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Role of standards in Promotion of Technical Textiles. Presentation on Use of Geotextiles in highway sector On behalf of Indian Roads Congress By A.V.Sinha , Former DG(RD) & Spl Secretary, Ministry of Road Transport & Highways. Geosynthetics and their varieties. Geotextiles
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Role of standards in Promotion of Technical Textiles Presentation on Use of Geotextiles in highway sector On behalf of Indian Roads Congress By A.V.Sinha, Former DG(RD) & Spl Secretary, Ministry of Road Transport & Highways
Geosynthetics and their varieties • Geotextiles • Synthetic fibres (Polypropylene, Polyester, Polyvinyl Chloride, Polyamide, or Polyethyleyne) converted into fabric by (a) weaving (woven), or (b) bonding of random fibres (non-woven), or (c) knitting • Good drainage property • Geogrids • Extruded sheets of Polypropylene and Polyethyelne punched to form a grid pattern having large apertures • Good strength properties • Geonets • Polymer strands crossing one another at an angle (usually acute angle to give a diamond pattern aperture) and bonded at joints by thermal bonding • Used in combination with Geotextile or Geomembrane for drainage • Not used for strength
Geosynthetics and their varieties (..contd) • Geocomposites • A composite material of usually three out of geotextile, geogrid, geonet, and geomembrane in laminated or other form. • Good drainage property and used for Prefabricated Vertical Drain • Geomembranes • An impervious geosyntheitc material • Used for checking migration of water(e.g lining of drains/ canals) • Geomats • A three dimensional (as opposed to two dimensional geotextile and geogrid) open mat • Good drainage property, suitable for draining filling behind bridge abutment
Geosynthetics and their varieties (..contd) • Geocells • These are formed by connecting HDPE strips in series to form a pattern of grid in three dimensions, the width of strips forming the walls of the cells which are filled with soil/gravel/stones etc • The confinement provided by cell walls gives strength • Improves the bearing capacity of weak foundations • Natural geotextiles • Naturally growing fibres (like jute) and their strands form these geotextiles • Usually biodegradable and used for slope protection by vegetation
Areas of Application of Geo Synthetics and predominant properties • Retaining Wall: Strength • Embankment in soft soil: Strength, drainage • Repairs of damaged Pavement: Strength • Slope protection and Erosion Control: Separation, filtration, aperture size • Drainage of embankment, subgrade, fill behind abutment, and surface drains: Separation, filtration, drainage
Standardization of Geotextile applications • Indian efforts: • 1994: Indian Roads Congress published a State-of-the-Art Report: Application of Geotextile in Highway Engineering (IRC:SP12) • 2001: Ministry of Road Transport and Highways included a chapter in its Specifications (MORTH Specficification for Roads and Bridges) • 2002:Indian Roads Congress published Guidelines for use of Geotextiles in Road Pavements and associated works • 2011: MORTH Specifications including chapter on Geptextile under revision • 2011: IRC Council approved for publication the State-0f-the-Art Report on use of Jute Geo textile (under print) • 2011: IRC Council approved for publication Guidelines for the Deesign and Construction of Geosynthetic reinforced embankment on soft soils
Standardization of Geotextile applications (..contd) • International efforts • 1995/2010: British Standard BS 8006 Code of Practice for Strengthened/ Reinforced soils and other fills was published • 1998/2001: Federal Highway Administration of US published a document (Publication No. FHWA-NHI-00-43) on reinforced soils
General Specifications for Geosynthetic Systems • Material properties: These are generally specified and accepted if the material tests are as per standard procedures specified by • American Society for Testing of Materials (ASTM) • International Standardization Organization (ISO) • British Standards (BS) • Accredited laboratories • Design: This required to be done as per BS or FHWA procedure • Certification: A certification by the system supplier about conformity with • ISO for manufacturing process • BBA (British Board of Agreement, AASHTO (American Association of State Highway and Officials) • Accredited laboratories • Warranty:Client seeks a warranty from the supplier • The warranty can be for as long as for 50 years
Indian Test Procedures • IS 13162 (part2): Test Method for deterioration of Geotextile for exposure to Ultraviolet Light and Water • IS 14324: Test methods for Water Permeability of Geotextile by Permittivity • IS 14294: Test Method for Detrming Apparent Opening Size for Geotextiles • IS 13162 (Part 4):Test Method for Index Puncture Resistance of Geotextiles and related products (Source : IRC SP 59:2002)
Gaps in Design Procedures • Indian standards on Geotextiles are practically absent • One Guideline recently approved by IRC Council and will be released shortly • Design, particularly where strength is the main concern ( like retaining walls, embankment, pavement rehabiltation) is an involved process • Design Approach particularly for internal stability of structures (i.e where geotextiles come into play) has to be standardized
Gaps in Design Procedures • Design (..contd) • Factors of safety, reduction factors, partial factors etc used in the British and US standards have to be evolved for our national codes and Guiodelines • Testing Standards • There is huge gap in the requirement and availability of national testing procedures • An indicative list of subjects on which test procedures need to be developed are as follows:
Gaps in Design Procedures • Indicative list of tests • Determination of friction between the soil and geotextile reinforcement at different levels of strain • Determination of vulnerability of geotextiles to chemicals and microbiological substances present in soil and water • Detrmination of the effects of creep and long term stability • Determination of relationship between ultimate strength and design strength • Suggesting reduction factors (or partial factors or factors of safety on the basis of • Tests • Manufacturing Process • Serviceability conditions • Installation factors • Temperature variations • Durabilty factors • Construction imperfections