Innovative Geotextiles for Reinforcement of Roadside Ditch

Geotextiles consisting of meandrically arranged coarse ropes were produced. For the production of the ropes Kemafi l technology was applied and the wastes of various nonwovens were used. The geotextiles were used for the protection of the roadside ditch in a clay ground. After instalation of the geotextiles ensured immediate and eff ective protection of the ditch. During heavy rains the meandrically arranged geotextiles formed a system of cascades which slowed down the stream of water fl owing in the ditch. Additionally, the retention of water between the meanders of geotextiles and water absorption inside the ropes was observed. The materials used for the production of geotextiles had suffi cient resistance to biodegradation and ensured the protection of the ditch at least for one growing season.


Introduction
Road side ditches are built to protect the road construction and ensure safety of drivers.Th e ditches prevent overland runoff from reaching the roadway, as well as drain water from the road surface.Th e road side ditches are fi lled with water periodically, depending on weather conditions.With high rainfall the ditches are quickly fi lled up and are exposed to strong erosive action.Erosion is the highest during the construction phase in the period before a resistant grass cover is established in the ditch.Ditch erosion problems are related to soil type, intensity of runoff and ditch geometry.Because of erosion temporary and/or permanent protective linings of ditches are necessary.Temporary linings provide protection against erosion through the establishment of vegetation and then degrade over time, typically in a 2-year period.For temporary protection jute mats, straw and wood chips are applied.Permanent protection, which consists of fl exible or rigid linings secures ditches over a long term.
Typically, rigid linings include concrete and paved elements which reveal low permeability and inhibit the water infi ltration into the soil.In the ditches protected with such linings high velocities of the water stream are generated, which may cause erosion problems at ditch outlets.In addition, rigid linings have been associated with water seeping beneath the structure, at the sidewalls and structure inlet, causing soil piping under the structure and consequent failure of the structure.Flexible linings, more oft en in the form of natural vegetation, have the ability to re-establish themselves seasonally.Natural permanent lining, typically grass, off ers high hydraulic resistance which promotes lower velocities and increased infi ltration.Th e grass blades serve to reduce fl ow velocity and thereby lower shear stress, while the root structure reinforces shear resistance of the soil.In addition to the above mentioned methods geotextile materials can be used for the protection of road side ditches.Diff erent products made from non-degradable and degradable materials are available on the market [1].
Tekstilec, 2016, 59 (2), [115][116][117][118][119][120] Innovative Geotextiles for Reinforcement of Roadside Ditch Some years ago innovative geotextiles created from meandrically arranged coarse ropes, produced by Kemafi l technology, were invented [2].Th e technology involves the use of a small circular knitting machine which is equipped with four hooked loopers arranged around a guide tube (Figure 1).Th e threads guided by the loopers form a tubular knitted sheath around the core.Th e sheath consists of four stitch courses running parallel to the longitudinal axis of the ropes and the stitch wales running spirally around the rope [3].

Figure 1: Th e guide tube with loopers in the Kemafi l machine
Th e geotextiles created from meandrically arranged Kemafi l ropes were successfully used in Germany for the protection of steep slopes at road construction [4].In our investigations the geotextiles were applied for the reinforcement of a roadside ditch in a clay ground.Th e geotextiles were installed in a trapezoidal roadside ditch, which was built along the new road in the hilly terrain near Bielsko-Biala (Silesia, Poland) (Figure 2a).Th e ditch was built in the clay soil with a compact structure characterised by law water permeability.Initially, the ditch was lined with openwork concrete panels.During high precipitation the ditch was quickly fi lled with large quantities of water.Due to the inclination of the road (inclination angle 3%) the stream of water in the ditch quickly accelerated and fl owed down at high speed.As a result, a serious erosive damage was observed at the ditch outlet (Figure 2b).

) the ditch lined with concrete panels fi lled with rainwater
To minimize the eff ect of erosion geotextiles were installed in the ditch and their behaviour during one vegetation season was observed.

Materials
Th e coarse ropes with a diameter of 12 cm made from nonwoven wastes were produced.For the production of ropes the strips of woollen nonwoven,

Tekstilec, 2016, 59(2), 115-120
Innovative Geotextiles for Reinforcement of Roadside Ditch layered needle-punched composite built from two layers of woollen nonwoven separated by jute fabric and a stitch-bonded nonwoven from recycled fi bres were used.Th e parameters of the nonwovens are presented in Table 1.Th e stitch-bonded nonwoven was produced by Maliwat system from the blend of recycled natural and synthetic fi bres.For stitching of the web a polyester multifi lament thread with a linear mass density of 148 dtex was applied.Th e ropes were sheathed by a cotton twine with a diameter of 3 mm.Th e ropes were meandrically arranged in segments of a width of 1.8 m.Th e subsequent turns of meanders were connected with polypropylene chains produced by using a knitting technique.

Results and discussion
Th e meandrically arranged geotextiles were installed as the lining of the part of the ditch between the sections lined with the concrete panels (Figure 3a).For the installation of geotextiles the site with the highest road inclination was chosen.Th e segments of geotextiles were arranged in the ditch with turns perpendicular to the ditch axis.Th e middle zone of the segments was laid in the bed of the ditch, while its both lateral zones were bent on the ditch banks.Th e ropes were anchored to the soil with steel "U-shaped" pins, both to the bottom and the banks of the ditch (Figure 3b).Th e geotextiles were installed in the spring at the beginning of the growing season.In the following weeks the behaviour of the geotextiles in the ditch was monitored.
During heavy rains a system of transversal microdams was observed on the neighbouring turns of ropes installed in the ditch (Figure 4a).On each rope a small cascade was formed, and thanks to that the stream of water successively slowed down and its erosive action was signifi cantly reduced.During light rains retention of water fl owing along the ditch was observed.Th e water stopped in the space between the neighbouring turns of meanders and was absorbed inside the ropes.Later, during dry days, water absorbed by the ropes was slowly released (Figure 4b).Th e water absorption capacity of the ropes depends on the materials used for their production.Th e absorption capacity of the ropes produced from woollen nonwoven and wool/jute composite is high and equals 535% and 510%, respectively (Figure 5).
During drying in the free state the water absorbed in the ropes is slowly released and the water content is systematically decreased to approximately 100% aft er one month of drying.Th e absorption capacity of the ropes made from recycled fi bres is much lower and amounts to 205%.During drying the ropes return to the weight of a dry product in one month.

Figure 5: Water absorption capacity of the Kemafi l ropes produced from diff erent materials
Aft er six months of exploitation in the ditch the signifi cant change of wool nonwoven parameters is observed (Table 2).Th e reduction of tenacity equals 50% in warp direction and 60% in weft direction.Th e reduction of the nonwoven tenacity is connected with the signifi cant decrease of elongation at break as well as static and dynamic puncture resistance.Th e reduction in static and dynamic puncture resistance equals 88% and 44%, respectively.Th e changes of mechanical parameters of the layered wool/jute composite are much greater.Th e drop of tenacity in warp and weft direction equals 95% and 97%, respectively.Elongation at break in both directions increased several times.Simultaneously, the coeffi cients of puncture resistance are several times lower.
For the nonwoven produced from the blend of various recycled fi bres in warp direction the minimal decrease of tenacity is observed.In the weft direction tenacity increases by 50%.Th e increase of tenacity is connected with the increase of the nonwoven elongation.Simultaneously, static and dynamic puncture resistance decreases by 36% and 31%, respectively.Th e weakening of the materials and gradual deterioration of their mechanical parameters is caused by the gradual biodegradation of the fi bres.Th e exploitation of the ropes in a ditch in wet environment favours the development of microorganisms which utilize fi bres Tekstilec, 2016, 59(2), 115-120 Innovative Geotextiles for Reinforcement of Roadside Ditch as a nutrient source.Microorganisms, bacteria and fungi secrete enzymes which systematically degrade the fi bres structure.In the case of jute biodegradation leading to fi bres fi brillization and complete disintegration occurs very quickly (Figure 6).Aft er six months biodegradation is far advanced and as a result a drastic reduction of mechanical strength of the jute-wool composite is observed.
In the case of wool biodegradation occurs much slower [5].Aft er six months the characteristic scales observed on fi bres surface are practically completely removed and biodegradation causes partial disintegration of the inner parts of the fi bres (Figure 7).As a result, a signifi cant reduction of the mechanical parameters measured for the nonwoven produced from wool fi bres is observed.

Conclusion
Geotextiles installed in the ditch ensure its immediate protection against erosion.Th e lining made from geotextiles is eff ective during six months of the exploitation in the ditch in diff erent weather conditions.Th e meandrically arranged ropes form a system of microdams which slow down the stream of water fl owing along the ditch.By absorbing the water geotextiles ensure retention of water fl owing along the ditch.Th e materials used to produce the ropes reveal suffi cient resistance to biological degradation.Slow biodegradation enables maintaining the protective potential of the geotextiles at least for one growing season.

Figure 2 :
Figure 2: Th e roadside ditch: (a) during the construction of the road; (b) the ditch lined with concrete panels fi lled with rainwater Th e parameters of the materials used for the production of ropes, before installation and aft er six months of exploitation in the soil, were determined.Th e basic parameters of nonwovens: thickness, mass per square meter, tensile strength and elongation at break were measured in accordance with PN-EN ISO 9863-1:2007, PN-EN ISO 9864: 2007 and PN-EN ISO 10319:2010 standards.Additionally, the static and dynamic puncture resistance of the nonwovens were determined according to PN-EN ISO 12236:2006 and PN-EN ISO 13433:2006 standards.Th e absorption capacity of the ropes was measured according to the PN-72/P-04734 standard.Th e samples were immersed in water for 12 hours and then their weight in the wet state was determined.Aft er immersion the change of the water content in ropes during subsequent air drying was analysed.Th e morphology of fi bres before and aft er six months of exploitation in the ditch were investigated by scanning electron microscopy (SEM).Th e microscope JEOL JSM 5500 LV operated in backscattered electron mode was used.Th e observations were carried out for the fi bres sputtered with gold in JEOL JFC 1200 ionic sputter.

a b Figure 3 :
Installation of the geotextiles in the roadside ditch: (a) the overall view of the ditch; (b) connection of concrete panels reinforcement with the geotextiles

Figure 4 :
Figure 4: Th e roadside ditch during exploitation: (a) cascades formed in the fl owing stream; (b) retention of water in the ditch

a b Figure 6 :
Th e morphology of jute fi bres used for the production of the ropes: (a) before and (b) aft er six months of the exploitation in the ditch a b Figure 7: Th e morphology of wool fi bres used for the production of the ropes: (a) before and (b) aft er six months of the exploitation in the ditch Th e nonwoven made from recycled fi bres was produced from the blend of natural and synthetic fibres.During six months of exploitation only the natural components of the nonwovens are biodegraded.Th e synthetic fi bres forming the nonwoven are biologically resistant and keep their mechanical parameters (Figure 8).Consequently, only a slight reduction of the mechanical parameters of the nonwoven made from recycled fi bres is observed.

Figure 8 :
Figure 8: Th e morphology of synthetic fi bres used for the production of the ropes: (a) before and (b) aft er six months of the exploitation in the ditch

Table 1 :
Characteristics of nonwovens used for the production of the ropes

Table 2 :
Mechanical parameters of nonwovens used for the production of the ropes