Development of a Large-Size Cyclic Direct Simple Shear Device for Characterization of Ground Materials with Oversized Particles

Zekkos, Dimitrios; Athanasopoulos-Zekkos, Adda; Hubler, Jonathan F.; Fei, Xunchang; Zehtab, Kaveh H.; Marr, W. Allen

doi:10.1520/gtj20160271

Cited by 25 publications

(4 citation statements)

References 53 publications

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“…To the authors' knowledge, the DSS devices in use today are unable to satisfy such high stiffness requirements. In addition, Zekkos et al (2018) and Zehtab et al (2019) conclude that a sample height change, even if it is limited to the value prescribed by ASTM D6528, can still significantly affect the monotonic and CDSS response of sand samples.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Apparatus Stiffness on the Results of Cyclic Direct Simple Shear Tests on Dense Sand

Konstadinou

Bezuijen

Greeuw

et al. 2021

Geotechnical Testing Journal

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A series of undrained cyclic direct simple shear (CDSS) tests on dense Toyoura sand has been performed with the aim to investigate the influence of the stiffness of the DSS device on test results. To this end, springs were installed to reduce deliberately the stiffness of the apparatus. It is shown that the cyclic resistance of the sand depends strongly on the rigidity of the apparatus frame. In particular, as the stiffness of the DSS device increases, the number of loading cycles required to reach liquefaction decreases. This pronounced apparatus-stiffness dependence is of great practical concern in geotechnical engineering because it directly implies that the CDSS response of a soil sample can be predominantly controlled by the stiffness of the apparatus and not by the soil behavior alone. In addition, the test results indicate that the effect of equipment compliance in cyclic undrained DSS testing can be minimized when the ratio of the stiffness of the tested sand sample to the stiffness of the apparatus has a significantly low value.

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Section: Discussionmentioning

confidence: 99%

The Influence of Apparatus Stiffness on the Results of Cyclic Direct Simple Shear Tests on Dense Sand

Konstadinou

Bezuijen

Greeuw

et al. 2021

Geotechnical Testing Journal

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“…An Electromechanical Dynamic Cyclic Simple Shear device manufactured by GDS Instruments was used to perform all the constant-volume cyclic DSS tests presented herein. Constant-volume conditions were enforced with Geotechnical Testing Journal the active height control system implemented in the Electromechanical Dynamic Cyclic Simple Shear device, which achieved vertical strain fluctuations of less than 0.01 % in all tests, which met the 0.05 % criterion recommended by ASTM D8296-19 and the 0.025 % threshold recommended by Zekkos et al (2018). Cylindrical samples near 22 mm in height and 70 mm in diameter were laterally enclosed within stacked Teflon-coated steel rings and a latex membrane of about 0.3 mm in thickness.…”

Section: Equipmentmentioning

confidence: 99%

Development and Evaluation of Preconditioning Protocols for Sand Specimens in Constant-Volume Cyclic Direct Simple Shear Tests

et al. 2022

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Textured platens are often used to improve the transfer of shear stresses from the platens to the soil specimen during direct simple shear (DSS) tests. However, constant-volume DSS tests when textured platens are used can be affected by inadequate engagement of the soil at the platen-soil interface, leading to large reductions in the vertical stress at the start of shearing.The application of a preconditioning sequence involving small-strain drained cycles prior to constant-volume shearing can improve engagement at the platen-soil interface, but when excessively implemented, it can also have adverse effects on the measured soil behavior (e.g., strength, stiffness). A series of constant-volume cyclic DSS tests preceded by different preconditioning sequences was performed to evaluate the effect of preconditioning on the engagement of sand specimens at the platen-soil interface and the stress-strain response of these specimens. Results showed that textured platens that are properly engaged with sand specimens can reduce slippage at the platen-soil interface. This engagement can be achieved by applying a limited number of small-strain drained cycles at a low vertical stress while still obtaining representative soil behavior during the subsequent equivalent undrained constantvolume cyclic loading. Although the preconditioning protocol presented herein is specific to the testing equipment and materials considered, similar procedures may be adopted to develop preconditioning protocols for other soils, platens, and testing devices.

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“…An electromechanical dynamic cyclic simple shear (EMDCSS) device manufactured by GDS Instruments was utilized to perform constant-volume (equivalent undrained) cyclic direct simple shear (DSS) tests. The active height control system implemented in the EMDCSS device allowed constant-volume DSS tests to be performed with vertical strains below the threshold of 0.05% recommended by ASTM (2019) and below the 0.025% threshold recommended by Zekkos et al (2018). Samples of about 70 mm in diameter and 22 mm in height were laterally enclosed within stacked Tefloncoated steel rings and a latex membrane of about 0.35 mm (60.05 mm) in thickness.…”

Section: Testing Equipment and Proceduresmentioning

confidence: 99%

Mechanisms of shear strain accumulation in laboratory experiments on sands exhibiting cyclic mobility behavior

Humire

Ziotopoulou

2022

Can. Geotech. J.

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The factors and mechanisms controlling the accumulation of shear strains of clean uniform sands exhibiting cyclic mobility behavior under level-ground conditions are examined. This phenomenon is investigated through a series of constant-volume cyclic direct simple shear (DSS) tests subjected to uniform and irregular loading conditions, and undrained cyclic element tests collected from the literature. Experimental data show that the rate of shear strain accumulation per loading cycle depends on the relative density, cyclic stress amplitude, and effective overburden stress. Mechanisms of shear strain accumulation are investigated by decoupling the shear strain developed in each loading cycle in two components: γ0, developed at near-zero effective stress, and γd, developed during dilation. Results show that γ0 mostly depends on the shear strain history, while γd depends on the cyclic stress amplitude and the relative density. These dependencies of γd and γ0 are used to provide an explanation for the gradual decrease of the rate of shear strain accumulation that is observed while increasing the number of post-triggering loading cycles in tests performed on dense specimens.

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Development of a Large-Size Cyclic Direct Simple Shear Device for Characterization of Ground Materials with Oversized Particles

Cited by 25 publications

References 53 publications

The Influence of Apparatus Stiffness on the Results of Cyclic Direct Simple Shear Tests on Dense Sand

The Influence of Apparatus Stiffness on the Results of Cyclic Direct Simple Shear Tests on Dense Sand

Development and Evaluation of Preconditioning Protocols for Sand Specimens in Constant-Volume Cyclic Direct Simple Shear Tests

Mechanisms of shear strain accumulation in laboratory experiments on sands exhibiting cyclic mobility behavior

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