In order to improve the understanding on static liquefaction phenomenon, this paper presents an insight into the instability mechanism of a silty sand originating from the Sakarya region (Turkey). Monotonic undrained simple shear tests were performed in either strain-controlled or stress-controlled modes. The interpretation of the experimental results allowed us to draw three interesting conclusions on instability conditions: (1) Hill’s stability postulate can be conveniently used to identify the onset of instability for strain-controlled tests, whereas in stress-controlled conditions, an alternative new parameter η (modified apparent viscosity) was introduced. Depending on the strain rate, η allows to identify stability conditions more clearly than second-order work; (2) the value of the pore pressure ratio at the onset of instability (ru;is), ranging between 0.30 and 0.50, is linearly linked to the state parameter ψ; and (3) at the onset of instability, the dependence of both the major and minor principal stress directions (αis and βis) and Lode’s angle (θis) on ψ was also observed. These findings are expected to be of some help for a more consistent approach to the constitutive modeling of the static instability mechanism.
Instability Conditions of a Silty Sand under Monotonic Loads in Simple Shear Tests / Mele, Lucia; Kocaman, Kadir; Özocak, Aşkın; Flora, Alessandro. - In: JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING. - ISSN 1090-0241. - 150:11(2024). [10.1061/jggefk.gteng-12494]
Instability Conditions of a Silty Sand under Monotonic Loads in Simple Shear Tests
Lucia Mele
;Alessandro Flora
2024
Abstract
In order to improve the understanding on static liquefaction phenomenon, this paper presents an insight into the instability mechanism of a silty sand originating from the Sakarya region (Turkey). Monotonic undrained simple shear tests were performed in either strain-controlled or stress-controlled modes. The interpretation of the experimental results allowed us to draw three interesting conclusions on instability conditions: (1) Hill’s stability postulate can be conveniently used to identify the onset of instability for strain-controlled tests, whereas in stress-controlled conditions, an alternative new parameter η (modified apparent viscosity) was introduced. Depending on the strain rate, η allows to identify stability conditions more clearly than second-order work; (2) the value of the pore pressure ratio at the onset of instability (ru;is), ranging between 0.30 and 0.50, is linearly linked to the state parameter ψ; and (3) at the onset of instability, the dependence of both the major and minor principal stress directions (αis and βis) and Lode’s angle (θis) on ψ was also observed. These findings are expected to be of some help for a more consistent approach to the constitutive modeling of the static instability mechanism.File | Dimensione | Formato | |
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