This study investigates the mechanical response and performance of biaxial polypropylene geogrid specimens cyclic loading. This work assesses the influence of embedment depths and subgrade strengths on the of geogrids. The experimental program involved subjecting the geogrid specimens to 100 repeated tensile loading cycles at four distinct load targets: 20%, 40%, 60%, and 80% of the geogrid ultimate tensile strength. The analysis focused evaluating the effects of preloading factors such as California Bearing Ratio (CBR) values, embedment depth, and the response to cyclic testing. Results show trends in stiffness reduction and changes in damping ratio with increased number of cycles. A comparative analysis was conducted with a control specimen from the same batch, highlighting the difference in mechanical response attributed to precycling variables. The findings indicate that the overall mechanical behavior of recovered geogrids is comparably consistent with new geogrids. However, variations in strain and stiffness reduction were observed among the recovered specimens, suggesting a pattern of yielding before failure. The findings suggest a minimal effect of embedment depth on the damping ratio at lower CBR. Overall, it was found that precycling and subgrade conditions have minimal effect on the mechanical response of the recovered specimens when tested in isolation.

The use of recycled polyester (rPET) in construction materials offers significant benefits, including energy conservation, cost reduction, and decreased solid waste. This study compares the performance of rPET with that of virgin polyester (vPET) products. Therefore, two main testing programs including pull-out tests and creep performance tests were carried out in order to determine the interfacial properties of the geogrid-reinforced soil and time-dependent manner of the geogrids, respectively. Broadly speaking, this study showed that the performance of rPET geogrid is comparable with vPET geogrids. Pull-out tests revealed that pull-out resistance of both vPET and rPET geogrids were roughly the same and the vPET geogrid mostly had lower dilation angles in comparison with rPET. Moreover, based on the performance creep tests, it was understood that the long-term mechanical behaviour of rPET does not differ from the long-term behaviour of vPET products.

Geosynthetic-reinforced pile-supported (GRPS) embankments are a primary method for mitigating subgrade settlement. However, the load transfer mechanism between piles and soil remains incompletely understood, with the load sharing ratio (LSR) between piles and soil serving as a critical indicator for this mechanism. This study conducted a model test at a similarity ratio of 1:10 to investigate the effects of load amplitude, load frequency, number of geogrid layers, and pile types on the LSRs of piles and soil in GRPS embankments. The test results show that the pile's LSR increases with rising values of these parameters, while the corresponding LSR of the soil decreases. Among these parameters, the number of geogrid layers has the least effect on the LSRs of both piles and soil. Furthermore, the rigid long pile demonstrates a higher LSR than the flexible short pile, attributed to its greater stiffness. The influence of load frequency on the LSRs of the rigid long pile is also less significant compared to the flexible short pile. Variations of LSR increment can be predicted using a formula that incorporates the number of loading cycles. These findings provide deeper insights into the load transfer mechanism in the pile-soil system, contribute to the optimization of GRPS embankments design practice, and ultimately enhance performance and reliability of the GRPS embankments in geotechnical engineering applications.

Geogrid stabilization has gained significant attention in recent years as an effective method for enhancing the performance of subgrade soils. However, the reinforcement effect of the geogrids under different loading conditions has not been thoroughly investigated, which hinders a comprehensive understanding of subgrade stabilization. Therefore, this paper aims to investigate and compare the behavior of a stabilized subgrade with geogrids reinforcement under cyclic loading and monotonic loading conditions. The experiments were conducted within a steel model box measuring 1.0 m (length), 1.0 m (width), and 1.2 m (height). The subgrade layer was consistently maintained at a thickness of 500 mm and strength of 2.5% California Bearing Ratio (CBR). A granular layer of high-quality material with a thickness of 200 mm was applied on top of the weak subgrade and geogrid was placed at the interface between the granular layer and subgrade. The tests were conducted in a controlled laboratory setting, specifically measuring vertical displacement in response to monotonic and cyclic loading. The results were then analyzed to evaluate ultimate bearing capacity, stiffness and rutting thereby estimating the effect of geogrids on stabilization of weak subgrades. These findings are anticipated to contribute significantly to the development of design guidelines for stabilized subgrade with geogrids reinforcement. By incorporating these insights, the design, and optimization of geogrid reinforcement systems for subgrade stabilization can be enhanced, ultimately resulting in improved performance and increased longevity of transportation infrastructure.

Geosynthetic-reinforced soil (GRS) walls built on hillslopes are more increasingly incorporated with geocomposite 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 inter 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.

The tensioned reinforced soil retaining wall, a novel retaining structure, utilizes either anchors or geosynthetic materials as reinforcements that contribute to load-bearing and friction within the structure. This study aims to explore the tension distribution and strain patterns in the reinforcements, and their influence on the reinforced soil retaining walls. To this end, tensile, direct shear, and pullout tests were conducted on GeoStrap@5-50 geotextile strips and TGDG130HDPE geogrids to evaluate the tensile strength and interface strength between the reinforcement and the soil. The characteristics of the reinforcement-soil interface and the deformation behavior under stress were examined, with a comparative analysis of the technical merits of the two types of reinforcements. The results indicate that both the geotextile strips and geogrids enhanced the strength of the reinforced soil, primarily by increasing cohesion. The GeoStrap@5-50 geotextile strips exhibited superior tensile strength compared to the TGDG130HDPE geogrids; the reinforcement with the geotextile and geogrids both enhanced the cohesion of the standard sand, albeit with a slight decrease in the internal friction angle, by 4.6% and 3.1%, respectively, offering enhanced mechanical properties and economic value in reinforced soil retaining wall applications.

In this paper, a triple large-scale biaxial tensile test system for geosynthetics developed by the authors was used to study the tensile mechanical properties of warp-knitted polyester (PET) geogrids. In-isolation tensile (in air) tests with various strain rates were conducted to investigate the effects of tensile modes (uniaxial and biaxial tension) on the tensile mechanical properties of warp-knitted PET geogrids. To evaluate the influences of normal stress and confined soil types (sand and gravel) on the tensile load-strain characteristics of warp-knitted PET geogrids under uniaxial and biaxial tensile loading, strain rate-controlled tensile tests in soil were also carried out. The results demonstrated that the low strain rate leads to low tensile load and secant tensile stiffness of geogrids in-isolation tensile tests. The biaxial in-isolation tensile tests mobilized a lower tensile load throughout the tensile process. The constraint of soil types and the application of normal stress increased the tensile load and secant tensile stiffness of geogrids. In general, the confined soil reduces the impact of uniaxial and biaxial tensile loading on the tensile tests. Geogrids embedded in sandy soils showed improved mechanical properties.

This paper evaluated the benefits of geogrid-reinforced sand samples and investigated the effect of different factors contributing to the dynamic behavior, which included the geogrid type, arrangement of reinforcement, confining pressure and dynamic stress amplitude. Four geogrids of different aperture geometries (two biaxial geogrids and two triaxial geogrids) produced by 3D printing technology were used. The research was experimentally carried out by conducting dynamic triaxial tests to investigate the axial cumulative strain, dynamic elastic modulus and damping ratio of the samples. The test results demonstrated the potential benefit of installing geogrids in subgrade soils. Less axial cumulative strain, damping ratio and larger dynamic elastic modulus were measured under cyclic loading for geogrid-reinforced samples compared to those unreinforced samples. The geogrid type and reinforcement arrangement had noticeable impacts on the samples' dynamic performance. Of the four model geogrids tested, the triaxial geogrid with triangle aperture performed consistently better than the other three. Under large confining pressures and dynamic stress amplitudes, there was no appreciable improvement in the dynamic performance of the samples reinforced with the two triaxial geogrids. The results also showed that the double reinforcement arrangement consistently yielded better improvement. This study explored preliminarily the feasibility of applying 3D printing technology in geotechnical model tests, which shed light on the understanding of dynamic response of geogrid-reinforced soil and the optimization of geogrids.

Challenges related to sustainability arise in all areas of human activity, but with a significant impact on the environment considering that the construction industry is held accountable for nearly one-third of the world's final energy consumption. The aim of this paper is to assess through the use of the Bob-Dencsak specific model a sustainable slope design taking into account environmental, economic, and safety variables. Thus, analysis was performed on four intervention works, two versions of reinforced concrete retaining walls and two versions of reinforced soil with a biaxial geogrid, which ensure the stability of a slope that serves as a base for an access road to an ecological landfill located in Alba County, Romania. The study's analysis points out that reinforced soil retaining walls are far more sustainable, providing the best sustainability indices, which is also supported by the impact of geogrids compared to reinforced concrete, thus resulting in the finding that reinforced concrete is less sustainable, achieving increases of up to 23% for embodied energy and 66% of CO2 emissions in the atmosphere. Finally, the paper provides recommendations for future research on the sustainability assessment of slopes, with the intention of reducing environmental damage, while keeping costs to a minimum.