This study investigates the coupled effects of scaled geogrid axial stiffness and maximum particle size on the mechanical behaviour of geogrid-encased lightly cemented gravel materials (LCGMs). Unconfined compression tests were conducted on specimens with four maximum particle sizes and corresponding scaled geogrid axial stiffnesses at cement contents of 1 and 2% under controlled bulk density. The results show that strength and stiffness consistently decreased with increasing maximum particle size at both cement contents, with power-law-based extrapolated estimates indicating maximum reductions of approximately 65 and 70%, respectively, relative to the smallest particle size tested. In contrast, Poisson’s ratio and failure pattern were only marginally affected. Geogrid reinforcement provided an approximately consistent strength enhancement across the investigated scaling factors, indicating no clear interaction between geogrid scaling and particle-size scaling. Empirical power-law relationships were developed to describe the particle-size dependence of the mechanical properties of LCGMs and to estimate the corresponding properties at the prototype particle size.
Fiber reinforcement has been widely recognized as an effective approach for improving the liquefaction resistance of sandy soils. However, existing studies have predominantly focused on siliceous sand, whereas the liquefaction behavior of fiber-reinforced calcareous sand remains insufficiently understood. In this study, a series of cyclic simple shear tests was conducted to investigate the evolution of excess pore pressure and shear strain in fiber-reinforced calcareous sand, with emphasis on the effects of cyclic stress ratio (CSR) and fiber content (Fc). The results indicate that increasing Fc significantly improves the liquefaction resistance of calcareous sand, particularly under low CSR conditions. As CSR increases, the relationship between the excess pore pressure ratio (ru) and cycle ratio (N/NL) gradually evolves from an inverse S-shaped pattern to a hyperbolic pattern, whereas increasing Fc produces the opposite trend. Clean calcareous sand exhibits a flow liquefaction mechanism, while fiber reinforcement promotes a cyclic mobility response similar to that observed in dense sand. Furthermore, the coupled evolution of ru and double-amplitude shear strain (γDA) is closely correlated and is governed primarily by CSR rather than Fc, exhibiting two distinct stages. Based on this relationship, a shear strain-based excess pore pressure generation model was developed for fiber-reinforced calcareous sand, providing a useful framework for effective stress-based seismic analysis of reinforced calcareous sand geotechnical structures.
The longevity of three linear low-density polyethylene (LLDPE) geomembranes (GMBs) with thicknesses of 1.0, 1.5, and 2.0 mm exposed to a pH 13.5 pregnant liquor solution representative of some of the highly alkaline gold and silver heap-leaching solutions was investigated for over 14 years. The GMBs were manufactured from nominally the same resin; however, the 1.5 mm GMB was produced from a different resin lot and with a different antioxidant formulation. Changes in key index properties of samples immersed at 85, 75, and 65 °C were monitored, including oxidative induction time, high-load melt index, tensile break properties, and stress-crack resistance. Based on the observed laboratory degradation rates, Arrhenius modelling was used to project the time to nominal failure (tNF) for all three GMBs. The results show that the 1.5 mm-thick GMB exhibited the best overall performance, with tNF projections increasing from the 1.0 mm to the 2.0 mm and to the 1.5 mm GMB. Immersed in the same pH 13.5 solution, the 1.5 mm LLDPE had a longer tNF than a high-density polyethylene (HDPE) GMB of the same thickness. The practical implications of these findings are discussed.
Wicking geotextiles have been introduced with the aim of improving and accelerating drainage under both saturated and unsaturated soil conditions. This study evaluates the hydraulic performance of three wicking geotextile products in comparison with a control test without geotextiles. The tested wicking materials included one nonwoven and two wicking woven geotextiles. Laboratory experiments were conducted using a soil column test box incorporating a trench system, where the geotextiles were installed beneath the soil column and bent into a trench full of uniformly sized aggregate to simulate urban road subdrain conditions. Base materials investigated included virgin crushed limestone and recycled concrete aggregate. The soil was saturated and subsequently allowed to drain and monitored with moisture sensors. To assess potential suitability in cold regions, additional tests were performed after subjecting the soil column with geotextiles to one freeze-thaw cycle. Environmental scanning electron microscopy analyses were performed on the geotextile samples before and after freeze-thaw exposure. The results demonstrate that wicking geotextiles can significantly enhance the overall drainage performance of granular layers compared with the control section with varied improvement depending on the geotextile and fill material types. Freeze-thaw cycling influenced drainage efficiency and continued to outperform the control section after the conditioning.
One shaking table model test with a uniform-length geogrid layout was reproduced numerically for validation, followed by FLAC3D analyses of 14 full-scale cases with uniform-length and stepped layouts. The test showed a rotation-dominated facing response and migration of the largest monitored settlement from the near-facing region toward the geogrid-end region. Numerical results revealed three deformation stages, from near-facing localization through propagation into the reinforced backfill to middle-geogrid-dominated deformation, accompanied by downward migration of the geogrid high-strain zone. Geogrid length had little influence on maximum settlement at 0.05–0.20 g. At 0.30–0.60 g, settlement became concentrated near the geogrid terminations, and differences among geogrid-length cases became pronounced. At 0.50 g, increasing geogrid length from 0.60H to 1.50H, where H denotes the wall height, reduced maximum facing displacement and maximum settlement by 14.5% and 42.2%, respectively. Stepped layouts redistributed settlement between the short- and long-geogrid termination regions, producing single- or multi-peak profiles. With maximum surface settlement as the primary criterion, no stepped layout showed a clear advantage at 0.10 g. At 0.30 and 0.50 g, SL-3, comprising three upper 0.60H-long layers and 22 lower 1.00H-long layers, produced the lowest maximum settlements among the stepped layouts investigated.
