Multiple occurrences of liquefaction in recent earthquake events revealed the importance of studying reliquefaction characteristics of sandy soils. However, there is a lack of knowledge in determining dynamic properties of reliquefied soils. Through a series of hollow cylinder torsional shear tests, this paper presents a first-hand experimental study to investigate the shear modulus reduction and damping of reliquefied Toyoura sand under the integrated effects of strain history and induced anisotropy. Reliquefaction resistance and modulus reduction are highly dependent on strain history and the state of reconsolidation. On the contrary, a unique damping curve was found for all liquefaction and reliquefaction tests. An excess pore-water pressure model was proposed as a function of secant modulus for virgin and moderately preshaken Toyoura sand. Finally, the experimental results were interpreted based on energy concept. For the first time, a relationship between cumulative dissipated energy and cumulative strain energy was proposed for all liquefaction and reliquefaction tests, which can be used to assess liquefaction/reliquefaction resistance in seismic analyses.

中文翻译：

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Toyoura砂在再液化试验中的动态特性

近期地震中多次发生液化现象，揭示了研究砂质土壤再液化特性的重要性。然而，在确定再液化土壤的动态特性方面缺乏知识。通过一系列空心圆柱扭转剪切试验，本文提供了第一手实验研究，以研究在应变历史和诱导各向异性的综合影响下再液化的 Toyoura 砂的剪切模量降低和阻尼。再液化阻力和模量降低高度依赖于应变历史和再固结状态。相反，所有液化和再液化测试都发现了独特的阻尼曲线。提出了一个超孔隙水压力模型，作为原始和适度预震的 Toyoura 砂的割线模量的函数。最后，基于能量概念对实验结果进行解释。首次提出了所有液化和再液化测试的累积耗散能和累积应变能之间的关系，可用于评估地震分析中的液化/再液化阻力。