Nonwoven Polypropylene Geotextile Research Articles

Are Geotextiles Silent Contributors of Ultrashort Chain PFASs to the Environment?

We investigated the presence of per- and poly fluoroalkyl substances (PFASs) in woven and nonwoven polypropylene geotextiles and four nonwoven polyester geotextiles commonly used in modern geosynthetic composite lining systems for waste containment facilities such as landfills. Targeted analysis for 23 environmentally significant PFAS molecules and methods for examining "PFAS total" concentrations were utilized to assess their occurrence in geotextiles. This analysis showed that most geotextile specimens evaluated in the current investigation contained the ultrashort chain PFAS compound pentafluoropropionic acid (PFPrA). While the concentrations ranged from nondetectable to 10.84 μg/g, the average measured concentrations of PFPrA were higher in polypropylene than in polyester geotextiles. "PFAS total" parameters comprising total fluorine (TF) and total oxidizable precursors (TOPs) indicate that no significant precursor mass nor untargeted intermediates were present in geotextiles. Therefore, this study identified geotextiles as a possible source of ultrashort PFASs in engineered lined waste containment facilities, which may contribute to the overall PFAS total concentrations in leachates or liquors they are in contact with. The findings reported for the first time herein may lead to further implications on the fate and migration of PFASs in geosynthetic composite liners, as previously unidentified concentrations, particularly of ultrashort-chain PFASs, may impact the extent of PFAS migration through and attenuation by constituents of geosynthetic composite liner systems. Given the widespread use of geotextiles in various engineering activities, these findings may have other unknown impacts. The significance of these findings needs to be further elucidated by more extensive studies with larger geotextile sample sizes to allow broader, generalized conclusions to be drawn.

Weathering of a Nonwoven Polypropylene Geotextile: Field vs. Laboratory Exposure.

Like other plastic materials, geosynthetics can undergo changes in their properties due to weathering. These changes must be known and, if necessary, duly accounted for in the design phase. This work evaluates the resistance of a nonwoven polypropylene geotextile to weathering, both in the field (under natural degradation conditions) and in the laboratory (under accelerated degradation conditions). The damage experienced by the geotextile in the field weathering tests was evaluated by monitoring changes in its physical (mass per unit area and thickness), mechanical (tensile, tearing and puncture behaviour) and hydraulic (water permeability normal to the plane) properties. Microscopic damage was assessed by scanning electron microscopy. In the laboratory weathering tests, only the tensile behaviour of the geotextile was monitored. The results showed that all geotextile properties were affected by weathering. The mechanical strength of the geotextile decreased in the field weathering tests. Microscopic transverse cracks were found in the weathered polypropylene fibres, which may explain the reduction in mechanical strength. The accumulation of dirt on the nonwoven structure altered the physical and hydraulic properties of the geotextile. Comparing the field and laboratory weathering tests, the reduction in tensile strength found after 24 months outdoors (roughly 30%) was very similar to that observed after 4000 h in the laboratory. This relationship may not be valid for other geotextiles or other exposure locations.

Effect of mechanical damage under repeated loading and abrasion on the tensile behaviour of a reinforcement geocomposite

The installation process and the occurrence of abrasion may cause unwanted changes on the properties of the geosynthetics. When identified as relevant degradation agents for a given application, their effect has to be properly taken into account during the design phase in order to guarantee that the geosynthetics will perform correctly their functions over time. In this work, a reinforcement geocomposite (formed by a nonwoven polypropylene geotextile reinforced with polyethylene terephthalate filaments) was exposed to the isolated and combined effects of two degradation tests: mechanical damage under repeated loading and abrasion (the geocomposite was tested on both sides, which were structurally different). Damage assessment was performed by visual inspection and tensile tests. Based on the changes occurred in tensile strength, reduction factors were determined. The degradation tests provoked extensive damage on the geocomposite, having a negative impact on its tensile behaviour. Contrary to mechanical damage under repeated loading, the effect of abrasion on the geocomposite was influenced by the side that was tested. Finally, some differences were found between the reduction factors determined by the traditional method (multiplication of reduction factors obtained in isolation for each agent) for the combined effect of mechanical damage under repeated loading and abrasion and those resulting from the successive exposure to both degradation agents.

Elevated Temperature Effects on Geotextile–Geomembrane Interface Shear Behavior

The performance of geosynthetic layered systems during their service life in terms of interface shear behavior and strength properties is of major importance in certain geotechnical applications. The interfaces between geotextiles and geomembranes in landfill applications are subject to temperature changes. In this respect, interface shear behavior requires assessment of the engineering strength properties of the components, both independently and collectively, at different temperatures. To this end, an extensive research study was undertaken to investigate temperature effects on the interface shear behavior between needle-punched nonwoven (NPNW) polypropylene (PP) geotextiles and both smooth polyvinylchloride (PVC), as well as smooth and textured high-density polyethylene (HDPE) geomembranes. A temperature-controlled chamber (TCC) was utilized to simulate the field conditions at elevated temperatures and evaluate shear displacement and frictional response mobilized at different temperatures. The physical laboratory testing program consisted of interface shear tests between material combinations found in landfill applications under a range of normal stress levels from 10 to 400 kPa and at a range of ambient temperatures from 21°C to 50°C. An increase in temperature from the standard laboratory test temperature of 21°C to an equivalent in situ temperature of 50°C increases the peak and postpeak interface friction values by a minimum of 14%. For selected combinations of materials, the amount of increase can be in excess of 20% and as high as 22%. Consequently, interface shear behavior determined at room temperature yields interface friction values that are conservative at higher temperatures.

Evaluating the Degradation of a Nonwoven Polypropylene Geotextile Exposed to Natural Weathering for 3 Years

Evaluating the Degradation of a Nonwoven Polypropylene Geotextile Exposed to Natural Weathering for 3 Years

Improving stormwater quality at source using catch basin inserts

Stormwater runoff transports contaminants, including gross pollutants (GPs) accumulated on surfaces to nearby receiving water bodies. These may clog storm drainage systems, seal side entry pits and increase dissolved pollutants in receiving water bodies. Best management practices (BMPs) such as oil and grit separators, grassed swales, vegetated filter strips, retention ponds, and catch basin inserts (CBIs) are implemented to reduce stormwater pollutants in urban runoff. However, the information on physicochemical characteristics of the pollutants are still few in literature but important to improve the design of BMPs, considering qualitative aspects, and their operation. CBIs are devices used to remove GPs at source without requiring any extra land use because they are typically mounted within a catch basin (e.g. side entry pit) or existing drain. In this study, improvement of stormwater quality was investigated at two different sites (Subiaco, a residential area and Hillarys Boat Harbour, a commercial-marine-recreational area; Western Australia) where a new CBI made of non-woven polypropylene geotextile was installed in side entry pits to capture GPs at source. Influent and effluent water from the CBIs was collected and analyzed for BOD, COD, TSS and PO4-P with maximum improvements in water quality of 90%, 88%, 88% and 26% respectively. The heavy metals in influent and effluent water were found very low and below the guideline values. Analysis of particle size distribution, specific surface area of solids, SEM images and heavy metal content (Cu, Fe, Ni, Pb, Zn, Cd) in solids showed that the residential area contained more finer particles than the commercial area but that solids in the commercial area contained greater concentrations of heavy metals than those from the residential area. The specific surface area was found to be higher in the residential area and particles were thought to be largely sourced from traffic. However, these characteristics may be monitored for longer term for more CBIs installed in different locations.

Dynamic friction and the seismic performance of geosynthetic interfaces

The stability of geotechnical structures which contain geosynthetic interfaces is closely linked to the shear strength between the geosynthetics themselves, both in static and dynamic conditions. Static friction is the maximum interface shear strength mobilised before displacement, whereas dynamic friction is related to the kinematics of the displacement itself. In polymer materials, dynamic friction may be widely variable, depending on the type, geometry and integrity of the surfaces in contact, as well as on the intensity and time-history of the seismic signal. This means that predicting interface shear strength is not simple. This paper focuses on the evaluation of dynamic interface shear strength between geosynthetics, using the results of both inclined plane tests and shaking table tests; this latter test also provided a means to analyse interface behaviour under the conditions of real seismic records. To this purpose, two common geosynthetic interfaces, which exhibit different behaviour under dynamic loading, were tested. One interface was a smooth HDPE geomembrane in contact with a nonwoven polypropylene geotextile, while the second was a textured HDPE geomembrane in contact with a different type of nonwoven polypropylene geotextile.The test results shows that dynamic friction mobilised during seismic events depends on the relative speed according to the same law outlined by the free sliding tests and by the shaking table tests carried out with sinusoidal base motions. Moreover, for the two different types of studied interfaces dynamic friction may be greater, lesser or equal to the static friction and the assumption of a constant value of dynamic friction does not lead to an accurate prediction of the seismic displacements under various earthquakes.

Evaluation of the Resistance of a Polypropylene Geotextile Against Ultraviolet Radiation.

The exposure to solar radiation (mainly due to the action of ultraviolet radiation) is one of the main causes for the premature failure of many polymeric materials, including the geotextiles. In this work, a nonwoven polypropylene geotextile (stabilized with a known amount of a hindered amine light stabilizer) was exposed to ultraviolet-aging tests, both in the laboratory (accelerated conditions) and outdoors (natural conditions). The damage occurred in the geotextile (caused by the ultraviolet-aging tests) was evaluated quantitatively (by monitoring changes in its mass per unit area, thickness, and tensile properties) and qualitatively (by scanning electron microscopy). The results, among other findings, showed that: (1) the ultraviolet-aging tests (both in the laboratory and outdoors) induced relevant damage in the polypropylene fibers of the geotextile (transverse cracks), leading to the deterioration of its tensile behavior, (2) the amount of degradation increased with the increase of the ultraviolet radiant energy, (3) the laboratory tests caused a faster deterioration of the polypropylene fibers than the outdoor tests, and (4) the degradation found by scanning electron microscopy in the polypropylene fibers correlated well with the deterioration occurred in the tensile behavior of the geotextile.

Degradation of polypropylene geotextiles with different chemical stabilisations in marine environments

The geosynthetics applied in coastal engineering structures can be in contact with degradation agents capable of causing unwanted changes in their properties. In this work, three nonwoven polypropylene geotextiles with different stabilisation packages (different known amounts of Chimassorb 944 and carbon black) were exposed in situ to some degradation agents present in marine environments (weathering, seawater and action of tides). These exposures were carried out in Portugal (Archipelago of the Azores) and lasted for 36 months. The damage suffered by the geotextiles (in the different degradation tests) was evaluated quantitatively by monitoring changes in their physical (mass per unit area and thickness) and mechanical (tensile behaviour) properties. The results, among other findings, showed that: (1) weathering led to the highest damage in the geotextiles, (2) the weathering resistance of the geotextiles was highly enhanced by Chimassorb 944 and carbon black, (3) the geotextiles had a good resistance against the action of seawater and (4) the algae and dirt accumulated in the nonwoven structures during the exposure to the action of tides protected the geotextiles from UV-degradation (sunblind effect).

A Study on Geotextile—Sand Interface Behavior Based on Direct Shear and Triaxial Compression Tests

The effect of shear box size, geotextile type and properties and sand grain shape and size on the sand–geotextile interaction was investigated experimentally by conducting interface tests with conventional (100 mm) and large-scale (300 mm) direct shear boxes. Triaxial compression tests were also conducted on reinforced sand samples in order to evaluate the effectiveness of a methodology developed for obtaining interface friction coefficient values. Four uniform sands, one with subangular grains and three with rounded grains of different sizes were tested in dry and dense condition. Seven nonwoven polypropylene geotextiles of various types and properties and seven woven geotextiles with or without apertures were used in the tests. The conventional shear box is satisfactory for testing materials like those used in the present investigation because it gave comparable interface friction coefficient values to those obtained by the large-scale shear box. The sand–geotextile interaction behavior depends on the surface characteristics of the geotextiles and the interlocking of sand grains in geotextile apertures. The rounded shape and decrease in size of sand grains more effectively mobilize the soil–geotextile interface friction. The results of triaxial compression tests are in quantitative and qualitative agreement with the results of direct shear tests, for geotextiles without apertures. The friction efficiency for geotextiles with apertures obtained from triaxial compression tests attains a maximum value for an aperture ratio (aperture size of geotextile / mean grain size of sand) value approximately equal to 1.9, in agreement with the results of other studies.

Laboratory Evaluation of Interactions in the Degradation of a Polypropylene Geotextile in Marine Environments

The long-term behaviour of geosynthetics applied in coastal engineering structures can be adversely affected by many agents. This paper studies the resistance of a nonwoven polypropylene geotextile against some degradation agents present in marine environments and evaluates the existence of interactions between them. For that purpose, the geotextile was exposed to some laboratory degradation tests: immersion tests (in seawater, deionised water, and sodium chloride 35 g·L−1), thermooxidation, and artificial weathering. The geotextile was (1) exposed separately to each degradation test and (2) exposed successively to combinations of two or three degradation tests. The damage caused by the degradation tests was evaluated by monitoring the tensile properties of the geotextile. Based on the changes occurred in tensile strength, reduction factors were determined. The reduction factors obtained directly in the multiple exposures were compared with those obtained by the traditional methodology for the combined effect of the degradation agents. The results, among other findings, showed the existence of relevant interactions between the degradation agents and showed that the reduction factors obtained by the traditional methodology were unable to represent accurately (by underestimating) the degradation occurred in the geotextile.

A Comparative Numerical Study on Soil–Geosynthetic Interactions Using Large Scale Direct Shear Test and Pullout Test

The direct shear test and the pullout tests are two widely used test procedures for determining the properties of the soil–geosynthetic interface. It is evident from the previous literature that the interface properties obtained from these tests differ considerably. In the present study, an attempt has been made to compare the interface properties obtained from the direct shear test and the pullout tests using the numerical simulations. A nonwoven polypropylene geotextile was used in the study. Three different types of sands with different fines content were considered. The analyses were carried using finite element package PLAXIS2D in two dimensional frameworks. Initially, the numerical model was validated with the existing literature and the validated model was used to study the interface behaviour of the sand-geotextile interface. The results revealed that the interface properties obtained from the direct shear test and the pullout tests vary significantly. The presence of the fines content in the soil reduces the frictional resistance of the soil-geotextile interface. The interaction ratio value was found to vary between 0.67 and 0.97 for different types of sand. The friction coefficient of the pullout test was about 50% of the friction coefficient value obtained from the direct shear test. The friction angles obtained from the pullout test were found to vary between 30 and 50% of the direct shear tests. However, the apparent cohesion of the pullout test was found approximately four times the cohesion value obtained from the direct shear test.

Natural weathering of polypropylene geotextiles treated with different chemical stabilisers

Weathering (mainly due to solar radiation) may cause unwanted changes in the properties of geosynthetics, affecting their performance and shortening their lifetime. In this work, four nonwoven polypropylene geotextiles were exposed to natural weathering in Portugal during a maximum period of 3 years. The geotextiles were structurally identical, but had different known amounts of a hindered amine light stabiliser and carbon black in their composition. The damage suffered by the geotextiles (caused by weathering) was evaluated qualitatively (by visual inspection) and quantitatively by monitoring changes in their mechanical properties (tensile and static puncture tests). The results, among other findings, showed that: (1) weathering led to the deterioration of the mechanical properties of the geotextiles, (2) the behaviour of the geotextiles was highly dependent on their chemical composition, (3) the weathering resistance of the geotextiles was highly enhanced by the hindered amine light stabiliser and/or by carbon black, (4) a higher amount of the hindered amine light stabiliser (an increase from 0.2% to 0.4%, w/w) led to better weathering resistance and (5) the presence of carbon black (1.08%, w/w) in combination with the hindered amine light stabiliser (0.2%, w/w) resulted in the best protection against weathering.

Resistance of a nonwoven geotextile against mechanical damage and abrasion

The installation procedures (which induce mechanical damage) and abrasion can cause unwanted changes on the properties of the geotextiles. In this work, a nonwoven polypropylene geotextile was subjected to three degradation tests: (1) mechanical damage, (2) abrasion and (3) mechanical damage followed by abrasion (successive exposure). The damage caused by the degradation tests was evaluated by tensile, tearing and static puncture tests. Based on the changes occurred in the mechanical properties, reduction factors were determined. Results showed that the degradation tests provoked relevant reductions in the mechanical strength of the geotextile (higher reductions in the successive exposure to both degradation tests). The reduction factors for the combined effect of mechanical damage and abrasion obtained in the successive exposure to both degradation tests were different (slightly higher) than those obtained by the traditional methodology (determination of reduction factors separately for each degradation test and further multiplication).

Influence of soil confinement on the creep behavior of geotextiles

This work addresses the influence of soil confinement on the creep behavior of geotextiles by presenting the results of a full scale field test. Two samples of nonwoven polypropylene geotextile were inserted at different depths in a 3 m high compacted sand fill. The samples were loaded with a constant tensile load during a 1000 h period. To maintain a constant load during the test, a system of weights, pulleys and load cells was used. The sand fill and the samples were instrumented with several types of transducers in order to measure strains, displacements, applied forces, soil stresses and temperature. Direct shear and inclined plane tests were conducted to measure the mechanical properties of the interfaces. An interpretive model is proposed to analyze the field results. The confined creep behavior in the field is compared with results obtained by other authors and with in-isolation creep results obtained from laboratory tests.

Designing and testing of a portable filter for groundwater defluoridation and desalination, equipped with non-woven geotextiles

Using non-woven polypropylene geotextile, a filtration unit was designed for portable prototype filter capable of defluoridation and desalination. The filtration unit contains geotextile bag filled with mica and graphite sand. Emphasis was given to make the filter design as simple as possible that is suitable for rural areas. The designed filter was continuously tested for three months along with ceramic (Candle) filter and Pureit filter for comparative studies. The performance of the filters was evaluated on the basis of the percentage of residue removed by the individual filters and cleaning period of the filters. The results of the improvement in the water quality made by prototypes filter without cleaning show reduction in concentration of fluoride and electrical conductivity (EC) by 83.06 and 45.75%, respectively. While the other two filters despite weekly cleaning shows reduction in concentration of fluoride and EC by 74.20 and 30.04%, (ceramic filter) and 93.68 and 86.37% (Pureit filter), respectively. The prototype filter with very simple in design has performed better than other filters with complex designs. The test shows that uses of non-woven geotextiles (polypropylene) along with sand can provide an alternate solution to the expensive defluoridation and desalination processes.

Performance of two geosynthetic reinforced walls with recycled construction waste backfill and constructed on collapsible ground

ABSTRACT: Geosynthetic reinforced soil walls are now an accepted technology for the solution of earth-retaining problems due to cost savings, easy and quick construction, and associated environmental benefits. Additional savings and reduction in environmental impact can be realised by using recycled construction and demolition waste (RCDW) as the backfill material. This paper describes two such structures that were built to full scale and instrumented. One of the walls was reinforced with a woven polyester geogrid (wall 1) and the other (wall 2) with a relatively more extensible nonwoven polypropylene geotextile. Both walls were constructed using RCDW as backfill material and were built on a foundation soil prone to fabric collapse due to increased stress and/or increase in moisture content. During the monitoring period the walls were subjected to a rainy season followed by induced inundation of the foundation to trigger soil fabric collapse. The results showed that foundation soil collapse influenced wall behaviour more than geosynthetic type. The exception to similar performance was local face bulging which was greater for wall 2 (geotextile) with the more extensible reinforcement under unconfined conditions than for wall 1 (geogrid) which was expected in the moving formwork construction method. However, directly behind the wall face where both reinforcement material types were confined the horizontal displacements were similar. In addition, at locations beyond half of the wall base length the strain distributions were low (1% or less) for both walls. A practical conclusion from this study is that if the wrap-face appearance at end of construction is not a concern (i.e. large bulging) then wall performance is unaffected by the choice of reinforcement types used in this investigation.

Apparatus for Geosynthetic Interface Testing and Evaluation Under Elevated Temperature Conditions

Abstract Temperature is one of many important environmental variables that can impact the long-term performance, strength, and deformation characteristics of many man-made construction materials, including geosynthetics. The functional engineering properties of these materials must remain within acceptable limits during their service life to ensure that the overall design and performance are acceptable. In the case of geosynthetics used in landfills and other applications, laboratory interface shear tests are performed under standard test conditions, including temperature. Information emerging today shows that geosynthetic interfaces (i.e., in landfill liner applications) experience elevated temperatures resulting from exothermic reactions occurring in the waste body, amongst other factors. To this end, the field conditions at elevated temperatures should also be simulated in the laboratory during physical/mechanical laboratory tests in order for researchers to better understand in situ functional engineering properties and operational performance of manmade geo-construction materials. For this purpose, a temperature-controlled chamber was designed and developed to allow the shear behavior of geosynthetic–geosynthetic and soil–geosynthetic interfaces to be evaluated at different temperatures. This paper describes both the development and the validation of the test system. The results of experimental investigations are presented to illustrate how the shear behavior of interfaces between nonwoven polypropylene geotextile and smooth and/or textured high density polyethylene geomembrane, as well as those between rounded and/or angular sand and geomembranes, change with temperature. The results provide insight into the importance of being able to independently control this variable during mechanical testing in the laboratory.

Modeling Effect of Geocomposite Drainage Layers on Moisture Distribution and Plastic Deformation of Road Sections

AbstractThe effect of geosynthetic layers on moisture distribution and plastic deformation of paved and unpaved road sections is studied using numerical simulations. The geosynthetic layers consisted of, from top to bottom, a transport layer, a geonet, and a nonwoven geotextile (referred to as a geocomposite capillary barrier drain by previous researchers). Two geotextile types were modeled as the transport layer: woven fiberglass and nonwoven polypropylene. The numerical models were verified against published results obtained from a soil-geotextile column. Inclusion of the geosynthetic layers at the interface of the aggregate base course (ABC) and subgrade increased suction in the subgrade and decreased it in the ABC during a simulated rainfall event. The woven fiberglass geotextile led to higher suctions in the ABC compared with the nonwoven polypropylene geotextile. The geosynthetic layers decreased the plastic deformation in both paved and unpaved road sections through combined mechanistic and hydraul...

Cold temperature testing of geotextiles: new, and containing soil fines and moisture

A test program examined the behavior of geotextiles at very low temperatures, and tested the hypothesis that the presence of soil fines and moisture would result in decreased strength values compared with geotextiles at cold temperatures. Wide-width strip tensile and static puncture tests were performed on needle-punched nonwoven polypropylene geotextiles at 20°, 0°, –20°, –40° and –54°C for the wide-width strip tests and at –51°C for the puncture tests on new specimens and specimens that contained soil and moisture. At all sub-freezing temperatures, the specimens that contained ice and soil were much stronger and more brittle in tension than the new specimens. Soil and moisture did not significantly influence puncture strength.