Drained cyclic behaviour and state-dependent stress–dilatancy relationship of sand in direct simple shear tests

• Published in: Soil dynamics and earthquake engineering (1984) 2023-05, Vol.168, p.107801, Article 107801
• Main Authors: Al Tarhouni, Mahmud Amer, Hawlader, Bipul
• Format: Article
• Language: English
• Subjects: Constant stress; Cyclic compaction; Cyclic stress–dilatancy; Direct simple shear; Multi-stage loading
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2023.107801

Direct simple shear tests were conducted to investigate the cyclic behaviour, dynamic properties, and stress–dilatancy relationship of fine-grained silica sand for a wide range of constant vertical stresses, including low stresses. Multi-stage cyclic tests were conducted by increasing the shear strain amplitude from low to high values in subsequent loading stages. Test results show that the volumetric strain is related to the vertical stress and shear strain amplitude. The cyclic shear modulus decreases and the damping ratio increases with shear strain amplitude, and they are influenced by the low-amplitude cyclic loading history. The volume change is related to the cyclic stress–dilatancy relationship, which depends on the vertical stress, shear strain amplitude, number of cycles, and shearing direction. In some tests, the stress–dilatancy relationship can be represented by two parallel lines for unloading and reloading, except for the initial parts. The increase in density with cyclic loading reduces the contractive behaviour and increases the dilative response in the large-amplitude loading cases, which reduces the rate of volumetric compaction with the number of cycles. •Multistage cyclic tests were conducted using a direct simple shear apparatus that has been designed for relatively low-stress level tests.•Tests were conducted under constant vertical stress of 12.5–400 kPa to investigate normal stress effects on drained cyclic behaviour.•Test results show that stress–dilatancy of sand in cyclic loading is not unique but highly depends on normal stress, density, number of the loading cycles, shear strain amplitude and loading direction.•Unique linear or two almost parallel nonlinear lines of stress–dilatancy, as found in some previous studies, is valid only for certain normal stresses and shear strain amplitudes.