Shear behaviors of recycled aggregate sand in constant volume simple shear tests interrelated with particle shape

Compared with quartz sand, recycled aggregate sand is characterized by the high liquefaction and shear resistance because of its irregular particle shape. However, the interrelationship between its particle shape and shear behaviors is seldom investigated. This paper investigates the role of the particle shape on the shear behaviors of recycled aggregate sand by conducting a series of monotonic and cyclic simple shear tests under undrained constant volume conditions. The particles’ morphology parameters are assessed in terms of sphericity, roundness and regularity with microscopic observation and image processing. According to the experimental results, the recycled aggregate sand with irregular shapes mobilizes greater gradients of the flow liquefaction lines under monotonic shear conditions. The irregularity of the particle shape also leads to greater peak shear stress and dynamic shear modulus, indicating stronger shear and liquefaction resistances under the cyclic shearing. Furthermore, the interrelationships between the peak shear stress, dynamic shear modulus and particle shape of the samples are revealed and established by well fitted functions, which could serve as references for the selection of recycled aggregate sand and corresponding designs of the foundation.