Geotextiles and Geomembranes最新文献

The polymer-alloy geocell sheets (PAGS) represent a novel geocell material developed to replace conventional geocell materials. Accelerated creep testing, a convenient and precise performance evaluation method, presents a viable alternative to traditional creep testing for obtaining long-term creep strains. Nonetheless, there is a lack of prediction and in-depth exploration of accelerated creep testing. This paper aims to assess the efficacy of using the non-linear three-component (NLTC) model to simulate the accelerated creep behavior of PAGS. The predictive accuracy of the NLTC model has undergone evaluation through a comparison between stepped isothermal method (SIM) accelerated creep experimental tests and numerical simulations. Subsequently, the validated NLTC model was employed to simulate the time-temperature superposition method (TTSM), time-stress superposition method (TSSM), and stepped isostress method (SSM) accelerated creep tests, thereby verifying its effectiveness in predicting all accelerated creep tests. The results indicate that the NLTC model can effectively simulate creep deformation induced by temperature increases, particularly the temperatures below 41 °C. Although some errors are observed at elevated temperatures, it is within the acceptable range of 17.4%. Numerical simulation results of TTSM, TSSM, and SSM tests also suggest the model's proficiency in simulating the accelerated creep behavior by temperature and creep load increasing.

Although Novel Polymeric Alloy (NPA) geocells have been applied to stabilize road bases against the freeze-thaw (F-T) damage in practice, the relevant research lags the application. A scarcity of research has been reported to comprehensively evaluate the benefits of geocell stabilization in enhancing the F-T performance of bases. This study aims to investigate quantitatively the F-T performance of geocell-stabilized bases, focusing on two influencing factors-i.e., water supply and degree of compaction in the bases. A series of model-scale experimental tests (19 tests) was conducted using an upgraded customized apparatus. The results showed that the inclusion of geocells was beneficial for reducing frost heave and thaw settlement as well as mechanical properties (i.e., stiffness and ultimate bearing capacity) of road bases. The benefit of geocells was more remarkable for the well compacted bases than for the poorly compacted bases. The benefit was more pronounced in the open system than in the closed system.

Accurately predicting stress-strain characteristics is crucial to ensuring the regulated capacity and controlled deformation of the tubes during and after construction. However, research on the shear strength of geotextile tubes under surcharge loading, especially after dewatering, is insufficient. This study proposes an analytical model with a Stress-State Boundary (SSB) and Yield Function to comprehensively describe the stress-strain behavior of Load-Bearing Geotextile Tubes (LGTs). The SSB is designed to predict the initial state of stress in the infill soil prior to load application, while the Yield Function is formulated to express the shear stress path experienced by the LGT before fabric failure. The model considers various factors that affect LGT behavior, including diverse soil mechanical parameters, nonlinear fabric stiffness, initial tension due to self-weight and principal stress axes rotation. Results show that a decrease in Poisson's ratio corresponds to an increase in failure stress. Moreover, it was demonstrated that the axial failure strain can be influenced by the geotextile linear or nonlinear behavior. Notably, the study highlights that tube height and inclination angle significantly affect the geotextile's confining effect. Beyond theoretical contributions, the analytical model serves as a valuable tool for optimizing geotextile tube design and execution, contributing to project success and longevity through enhanced structural stability.

This study conducted laboratory tests on soft clayey soils to investigate the effectiveness of the combinations of vacuum-surcharge preloading and electro-osmotic treatment (EOC-VPM-SPM). To minimize the loss of vacuum pressure and mitigate clogging of the drainage system during the consolidation process, two improved methods were developed by optimizing technical characteristics and geometric layout of drainage boards. In the EOC-Alternate VPM-SPM method, alternate vacuum pressure was incorporated using two drainage boards with different lengths in the VPM system, combined with EOC to improve consolidation efficiency. In the multiple-electrodes EOC-VPM-SPM method, a new design of multiple drainage boards in a square tube layout fabricated through 3D printing was employed to provide efficient connections of the consolidation system. Furthermore, electrokinetic geosynthetics (EKG) was utilized as the cathode in the EOC system to minimize erosion and passivation of electrodes for the enhancement in consolidation efficiency. The properties of tested soils were analyzed to evaluate the feasibility of the improved methods. Test results indicated that the consolidation effects were significantly improved, with effectively mitigated clogging of the drainage system. Compared to the traditional method, the water content of the tested soil was reduced through the improved methods, resulting in increased uniformity of strength distribution.

It is essential to protect sensitive equipment located in the vicinity of vibration sources (VS). As the well-known method of using wave barriers is ineffective to protect facilities that are located very close to a VS, in this study the effect of a thin rubber sheet to protect a nearby foundation (NF) was assessed. This was achieved experimentally at a site using a semi-large scale machine foundation model as the VS and a similar concrete foundation as the NF. The effects of the rubber sheet position (beneath the VS and NF) and of the rubber sheet thickness (6, 12, 18 and 24 mm) were assessed within the vibration frequency range 10–70 Hz and at various NF to VS distances (Distance/Foundation Width = 1 to 10). The testing illustrates that, by increasing the rubber sheet thickness beneath the VS/NF, there is a consequential resonant response frequency reduction at the NF. Moreover, it was found that placing the rubber sheet beneath the VS is more efficient at reducing the NF's resonant amplitude while placing the rubber sheet beneath the NF is more effective in protecting the NF from the resonant frequency variation. This is due to the dominance of the VS's resonant frequency.

The smooth surface texture of the commercially available geogrids limits the shear strength mobilization at the interfaces. This study presents the design, manufacturing, and interface performance evaluation of innovative textured geogrids. Geogrids with square, triangular, and hexagonal apertures with and without inherent surface texture were manufactured through additive manufacturing (3D printing) technique, using PLA (Poly Lactic Acid) filament. The texture includes elevated pins of 3 mm height at the junctions and inherent diamond pattern of 1 mm height on the ribs. The individual and combined effects of surface texture and aperture shape on the stress–displacement relationship, dilation angle, and the thickness of shear zone are quantified using large-scale direct shear tests and Particle Image Velocimetry (PIV) analysis. Results showed that the textured geogrid with hexagonal aperture has exhibited the maximum interface coefficient of 0.96 with sand followed by the geogrids with triangular and square apertures. Irrespective of the aperture shape, provision of the surface texture resulted in an overall increase of interface shear strength by more than 13%. Further, PIV analysis revealed that the shear zone is 25% thicker for textured geogrids of different aperture shapes, suggesting higher interlocking and passive resistance offered by their textured surfaces.

There are situations where geotextiles are subjected to uniaxial tensile strain, which may result in noticeable variations in their filtration performance. This study accordingly investigated the behaviors of needle-punched nonwoven geotextiles during tensile testing using in-situ X-ray computed tomography. Furthermore, a numerical analysis of the variation in pore size characteristics was performed by establishing a geotextile model based on the web formation and bonding manufacturing process. The pore size and fiber orientation distributions were subsequently investigated and a model for the changes in the pore characteristics was established and validated. With increasing tension strain in the machine direction, the pore throat size distribution curve exhibited an overall shift towards larger sizes, and the characteristic pore sizes ranging from 10% to 98% either initially decreased, then increased or consistently increased. Furthermore, the fiber distribution was predominantly within the geotextile plane along the machine direction, and as the strain increased, the fibers stretched and aligned along the direction of the tensile load along the machine direction. Finally, the experimental findings of this study and relevant test results from the literature were thoroughly interpreted. The numerical model align well with the actual changes in pore size characteristics observed under tensile strain.

We conducted accelerated aging experiments on two types of polypropylene (PP) nonwoven geotextiles (filament geotextile and staple fiber geotextile), immersing them in five different simulated liquids at temperatures of 25 °C, 55 °C, and 85 °C for 200 days. At 85 °C and a pH of 1, the tensile strength and elongation at break of PP filament materials decreased by 95% and 86%, respectively. The presence of heavy metals(arsenic and cadmium), speeds up the aging process in both types of PP geotextiles. Under identical conditions, these heavy metals can increase the loss of tensile strength in geotextiles by more than 7% in 200 days. Increases in temperature, acidic environment, and heavy metal concentration all contribute to faster aging of these geotextiles. Although filament geotextiles exhibit higher tensile strength and elongation at break, staple fiber geotextiles show a lower rate of tensile strength loss during aging and better maintain their tensile strength in high-temperature acidic conditions. During the aging process, cross-linking and recrystallization occur, both of which control the aging rate and the formation of microplastics.

The geosynthetic-reinforced pile-supported (GRPS) embankment is an effective method for improving soft ground, widely adopted in engineering applications. In this paper, a concentric ellipsoidal soil arching model was proposed to describe the stress distribution within the GRPS embankment. An analytical solution for soil arching efficacy was derived by solving the loads acting on the pile caps and geosynthetics under piles arranged in a squared pattern. Subsequently, finite difference models were established to verify the accuracy of the derived analytical solution. Meanwhile, four field tests were introduced to validate the analytical model. Finally, parametric studies were conducted on the concentric ellipsoidal soil arching model, considering parameters such as the embankment height, the pile spacing, the pile cap width, the unit weight, and the friction angle of fill soil.

In this study, the dynamic response and damage mode of a pile-geogrid composite reinforced high-speed railway subgrade under seismic action were investigated based on a unidirectional shaking table test. Various seismic waves were applied to the subgrade, allowing for an analysis of acceleration, dynamic soil pressure, displacement, and strain responses. The displacement field of the subgrade was visualized using particle image velocimetry (PIV). The study shows that changes in peak ground acceleration (PGA) amplification factors become evident with height due to the presence of geogrid layers. The increase in peak ground motion causes a redistribution of dynamic soil pressures inside the subgrade. The transverse and longitudinal ribs of the geogrids provide an “anchoring effect”. The peak strain of the piles in the center is greater than that of the piles on the sides. The direction of soil particle displacement is closely related to the damage patterns observed in the subgrade. Damage begins to occur once the peak ground motion exceeds 0.4 g, characterized by collapse at the bottom of the subgrade.