Geotextile performance of fabrics woven by polyethylene terephthalate yarns prepared directly from drinking bottles

Abstract

This research article describes the preparation and characterization of geotextile-reinforced embankment made from yarns produced from polyethylene terephthalate bottles by the bottle cutter and stretching yarn prototype. The yarns produced from plastic bottles were weaved to obtain fabrics with different pattern structures. Yarns and fabrics samples were characterized including yarn number, yarn tensile, fabric thread density, fabric weight, fabric thickness, fabric breaking strength, and fabric bursting strength. The performance of the fabric samples as a geotextile was evaluated by direct shear test, California bearing ratio, and water permeability. The results show that the fabric pattern structure plausibly was the main factor for geotextile performance. The fabric samples with low thread density could develop both interlocking and interbedding mechanisms resulting in higher shear stress and California bearing ratio. Lastly, PLAXIS 2D program simulation with finite element method was used to estimate the possibility of the use of fabric samples as geotextile-reinforced embankment. It was found that the predicted safety factor of soil erosion with fabric sample could reach the value of one which is higher than the safety factor of the soil erosion without fabric sample.

Keywords

Polyethylene terephthalate yarn polyethylene terephthalate fabric bottle cutter geotextile reinforcement

Nowadays, plastic products are worldwide used in different applications. Plastic production has continuously increased every year with an annual growth rate of 9%.¹ It was reported that 150 m tons or 50% of the annual global production of solid plastics was disposed to the environment each year.² Moreover, there was another report which showed that in 2021, 40 m tons of plastic waste were generated in the USA and only 5–6% of plastic waste was recycled.³ Consequently, the high accumulation of plastic waste in the environment has become a seriously environmental issue and needs to be solved urgently.

One of the most favorable drink packaging materials in the world is polyethylene terephthalate (PET). This is because of the excellent properties of PET including mechanical properties and lower weight than glass bottles.⁴ In 2021, PET was produced at the rate of around 32.31 m tons per year.⁵ However, regarding the end life of PET products, PET plastic wastes were turned into solid wastes, including microplastics and macroplastics, that were disposed to environment for up to 5% of total plastic wastes.¹ One approach to reducing PET plastic wastes, especially PET bottles is the recycling process. Recently, waste PET plastic bottles were mostly considered to be recycled due to lower absorbed contamination than other plastic materials, easy separation from the waste stream, and mostly colorless materials.^4,6 Several industrial companies set targets to recycle and reuse about 65% of PET drink packaging material by 2030.⁶ It was reported that the end markets of recycled PET plastic were fiber, sheet, bottle, and strapping products.⁴ Recently, to reduce PET wastes, various recycled processes were developed.

Typically, the recycled PET was obtained by conventional recycling processes including thermal and chemical methods.⁷ For the thermal recycling process, PET plastic wastes were shredded and heated for extrusion to pellets or filaments.⁸ Nevertheless, the duration time and energy consumption caused meant a higher cost with this recycling process. For the chemical process, the recycled PET was produced by depolymerization process of PET to monomers (ethylene glycol and terephthalic acid or terephthalic acid methyl ester) using hydrolysis or methanolysis reactions.^4,7 The obtained monomers have to be purified before re-polymerization to PET.⁴ However, this recycling process is too complicated and not widely used commercially. To reduce energy consumption and cost of additional chemicals in the thermal and chemical recycling processes, a novel mechanical recycling process of PET plastic bottles was introduced in this research study. For this recycling technique, the used PET plastic bottles are cut and stretched using the bottle cutter and stretching yarn machine that was built and patented⁹ to produce recycled PET yarns without melting or any chemical means. Obviously, this method of PET yarns production is simpler, more environmentally friendly, and lower in cost than the conventional processes. Besides, this process encourages the zero-waste concept, reduces carbon emissions, and pursues carbon neutrality.

Recently, recycled PET fiber or yarn was used for several applications including fiber reinforced concrete, water filtration, automobile, and geotextile uses.^10–15 Over the past decades, geotextiles were broadly used in geotechnical engineering with different functions such as separation, filtration, drainage, reinforcement, stabilization, barrier, and erosion protection.¹⁶ It was reported that there are more than 1.4 billion m² of geotextiles used every year.¹⁶ Most geotextile products are made of non-biodegradable polymeric materials including polyolefin, polyester, and polyamide due to long-term use. Therefore, the obtained recycled PET yarn from this research was investigated for its potential uses as geotextile for reinforcement function.

The main objective of this research is to produce woven geotextile materials from recycled PET yarn. The PET yarn was made from postconsumer PET drinking bottles using the bottle cutter and stretching yarn machine. The recycled PET yarns were woven to obtain PET fabrics in different structures. Both PET yarn and fabrics were characterized for their basic attributes including yarn number, tensile strength, fabric thread density count, fabric weight, and fabric thickness. In addition, direct shear test, California bearing ratio, and water permeability were measured to investigate the possibility of using these materials as geotextile-reinforced embankment. To further confirm the possibility of using the prepared fabrics in geotextile application, PLAXIS 2D 2012 program simulation was used to analyze the soil erosion and calculate the predicted safety factor in the cases of with and without geotextile-reinforced embankment.

Experiments

Materials and yarn preparation

Materials

The materials for this study were used PET plastic bottles 600 ml (Crystal, 600 ml), commercial polyester yarn (No. 500 D, Teijin Polyester, Thailand), commercial polypropylene (PP) nonwoven (Tencate Polyfelt, Model: TS60, Tencate Geosynthetics, Bangkok, Thailand).

Yarn preparation

A used plastic bottle made from PET was prepared by hot air blowing at 85°C for 5 min for polishing the bottle edges. Afterward, the PET bottle was cooled down to room temperature and 1 in cut off from the bottom part. The PET yarns were prepared from the bottle cutter and stretching yarn machine⁹ as shown in Figure 1. According to the schematic illustration in Figure 2, the bottom cut bottle was placed at the bottle stand (A) and cut by the blade to create a 2 mm width of flat yarn. The flat yarn manually collected at the winder (B). Afterward, the flat yarn was stretched by two rollers (C and E) with the rate-controlling of 8 rpm of the first motor and 17 rpm of the second motor. Between two rollers, there was a heating plate (D) set up at 100°C for polishing the edges of the flat yarn. The speed and temperature of rollers and heating plate were controlled using control panel (F). The stretched yarn was manually collected under the table and ready for warping and weaving process.

Figure 1.

Bottle cutter and stretching yarn prototype.

Figure 2.

Schematic illustration of yarn produced from polyethylene terephthalate (PET) bottle cutter and stretching yarn machine.

Yarn characterization

Yarn number measurement

Yarn number was measured following the standard test method for yarn number based on short-length specimens (ASTM D1059-01). Prepared PET yarn was cut to the length of 1 m and weighed by digital balance with a four-decimal weighing scale. Yarn number was calculated following equation (1).

Yarn number (Denier) = \frac{W \times 9000}{L}

(1)

where

W

is the weight (g) and L is the length (m) of the yarn sample.

Tensile strength measurement

The tensile strength of the prepared PET yarns and the commercial polyester yarns were measured by a tensile tester (model 5566, Instron, Norwood, Massachusetts, USA) using the procedures outlined in the standard test method for tensile properties of yarns by the single-strand method (ASTM D2256). The standard deviations of each yarn were measured between 10 samples.

Woven textile fabrication

Warping process

The recycled PET yarns obtained from the bottle cutter and stretching yarn machine were prepared by a warping machine (model: SW550, CCI Tech Inc., New Taipei City, Taiwan) before the next process. The number of yarn and rolling speed were set up before collecting yarns in the warping beam. To maintain the tension uniform throughout the warping process, the rotational speed decreases with increasing the beam diameter and the yarn warping speed remains constant.

Weaving process

The woven fabrics of PET yarns from warping process were produced using weaving machine (model: SL1900 EG, CCI Tech Inc., New Taipei City, Taiwan) with one yarn per one hole in weaving comb number 48. Fabric pattern structures were designed using ArahWeave DEMO program (Ljubljana, Slovenia). The recycled PET yarns were used as warp yarns for samples A, B, C, D, and E. On the other hand, samples F and G were prepared using the recycled PET yarns as warp yarns and the commercial polyester yarns were used as weft yarns. Fabric structure and nomenclature are given in Table 1, while the fabric weave pattern images are shown in Figure 3.

Table 1.

Fabric structure and nomenclature

No.	Structure	Yarn
No.	Structure	Warp yarns	Weft yarns
A	Plain	PET bottle	PET bottle
B	Twill	PET bottle	PET bottle
C	Plain	PET bottle	PET bottle
D	Twill	PET bottle	PET bottle
E	Basket	PET bottle	PET bottle
F	Plain	Commercial polyester	PET bottle
G	Twill	Commercial polyester	PET bottle
H	Nonwoven	Commercial polypropylene

PET: polyethylene terephthalate.

Figure 3.

Fabric structures of all fabric samples A to H.

Woven textile characterization

Fabric thread density count measurement

Fabric thread density count measurement of all samples of PET woven fabrics and commercial PP nonwoven fabric was conducted using the standard test method for fabric count of woven fabric (ASTM D3775-98). Briefly, the fabrics were counted the number of yarns both warp and weft yarns in 1 in at random positions using a magnifying glass and counting pin.

Fabric weight measurement

Fabric weight measurement was performed following ASTM D3776-96. All fabric samples were cut to 10 × 10 cm² and weighed by digital balance with a four-decimal weighing scale. The standard deviations were measured between five pieces of each sample.

Fabric thickness measurement

Fabric thickness measurement was conducted following ASTM D1777 using a feather touch digital thickness tester (model M034E, Union TSL Ltd, Bangkok, Thailand). Briefly, all fabric samples were cut to 10 × 10 cm² and measured by a thickness measurement machine for 6 s or until constant values were shown. The standard deviations were measured between 10 positions of each sample.

Mechanical property measurement

Fabric breaking strength was measured following ASTM D5035-11 (2015) using a tensile tester (strip test, model 300ST, Tinius Olsen Ltd, England). The standard deviations were measured between three pieces of each sample. Additionally, fabric bursting strength was measured following ASTM D6797-2015 using a fabric ball-bursting strength tester (Model TF003, Testex, Guangdong, China). The standard deviations were measured between three pieces of each sample.

Geotextile performance evaluation

Direct shear test of soils under the consolidated drained condition

A direct shear test of soil under consolidated drained condition was conducted following ASTM D3080-98. Briefly, dried soil was contained and compressed in the bottom part of a shear box with cross-sectional sizing 6 cm × 6 cm. The amount and the height of dried soil in the shear box were maintained for every experiment. Each sample was placed on top of the dried soil and connected with the top part of the shear box using screws. Afterward, the dried soil was added and compressed in the top part of the shear box and was set up into the direct shear test machine. Three loading tests were performed to measure the shear stress of each sample at 5, 10, and 20 kg. The shear stress was measured following equation (2).

τ = \frac{F}{A}

(2)

where

τ

is the direct shear stress (kg/cm²), F is the load (kg) which was calculated from the spring constant (0.0174 kg/Div) and reading dial (Div) at the machine, A is the cross-sectional area (cm²).

The maximum direct shear stress values were plotted with the compressive stress values at three loading tests. The linear regression was applied to the plots. The angles between the direct shear stress and the compressive stress are the angle of internal friction.

California bearing ratio (CBR) of laboratory-compacted soils

The dry density of the compressed soil sample was tested following ASTM D-1557. The weight and volume of soil were measured to plot the value of the dry density and moisture contents in the range of 6–11%. The optimum moisture content at the maximum value of dry density was used to prepare a compressed soil sample for CBR testing.

The CBR was measured following ASTM D 1883-99. Briefly, 6 kg of dried soil was soaked with water and added to the mold with a diameter of 6 in and height of 2 in. The soil in the mold was compressed consistently 56 times following the standard for each layer. After three layers were compressed, each sample was placed over and compressed as previously 56 times. The other layer of soil was added above the sample and compressed as previously. The metal surcharge was placed over the mold and set up the mold to the testing machine. The piston (3 × 3 in²) was set up to the machine over the setting mold for compressing at 0.05 in/min. The reading dial gauge were read at different penetration distances at 0.025, 0.050, 0.075, 0.100, 0.125, 0.150, 0.175, 0.200, and 0.5 in, respectively. The %CBR was calculated following equation (3).

% CBR = \frac{Test unit stress}{Standard stress} \times 100 %

(3)

where the test unit stress (psi) was read from the gauge at the machine, the standard stress of the penetration at 0.100 in (1000 psi) and 0.2 in (1500 psi) following the standard. The standard deviations were measured between two samples.

Water permeability test of granular soils (constant head)

The water permeability in granular soil was tested following ASTM D2434-68. Summarily, 3 kg of dried soil was mixed with water 255 g and added to the mold with a diameter of 14 cm for three layers. Each sample was placed between the second and third layers. The soil in the mold was compressed consistently 25 times following the standard for each layer. The mold was connected to the valve with a glass pipette containing water. The valve was opened to let the water flow in the mold. Volumes of water and times were collected in each experiment. Each sample was measured with the standard deviations between three experiment times.

Numerical simulation by PLAXIS 2D

The interaction behavior of soil deposit with the geotextile was investigated by the finite element method (FEM) using the commercial geotechnical software as PLAXIS 2D 2012. In the numerical analysis, the fifteen-node triangular elements were used to represent the foundation soil. The sand embankment with the side slope of 1:1 (vertical: horizontal) was simulated. The height of embankment assumed was 1 m as the general height of embankment used in Thailand. The sand behavior was simulated by the Modified Cam Clay (MCC) stress-strain model. One of the important aspects in the design of embankment is the calculation of the safety factor. When the slope of embankment is reinforced horizontally with the tensile materials such as geogrid or steel strip, the safety factor is generally higher than the without reinforcement case. In attempt to investigate the performance of studied geotextiles, the two layers of geotextile were simulated by the elastic model and replaced at the side slope. The safety factor of embankment with/without reinforcement were computed by using the c-phi reduction method in PLAXIS 2D. The constrained modulus of geotextile was 18,000 kPa based on the results of tensile testing. The input soil properties are listed in Table 2. The uniformly loading were applied at 28, 56, and 112 kPa respectively at the top of embankment as a service loading in engineering practice.

Table 2.

Soil properties for finite element method (FEM)

Properties	Value
Dry unit weight ( $γ_{d}$ )	18.1 kN/m³
Cohesion value (c)	0 kPa
Angle of friction ( $\emptyset$ )	44.3°
Young’s modulus (E₅₀)	15,000 kPa
Reduction factor (R_inter)	0.55, 0.60, and 0.65

Results and discussion

Yarn preparation and characterizations

The bottle cutter and stretching yarn machine were designed and built to produce PET yarns from PET plastic bottle wastes. This yarn production is simple and could reduce chemical and energy consumption during the process compared to the conventional PET recycling process. The highest temperature used in this yarn preparation is only 85°C for polishing the bottle edges before setting up in the cutter and stretching yarn machine while the conventional PET recycling process requires the heating temperature at 250–280°C or higher than the PET melting point for the spinning process.¹⁰ In addition, various chemicals for depolymerization are not necessary for this form of production.

Table 3 demonstrates the physical and mechanical properties of PET yarn from plastic bottles compared to commercial polyester yarn. The results show that the yarn number of PET yarn is six times higher than commercial polyester yarn. As a result, the maximum load and tenacity of PET yarn are higher. As shown in various studies, the strength property and tenacity of textile are important and needed to be improved for geotextile application due to the bearing capacity of soil and to protect from landslide disaster.^17–20 The maximum load of yarn directly impacts the fabric tensile strength. Therefore, PET yarns from plastic bottles have more potential to be used as a geotextile-reinforced embankment.

Table 3.

Physical and mechanical properties of yarns

Yarn type	Yarn number	Maximum load	Tenacity
Yarn type	(Denier)	(N)	(gf/den)
PET yarn from plastic bottle	3246.10 ± 58.73	6593.43 ± 433.01	12.66 ± 0.83
Polyester yarn	512.46	38.66	7.70

PET: polyethylene terephthalate.

Woven textile fabrication and characterizations

The fabric pattern structure and nomenclature of the various textiles are shown in Table 1 and Figure 3. The samples A, B, C, D, and E were woven using PET bottle yarn obtained from the cutter and stretching yarn machine for both warp yarn and weft yarn. On the other hand, samples F and G were fabricated using commercial polyester for warp yarn and PET bottle yarn for weft yarn. For the fabric pattern structures, samples A, C, and F provided the plain pattern structure, while samples B, D, and G provided the twill pattern structure. Only sample E was the basket pattern structure. All fabric samples were characterized and evaluated for geotextile performance compared to sample H which was commercial polypropylene nonwoven fabric.

Fabric thread density count, fabric weight, and fabric thickness were measured for the physical properties of all fabric samples. According to Figure 4(a), it was found that the thread densities of all samples were in the range of 10–40 yarns/in or the low type of fabric count. ¹⁹ However, the thread density of sample G for both warp and weft was higher than most samples (except sample B). This result agreed with the observation in Figure 3 that sample G revealed a higher thread density. As a result, sample G provided the highest fabric weight at more than 400 g/m² which was in the heavyweight type of fabric weight as shown in Figure 4(b).²¹ Likewise, samples A and B which provided higher warp thread density at around 25–26 counts per inch demonstrated higher fabric weight at approximately 400 g/m². Other samples with lower thread density had a tendency to lower fabric weight mostly in the range of medium-weight type.²¹ As shown in Figure 4(c), the fabric thicknesses for all samples were in the range of thick type of fabric thickness or higher than 0.47 mm.²¹ It can be observed that samples A, B, C, and D were very close, while samples E, F, and G were lower. It can be concluded that the fabric sample E with basket structure provided lower thickness. Additionally, samples F and G fabricated using commercial polyester yarn which had a much lower yarn number than PET yarn from a plastic bottle as reported in Table 3 provided lower fabric thickness than samples fabricated by only PET yarn from plastic bottles. However, samples A, B, C, and D with plain and twill fabric structures have similarities in fabric thicknesses.

Figure 4.

(a) Thread density count; (b) fabric weight; and (c) fabric thickness of fabric samples.

Tensile testing and bursting strength of all samples were performed to evaluate mechanical properties. Typically, the most important property of the fabric is strength such as tensile and bursting strengths. The maximum loads of fabric samples obtained from the tensile test were measured in both warp and weft directions. As shown in Figure 5(a), samples A and B had the maximum loads in the warp direction and were higher than other samples. The results agreed with the warp thread density as shown in Figure 4(a). Moreover, it was found that the maximum loads of samples C and D especially in the weft direction were lower than other samples. The results show good agreement with previous findings of the warp and weft thread density of samples C and D. Likewise, the highest maximum load in the weft direction as shown in sample G had the highest thread density in the weft direction. However, the maximum load in the warp direction of F and G were lower than sample A and B, although samples F and G had thread densities in the same range as samples A and B. As in previous results showing that samples F and G fabricated from commercial polyester yarn in warp direction with a lower strength of the yarn, the maximum loads of fabric samples were obviously lower. It was also reported that various factors including fabric structure, yarn count or thread density, and yarn strength impacted the strength of fabric.²² Therefore, for samples F and G, the strength property of yarn had more impact on the tensile strength of the fabrics than the thread density. The maximum loads of all fabric samples were measured and compared to commercial PP nonwoven (sample H). It was found that sample H displayed a lower maximum than several fabric samples in this research study. According to Figure 5(b), it was found that samples A, B, and G displayed the highest bursting strength at 2000 N. It was also shown in the literature that the minimum bursting strength of commercial geotextile is at least 1200 N.²² Therefore, these samples could possibly be used for geotextile application. This could be explained by the bursting strength being affected by thread density and the tensile strength of fabric samples. In addition, the literature shows that the yarn tenacity or strength is the most important parameter that affects fabric bursting strength.²³ Unfortunately, it was found that there was no significant difference between the plain, twill, and basket structures.

Figure 5.

(a) Tensile testing and (b) bursting strength of fabric samples.

Geotextile performance evaluation

Apart from the physical and mechanical properties of textiles, geotextile performance including direct shear stress, %CBR and stress penetration, and water permeability were investigated in this research. Direct shear stress property was typically tested for geotextiles to study the interface behavior between soil and geotextiles.^24–26 Figure 6 shows direct shear stress between soil and all fabric samples compared to without fabric samples for three different loading tests of 5, 10, and 20 kg. The linear regression parameters of the direct shear stress test in Figure 6 including slope, Y-interception (cohesion factor), R-square, and the angle of internal friction were estimated and are reported in Table 4. Typically, the direct shear stress can explain the interaction between soil and reinforcement. According to Table 4, it was found that sample C displayed the highest angle of internal friction at 45.16°. It is known that interlocking and interbedding mechanisms are the main factors to affect shear stress.²⁷ According to the fabric pattern structures in Figure 3, it was observed that sample C with low thread densities demonstrated the higher roughness and larger holes that plausibly developed both interlocking and interbedding mechanisms resulting in the highest shear stress. Furthermore, at 20 kg of loading, sample C exhibited the highest direct shear stress at 60.78 kPa. Therefore, sample C was selected to be the representative of geotextiles in the PLAXIS simulation.

Figure 6.

Direct shear stress of fabric samples.

Table 4.

Linear regression parameters of shear stress of fabric samples

No.	Slope	Cohesion value (Y-interception)	R²	The angle of internal friction
Non	0.7845	0.0283	0.9729	38.11418
A	0.8744	0.0900	0.9969	41.16645
B	0.7093	0.0994	0.9722	35.34808
C	1.0047	0.0360	0.9987	45.13433
D	0.9126	0.0620	0.9996	42.38358
E	0.7973	0.0929	0.9999	38.56536
F	0.734	0.0696	0.9914	36.27867
G	0.7798	0.0559	0.9953	37.94711
H	0.5781	0.1046	0.9635	30.03221

To avoid sliding soil, geotextiles can improve the load-bearing capacity of soft soils by increasing frictional forces at the interface of soil and a smooth surface.²⁸ Therefore, the load-bearing capacity property is one of the main properties of geotextiles that should be considered. Before measuring the bearing property, the optimum moisture content at 8.53% was obtained from Figure 7(a). The %CBR of all fabric samples were measured at 0.1 in and 0.2 in of stress penetration following the standard as shown in Figure 7(b). The %CBR at 0.1 in penetration was higher than at 0.2 in penetration, which is similar to routine CBR test results.²⁹ The results showed all fabric samples can improve %CBR compared to the soil without fabrics (except sample E). Moreover, samples C and D tended to have the highest %CBR, which agrees with the direct shear stress property but is not significantly different from other samples. Test unit stress values at different penetrations in the range of 0.0–0.5 in are also reported in Figure 8. It was found that test unit stress values increased with increasing penetration.

Figure 7.

Moisture content of (a) soil and (b) percentage California bearing ratio (%CBR) of fabric samples.

Figure 8.

The test unit stress values for all fabric samples.

Water permeability is a hydraulic property, one of the main properties of geotextiles.²⁸ The coefficient of water permeability was measured through all fabric samples compared to the soil without fabric samples. As shown in Figure 9, the coefficient of water permeability significantly reduced after adding fabric samples to the soil. Only fabric sample H can reduce the water permeability insignificantly. As the reduction of water permeability by fabric samples, these geotextiles can be plausibly used as a function of a liquid barrier to prevent the passage of liquid that contacts with the geotextiles.

Figure 9.

The coefficient of water permeability for all fabric samples.

The prediction of the safety factor of the soil erosion was conducted using the PLAXIS 2D 2012 program simulation with FEM. Sample C was the representative geotextile for the simulation. The soil properties input to the program were defined and estimated following the properties of pure beach sand as shown in Table 2. Figures 10 and 11 display the soil analysis and safety factor value in the case of soil without a geotextile. On the other hand, Figures 12 and 13 demonstrate the soil analysis and safety factor value in the case of soil with two layers of geotextile sample C. The simulation and analysis showed that the safety factor in the case of soil with two layers of geotextile sample C with could reach one which is higher than the safety factor in the case of soil without geotextile that showed the safety factor at 0.79.

Figure 10.

Soil analysis without geotextile by PLAXIS 2D 2012.

Figure 11.

Safety factor of soil without geotextile by PLAXIS 2D 2012.

Figure 12.

Soil analysis with geotextile by PLAXIS 2D 2012.

Figure 13.

Safety factor of soil with geotextile by PLAXIS 2D 2012.

Conclusions

To reduce PET bottle wastes, PET yarns were successfully produced from PET bottles using the bottle cutter and stretching yarn prototype. This alternative recycling process of PET bottle wastes required lower chemical and energy consumption than the conventional process. Additionally, the tensile strength of PET yarns was higher than the commercial polyester yarns, so they have the potential to be used as a geotextile-reinforced embankment. Fabrics in different weave structures were then made from the prepared PET yarns and commercial polyester yarns for geotextile performance tests. The results showed that the fabric structure is the main factor affecting geotextile performance. The fabric samples with low thread density develop both interlocking and interbedding mechanisms resulting in higher shear stress and CBR. It was confirmed that the fabric samples made from recycled PET yarns could be utilized for geotextile-reinforced embankment as confirmed with PLAXIS 2D program simulation with FEM.

Footnotes

Acknowledgements

The authors thank the Department of Civil Engineering, Faculty of Engineering, Rajamangala University of Technology Thanyaburi, Thailand for giving access to the direct shear test and CBR test machines. The authors thank Phatchphum Sinuansuk, Solos Kaewkling, and Kitsada Thattajaru for collecting experiment data results.

Declaration of conflicting interests

The author(s) declare that there is no conflict of interest regarding the publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by National Science and Technology Development Agency (NSTDA), Thailand with A New Researcher Grant sponsored by the Ministry of Science and Technology (research grant number FDA-CO-2563-12856-TH, 2020).

ORCID iD

Bintasan Kwankhao

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