Risks and Sustainability in Construction

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Tensile behavior of weathered thermally bonded polypropylene geotextiles: analysis using constitutive models

Publication . Carneiro, José Ricardo; Paula, António Miguel; Pinho-Lopes, Margarida

Weathering agents can significantly affect the mechanical response of geotextiles, particularly when long exposure periods are involved. Usually, in design, changes in the mechanical behavior of geotextiles are represented by reduction factors for their tensile strength. However, their full tensile force versus elongation response can be affected. The main aim of this work was to contribute to defining simple procedures to estimate tensile force versus elongation curves for weathered samples of geotextiles. The tensile response of two thermally bonded polypropylene geotextiles, before and after natural and artificial weathering, was assessed experimentally and analyzed using different constitutive models: polynomial (Orders 4 and 6) and hyperbolic. The influence of weathering on the mechanical response of the geotextiles was analyzed, polynomial and hyperbolic models for representing the tensile force versus elongation response were adopted and their parameters derived, and simple relations were implemented to estimate model parameters for weathered samples. Results revealed the occurrence of changes in the tensile behavior of the geotextiles, both under natural and artificial weathering conditions. Both groups of models fitted the experimental data properly. The Order 4 and 6 polynomial models are shown to have limited application, as the model parameters had no link to the tensile properties of the geotextiles. By contrast, the parameters of the hyperbolic model were linked to the tensile properties, particularly if affected by correction factors. The hyperbolic model parameters of the weathered samples were estimated using the model parameters of the reference samples and the reduction factors to allow for weathering (initial stiffness and tensile strength). These estimates proved to be adequate for representing the tensile response of weathered samples, particularly for low ranges of elongation. Finally, a simple procedure to represent the tensile response of weathered geotextiles was proposed. This procedure has shown promise in generating realistic tensile versus elongation curves.

2023Journal article

Restricted access

Constitutive models and statistical analysis of the short-term tensile response of geosynthetics after damage

Publication . Lombardi, Giovani; Paula, António Miguel; Pinho-Lopes, Margarida

The objective of this research was to analyse the tensile response of three geosynthetics, to apply constitutive equations, and propose values for model parameters to represent the nonlinear behaviour of these materials in the short-term, supported by statistical analysis. Data for specimens of a nonwoven geotextile, a woven geogrid and a reinforcement geocomposite previously submitted to mechanical damage, abrasion damage, and mechanical damage followed by abrasion damage were analysed. Nonlinear regressions of the experimental results were performed to fit the load vs. strain curves to constitutive equations. For each geosynthetic, the results of damaged specimens were statistically compared to those of the undamaged ones to observe the influence of the induced damage on the tensile behaviour of the material. Experimental results were statistically compared with those obtained by the constitutive models to verify if the tensile properties and the model parameters were properly estimated. For the geotextile, significant changes in tensile properties were noticed only after sequential mechanical damage and abrasion damage. For the geogrid and the reinforcement geocomposite, abrasion damage was predominant due to considerable changes in the tensile properties and the shape of the load vs. strain curves. In general, the polynomial models fitted the ultimate tensile strength slightly better, while the hyperbolic-based models presented better approximation of the secant stiffness. For hyperbolic-based models, estimating curves for damaged materials from model parameters of undamaged specimens by applying adjustment coefficients and reduction factors allowing for damage was considered promising, with slight differences for average and median curves. Contrary to the literature, model parameter α was not a material constant, as it varied according to the material condition and the shape of the load vs. strain curve.

2022Journal article

Restricted access

3D numerical modeling of geosynthetics for soil reinforcement: a bibliometric analysis and literature review

Publication . Paiva, Lucas; Pinho-Lopes, Margarida; Paula, António Miguel; Valente, Robertt

Soil reinforcement using geosynthetics is an efficient and cost-effective solution for a variety of geotechnical structures. Along with the increasing use of geosynthetics, there is a need to expand and enhance the design methodologies for these elements, which are still frequently based on conservative limit equilibrium approaches. In this paper, a bibliometric analysis was conducted on geosynthetic-reinforced soil structures (GRS), identifying the state of the art, research trends, and other indicators. The data were obtained from the Scopus platform and processed by VOSViewer v1.6 software. The initial search comprised 552 papers and the screening process selected 516 relevant papers from 1992 to October 2023. The study analyzed the occurrence of publications by year, keyword trends, authors, citations/co-citations, and bibliographic coupling. Then, a focus was given to 3D modeling research on geosynthetics, highlighting the dominant modeling techniques, material properties, and design challenges in GRS. The bibliometric analysis provided a crucial guideline in the identification of relevant papers and research trends, and a series of conclusions were presented regarding the 3D modeling techniques, choice of material properties, and boundary conditions.

2024Journal article

Open access

Constitutive modelling of short-term tensile response of geotextile subjected to mechanical and abrasion damages

Publication . Paula, António Miguel; Pinho-Lopes, Margarida

This paper discusses simple constitutive models to represent the tensile response of a geotextile (GTX) and the influence of two endurance durability factors on that response: mechanical and abrasion damage, acting independently and sequentially. The damage was induced in laboratory under standard conditions. Two types of models were used: polynomial and hyperbolic. The polynomial models (order 4 and 6) approximated the short-term tensile experimental data very well (and better than the hyperbolic model), but its model parameters have no physical meaning. The hyperbolic model parameters did not always have the physical meaning reported in the literature. Correction factors were introduced successfully, to achieve that physical meaning. These correction factors were not materials constants and were affected by the damage induced, and by the type of aggregate used in the mechanical damage tests. Equations to estimate the model parameters of the damaged samples were proposed using the model parameters for the undamaged sample and its properties (tensile strength and corresponding correction factor), and the reduction factors allowing for damage for the initial stiffness (Ji) and tensile strength (Tmax).

2021Journal article

Open access