings dams to dynamic excitation, which will result in improved estimates for earthquake-induced loading in terms of cyclic stress ratio (CSR). They will be able to better predict reductions in effective stress and reductions in strength due to earthquake-induced excess pore pressures and liquefaction, which will allow them to more accurately assess the stability of dams during earthquakes and under post-earthquake conditions.