Key Takeaways & Executive Findings
- •• Transparent sand made of fused quartz and refractive index-matched oil exhibits dynamic characteristics similar to natural sands, validating its use in dynamic model tests. • Higher initial shear stress ratios, lower relative densities, and higher cyclic stress ratios accelerate cyclic deformation, pore pressure buildup, and stiffness degradation. • Cyclic liquefaction resistance decreases with increasing initial shear stress ratio or decreasing relative density, and both Booker and power law models accurately predict pore pressure. • Transparent sand shows comparable cyclic liquefaction resistance and Kα correction factor to natural sands, supporting its application in visualizing internal soil behavior under seismic loading.
Abstract
Transparent sand is a special material to realize visualization of concealed work in geotechnical engineering. To investigate the dynamic characteristics of transparent sand, a series of undrained cyclic simple shear tests were conducted on the saturated transparent sand composed of fused quartz and refractive index-matched oil mixture. The results reveal that an increase in the initial shear stress ratio significantly affects the shape of the hysteresis loop, particularly resulting in more pronounced asymmetrical accumulation. Factors such as lower relative density, higher cyclic stress ratios and higher initial shear stress ratio have been shown to accelerate cyclic deformation, cyclic pore water pressure and stiffness degradation. The cyclic liquefaction resistance curves decrease as the initial shear stress ratio increases or as relative density decreases. Booker model and power law function model were applied to predict the pore water pressure for transparent sand. Both models yielded excellent fits for their respective condition, indicating a similar dynamic liquefaction pattern to that of natural sands. Finally, transparent sand displays similar dynamic characteristics in terms of cyclic liquefaction resistance and Kα correction factor. These comparisons indicate that transparent sand can serve as an effective means to mimic many natural sands in dynamic model tests.
1. Introduction
Currently, transparent soil is widely used in tests to facilitate the visualization of internal soil deformation, akin to the CT fluoroscopy technique employed in geotechnical engineering [1−3]. Fused quartz saturated with refractive index-matched oil mixture has been identified to effectively mimic the static characteristics of natural sand as through a series of triaxial compression tests [4]. EZZEIN et al [5] demonstrated that fused quartz grains exhibit similar behaviors in shape, material composition, shear strength, and permeability to natural silica sands. Based on these results, transparent sand manufactured by fused quartz has been applied in various statics model tests. WANG et al [6] utilized fused quartz particles ranging from 0.5 to 1 mm to investigate the internal sliding mechanism attributed to the soil-rock contact interface in slopes. ZHOU et al [7] examined the reinforced effect of umbrella-shaped cables by analyzing the deformation characteristics of transparent sand under rapid water drawdown conditions. The application of transparent sand has led to extensive research on deformation around piles, including the installation effect of X-section cast-in-place concrete pile [8], soil movement during the installation of flat-ended piles and pipe piles [9], and pile buckling deformation under axial load [10]. Furthermore, fused quartz has been employed to investigate excavation-induced sand deformation processes associated with tunneling, with results subsequently validated through discrete element method (DEM) simulations [11].
In previous studies, transparent sand manufactured by fused quartz has primarily been employed in statics model tests. For geotechnical engineering, dynamic model test is also an essential method to investigate the earthquake-induced issues [12−14]. It is necessary to investigate the dynamic internal deformation of soil and structures using transparent sand. Due to the significant application prospects, relevant dynamic characteristics and similarities to natural sands should be studied with appropriate dynamic unit tests. Utilizing resonant column tests and cyclic torsional shear tests, KONG et al [15−17] measured the evolution of dynamic shear modulus and damping ratios with increasing shear strain, as well as the liquefaction resistance of fused quartz saturated with different pore liquids. The results showed that transparent sand with mixed oil exhibits similarities to natural sands in these three properties. KHASHILA et al [18] conducted a comparative study on liquefaction resistance of natural sand under cyclic simple shear test and cyclic triaxial test. They proposed that cyclic simple shear apparatus is superior for assessing liquefaction susceptibility compared to the cyclic triaxial apparatus, as the horizontally loaded cyclic shear stress more closely emulates the field conditions during vertical wave propagation.
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ZHAO Jin-qiao, OU Qiang, JIANG Chun-yong, DING Xuan-ming, ZHOU Hang, YANG Chang-wei, DENG Wei-ting (2025). Undrained cyclic simple shear characteristics of transparent sand manufactured by fused quartz. Journal of Central South University. https://doi.org/10.1007/s11771-025-6053-9
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Frequently Asked Questions
What is transparent sand and how is it manufactured?
Transparent sand is a special material made by saturating fused quartz grains with a refractive index-matched oil mixture, which makes the soil transparent to visualize internal deformations in geotechnical model tests.
What dynamic properties of transparent sand were investigated in this study?
The study investigated undrained cyclic simple shear characteristics, including hysteresis loop shape, cyclic deformation, pore water pressure generation, stiffness degradation, and cyclic liquefaction resistance under various initial shear stress ratios and relative densities.
How does initial shear stress affect the behavior of transparent sand?
Increasing initial shear stress ratio significantly affects the hysteresis loop shape, leading to more pronounced asymmetrical accumulation, and accelerates cyclic deformation, pore pressure buildup, and stiffness degradation, while reducing cyclic liquefaction resistance.
Can transparent sand mimic natural sands in dynamic tests?
Yes, transparent sand exhibits similar dynamic characteristics to natural sands, including cyclic liquefaction resistance and Kα correction factor, making it an effective substitute for visualizing internal soil behavior in dynamic model tests.
What models were used to predict pore water pressure in transparent sand?
The Booker model and a power law function model were applied to predict pore water pressure, and both provided excellent fits for their respective conditions, indicating similar dynamic liquefaction patterns to natural sands.
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