Geotextiles and Geomembranes最新文献

This paper presents an upgraded nonlinear creep consolidation model for VDI soft ground, incorporating a modified UH relation to capture soil creep deformation. Key novelties also include considering linear construction loads, TDP boundary conditions, and Swartzendruber's flow in the small strain consolidation domain. The system was solved using the implicit finite difference method, and numerical solutions were rigorously validated. A parametric analysis reveals that soil viscosity causes abnormal EPP increases under poor drainage conditions during early consolidation. Meanwhile, neglecting the time effect of the secondary consolidation coefficient delayed the overall EPP dissipation process and overestimated the settlement during the middle and late consolidation stages. Furthermore, TDP boundaries, Swartzendruber's flow, and construction processes significantly influence the creep consolidation process but not the final settlement. These findings offer fresh insights into the nonlinear creep consolidation of VDI soft ground, advancing the field.

In this study, the microstructural characteristics of geotextile envelopes were investigated via two-dimensional (2D) and three-dimensional (3D) image analysis. A pore network model was constructed to predict the hydraulic properties of the geotextile envelopes. Based on image analysis, the representative domain size of the geotextile envelopes was estimated and was further confirmed by pore network modeling. The results showed that while nonuniformity existed in geotextile envelopes, no noticeable difference was observed in porosity among samples of different sizes. The porosity derived from 3D image analysis was much closer to the theoretical value, with relative error less than 12%. The fibers of the geotextile envelopes were mainly distributed in the in-plane direction and were nearly uniform. The prediction of the permeability coefficient was optimal when hybrid cones and cylinders were considered as the geometric shapes and when the equivalent diameter, inscribed diameter, and total length were used as the geometric properties of the extracted pore network. The capillary pressure curves matched experimental values more closely when using the equivalent diameter for throat diameter. The representative domain size of geotextile envelopes was at least 3500 μm, but no meaningful length could be found along the through-plane direction.

This study repurposed discarded carbon fiber fabric by mechanically cutting it into short-cut carbon fibers and utilized these fibers in electro-osmosis experiments with varying lengths (5 mm, 10 mm, and 15 mm) and mixing ratios (0.05%, 0.10%, and 0.25%). The results indicated that increasing the length and mixing ratio of recycled carbon fibers effectively reduced the soil resistivity. Furthermore, incorporating an appropriate amount of carbon fibers not only reduced the energy consumption coefficient but also enhanced the electro-osmotic drainage performance. Increasing the length and mixing ratio of carbon fiber also improved the vane shear strength after electro-osmosis consolidation. To promote the application of carbon fiber in electro-osmosis consolidation and to provide support for the development of electro-osmosis consolidation theory and numerical analysis, a resistivity calculation model of carbon fiber-reinforced soil during the electro-osmosis process was developed based on the Ohm's Law and tunneling transmission theory. The model elucidates that during the electro-osmosis process, soil resistivity is influenced by the increase in barrier thickness, which consequently raises the tunneling transmission resistance.

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.