Geotextiles and Geomembranes最新文献

This paper presents a novel methodology for assessing water vapour transmission rates (WVTRs) through geomembranes across a wide temperature range, from 20 °C to 90 °C. This expands upon the existing ASTM E96 standard, limited to temperatures up to 32 °C. The study focused on 1.5 mm thick high-density polyethylene (HDPE) and polyvinyl chloride-ethylene interpolymer alloy (PVC-EIA) geomembranes. The WVTR results—0.15 g/m²h at 25 °C for PVC-EIA and 0.02 g/m²h at 30 °C for HDPE—align closely with values reported in existing literature for similar geomembranes at lower temperatures, validating the methodology proposed in this study. Under elevated temperatures, the WVTR of PVC-EIA increased significantly to 4.7 g/m²h at 90 °C, while HDPE showed a slower increase, reaching only 0.4 g/m²h at the same temperature. This disparity is attributed to polymer composition and behaviour differences under high temperatures. This study's methodology provides a dependable approach for accurately measuring WVTR, including high temperatures relevant to various applications where such data is currently lacking.

The role of wall facing is crucial in the design of MSE walls. This study employed two centrifuge model tests specifically designed to analyze walls with two distinct facing types: full-height panel facing and modular block facing. Additionally, surcharge loads were applied to these MSE walls to simulate real-world conditions. The findings from these tests revealed that MSE walls with full-height panel facing exhibited superior performance under the combined effects of self-weight and surcharge loads. The measured maximum horizontal displacements in walls with full-height panel facing and modular block facing were about 55% and 85% of those predicted from current design guidelines at EOS3, respectively. The influence of the surcharge loads on the reinforcement loads was found to be substantial for both wall types, especially for the case of model wall with modular block facing, where the reinforcement loads in the upper half of the wall increased by about 30% from EOS2 to EOS3. The insights garnered from this study contribute to a deeper and more nuanced understanding of the impact of facing types on the practical construction and design of MSE walls, offering valuable guidance for future engineering applications.

The effective interaction mechanisms in the pullout resistance of reinforcements include skin friction mobilized at the soil-solid surface, soil-soil shear resistance, and compressive resistance created against transverse elements. The third component is obtained from passive lateral pressure (LPM) or bearing capacity (BCM) methods. An analytical solution is proposed to determine the pullout capacity of geocell, geogrid, and strengthened geogrids embedded in ordinary and unsaturated soils. For unsaturated soils, the effective stress approach was employed. The solution-predicted results were compared with those obtained from large-scale pullout tests reported in the literature. Results indicated that considering LPM for 2D and 3D reinforcements better agrees with experimental results. The mobilized frictional rib-soil interfaces and the soil-soil shear resistance components generally contribute more to the pullout capacity of the geocell and geogrid, respectively. For the extensibility represented by $m_{pi}$ and flexibility of geocell denoted by ${\alpha }_{pi}$, the values of $m_{pi}$ = 1, 0.7, and 0.3 for the first, second, and third row of geocell, ${\alpha }_{pi}=$ 0.4 for the first row of geocell and 0.25 for the second and subsequent rows are suggested to be considered. Parametric studies showed that the optimum transverse rib spacing is over 50 times the equivalent rib thickness (B_eq).

This paper presents a numerical study on the investigation of microscopic mechanism governing the interaction of woven geotextile and angular sand employing the 3D discrete element method (DEM). The surface texture and tensile properties of the geotextile were simulated using overlapping spherical particles, and the angular sand was simulated using rigid blocks. The DEM models were fully calibrated based on previous experimental data. The shear and dilation zones of sand near the interface were quantitatively determined based on particle displacement gradients. Analysis of contact forces was conducted to explain the microscopic mechanism behind the macroscopic strength evolution. The influence of geotextile surface roughness on the shear strength of the geotextile-sand interface is also discussed. The results show that the failure mode of the woven geotextile-sand interface is a combination of particle sliding failure along the geotextile surface and shear failure of the sand within the shear zone above the interface. There is a rapid redistribution of contact forces prior to reaching peak shear resistance, and the average normal contact force within the shear zone remains relatively constant after the peak shear stress is achieved. A completely developed shear zone stabilizes soil deformation, typically after achieving the peak shear resistance.

Geosynthetics-soil interfaces are exposed to varying temperatures coupled with complex stress states. Quantifying the mechanical response of the interface considering this combined influence of temperature and complex stress is always a huge challenge. This study proposes a new displacement and stress-loading static and dynamic shear apparatus that is capable of testing the geosynthetics-soil interfaces with high and low-temperature controlling function. The apparatus satisfactorily simulates monotonic and cyclic direct shear tests, and creep shear tests on geosynthetics-soil interfaces at temperatures ranging from −30 °C to 200 °C. To validate the functionality of this device, a series of temperature-controlled experiments were conducted on different types of interfaces (sand-geogrid interfaces, sand-textured geomembrane interfaces, sand-smooth geomembrane interfaces). The experimental results indicate that the apparatus can simulate static, dynamic, and creep shear loading on geosynthetics-soil interfaces in high and low temperature environments, and these can be measured reliably. It also manifests that temperature has a non-negligible influence on all mechanical interface responses. These findings highlight the significance and potential of the proposed apparatus and its practical implications.

The method of using Prefabricated Horizontal Drains (PHDs) placed in layers under vacuum preloading can significantly speed up consolidation of staged-filled soil slurry. The PHDs can settle with the soil slurry and maintain their shape/pattern and dewatering capacity largely in comparison with Prefabricated Vertical Drains (PVDs). This study presents a field trial focused on treating dredged sediments using PHDs under vacuum preloading for land reclamation purposes. The staged filling involved in the field trial is analyzed using a finite strain consolidation model based on the piecewise-linear finite-difference method. Then, the effects of horizontal and vertical spacings of PHDs on settlement and vacuum consolidation rate are evaluated, considering various combinations of variables for staged-filled soil. It is found that for soils with low compressibility, the consolidation rate is primarily affected by the vertical spacing of PHD layers. For soils with higher compressibility, the consolidation rate is more significantly affected by the horizontal spacing of PHDs, and the final settlement after vacuum preloading is mainly influenced by the vertical spacing of PHD layers. This study provides practical recommendations for cost-effective design of horizontal and vertical spacings of PHDs in efficiently treating soil slurry with different compressibility and initial conditions.

A theoretical study was conducted to investigate the cross-sectional configurations and the tensile forces of an air-inflated rubber dam anchored on the sidewall of the rigid base. A series of large-scale model tests were conducted using rubber dam models with a cross-sectional perimeter of 1.0 m and a length of 8.5 m. The results obtained from the analytical solutions agree well with those obtained from model tests. It is found that there is an optimum height of the rubber dam, especially for larger anchor depth with the increase of the inflated air pressure. The smaller the anchoring depth the higher the optimum inflated air pressure. The contact length between the rubber dam and the rigid base gradually decreases with the increasing inflated air pressure. The greater the anchor depth, the faster the contact length decreases to zero. Generally, the tensile force linearly increases with the increase of the normalized air pressure and the decrease of the anchor depth.

The present investigation includes experimental and ANN-based intelligent modeling to explore the dynamic interference effect of closely positioned vibrating foundations placed on unreinforced and geogrid-reinforced soil beds. Large-scale field block vibration tests are conducted on isolated and interacting block footings placed on prepared foundation beds at IIT Kanpur, India. The dynamic interaction of various combinations of two-footing assemblies is examined where one footing (active footing) is excited with dynamic loadings, and the other (passive footing) carries static loadings. The tests involve three eccentric force settings for four distinct footing combinations at different clear spacings and reinforcement conditions. The responses of both footings are recorded at different loading frequencies. The interaction effect is presented in terms of the transmission ratio plotted against the frequency ratio. Additionally, an Artificial Neural Network (ANN) model is developed using the recorded field datasets to anticipate the dynamic interference effect. The predicted outcomes of the ANN model demonstrate promising agreement with the experimental findings reported in the literature, indicating the reliability and robustness of the intelligent model.

The efficiency of geosynthetics has been proven in stone column-reinforced foundations. In this paper, loading tests were conducted on three stone column-reinforced foundations, experiencing four freeze-thaw cycles. The effects of geosynthetic encasement and lateral reinforcement were investigated on the behavior of ordinary stone column (OSC) – reinforced and geosynthetic encased stone column (GESC) – reinforced foundation. The results showed that particles of OSCs spread into foundation soil during freezing and thawing, and top of OSCs were replaced by foundation soil. The temperature gradient along the depth in OSC-reinforced foundation was smaller than in GESC-reinforced foundations, resulting in a lower negative pore pressure at the beginning of freezing. However, it was found that geosynthetic encasement helped maintain the integrity of GESCs, and increased the stress concentration ratio (SCR) during thawing, which led to a lower excess pore pressure in GESC-reinforced foundations. The lateral reinforcement was also found to not only reduce the differential settlement between GESCs and soil during thawing, but also restrain the frost heave during freezing. The tensile membrane effect of lateral reinforcement redistributed the stress and the overburden pressure throughout the freeze-thaw process. More water moved upwards during freezing in the OSC-reinforced foundation, leading to a larger amount of frost heave. However, the moisture migration became complex in the OSC-reinforced foundation, as OSCs were damaged by freeze-thaw cycles.

This study conducted five centrifuge model tests to investigate the deformation characteristics of the Geosynthetics Reinforced Soil (GRS) abutments under vertical loads, considering the setback distance a_b and beam seat width B as two major influencing factors. Test results show that a linear correlation existed between the maximum lateral facing displacements D_L and the maximum settlements at the top of the GRS abutments D_v. The a_b and the B had different effects on the deformation characteristics of the GRS abutments as well as the relationship between the D_L and the D_v. The total volumetric strains of the GRS abutments were smaller than 0.3% for all the cases investigated in this study, indicating that it was reasonable to use the assumption of zero-volume change for the deformation calculation of the GRS abutments. This study proposed an improved semi-empirical method to describe the relationship between the D_L and the D_v. Centrifuge test results and data collected from the literature were used to validate the improved method. It was concluded that the improved method had the advantage of considering the effects of the a_b and the B separately and therefore significantly improved the prediction accuracy of the deformations of the GRS abutments.