Presentation on theme: "Koushik Das, P K Choudhury, S.K.Chakrabarti, and Prabir Ray."— Presentation transcript:
Koushik Das, P K Choudhury, S.K.Chakrabarti, and Prabir Ray
Core Activities : Undertakes wide range of research activities for the improvement Jute and Jute Geotextiles. Responsibility : To design of Potentially Important Jute Geotextile and fabric engineering To provide installation guidance for field applications of JGT in erosion control of river bank & hill slopes and rural road construction in India. Tasks of IJIRA under The Project
Identification of Potentially important JGT on the basis of previous performance evaluation jointly by NJB / BESUS / BUET / PwC / IJIRA Types of JGT primarily chosen were – 20, 25 & 30 kN/m tensile strength woven and micron AOS. In the process 26 samples were developed at 7 jute mills of 5 varieties DW plain weave woven JGT (627,665,724,760 & 810 gsm) & 4 new varieties of open weave JGT (365,500,600 &700 gsm) were design and developed Fabric Engineering
FABRIC ENGINEERING Effectiveness in performing the basic geotechnical functions Ensuring manufacturing new varieties of JGT by any jute mills Economy & easy of availability Selection of the appropriate cost effective jute batch Need base development of Potentially Important JGTs was mooted for the project. Procedure for development of the targeted fabric was based on “design by experience” followed by “design by approach” to ensure - Careful assessment of tensile strength & porometry requirements for the 3 specified end- uses was carried out. And the fabric design was optimized meeting the technical needs as well as economy
Fabric Engineering Weight of Fabric ( gsm) = ( N 1 G 1 + N 2 G 2 ), where, N 1 = Ends /inch & N 2 = Picks / inch and G 1 = Warp count in lbs & G 2 =Weft count in lbs. Tensile strength ( MD ), F S ( kgf) = C x QR x N’ 1 X U% where F S is Tensile Strength of Fabric in warp way (MD), C is warp count, N 1 for ends / inch & QR is a factor derived by dividing tensile strength with warp count of yarn & expressed in percentage & U stands for utilization %, Tensile strength ( CD ), F’ S ( kgf) = C’ x QR x N’ 2 X U% Where F’ S is Tensile Strength of Fabric in weft way (CD),C’ is weft count, N 2 for picks / inch & QR is a factor derived by dividing tensile strength with weft count of yarn & expressed in percentage & U stands for utilization Parameters Considered during fabric Engineering Tensile Strength Opening Size Weight of fabric / cost of product / batch composition Type of weave & ease of manufacture by any jute mills Empirical Relationship adopted and developed for prediction of the Parameters
Determination of opening size of woven JGT – Method 1: Calculation from yarn diameter and pore size of JGT Particulars of Warp and WeftMethod of calculation Warp/dm102Weft/dm39 Count of warp in ld/spyndle9.75Count of weft28 Diameter of yarn in inch0.035Diameter of yarn in inch0.059(√ count)/90 Diameter of yarn in cm0.088Diameter of yarn in cm0.149 Distance covered by the warp yarns in one dm (cm) (L1) Distance covered by the weft yarns per dm (cm) L1 = (Threads/dm) X diameter of the yarn(cm) Gap (Open area) left by the warp yarns in one dm (cm) (L2) Open distance left by the weft yarns per dm (cm) 4.176L2 = 10 – L1 Open distance between the warp yarns (mm) Open distance between the weft yarns (mm) L3 = L2 X 10 / (no of threads – 1) Area of each open space (pore) in the fabric (Sq mm) (L3) 0.110L3 of warp X L3 of Weft Diameter of the pore (mm)0.332 Assuming shape of the pore as square, the side of the square will be the pore diameter. Diameter of the pore (micron) 332
Determination of opening size of woven JGT – End s / dm Pick s / dm Count threads (Warp X Weft) (lb/spindl e) Warp cover (K 1 ) Weft cover (K 2 ) Fabric cover (K c ) (%) Ope n area (%) No of mesh in one squar e dm Open area in one square dm (sq mm) Open area/ mesh (sq mm ) (A) Diam eter of one pore (mm) * (√ A) Diame ter of one pore (micro n) X X Method 2 : Calculation from cover factor of JGT Established equations for calculation of cover factors of Jute fabric are : Warp cover : K 1 = No of warp / inch X √ (Count of warp in ld/spyndle) Weft cover : K 2 = No of weft / inch X √ (Count of weft in ld/spyndle) Fabric Cover : K c = K 1 + K 2 – (K 1 K 2 / 120)
The fabrics developed were tested at the geotextile testing laboratory of DJFT & IJIRA and the results were found technically suitable for application under the project However, among the 9 varieties of JGT developed, PEA has zeroed in on 2 types of woven (20 kN/m- 627 gsm & 25 kN/m gsm and 3 types of open weave JGT (500, 600 & 700 gsm) in view of meeting end-use requirements, ease of manufacture and economizing cost of production DEVELOPMENT OF WOVEN JGTs
DEVELOPMENT OF OPEN WEAVE JGTs 292 gsm,500 gsm & 730 gsm Open Weave ( OW ) JGT available off the shelf are being widely used world wide mainly for stabilizing the slopes of earthen embankment. CSWCRTI, who is one of the PIUs recommended to develop three new varieties of OW JGTs viz, 500 gsm,600 gsm & 700 gsm for use in hill slope stabiliztion. Accordingly, the products were developed by IJIRA. In designing the newer variety of 500 gsm fabric 170 lbs weft yarn was used instead of conventional 124 lbs for higher yarn dia. in anticipation of getting better effect in controlling surface run-off. As there is no significant role of warp yarn in entrapping the soil particles as well as to keep the weight of the fabric at lower side lighter warp count of 70 lbs was used which also controlled the cost The fabrics were tested at IJFT & IJIRA laboratories prior to put them to use in hill slope stabilization works by CSWCRTI at three different hill sites.
Identified chemical additives (aqueous) used to improve durability of JGT The effective add-on of the chemicals is low (0.5 %, w/w, approx.) and the weight gain of JGT fabric is negligible Loss of strength of the JGT fabric after treatment is within normal range (5%) JGT characteristics of woven JGT are not affected much due to treatment Specially treated woven JGT is rot-resistant & water repellent Improved functional properties is likely to increase the effectiveness of using such durable JGT in river bank protection The treated JGT does not increase much the BOD and COD of water Formulation developed for special treatment of JGT is user friendly Predicted life of durable JGT is about two years in combined water-soil ambience Considered as a cost effective alternative of copper and bitumen treatment Identified chemical additives (aqueous) used to improve durability of JGT The effective add-on of the chemicals is low (0.5 %, w/w, approx.) and the weight gain of JGT fabric is negligible Loss of strength of the JGT fabric after treatment is within normal range (5%) JGT characteristics of woven JGT are not affected much due to treatment Specially treated woven JGT is rot-resistant & water repellent Improved functional properties is likely to increase the effectiveness of using such durable JGT in river bank protection The treated JGT does not increase much the BOD and COD of water Formulation developed for special treatment of JGT is user friendly Predicted life of durable JGT is about two years in combined water-soil ambience Considered as a cost effective alternative of copper and bitumen treatment
Installation Guidelines of Jute Geotextile
Check the name of the supplier-mill, brand-mark if any, type of JGT supplied vis-à-vis specifications stated in the contract document, test certificate (whether by the mill or by any independent testing outfit), whether the material recommended for laying by the competent authority and the quantity in the consignment Note: One set of tests for each consignment of 16,000 sqm of JGT or as specified shall be carried out. Any palpable shortcoming in JGT-construction should be brought to the notice of the Engineer JGT-Acceptance at site
JGT to be kept in a covered shed without removing the protective pack-sheet & not to be kept directly on ground/floor JGT not to be stored normally beyond 1 month JGT to be carried by inserting a bamboo or similar pole into the central hole of the roll when the fabrics come in the form of roll Check that the fabric does not get damaged during handling JGT-Storage & handling
Installation Guidelines for the application of Jute Geotextile for Hill Slope Protection Installation Guidelines for the application of Jute Geotextile for Hill Slope Protection
Direction of laying Jute Geotextile Fixing nail Graded slope Grass plant Toe anchor (150 mm x 150mm) 150 Shoulder anchor (150 mm x 150mm) + Impounded of 2.87 litres / sq.m. of water on a 1:2 slope by 500 gsm open weave JGT having 45 wefts/metre, and dia of 4mm Jute Geotextile for slope protection – a typical arrangement
The slope was made free from undulations, soil slurry, mud and sharp projections and compacted with additional earth where necessary. Anchoring trenches was excavated at the top and toe of the slope along the length the embankment. Recommended dimensions of the trench (usually rectangular) are 300 mm depth X 250 mm wide. The selected OW JGTs was unrolled across the top trench and along the slope to downward, caring to see that it touches the soil surface at all points. 100 mm overlapping of the JGT over previous laying was also ensured. Installation Guidelines of Jute Geotextile for Hill Slope Protection
The JGT was fixed in position by steel staples (usually of 11 gauge dia) or by split bamboo pegs. Stapling was done normally at an interval of 500 mm. The anchoring trench was filled up with sand / brick- ballast / gravel etc. for keeping JGT in position. Seeds of vegetation (grass, legumes etc. of appropriate variety) was spread. Saplings of the appropriate plant species may be planted at suitable intervals through the openings of the JGT where seeds were unavailable,. In special circumstances, a second dose of seeds were spread with dibbling of locally available grass. Attempts were taken to install JGT preferably before the monsoon to take advantage of the rains for quick germination of seeds and growth of vegetation. Installation Guidelines of Jute Geotextile for Hill Slope Protection Special care was taken to staple the JGT within the anchoring trenches both at the bottom and at the sides. It was also ensured that the JGT in trench should touch all the three sides. Care was taken so that the overlaps are not displaced during installation. Precaution was taken to ensure that the JGT should not damaged due to puncture, tear and other installation stresses.
Jute open mesh Soil Saver for Hill slope Stabilization
Construction Open weave jute geotextile for hill slope management Width (cm) at 20 % MR ≥ 122 cm Weight (gsm) 500 (- 5%, + 10%) 600 (- 5%, + 10%) 700 (- 5%, + 10%) Tensile strength (kN/m) MD X CD ≥ 6.5 X 6 ≥ 12 X 6 ≥ 14 X 7 Ends X Picks / dm ≥ 6.5 X 4.5≥ 8 X 7 ≥ 8 X 8 Thickness (mm) 4.50 (± 10%)5.25 (± 10%)5.50 (± 10%) Elongation at break (%) MD X CD ≤ 14 X 14 Puncture Resistance (kN) --- Burst Strengnth (KPa) --- Permittivity at 50 mm constant head (/sec) --- A.O.S. (Micron) O Open Area (%) Water Holding Capacity (%) on dry weight – 600 Specifications of the JGTs for Hill Slope Protection
Installation Guidelines for the application of Jute Geotextile for Road Construction Installation Guidelines for the application of Jute Geotextile for Road Construction
JGT in Road Construction – A typical Arrangement
Installation Guidelines of Jute Geotextile for Road Construction Sub- grade excavated to the required level, cleared of all foreign materials, uprooted vegetation, if any, rolled and compacted to the OMC. Sub-grade was leveled and prepared with the specified profile. A thin cushion of local sand of 25 mm thick spread over the prepared sub-grade to facilitate better drainage and less chances of microbial attack on JGT. JGT was laid by unrolling, ensuring proper drapability so that the fabric touches the sand layer at all points and stapled with U-shaped nails (11 gauge) or suitable similar material at an interval of about 750 mm with longitudinally overlaps of mm. Again a thin cushion of local sand of about 25 mm thick was spread over the JGT to prevent puncture/damage due to rolling of the overlying sub-base.
Installation Guidelines of Jute Geotextile for Road Construction The first layer of graded aggregates in the base-layer was spread over sand layer spread over JGT. Traffic was restricted on an uncompacted base course. Thereafter subsequent layers of GSB, WBM,PMC and Seal Coat were laid as per practice and rolled as mentioned in DPR. It was targeted that at least WBM layer be completed before onset of monsoon Rutting occurred in few cases during construction was made good with fill material. For application in curves, JGT was folded / cut and overlapped in the direction of the turn. Folds in JGT are generally stapled at an interval of 300 mm in curves. Before covering up the JGT, its condition was assessed for any construction/ installation damage. Torn/damaged portions were covered by pieces of JGT and duly stapled on all sides preferably at an interval of 300 mm. The extent of overlap was such as to fully cover the damage/torn portion fully plus at least 75 mm beyond on all sides.
Installation Guidelines for the application of Jute Geotextile for River Bank Protection Installation Guidelines for the application of Jute Geotextile for River Bank Protection
JGT in River bank Protection – A typical Arrangement
Installation Guidelines of Jute Geotextile for River Bank Protection The bank was first cut to a stable slope preferably at the angle of internal friction of the bank soil. The surface leveled and made free from angular projections, undulation, soil-slurry or mud. Anchoring trench (usually rectangular) was excavated at the top of the slope. Recommended dimensions of the trench mm deep and at least 250 mm wide at the bottom. The trench was ensured to be free from foreign materials, mud etc. JGT should then be unrolled across the trench and along with slope from top to down side to the lowest water-level. The fabric was stapled with U-shaped nails (usually 11 gauge) within the anchoring trench both at the sides and bottom at an interval of 300 mm along the length of the trench. There should be at least 2 staples both depth-wise and width wise in each cross-section.
Installation Guidelines of Jute Geotextile for River Bank Protection JGT was laid with the overlapping in the direction of water-flow. Care was taken to ensure JGT does not suffer damage due to puncture, tear and installation stresses. The recommended overlap is 150 mm (minimum). The overlapped portion should be stapled at an interval of 300 mm. The anchoring trench was then filled with stones/boulders for securing and protecting the JGT. Care was taken to ensure that JGT touches the bank slope at all points to ensure proper drapability. Armor overlay of stone/boulder was then placed on the JGT carefully and properly arranged. A thin layer of sand ( 25 mm ) as a cushion on top of the JGT may be used to avoid puncture of the fabric by granular armour.
JGT for Road Construction and River bank Protection 627 GSM JGT 724 GSM JGT
Construction Double Warp Plain Weave (DW Plain) for application in rural road Double Warp Plain Weave (DW Plain) for application in river bank Width (cm) at 20 % MR ≤ 200 cm* Weight (gsm) 724 (- 5%, + 10%) 627 (- 5%, + 10%) (To be treated with Suitable additives) Tensile strength (kN/m) MD X CD ≥ 25 X 25≥ 20 X 20 Ends X Picks / dm ≥ 94 X 39≥ 85 X 32 Thickness (mm) 1.85 (± 10%)1.70 (± 10%) Elongation at break (%) MD X CD ≤ 12 X 12 Puncture Resistance (kN) (± 10%)0.400 (± 10%) Burst Strengnth (KPa) 3500 (± 10%)3100 (± 10%) Permittivity at 50 mm constant head (/sec) 350 x (± 10%) A.O.S. (Micron) O Open Area (%) -- Specifications of the JGTs for Road & River Bank Construction
Road Construction Short of adequate width of Right of way for which stable slope of embankment could not be maintained. In such cases it was suggested to use OW JGT for slope protection. Improper camber of sub-grade observed in few roads which were properly corrected as specified in the DPR In few stretches specified thickness of sand had to be maintained Hill Slope Protection In case of hill slope protection works, in some places slope angle much higher than the angle of internal friction had to be corrected to make a stable slope angle. During laying of OW JGT in slope some time drapability of JGT needed to be ensured with the removal of boulders / gravels / undulation present on the surface. River Bank Potection In river bank protection works presence of clay on the slope surface of bank was removed and replaced with sand / silt to prevent clogging of pores of JGT. Higher slope angle in some cases had to be modified as per angle of internal friction of bank soil. In all applications proper storing method of JGT at site were not followed which were rearranged properly to avoid early degradation and damage of JGT. Difficulties faced during installation of JGT and measures taken to address to: