Dr. S. K. Ghosh , Associate Professor, DJFT, IJT, C.U. Mr. M. M. Mondal , SRF, DJFT, IJT, C.U.

OPTIMIZATION OF PRORERTY PARAMETERS OF WOVEN JUTE GEOTEXTILES FOR POTENTIAL APPLICATIONS IN THE FIELD OF GEOTECHNICAL CONSTRUCTIONS Dr. S. K. Ghosh, Associate Professor, DJFT, IJT, C.U. Mr. M. M. Mondal, SRF, DJFT, IJT, C.U. Mr. R. Bhattacharyya, SRF, DJFT, IJT, C.U. DEPT. OF JUTE AND FIBRE TECHNOLOGY, INSTITUTE OF JUTE TECHNOLOGY (IJT), UNIVERSITY OF CALCUTTA (FACILITATING AGENCY)

INTRODUCTION • The global growth of Geosynthetics for the last one decade or so has been substantially soaring @ 10% per annum. • Jute Geotextiles (JGT), a class of natural Technical Textiles, has carved out a niche in this emerging technology. • The growth of JGT with respect to its man-made counterpart is not very far behind. • Effectiveness of JGT in addressing a host of geotechnical problems and more importantly its eco-compatibility is gaining increasing acceptability worldwide.

APPLICATIONS • The use of JGT has extended rapidly into nearly all areas of civil, geotechnical, environmental, coastal and hydraulic engineering. • Jute Geotextile has proved to be the most versatile in Separation, Filtration, Drainage, and Reinforcement besides providing a protective cover over soil. • JGT play a significant part in modern pavement design and maintenance techniques.

SCOPE AND AIM OF THE WORK • Several varieties of JGT – both woven and nonwoven have been developed for a number of geotechnical end uses e.g. improving pavement performance, soil erosion, embankment, drainage system etc. • All these available fabrics are not applicable as per the need of the different geotechnical constructions. • It is felt that there is an urgent need to design and engineer of such precise fabric for potential applications in emerging civil works.

In a recently concluded PMGSY Project and in other works on road constructions, in most of the cases traditional sacking quality jute woven fabrics (Plain Weave and Twill Weave) have been extensively used. • The previous studies and field applications carried out so far on rural road construction have confined the efficacy of the appropriate variety of jute material. • The applications, however, did not focus on engineering and manufacture of application specific and functions oriented varieties of JGT. • Added to this shortcoming is absence of appropriate standards in applications as well as in design and engineering of JGT in the rural road construction and river bank protection.

Use of conventional sacking fabrics being not application specific and function-oriented, deserves rethinking on adoption of the conventional jute fabrics used for flexible packaging in road construction. • It is in this context that development of potentially important JGT for strengthening rural roads assumes significance. • It was realized that such a JGT should be woven whose property parameters should be functionally apt for serving the purpose.

Optimization of the fabric property parameters of DW plain weave JGT of different gsms alongwith that of Open Weave JGT samples (soil savers) with respect to different geotechnical applications like road construction for strengthening of sub grade and river bank protection to control erosion of the river bank as well as Hill Slope protection. • Comparative Analysis (CA) of the results of different tests carried out with JGT samples supplied by the different Jute Mills of West Bengal and zeroing on the two types of woven JGT on the basis of evaluated property parameters for rural road construction and three types of soil savers for hill slope protection. • Determination of the tolerance limit of the prime property parameters of the optimized and selected DW JGT samples alongwith that of Open Weave JGT samples (soil savers) by statistical interpretation for formulation of the specification by relevant national and international statutory bodies for global acceptance of the said fabric. OBJECTIVES

In order to achieve the objectives of this work DW Plain Weave JGT Fabrics of different GSMs were produced by varying yarn and fabric parameters followed by conventional jute processing system in different commercial jute mills. • Different tests were carried out in the laboratory for assessing the physical, mechanical and hydraulic property parameters and the effect of change in yarn parameters and yarn density on the produced fabric properties before actual field trial on roads and river banks.

The following fabric property parameters were tested as per relevant ASTM standards in the laboratory- • Wide Width Tensile Strength • Index Puncture Resistance • Bursting Strength • Water flow rate, Permeability and Permittivity • Apparent Opening Size (AOS) /Equivalent Opening Size (EOS) • Open Area Percentage values • Subsequently on the basis of test results optimization of the fabric samples were carried out by Simple Average Weighted Ranking Procedure (SAWRP).

FABRIC SAMPLES PREPARATION

Three different counts of warp yarns viz., 9, 11 and 13 lbs/ spyndle and weft yarns viz., 24, 26, 28 lbs/ spyndle were produced in conventional slip draft spinning machine. • Twelve double warp plain weave fabrics of three GSM ranges, (600 -700), (700 – 800) and (800 – 900) were produced by using warp and weft count (9 X 24) lbs / spyndle, (11 X 26) lbs / spyndle and (13 X 28) lbs / spyndle, respectively in a conventional Jute loom.

CONDITIONING OF FABRIC SAMPLES The entire range of produced Jute based Woven DW Fabric Samples were conditioned according to ASTM standard using standard Temperature and humidity for 24 hours before commencement of testing work.

TESTING OF FABRIC SAMPLES • From the actual application point of view of Technical Textiles / Geotextiles, conventional testing parameters along with sample specifications for normal textile testing cannot generally be regarded as appropriate for Technical Textile/ Geotextile Testing. • Conventional textile testing methodology has only a limited usefulness in assessing the properties of a fabric relative to its engineering end use. • Test samples were selected in such a way that it could represent the whole population of the fabric and the piece of fabric cut out for the laboratory test was one meter long with full width of the fabric. • No samples have been taken from nearer than 50 mm to the selvedge of the fabric sample. Fabric samples were tested according to ASTM Standard Testing Methods.

Testing Parameters for Woven and Open Weave JGT samples for application on Rural Road Construction and Hill Slope Management

RESULTS AND DISCUSSIONS (Part-1) For DW PLAIN WEAVE JGT SAMPLES

Table (1): Physical and Mechanical Properties of the Fabric Samples

Fig. 1 Fig. 2 Fig. 3 Fig. 2 Fig. 1 Fig. 3 Graphical representation of the effect of GSM (600 – 700 ) on Tensile Strength (Warp Way and Weft Way), Index Puncture Resistance and Bursting Strength of JGT. Fig. 4

DISCUSSIONS • It was observed from the Table (1) and Fig.1, Fig.2, Fig.3 and Fig.4 that the fabric samples with higher GSM had shown higher tensile properties (tensile strength, index puncture resistance and bursting strength, etc.). • This can be accounted for by the fact that an increase in GSM in the fabric indicated an increase in the number of load bearing elements per unit length in the warp as well as weft directions leading to an increase in the tensile strength of the fabric.

Fig. 6 Fig. 7 Fig. 5 Fig. 5 Fig. 6 Fig.7 Graphical presentation of the effect of GSM (700-800) on the Tensile Strength (Warp Way & Weft Way), Index Puncture Resistance and Bursting Strength of JGT. Fig. 8

Fig. 11 Fig. 9 Fig. 10 Fig. 9 Fig. 11 Fig.10 Graphical presentation of the effect of GSM (800-900) on the Tensile Strength (Warp Way & Weft Way) , Index Puncture Resistance and Bursting Strength of JGT. Fig. 12

Table (4): Hydraulic Properties of the Fabric Samples

Fig. 15 Fig. 13 Fig. 14 Fig. 15 Fig.14 Fig. 13 Graphical presentation of the effect of different GSMs on Apparent Opening Size (AOS) of JGT.

DISCUSSIONS • Table No.(4) and Fig. 13, Fig. 14, Fig. 15 shows that, the values of AOS had decreased within a particular GSM range and between the GSM ranges. • This is due to the fact that the increase in the GSM with the increase in yarn density results in decrease in the percentage open area of the fabric causing reduction in average pore dimension of the fabric samples.

DISCUSSIONS • Apart from this, it was also observed that there is a decrease in AOS values in the produced fabric samples of different GSM ranges because of the increase in the count of the warp and weft yarns respectively. • Consequently, the water permeability and permittivity of fabric samples had shown a decreasing trend with the increase in fabric GSM, which is self explanatory from the results of Apparent Opening Size (AOS) of different produced fabric samples.

RANKING OF FABRIC SAMPLES • Values of all the dimensional and geotechnical (physical, mechanical and hydraulic properties etc.) property parameters obtained for all the jute woven fabric samples produced in this work by varying process parameters and machine parameters are compared by the method of Simple Average Weighted Ranking Procedure for three categories (600 – 700 gsm, 700 – 800 gsm and 800 – 900 gsm) of such woven JGT fabric samples separately for optimization of different fabric property parameters.

For ranking within the specified range of fabric area density, each property parameter of each sample is proportionately weighted as compared to the best values obtained in that property parameter to award ten (10) point and rest of the obtained values lower than the best value were weighted proportionately. • Finally considering all the property parameters together simple average were determined to get the rank within that class.

Table (5): Ranking of Fabric Samples in GSM Range 600 to 700

It has been observed from the ranking method that by optimizing mechanical, hydraulic and fabric area density (gsm) properties the fabric sample no. 4 within gsm Range 600 – 700, sample no. 8 within gsm range 700 – 800 and sample no. 12 within gsm range 800 – 900 have secured the highest rank mainly due to their higher gsm property parameters. • But considering the techno-economic aspect such a fabric was desperately needed to be selected which would not only confirm with the optimum requirement as per the design as well as end use with its satisfactory test results during its period of performance.

Therefore, keeping that in mind, sample no. 2 was found to be the best amongst the other fabric samples in the gsm category 600-700 both in terms of its test results, particularly in tensile and porometry properties, as well as cost-effective since its gsm was found to be lying near the lower value of its gsm category. • Similarly, it has been also observed for sample no.6 in the gsm category 700-800 that the sample depicts optimum test results of its property parameters best fitting to the end use requirements alongwith comparatively lower gsm, nearing the lower value of its gsm category thereby proving its economic benefit. • Hence, sample nos. 2 and 6 have been standardized for the application in roads as underlay for strengthening of sub-grades. Moreover, sample No.2 has undergone suitable rot resistant treatment for the application in river bank protection to enhance its durability and simultaneously paving the way for comparing the performance of both the grey and treated fabric.

Considering techno-economic viability no sample in the higher gsm range 800-900 has not been selected for the same since higher gsm values lead to higher expenditure both during bulk production as well as application on site. • After optimization and selection of the two fabric samples of gsm 626.44 (627 gsm approximately) and 724 respectively, their test results have been placed before the relevant Fabric Design and Engineering Committee, entrusted under the purview of this work, to furnish a full-scale specification to the different Jute Mills of West Bengal, India as well as in Bangladesh for the purpose of manufacturing of the several woven JGT samples as per the mentioned specifications (provided in next slide) for carrying out different field trial applications in both the case studies like road construction and river bank protection.

The specifications of the Jute Geotextile samples which have been optimized for rural road construction as well as for river bank protection are furnished in the Table (8) below - N.B.: *Width of the Woven JGT may be fixed as agreed between buyer and seller, subject to a lower limit of 100 cm. **To be treated with a suitable additive

DETERMINATION OF TOLERANCE LIMIT OF THE PRIME PROPERTY PARAMETERS OF DW PLAIN WEAVE JGT SAMPLES

To Determine the Tolerance Limit of a Textile Testing Parameter along with its Statistical Significance (Statistical Interpretation) • 1. Population Size: Population is the whole bulk of the material available for testing and that the sample is a relatively small fraction of that population. • No. of Specimens: n = 0.15 r²; Where r = co-efficient of variation (%) of the parameter under test. • 2.Sampling Distribution: Suppose we took a large a no. of samples, each of ‘n’ individuals, from a population which has a normal or nearly normal distribution and in each case the sample mean is calculated. We could then make a frequency distribution of the sample means. • 3. Calculation of standard Deviation of the Test Results. (S.D.) • 4. Estimation of Standard Error of the mean: (S.E.) S.E. = (S.D. / √n); n = sample size • Significance testing of Means : • (i) Physical Significance of ‘t’ (tolerance limit) • t = (Nominal Mean- Sample Mean) / Standard Error • (ii) The value ‘t’ has a SD of its own which is not normal even though the population from which the samples have been drawn has a normal distribution. • 6. Determination of Tolerance limit: • First Method: To calculate Sample mean, S.D. and S.E. • Nominal Mean = {Sample Mean ± (t × S.E.)}, where, S.E. = (S.D. / √n) • The value of ‘t’ may be found from table of Significant Limit where ‘t’ has sampling distribution of its own which is not regular. • Second Method: Nominal Mean = Sample Mean ± 1.96 × б • where 1.96 lies in 95 % level of confidence and б = S.D. and the sampling distribution is normal.mal.

The tolerance limit for the above stated parameters of the developed fabric has been calculated by using the • following method : • Usually all population values are not available that is why we take samples and express Standard Error (S.E.) as Standard Deviation (S.D.) /√n, where n is the population size. • In this case we take a sample and calculated the S.D. (gsm) of the same sample. • As per Statistical calculation Standard Error (S.E.) of Mean will be S.D./√n. • The average value of the determined fabric weights produced by the different Jute Mills is tabulated in Table 1. • ……(contd.)

Table 9 - gsm values of the JGT samples (626.44 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation-S.D. = √∑(x- x̅) 2/ (n-1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 10. Table 10- Different gsm values and calculation of S.D. Standard Error (S.E.) = S.D. / √n = 4.05, t = Nominal Mean — Sample Mean / S.E. for degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, “t” has sampling distribution of its own which is not regular). Nominal Mean = Sample Mean ± t × S.E., i.e., Nominal Mean = 627 ± 2.262 × 4.05 = 627 ± 9.16.Nominal Mean = Sample Mean ± 1.5 %.Considering Normal Distribution of Sample, Nominal Mean = 627 ± 1.96 × 12.81, Nominal Mean = Sample Mean ± 4.0%.

Table 11 - Bursting Strength values of the JGT samples (626.44 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation-S.D. = √∑(x- x̅) 2/ (n-1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 12. Table 12- Different Bursting Strength values and calculation of S.D. t = Nominal Mean — Sample Mean / S.E. For degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, t has sampling distribution of its own which is not regular).Nominal Mean = Sample Mean ± t × S.E., = 627 ± 2.262 × 0.196. Nominal Mean = Sample Mean ± 0.07 %. Considering Normal Distribution of Sample, Nominal Mean = Sample Mean ± 1.96 × 0.62 = 627 ± 1.22 .Nominal Mean = Sample Mean ± 0.19 %.

Table 13 - Apparent opening size values of the JGT samples (626.44 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation S.D. = √∑(x- x̅) 2/ (n- 1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 14. Table 14 - Different Apparent opening size values and calculation of S.D. t = Nominal Mean — Sample Mean / S.E. For degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, t has sampling distribution of its own which is not regular)Nominal Mean = Sample Mean ± t × S.E., = 627 ± 2.262 ×17.34. Nominal Mean = Sample Mean ± 6.26%. Considering Normal Distribution of Sample, Nominal Mean = Sample Mean ± 1.96 ×54.79= 627 ± 107.39. Nominal Mean = Sample Mean ± 17.13%.

Table 15 - gsm values of the JGT samples (724 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation-S.D. = √∑(x- x̅) 2/ (n-1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 16. Table 16- Different gsm values and calculation of S.D. Standard Error (S.E.) = (S.D. / √n) = 3.86, t = Nominal Mean — Sample Mean / S.E. for degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, t has sampling distribution of its own which is not regular).Nominal Mean = Sample Mean ± t × S.E., Nominal Mean = 724 ± 2.262 × 3.86, Nominal Mean = Sample Mean ± 1.21%.Considering Normal Distribution of Sample, Nominal Mean = Sample Mean ± 1.96 × б, 724 ± 1.96 × 12.20 = 724 ± 23.91. Nominal Mean = Sample Mean ± 3.30%.

Table 17 – Bursting Strength values of the JGT samples (724 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation-S.D. = √∑(x- x̅) 2/ (n-1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 18. Table 18 - Different Bursting Strength values and calculation of S.D. Standard Error (S.E.) = (S.D. / √n) = 0.4, t = Nominal Mean — Sample Mean / S.E., for degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, t has sampling distribution of its own which is not regular). Nominal Mean = Sample Mean ± t × S.E. Nominal Mean = 724 ± 2.262 × 0.41, 724± 0.93, Nominal Mean = Sample Mean ± 0.13 %. Considering Normal Distribution of Sample, Nominal Mean = Sample Mean ± 1.96 × б, 724 ± 1.96 × 1.28 ,724 ± 2.51. Nominal Mean = Sample Mean ± 0.35 %.

Table 19. Apparent opening size values of the JGT samples (724 gsm) produced by the different Jute Mills The S.D. of the samples have been determined, using the following mathematical correlation-S.D. = √∑(x- x̅) 2/ (n-1) where (x-x̅) = Deviation of the observation from the Specified value and the values have been depicted in Table 20. Table 20. Different Apparent opening size values and calculation of S.D. Standard Error (S.E.) = (S.D. / √n) =3.41, t = Nominal Mean — Sample Mean / S.E., for degree of freedom, v = n-l = 9, t = 2.262 at 5% significant level (obtained from table of significant limit, t has sampling distribution of its own which is not regular).Nominal Mean = Sample Mean ± t × S.E. Nominal Mean = 724 ± 2.262 × 3.41,7 24± 7.71. Nominal Mean = Sample Mean ±1.06 %.Considering Normal Distribution of Sample, Nominal Mean = Sample Mean ± 1.96 × б, 724 ± 1.96 × 10.79, 724 ± 21.15. Nominal Mean = Sample Mean ± 2.92 %.

RESULTS AND DISCUSSIONS (Part-2) For OPEN WEAVE JGT SAMPLES (SOIL SAVER)

Table 20–Physical, mechanical and porometry properties of the open weave JGT Samples within the GSM range 450-550

DISCUSSIONS • Among all of the supplied samples by the different Jute Mills, the Sample No. 02 of GSM 482.22 is found to be closely matching with the specified GSM 500 (range considered 450-550 GSM)along with its physical and mechanical properties . • For other samples the GSM values are not matching with the specified GSM as well as their tensile properties are not compatible with that of the specifications of the Sample No.02. • Specifications of the sample of GSM 482.22 supplied by Sample No.02 can be considered nearest to the specified GSM.

Table 21 –Physical, mechanical and porometry properties of the open weave JGT Samples within the GSM range 551-650

Dr. S. K. Ghosh , Associate Professor, DJFT, IJT, C.U. Mr. M. M. Mondal , SRF, DJFT, IJT, C.U.