Nonwoven Geotextiles Research Articles

Long-term hydraulic performance of geotextiles filtering recycled materials

Use of recycled materials instead of earthen materials is one way to improve the sustainability of highway infrastructure. Since geotextile filters and separators are used in such construction schemes, hydraulic compatibility of geotextile filters with recycled materials and their long-term performance is essential. A series of long-term filtration (LTF) tests were performed to evaluate the hydraulic compatibility of several woven and nonwoven geotextiles with four recycled materials commonly used in construction (recycled concrete aggregate, recycled asphalt pavement, foundry sand, and recycled asphalt shingle). Upon completion of the LTF tests, grain size analyses, permittivity tests, image analyses, and piping measurements were conducted to investigate the clogging and retention behavior of the geotextiles. The results indicated that majority of the recycled materials tested were compatible with the nonwoven and woven geotextiles. Excessive piping was not observed even under relatively high hydraulic gradients. Permittivity and percent open area were the main parameters that influenced the retention performance of the nonwoven and woven geotextiles, respectively. The success of the existing criteria in predicting the filtration performance was inconsistent, suggesting that a detailed parametric study was needed to propose new filter criteria for these materials.

Evaluating wettability of geotextiles with contact angles

Geotextiles have been used for drainage purposes in pavements for many years. To drain water out of road sections, the geotextiles need to get wet first. In this study, the wettability of three different types of geotextiles, namely wicking woven (WW) geotextile, non-wicking woven (NWW) geotextile, and nonwoven (NW) geotextile, was investigated in terms of their contact angles dependent on water-geotextile interaction. Contact angle was observed by the VCA Optima XE tensiometer for up to 12 s after a water droplet was dropped at the center of a geotextile's surface. Water droplets of two different sizes (2 μL and 5 μL) were used to demonstrate the droplet size effect on the contact angles of water on undisturbed geotextiles. Test results show that the contact angle decreased to smaller than 90° and the droplet disappeared on the wicking woven geotextile within a few seconds after water dropping, while the contact angle remained larger than or approximately equal to 90° on the other two types of geotextiles within the observation period. This comparison indicates that water penetrated faster into the wicking woven geotextile than other geotextiles. Furthermore, this study investigated the effects of soil particle intrusion and geotextile or fiber deep groove flattening associated with compaction on the wettability of geotextiles.

Damage of geotextile due to impact of stones

Impact tests of stones on a geotextile or two loosely connected geotextiles (composites) have been performed and analysed to investigate the mechanisms that lead to perforation. The geotextiles were mounted on a concrete cylinder of 0.8 m internal diameter, filled with uniformly graded dry sand. Drop tests were performed with concrete blocks of different shapes weighing approximately 40 kg. The drop heights varied between 0.25 and 5.5 m. Results show that the shape of the stone has an important influence on the critical drop height at which the geotextile is perforated. Furthermore, it appeared from image processing that the tensile strains in a woven geotextile develop in the direction of the yarns, starting from the point of impact. However, in a nonwoven geotextile, the tensile strains develop rather uniformly centred at the point of impact. An important result for composite material consisting of a woven and a nonwoven geotextile was that the lower geotextile was always the first to be damaged. This was also found in the field tests. A possible explanation is the friction between the sand and the lower geotextile, resulting in an additional tensile loading on that geotextile. This explanation is confirmed by numerical simulations.

Ecological Appraisal of Geotextiles in Coastal Erosion Protection Engineering

Jebakumar, J.P.P.; Nandhagopal, G.; RajanBabu, B.; Ragumaran, S.; Kiran, A.S., and Ravichandran, V., 2022. Ecological appraisal of geotextiles in coastal erosion protection engineering. Journal of Coastal Research, 38(2), 345–354. Coconut Creek (Florida), ISSN 0749-0208. The emergence of geotextiles in coastal erosion protection as an alternative material to stone boulders and concrete tetrapods is evident in the recent past. The submergence of geotextiles being colonized by epibiotic organisms on their surface is called marine growth, similar to all other materials inundated in seawater. It includes organisms of the primary producers of algal populations, secondary consumers, and filter feeders of benthic-fouling communities crusting geotextiles' surface. In-situ experimental studies of more than a year of research at a fishing harbour along Chennai coast, India, projected a typical pattern of epibiotic encrustation and its impact on tensile strength nonwoven geotextiles fabrics. Results demonstrated a patchy-mosaic design of marine growth on the geotextile comprising 41 species of sessile invertebrates, including seaweeds, showing a natural succession of biotic density and diversity. Noted distinct stages in colonization were commencing with the domination of deposit feeders, followed by filter feeders, secondary consumers, and primary producers, where later filter feeders subjugated them. The incidence of fundamental ecological succession based on food availability, nature of trophic consumers, and intra/interspecific competition lead to dynamic population shifts on geotextiles. The monolayer settlement pattern of marine growth on the surface is dominated by the benthic filter-feeding community, forming an inverted trophic pyramid structure. Significant differences in tensile strength between geotextile with and without marine growth (p = 0.042) and the progressive improvement in tensile strength indicated no adverse impact on the erosion protection structure's stability. Thus, a harmonious relationship between population density and tensile strength (r = 0.8) represents a mutual relationship between encrusting biota and geotextile substrate, resulting in camouflaging with the coastal background ecosystems as an innovative ecodesign for coastal erosion protection engineering.

Clayey sand–nonwoven geotextile interface characterisation through gradient ratio test

Nonwoven geotextiles have been widely used as a substitute for mineral materials to provide filtration functions in civil engineering. However, in filter systems, geotextiles are the first to be in contact with soft, saturated, and fine soils. For that reason, the selection of a geotextile filter depends on the characteristics of the geosynthetics and the base soil (e.g. grain size distribution, internal stability, permeability) and on the design and boundary conditions such as continuity of the soil–geotextile filter contact interface. The geotextile filter must be properly designed to avoid clogging. The most commonly method used for measuring filtration compatibility of soil–geotextile systems is the gradient ratio test. This paper presents the gradient ratio test program for needle-punched nonwoven geotextile used as a filter layer and internally unstable soil. Laboratory tests were conducted in a modified gradient ratio test apparatus. Test results show that gradient ratio increases with time due to clogging. Also the need for a measurement of water heads very close to the geotextile to measurement of water heads very close to the geotextile to provide additional information on the soil–geotextile system behaviour were presented.

Influence of physical clogging on filtration performance of soil-geotextile interaction

During the past four decades the use of nonwoven geotextiles as filter materials in geotechnical works has experienced a marked increase. In this study, the water permeability coefficient of nonwoven geotextiles after 23 years of exploitation in drainage system was determined to evaluate the influence of physical clogging on filtration performance of geotextiles. The obtained results showed that the geotextiles were clogged by soil particles. What is more, the objective in this study was to establish a gradient ratio test method for estimating a clogging phenomenon of geotextile filter adequately. A series of gradient ratio tests on three kinds of needle-punched nonwoven geotextile filters whose number of constrictions differs was performed. A geotextile filter was put under a silty sand layer. Based on the test results, it was confirmed that the water permeability coefficient became small as gradient ratio increased depending on the number of constrictions of the geotextile. It was also found that the modified gradient ratio GR4 is more sensitive than GR8 and GR25. Based on interpretation of the experimental results, the authors recommend the acceptance limit of GR8 equal to 3.7 and of GR4 equal to 4.8.

Effect of internal drainage on deformation behavior of GRS wall during rainfall

Global warming-induced changes in the pattern and amount of precipitation are important from the viewpoint of long-term stability of geo-structures. In this paper, the effectiveness of in-plane drainage provided by permeable geosynthetic reinforcement was evaluated as a means to relieve the rainfall infiltration effect on GRS walls backfilled with marginal soil. A series of laboratory tests were performed using a reduced-scale model geosynthetic reinforced soil (GRS) wall (constructed with due consideration of the similitude law) with different rainfall characteristics and backfill soils. Layers of nonwoven geotextiles were used as reinforcement as well as in-plane drainage media. The results showed that the inclusion of internal drainage facilitated the dissipation of pore water pressure, thereby reducing the wall facing displacement. The discharge water volume and volumetric water content data measured in the reinforced soil zone supported the observation. The degree to which the internal drainage improves the deformation behavior of the GRS wall during rainfall was found to depend on the rainfall characteristics and the backfill soil type. Practical implications of the findings are discussed in detail.

Mechanical and hydraulic compatibility of RAP with geosynthetics used in MSE walls

Mechanical and hydraulic properties of recycled asphalt pavement (RAP) as backfill in mechanically stabilized earth (MSE) walls were evaluated. Woven and nonwoven geotextiles and uniaxial and biaxial geogrids were used as reinforcements. Results of interface direct shear tests showed that the interface friction angle (δ) of RAP-geogrid was higher than that of RAP-geotextile. On average, the δ for RAP-biaxial geogrid was 15% higher than δ for RAP-uniaxial geogrid. For geotextile reinforcement, the δ for RAP-woven geotextile was 20% higher than δ for RAP-nonwoven geotextile. Compaction of RAP at elevated temperatures only slightly affected δ. Pullout capacities of RAP-uniaxial geogrid and RAP-woven geotextile are comparable to those of sand-uniaxial geogrid at different overburden pressures. The compacted RAP reinforced with uniaxial geogrid, however, exhibited significant creep strains at a range of sustained pullout forces that led to failure of the RAP-uniaxial geogrid. Reducing the pullout capacity by 40% is recommended for design to reduce the potential of creep failure. Long-term filtration tests showed that in all cases RAP-geosynthetic systems were able to drain freely and this behavior could be predicted with the existing clogging criteria that have been previously developed for sands and gravels.

Experimental Study of Strength Development in Black Cotton Soil and Granular Material Reinforced with Geogrid and Non-Woven Geotextile

Reinforcement of flexible pavements using geosynthetics is gaining widespread application. However, there is inadequate understanding of strength development for non-woven geotextile and geogrid as reinforcement in Black Cotton Soil (BCS) and granular material in relation to cement stabilization method. Therefore, this paper presents experimental study to investigate strength development for BCS and granular material reinforced with geogrid and non-woven geotextile using California Bearing Ratio approach. The categories of samples tested were; neat, reinforced and cement stabilized. All samples were tested after 4 days’ soak. Placement of reinforcement material in BCS was done at 0.3H and 0.6H for single layer reinforcement while for double layer reinforcement, it was done at both 0.3H and 0.6H. In granular soil, single layer reinforcement condition only was considered at 0.2H, 0.4H and 0.6H. Cement stabilization for both BCS and granular soil was done by the following percentages of cement increment; 1%, 2%, 3% and 4%. From the study, the strength improvement considering single layer reinforcement by geogrid and non-woven geotextile in BCS was 37.5% and 45% respectively. In granular material, CBR strength increased by 21% and 14% due to geogrid and non-woven geotextile respectively. Percentage increase in CBR of reinforced BCS corresponded to that of over >1% cement stabilization. To further enhance decision making between these strength development alternatives, it is recommended to advance it to cost analysis.

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

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.

Filtration performance of non- woven geotextiles with internally-stable and -unstable soils under dynamic loading

In many applications, geotextiles are subjected to dynamic loading conditions, for example, below roads and railways, for which a Gradient Ratio (GR) test is often used to assess filtration compatibility of soil-geotextile systems. This paper presents results from GR filtration tests with internally-stable and -unstable soils under dynamic loading conditions. In the tests, four non-woven geotextiles were used with varying types of soils under a hydraulic gradient of 5. Test results were interpreted in terms of GR values, permeability values, and mass and gradation characteristics of the soil before/after testing as well as the particles passing through the geotextiles. The test results show that the dynamic loading resulted in an increase of soil migration within the soil as well as an increase in the quantity of soil passing through the geotextiles. The available criteria for evaluating the internal stability of soils are evaluated based on the experimental data. Based on the test results, improvements to filter retention design criteria are suggested which take into account the internal stability of soils under dynamic loading.

The heavy metal adsorption and plant cultivation performance of grafting modified plant medium made with recycled fibers

This paper proposes an environmental friendly nonwoven geotextile with good heavy metal adsorption properties and beneficial promotion of plant cultivation to potentially replace the riverbank soil or cover on the shoreline surface to rebuild up a healthy ecosystem. In this paper, waste fibers were adopted and carded into even fiber web, followed by needle-punching technology with several layers of fiber web to strengthen the plant medium with satisfying mechanical properties. Then, the grafting modification was conducted on the needle-punched nonwoven geotextiles and the optimum combination of grafting factors were obtained via orthogonal experiments. The tensile, heavy metal adsorption and plant cultivation performances of modified and untreated plant medium were systematically compared and analyzed by infrared absorption spectrum, SEM, XRD, TG, ICP-OES, universal material testing machine, and contact angle tester. The results showed that β-cyclodextrin was well grafted on the substrate. The orthogonal experiments results showed that the best combination of Pb2+ and Cu2+ adsorption was 4% sodium hydroxide (NaOH), 2% β-cyclodextrin, 170 °C heating temperature, and 50 min heating. The adsorption effects of Pb2+ and Cu2+ were 14.32 mg/g and 38.99 mg/g, respectively. The grafted fabric was hydrophilic and a more suitable culture medium for plants. These results provide not only a novel solution for reuse of recycled fibers but also a feasible strategy to construct a new water ecosystem.

An experimental evaluation of geocomposite-reinforced soil sections

The present study aims to investigate the performance of soil-aggregate sections reinforced by three types of geosynthetics. The main focus of this research was on a geocomposite material comprised of a geogrid and a nonwoven geotextile. Along with investigating this reinforcement, its components (i.e., geogrid and nonwoven geotextile) were also studied individually to make a comparison between their functionalities in soil-aggregate systems. Two sandy soils, one of which was a case study, were chosen as the subgrade layer in this research. The California Bearing Ratio (CBR) was the index to examine the strength of specimens. The scale effect of the conventional CBR mold, as well as geosynthetics anchorage, were investigated through fabricating a modified CBR mold. Strain analysis was also carried out by utilizing some foil strain gauges to assess the strain mobilized in the geosynthetics in various reinforced sections. In the presence of both geocomposite and geogrid, load-penetration responses of the specimens enhanced significantly, while the geotextile inclusion effect was in a negative way. Improved functionalities of reinforcing materials were seen in the modified mold.

The Assessment of Water Retention Efficiency of Different Soil Amendments in Comparison to Water Absorbing Geocomposite.

Soil amendments are substances added to the soil for moisture increment or physicochemical soil process enhancement. This study aimed to assess the water conservation efficiency of available organic soil amendments like bentonite, attapulgite, biochar and inorganics like superabsorbent polymer, and nonwoven geotextile in relation to the newly developed water absorbing geocomposite (WAG) and its biodegradable version (bioWAG). Soil amendments were mixed with loamy sand soil, placed in 7.5 dm3 pots, then watered and dried in controlled laboratory conditions during 22-day long drying cycles (pot experiment). Soil moisture was recorded in three locations, and matric potential was recorded in one location during the drying process. The conducted research has confirmed that the addition of any examined soil amendment in the amount of 0.7% increased soil moisture, compared to control, depending on measurement depth in the soil profile and evaporation stage. The application of WAG as a soil amendment resulted in higher soil moisture in the centre and bottom layers, by 5.4 percent point (p.p.) and 6.4 p.p. on day 4 and by 4.5 p.p. and 8.8 p.p. on day 7, respectively, relative to the control samples. Additionally, an experiment in a pressure plate extractor was conducted to ensure the reliability of the obtained results. Soil density and porosity were also recorded. Samples containing WAG had water holding capacity at a value of −10 kPa higher than samples with biochar, attapulgite, bentonite, bioWAG and control by 3.6, 2.1, 5.7, 1 and 4.5 percentage points, respectively. Only samples containing superabsorbent polymers and samples with nonwoven geotextiles had water holding capacity at a value of −10 kPa higher than WAG, by 14.3 and 0.1 percentage points, respectively. Significant changes were noted in samples amended with superabsorbent polymers resulting in a 90% soil sample porosity and bulk density decrease from 1.70 g∙cm−3 to 1.14 g∙cm−3. It was thus concluded that the water absorbing geocomposite is an advanced and most efficient solution for water retention in soil.

Thermography and physiology of stress in dairy calves in outdoor holding pens covered with geosynthetics

ABSTRACT This study aimed to assess the environmental variables, thermal comfort indices and physiological responses of calves in outdoor holding pens shaded with geosynthetics. Twenty crossbred females (Giroland, Jersey and Holstein) in the suckling phase (from birth to 90 days old) with an average initial live weight of 40.6 kg were used. A completely randomized block design was used, in a 4 × 3 factorial scheme with five replicates. The roofing materials (polyethylene mesh, geocomposite drainage layer, nonwoven geotextile and woven geotextile) were the first factor and time periods (8 to 10 a.m., 12 to 2 p.m. and 4 to 6 p.m.) the second factor. The following environmental variables were measured to calculate thermal comfort indices: temperature-humidity index, black globe-humidity index and enthalpy. The physiological variables analyzed were respiratory rate, rectal temperature and skin temperature. Environmental variables and thermal comfort indices did not differ between the different roof types, however, a significant difference (p ≤ 0.01) was observed between the time periods, with 12 to 2 p.m. being the most critical period. The lowest average respiratory rate (60.3 breaths min-1) and rectal temperature (38.9 °C) were recorded for the animals kept under the geocomposite drainage layer roof. There was a significant difference (p ≤ 0.05) for interaction between treatment and time periods for the cannon area. The geosynthetics studied can be used as roofing material for outdoor holding pens, with the geocomposite drainage layer being the most indicated for tropical regions.

Influence of the Non-Woven Geotextile (NWG) on the engineering properties of clayey-sand treated with copper slag-based geopolymer

This study investigated the potential effect of the non-woven geotextile reinforcing of the clayey sand treated with the copper slag (CS)-based geopolymer. To this end, preliminary tests such as standard compaction, P-wave velocity, pH, and Atterberg limits (Plasticity index) were conducted on variously treated samples. In addition, complementary tests including unconfined compressive strength (UCS), unconsolidated-undrained compression triaxial (UU), and scanning electron microscopy (SEM) analysis were performed on the reinforced samples. Furthermore, 0, 10, and 15% of CS and 0, 2, 4, 8, 12, and 16 M (M) NaOH concentrations were utilized in the investigation. The alkaline-activator solution (AAS) contained 70% of Na2SiO3 and 30% of NaOH, and the weight ratio of CS-ASS was one. Subsequently, the selected samples were reinforced with 0, 1, 2, and 3 non-woven geotextile (NWG) layers by various arrangements. The results indicated the acceptable increase in the peak, residual strength, and failure axial strain. The UU results further demonstrated the improvement in shear parameters. The negligible and significant increases in the internal friction angle and the undrained cohesion were evaluated, respectively. The microstructural analysis elaborated the three mechanisms of geotextile, which helps to improve the mechanical behaviour of the reinforced samples. These mechanisms include contact, bending action, and interweaving action; interweaving action plays a vital role in the strength enhancement of samples.

Transport and retention of bacteria through a filtration system consisting of sands and geotextiles

Water-saturated column experiments were conducted to study the effect of nonwoven geotextiles on bacteria transport and deposition through two sandy porous media with grain sizes 1.05 and 3.25 mm. The breakthrough curves (BTCs) of tracer for the all porous media exhibited an asymmetrical shape with a substantial tailing, indicating that non-equilibrium and dispersive flow patterns in these porous media. The mass recovery of the bacteria from the effluent (Meff) increased with grain size. The retention profiles (RPs) exhibited hyper-exponential behavior, especially in the finer sand. The presence of the geotextiles increased bacteria retention rate. For a given geotextile, greater retention was observed in the surrounding region close to the geotextile. Moreover, the retention of bacteria became more significant in the geotextile with a lower porosity. Results demonstrated that model simulations of bacteria transport and fate need to accurately account for both observed BTC and RP behaviors and also the geotextile placement can impact mechanisms of retention.

Investigation of drainage function of geosynthetics for basal-reinforced embankments

This study investigates the behaviour of basal-reinforced embankments under seepage flow. For this purpose, physical embankment models with dimensions of 195 cm long, 100 cm wide and 110 cm high were constructed in the laboratory. The seepage gradient within the embankment was generated by applying a constant water head of 100 cm at the water compartment located behind the models. The unreinforced embankment experienced seepage erosion at the toe section which triggered deep-seated global failure. Due to the limited transmissivity of the non-woven geotextile, the geotextile-reinforced embankment exhibited similar pore-water pressure distribution to that of the unreinforced embankment, which resulted in lateral spreading failure between the base of the embankment and the non-woven geotextile. In contrast, the geocomposite drain, which has a higher in-plane flow capacity compared to that of the geotextile, significantly alleviated the pore-water pressures within the embankment. The behaviour of the physical models was verified numerically by variably saturated flow modelling conducted for a wide range of in-plane permeabilities for the basal reinforcement. The effect of increasing in-plane permeability of the basal reinforcement layer on pore-water pressure reduction was quantified irrespective of the geosynthetic type.

Bearing Ratio Behavior of Sand Overlying Clay with Treated Coir Geotextiles at the Interface

ABSTRACT The paper presents the bearing ratio behavior of sand overlying clay with two woven and two non-woven treated coir geotextiles at the interface. The chemicals such as p-aminophenol, sodium periodate and sodium hydroxide were used to treat the coir geotextiles. The results indicated that the unsoaked/soaked bearing ratio of the sand overlying clay with woven coir geotextiles at the interface decreased after the chemical treatment whereas the trend was reverse in case non-woven geotextiles. The unsoaked bearing ratio of the sand overlying clay with the treated/untreated woven and non-woven coir geotextiles at the interface was higher than the soaked bearing ratio. The C: O ratio both for the woven and the non-woven coir geotextiles increased after the chemical treatment. The emissions of Si increased for the woven coir geotextiles whereas it decreased for the non-woven coir geotextiles after the chemical treatment. The chemical treatment results in the modification of the surface of both the untreated woven and non-woven coir geotextiles.

Classification of geotextiles and analysis on tests for their tensile properties

Geotextiles are classified into various types which are Synthetic staple fibers needle-punched nonwoven geotextiles, Synthetic filament spunbond and needle-punched nonwoven geotextiles, Synthetic filament woven geotextiles, Slit and splitfilm yarn woven geotextiles, Plastic woven film yarn geotextile based on different weaving methods and property parameters. The applicability of wide-width strip method and narrow strip method for testing the tensile properties is compared and analyzed.