ABSTRACT:

This study is undertaken to find out the feasibility ofusing jute geotextiles (JGT) produced in Bangladesh which may be used as analternative to synthetic geotextiles in civil engineering applications. Fourtypes of untreated and three types of treated JGT samples were obtained fromBangladesh Jute Mills Corporation (BJMC) and Bangladesh Jute Research Institute(BJRI). Laboratory tests were performed on these treated and untreated JGTsamples to determine their physical, mechanical and hydraulic properties. An attempt has been made to compare these test results with the data related to synthetic geotextiles available in Bangladesh. Based on these test results, some design examples have been presented using the design methods developed for synthetic geotextiles applications. An economicaspect related to synthetic geotextiles and JGT is also presented. It is appreciated that if synthetic geotextiles are replaced with JGT in civil engineering applicationsas exemplified, significant economic benefit can be obtained. However, qualitycontrol of the JGT products at factory level and the installation effects atsite are likely to play an important role in choosing the design parameters.

INTRODUCTION:

Jute geotextiles (JGT) has emerged as a strong alternativeto synthetic geotextiles for many civil engineering applications. Syntheticgeotextiles being made from non-biodegradable polymer based constituents suchas polypropylene, polyester or polyethylene, have inherent advantage overnatural fibre based biodegradable JGT for long-term applications. Due to theirshort life span, JGTs are used as separator, vegetation growing mesh on slopesor as vertical drains. Recently, Bangladesh Jute Research Institute (BJRI) andBangladesh Jute Mills Corporation (BJMC) have developed some treatmenttechniques for JGTs which may enhance their life up to or even more than twentyyears, Table 1. Development of such durable JGT materials is likely to allowthem to be used in short-term to medium-term soil reinforcement applications,e.g. rural roads, construction access roads, flood and road embankments etc.

Besides development of enhanced durability of JGT, it isequally important to set widely acceptable testing standard for thesematerials. Currently, in absence of any such recognized testing standard, theASTM, BS, DIN or ISO methods of testing usually employed for syntheticgeotextiles are most commonly adopted for the determination of the propertiesof JGT. Apparently there seems to be no reason why the standards used forsynthetic geotextiles should not be applicable for JGTs. However, as theindustry gains further momentum and use of JGT gets wider acceptance, the issuemay be settled based on technical and construction experiences.

Table 1. Summary of jute blendedwith different materials at BJRI:

Source: Abdullah (1999) A hand book on geotextiles particularlynatural geotextiles from jute and other vegetable fibres.

The costing of different jute products developed by BJRI in1997 by blending jute with hydrophobic fiber like coir or by modification withbitumen, latex and wax resinous materials with the collaboration of BJMC andother governmental and non-governmental organizations are listed in Table 9.

Table 9: Summary of cost of juteblended with different materials at BJRI

Source: Directorate of Technology, BJRI

ECONOMIC BENEFIT OF USING JGT IN DIFFERENT APPLICATIONS

On the basis of the analysis and design with JGT andsynthetic geotextiles undertaken in this study for different applications andalso on the basis of the costs of these materials mentioned above, it issuggested that by using JGT materials instead of synthetic geotextiles, a costbenefit of 35%-50% may be obtained. However, the technical shortcomings anddurability restrictions of JGT materials must be appreciated prior to anyapplication.

CONCLUDING REMARKS:

It is appreciated that the inherent drawback of theuntreated JGT materials is their short life span due to biodegradability. Thisrestricts the JGTs to be used as separator, filter, and vegetation growing meshon slopes or as vertical drains. Recently, BJRI has been able to develop sometreatment techniques by means of which it is possible to ensure designedbiodegradability of these materials. Development of such durable JGT materialsis likely to allow them to be used in short-term to medium-term soilreinforcement applications, e.g. rural roads, construction access roads, floodand road embankments etc. Although a lot requires to be done regardingdetermination and improvement of their index properties, mechanical properties,hydraulic properties, interaction behavior and reduction factors, based on thecurrent methods of designing with synthetic geotextiles, JGT materials seem tobe a potential alternative. This is further accentuated by the significant costbenefit that may be accrued from using JGT materials instead of syntheticgeotextiles.

Figure 8. Comparative costs of the untreated JGT samples (Mohy, 2005)

Table 8. Cost of woven and nonwoven synthetic geotextiles (Mohy, 2005)

Figure 9. Comparative costs of treated JGT samples with synthetic geotextiles available in Bangladesh (Mohy, 2005)

REFERENCES

1. Abdullah, A.B.M., (1999). A hand book on Synthetic geotextiles Particularly Natural Synthetic geotextiles from Jute and other Vegetable Fibres, Bangladesh Jute Research Institute, Dhaka, pp. 33-87.

2. ASTM D 3786 79 Standard Test Method for Hydraulic Bursting Strength of Knitted Goods and Nonwoven Fabrics-Diaphragm Bursting Strength Tester Method.

3. ASTM D 4491-96 Standard Test Methods for Water Permeability of Synthetic geotextiles by Permittivity.

4. ASTM D 4595-86 (Reapproved 1994) Standard Test Method for Tensile Properties of Synthetic geotextiles by the Wide-Width Strip Method.

5. ASTM D 4632-91 Standard Test Method for Grab Breaking Load and Elongation of Synthetic geotextiles.

6. ASTM D 4751-95 Standard Test Method for Determining Apparent Opening Size of a Geotextile.

7. ASTM D 5199-98 Standard Test Method for Measuring the Nominal Thickness of Synthetic geotextiles and Geomembranes.

8. ASTM D 5261-92 Standard Test Method for Measuring Mass per Unit Area of Synthetic geotextiles.

9. Carroll, R. G., Jr., (1983), Geotextile Filter Criteria, Engineering Fabrics in Transportation Construction, TRR 916, TBR, Washington, DC. pp. 46-53.

10. DIN 54307 Standard Test Method for Determination of CBR Puncture Resistance.

11. Koerner, R. M. (1997), Designing with Geosynthetics, 4^th Edition, Prentice Hall Inc., New Jersey.

12. Mohy, M. A. (2005), Evaluation of properties of JGT and its assessment for short term and long term civil engineering applications. MSc thesis, Department of Civil Engineering, BUET, Dhaka.

About the Author:

The author is associated with the Department of Civil Engineering, Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh.

To read more articles on Textile, Industry, Technical Textile, Dyes & Chemicals, Machinery, Fashion, Apparel, Technology, Retail, Leather, Footwear & Jewellery,  Software and General please visit http://articles.fibre2fashion.com

To promote your company, product and services via promotional article, follow this link: http://www.fibre2fashion.com/services/article-writing-service/content-promotion-services.asp

TEST RESULTS OF SOME JGT PRODUCED IN BANGLADESH:

Untreated samples of Jute were obtained from BJRI and untreated Canvas, DW Twill and Hessian were selected from BJMC for the purpose of this study. It should be appreciated that Jute is a densely woven fabric in which relatively flat type of yarn is used. It is manufactured in BJRI loom mainly for research purpose. However, if ordered Jute can be produced in all the jute mills for commercial purpose as well. Canvas is a very densely woven fabric, woven by round twisted yarns. Canvas used to be produced mainly in ABC Mill of Adamjee Jute Mills. After the layoff of Adamjee Jute Mills, all the machines were transferred to Latif Bawany Jute Mills situated at Demra of Dhaka. Canvas is the least porous out of the four and is now produced in Latif Bawany Jute Mills. DW Twill is also woven by using relatively flat type yarns like Jute. It is manufactured in many jute mills of Bangladesh. Hessian is the most porous amongst four and produced in all the jute mills of Bangladesh. Both DW Twill and Hessains are extensively used in the country mainly for packaging purpose.

Amongst the untreated JGT samples, Jute, Canvas and DW Twill samples were treated with bitumen by BJRI. The treatment procedure involved following steps:

• preparation of carbon black with required quantity of volatile oil
• addition of bitumen emulsion with paste followed by stirring
• after mixing homogenously, the emulsion was laminated on the jute fabrics by brush and dried in sunlight or open area at normal temperature and pressure (NTP).

The salient properties of the samples are presented in Table 2.

Table 2. Salient properties of JGT samples

Source: Bangladesh Jute Mills Corporation Handout, 2003

The tests were then performed on these treated and untreated JGT samples at the geotechnical laboratory of Bangladesh University of Engineering & Technology (BUET). The list of the tests carried out on these samples and the test methods employed for performing the tests are given in Table 3.

For the purpose of comparison of the test results of these JGT samples with the synthetic geotextiles commonly used in Bangladesh, test results of twenty different varieties of non-woven synthetic geotextiles were also obtained from BUET. The test results of JGT samples and non-woven synthetic geotextiles are summarized in Table 4. Some of the test results of JGT samples and non-woven synthetic geotextiles are also shown graphically in Figure 1 to Figure 5 for the purpose of comparison.

Table 3. Tests Performed on treated and untreated JGT samples:

Figure 1. Mass per unit area of synthetic geotextiles,
untreated JGT and treated JGT (Mohy, 2005)

Figure 2. Thickness of synthetic geotextiles, untreated JGT

and treated JGT (Mohy, 2005)

Figure 3. Grab tensile strength of synthetic geotextiles,

untreated JGT and treated JGT (Mohy, 2005)

Figure 4. Wide-width tensile strength of synthetic geotextiles,

untreated JGT and treated JGT (Mohy, 2005)

Figure 5. CBR puncture strength of synthetic geotextiles,

Untreated JGT and treated JGT (Mohy, 2005)

It may be noted from these test results that the properties of JGT samples generally improve after treatment. However, AOS and cross-plane permeability of some of the samples (Jute and Canvas) literally reduces to zero due to blocking of the openings by application of bituminous agents for treatment. It should be further appreciated that synthetic geotextiles have better index, mechanical and hydraulic properties compared to JGT materials. This indicates that manufacturers and researchers should put more technical efforts to improve the properties of JGT materials so that they become obvious alternative to synthetic geotextiles.

REDUCTION FACTORS/PARTIAL FACTORS FOR JGT:

Reinforced soil walls, embankments, slopes etc. are generally analysed and designed by Limit Equilibrium Method or Limit State Approach. Both of these design methods/approaches apply several reduction factors or partial factors to the ultimate values of synthetic geotextiles in order to obtain an allowable value of the mechanical and hydraulic properties.

Strength-Related Problems

In strength related problems the allowable value for synthetic geotextiles is obtained as:

T_allow = T_ult

T_allow = allowable tensile strength of synthetic getextile

T_ult = ultimate tensile strength of synthetic geotextile

RF_ID = reduction factor for installation damage

RF_CR = reduction factor for creep

RF_CD = reduction factor for chemical degradation

RF_BD = reduction factor for biological degradation

Typical values for strength reduction factors are given in Table 5. These values are usually tempered by the site-specific considerations.

Table 5. Recommended reduction factor values for strength-related problems (Koerner 1997)

Flow-Related Problems

For filtration and drainage applications problems dealing with flow through or within a synthetic geotextile, the formulation of the allowable values takes the following form:

q_allow = q_ult

q_allow = allowable flow rate of synthetic geotextile

q_ult = ultimate flow rate of synthetic geotextile

RF_SCB = reduction factor for soil clogging and blinding

RF_CR = reduction factor for creep reduction of void space

RF_IN = reduction factor for adjacent materials intruding into synthetic geotextile void

RF_CC = reduction factor for chemical clogging

RF_BC = reduction factor for biological clogging

Typical values for flow reduction factors are given in Table 6. It may be noted that these values are generally tempered by the site-specific conditions.

Table 6. Recommended reduction factor values for flow-related problems (Koerner 1997):

It should be appreciated that, to date, no such reduction factors/partial factors have been identified for JGT materials. This is an area where researchers and industries should pay immediate attention for successful implementation of JGT projects. Meanwhile, the values recommended for synthetic geotextiles may be adopted.

DESIGN EXAMPLES:

Anlysis and design for separation, filtration, drainage, reinforced wall and reinforced embankment using the properties of JGT samples have been carried out for the design examples given by Koerner (1997) for the purpose of comparison of outcome designs with those of synthetic geotextiles. By way of example, design of a JGT reinforced vertical wall and design of goejute filter behind a retaining wall are presented.

JGT reinforced vertical walls:

A 6-m-high wrap-around type of JGT wall is to carry a storage area of equivalent dead load of 10 kPa. The wall is to backfilled with a granular soil (SP) having the properties of γ = 18 kN/m³, φ = 36, and c_a = 0. A treated DW Twill with warp (machine) direction ultimate wide-width tensile strength of 25 kN/m (Table 4) and friction angle with granular soil of δ = 24 (since no test of DW Twill related to δ is carried out, the usual value applied for synthetic geotextile, i.e. 2/3 φ is taken) is intended to be used in its construction. The orientation of the JGT is perpendicular to the wall face and the edges are to be overlapped or sewn to handle the weft (cross machine) direction. A factor of safety of 1.4 is to be used along with site-specific reduction factors. For the design of this JGT wall, the method outlined by Koerner (1997) for synthetic geotextile reinforced walls is used. The outcome design is shown in Figure 6.

Figure 6. Outcome design of a 6.0m high wall using treated DW Twill JGT

JGT filter behind a retaining wall

Given a 3.5 m high gabion wall consisting of three 1 x 1 x 3 m long baskets sitting on a 0.5 x 2 x 3 m long mattress as shown below, the backfill soil is a medium-dense silty sand of d₁₀ = 0.03 mm, C_u = 2.5, k = 0.0075 m/s, and D_R = 70%. It is required to check the adequacy of four candidates untreated JGTs whose laboratory test properties are given below. The recommended reduction factors and design method outlined by Koerner (1997) are used.

Figure 7. Flow net behind the gabion wall (after Koerner, 1997)

The design of filter is intended to ensure:

• Adequate flow of water across the plane of JGT. This is achieved through a factor of safety of 2.0 against permittivity.
• No backfill soil loss through the JGT filter. This is achieved by satisfying the Carroll (1983) criteria O₉₅ < 2.5 d₈₅

On the basis of the above and the procedure outlined by Koerner (1997) the outcome analysis is summarized in Table 7.

Table 7. Summary of the outcome analysis of the JGT filter design (Mohy, 2005)

Thus, it appears that for the given problem untreated Jute may be considered to be the only competent candidate.

COMPARATIVE COSTS OF JGT AND SYNTHETIC GEOTEXTILES

In making a proper economic assessment or evaluation, a number of inputs are required such as material cost, labour cost etc. Again, these inputs vary from place to place. In this study, an attempt has been made to analyse the comparative costs of untreated and treated JGT collected from BJRI, BJMC and local market. The comparative costs of the untreated JGT samples are shown in Figure 8.

A cost comparison between different types of locally available synthetic geotextiles is shown in Table 8. It appears that locally manufactured synthetic geotextiles are cheaper than the imported ones. No woven synthetic geotextiles are produced locally and prices of imported woven synthetic geotextiles are around 10% more than the nonwoven ones. The comparative costs of treated JGT with synthetic geotextiles are shown in Figure 9.