Estimation of interface frictional anisotropy between sand and snakeskin-inspired surfaces

Abstract

The transmission of loads across the soil-structure mobilizes direction-dependent shear resistance, which can be selectively used to design geo-structures. A previous study confirmed the frictional anisotropy induced by the interface between the soil and snakeskin-inspired surfaces. However, it is necessary to estimate the interface friction angle quantitatively. In this study, a conventional direct shear apparatus is modified, and 45 cases are performed in two-way shearing directions between bio-inspired surfaces and Jumunjin standard sand under three vertical stresses (50, 100, and 200 kPa). The results show that: (1) shearing against the scales (cranial shearing) mobilizes larger shear resistance and produces a dilative response than shearing along the scales (caudal shearing) and (2) higher scale height or shorter scale length exhibits dilative tendency and produces higher interface friction angle. Further analysis is conducted to capture the frictional anisotropy as a function of the scale geometry ratio, which reveals that the interface anisotropy response is more pronounced during cranial shearing in all the cases, and the difference in the interface friction angle for the caudal → cranial test is higher than that for the cranial → caudal test at the given scale ratio.

Quantification of resistance to Meloidogyne incognita in okra cultivars using linear and nonlinear analyses of growth parameters and nematode infestations

“…The linear and non-linear equations estimated from both studies are shown in (Table 6). As suggested by previous studies, the correlation coefficient higher than 0.8 demonstrate excellent prediction capability of an equation (Lee et al 2023;Nawaz et al 2022 ). Based on this rationale, the results confirm the improved prediction ability of the proposed correlations.…”

Interface Frictional Anisotropy of Dilative Sand

“…Indeed, the changing trend of interface friction angle is affected by the starting shear direction while the shearing sequence has no effect on the interface friction angle. Previous studies 16,21 revealed that volumetric contraction at the trailing end of the scale during the starting shearing densified soil around the scale, difference in the interface friction angle between the cranial and caudal shearing directions was pronounced depending on the starting shearing direction, and thus the caudal first-caudal second shearing sequence produces larger friction difference than the cranial first-cranial second shearing sequence. However, the current study observes that the interface friction angle in the first shearing cycle is almost identical to that in the second shearing cycle, and thus densification effect during the first shearing is diminished.…”

“…Those potential problems eventually hinder quantifying shear response [28][29][30][31] . Previous study modified the conventional direct shear apparatus for soil-snakeskin-inspired surface tests and soil-soil tests 21 . Fig.…”

“…This study uses six snakeskin-inspired surfaces made of polycarbonate material. Each surface is comprised of a 72 mm textured central part and a 45 mm untextured part on both sides to ensure enough distance from the sidewalls of the shear box [more details refer to 21 ]. The different combinations of scale geometries are listed in Table 1.…”

“…The bioinspired pile pulled out in the cranial direction produces less vertical displacement and higher skin friction resistance than the caudal direction with smooth surface pile 18 . In addition, other studies explored the interfacial shear behavior between various sands and bio-inspired surfaces during the two-way interface direct shear tests 16,21 . Those sands showed pronounced contractive tendencies due to more rounded particle shape, and dependency of interface behavior on stress history.…”