Dynamic properties of Toyoura sand in reliquefaction tests: effects of strain history and induced anisotropy

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.