Geotextiles and Geomembranes最新文献

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.

Cavity formations by soil dissolution or underground collapses are at the origin of large surface subsidence that constitutes a risk of damage or failure for infrastructures. Soil reinforcement with geosynthetics positioned at shallow depth is an economical and functional solution to reduce the induced surface settlements. Previous research has mainly focused on the load transfer mechanism and the arching effect in cohesionless reinforced backfills when the cavity opens. Experimental and numerical studies dealing with cohesive soils are very rare, although this situation is commonly found in practice. To overcome this lack of knowledge, a numerical study based on Discrete Element Modelling is carried out to better understand the load transfer mechanisms that are mobilized in cohesive embankments prone to underground cavity opening. The results are compared with experimental data obtained on a small-scale laboratory model in terms of vertical and horizontal displacements of both soil and geosynthetics. The numerical results focus on the collapse mechanisms of the cohesive embankment, the load transfer mechanisms, the shape of the vertical load distribution acting on the geosynthetic layer, the strain and traction forces within the geosynthetic sheet.

Hydraulic conductivity of conventional mock sodium bentonite (Na–B) and bentonite-polymer (B–P) geosynthetic clay liners (GCLs) were evaluated with three synthetic leachates that are chemically representative of aggressive leachates from coal combustion product (CCR) (I = 3179 mM), mining waste (MW) (I = 2127 mM, pH = 2.0), and municipal solid waste incineration ash landfill (MSWI) (I = 2590 mM). The mock B–P GCLs were created by dry mixing bentonite with branched, linear, or crosslinked polymer. The polymer loading of mock B–P GCLs ranged from 3 to 15%. Comparative tests were also conducted with Na–B GCLs. The mock Na–B GCLs cannot maintain low hydraulic conductivity to aggressive CCR, MW, and MSWI leachates. Mock B–P GCLs with 10% branched polymer had low hydraulic conductivity (< 1.0 × 10⁻¹⁰ m/s) to synthetic MW and MSWI leachates at 20 kPa effective confining stress, whereas the hydraulic conductivity of mock B–P GCLs with 10% linear or crosslinked polymer ranged from 1.5 × 10⁻⁹ to 1.4 × 10⁻⁷ m/s. As the effective stress increased, the B–P GCLs branched polymer showed a faster decreasing trend than that of Na–B and B–P GCLs with linear or crosslinked polymer.

Nowadays, the utilization of prefabricated vertical drains (PVDs) or prefabricated horizontal drains (PHDs) in combination with vacuum preloading (VP) has emerged as a prevalent and effective strategy for treating dredged slurry. Nevertheless, both of these methods possess certain inherent limitations. In this study, three groups of parallel model experiments are conducted to compare the effectiveness of PVDs, PHDs and PHDs-PVDs under step VP in treating dredged slurry. Firstly, the water discharge, settlement and pore water pressure are monitored during the experiments. Then, the shear strength and water content of the soil at various locations after experiments are measured and the soil profiles at different cross sections are gauged. Additionally, soil excavation is conducted to evaluate the deformation characteristics of PHDs and PVDs. Finally, a scanning electron microscopy analysis is to assess the clogging of filter membranes. The results indicate that the proposed method can combine the advantages of both PHDs and PVDs, effectively enhancing the treatment effectiveness of the slurry. These findings elucidate the dewatering and reinforcement mechanism of PHDs-PVDs-VP and provide valuable insights for its practical engineering application.

Traffic-induced cyclic loading generates repetitive stresses and cumulative deformations on the GRS abutments, which affect the serviceability of GRS abutments. To evaluate the stress distribution of GRS abutments under cyclic traffic loading, this paper presents reduced-scale GRS abutment models constructed with sand backfill and geogrid reinforcements. The GRS abutment models were subjected to staged cyclic loading with different cyclic loading amplitudes to investigate the influences of cyclic loading amplitude, bridge superstructure load, and reinforcement vertical spacing on the dynamic soil stress distributions. The results indicate that the increase in residual stresses due to stress redistribution induced by cyclic loading is most pronounced at the top of the abutment, while there is little stress redistribution down to the foundation level. Increasing the static load of bridge superstructure or the amplitude of cyclic loading results in an increase in the incremental dynamic vertical soil stresses. Reinforcement vertical spacing does not significantly impact the incremental dynamic vertical soil stresses under cyclic loading, while the cyclic load has the most significant influence. Closer reinforcement vertical spacing could provide stronger lateral confinement, resulting in larger dynamic lateral soil stresses behind wall facing.

Geobag stability has not been extensively studied under river current loading. In this study, the impacts of geobag characteristics (shape, bag material, and fill ratio of sand) and channel side slope (flat and 1V:2H) on a single geobag's stability were systematically investigated in a physical model to form the solid foundation for the research of group geobags. Overall, a geobag with a higher fill ratio, combined with the more flexible cloth material, was found to be the most stable. Critical Shields parameters were estimated between 0.0018 and 0.019, and the cross-sectional averaged flow velocity at incipient motion ranged from 0.49 m/s to 1.08 m/s. A shape factor was introduced to better describe the relationship between geobag characteristics and their stability on both riverbed configurations. Both the fill ratio and the bed side slope had higher importance on the geobag's stability compared to the relative depth, bag shape, and angle of flexibility.

Innovation in the use of geosynthetics in roadway applications has resulted in the development of several different products, such as asphalt reinforcement geogrids and paving mats to minimize reflective cracks and limit moisture infiltration. For a proper performance of the reinforced asphalt systems, an adequate interface bond strength has proven to be crucial. However, the influence of the different paving interlayer characteristics, combined with tack coat types, and tack coat rates on the interface bond strength remains unclear. In this study, a comprehensive program of interface shear tests was conducted using Leutner shear device and laboratory-prepared reinforced asphalt specimens. The program involved eight geosynthetic types, two tack coat types, and three application rates. Results revealed that the geosynthetic type, tack coat type and rate, as well as the interactions among the parameters significantly affect interface bond strength. Multiple linear regression analysis indicated that geogrid aperture area, geosynthetic thickness, geotextile backing thickness, and the presence of bitumen coating are the most affecting parameters on bond strength. A predictive model for the bond strength based on geosynthetic parameters is presented. Based on literature results for specimens extracted from the field, the proposed predictive models were found to adequately predict interface bond strength.

Geosynthetic-reinforced soil (GRS) walls built on hillslopes are more increasingly incorporated with geo-composite side drain in order to prevent the side-seepage entering the fill. This study evaluates the long-term moisture, pore-water pressure, and shear modulus, of a 6.5 m-high geogrid-reinforced soil wall in western Thailand. Through extensive field monitoring and in-situ spectral analysis of surface wave (SASW) tests, conducted during the Years 2018–2019, as well as laboratory tests, several key findings emerge. Free-free resonant frequency (FFR) testing of non-reinforced samples reveals the role of soil wetting and drying history and hysteresis in the stiffness-moisture relationship. In-situ pore-water pressure was found to be highest below the road surface near the wall face, decreasing with depth due to underdrainage, with values ranging from −27 to 5 kPa. The intersection of the side drainage board with the underdrain bottom layer shows the highest water content. In-situ and laboratory-derived soil-water retention curve (SWRC) were found to differ at greater depths. In unsaturated conditions, the in-situ small strain modulus of GRS appeared insensitive to suction stress below 10 kPa but was slightly affected under positive pore-water pressure, with multiple linear regression modeling indicating a dependency of stiffness on depth and pore-water pressure.