Railway Waterway Maintenance

Protective Works for Waterways

• Guide bunds, marginal bunds, and spurs/groynes are provided to control waterways
• These works are implemented singly or in combination to achieve effective control

Maintenance of Waterways

• Obstructions in waterways should be cleared away on both sides of the line within railway limits for the full extent of the waterway
• Boundary pillars on each bank of a river or important waterway shall be erected to prevent and control encroachments

Maintenance of Substructure

Abutments, Piers, Wing Walls, and Return Walls

• Weathering, leaching of mortar, and leaning/bulging of abutments, wing walls, and return walls can occur
• To avoid build-up of hydrostatic pressure:
  • Weep holes should be provided at 1m intervals in both horizontal and vertical directions
  • Adequacy of existing weep holes should be checked and additional weep holes provided if required
  • Choked weep holes should be cleaned and made functional
  • Backfill material should be granular and not contain expansive soil like black cotton soil
  • Proper filter layer should be provided behind the masonry
• Excessive earth pressure can be taken care of by providing masonry or cement concrete buttress
• Undermining/scour and other rehabilitation problems can be tackled by referring to paras 204 and 513

Cracks in Masonry/Concrete

• Rivets should be heated almost to white heat and to a point when sparks are just beginning to fly off
• Rivets should be driven and the snap removed within 20 seconds of the rivet leaving the fire
• Rivets should be driven straight, while hot, keeping the hammer coaxial
• Rivetter should have his staging at a height which enables him to put the whole weight of his body behind the hammer
• Rivets conforming to IRS specifications only should be used
• Adequate air pressure of 5.6 to 7 kg/cm2 should be ensured for opening of the tools
• In the case of long bridges, the air compressor may be centrally located at a suitable trolley refuge, with main pipeline running in both directions with suitable tappings

Replacement of Loose Rivets in Plate Girders

• Renewal of slack rivets should be taken up for:
  • All rivets which are hand loose or which have lost 50% of their head by corrosion
  • All hammer loose rivets where corrosion has set in between the head and the plate
  • In end stiffeners when the percentage of hammer loose rivets is >30%
  • In flange splices when the number of hammer and hand loose rivets is 30% or more of the total rivets on any side of the splice location
  • All hammer loose rivets at main angle to web connection up to 1/12 span from either support of the girder
  • When loose rivets in end connections of lateral and cross bracings of plate girder spans require renewal, all the rivets in the end connections should be renewed

Maintenance of HSFG Bolts

• HSFG bolts should be painted as per normal painting schedules and painting methodologies as specified in the Indian Railways Bridge Manual for the girder as a whole
• Anti-theft and anti-sabotage measures:
  • Bolt threads may be destroyed by applying welding tack to the bolt projection beyond the nut after final tightening and inspection
  • Alternatively, proven bonding agent may be applied to the threads projecting beyond the nut to seize or lock the bolt in position

Corrosion and its Prevention

• Corrosion is deterioration of metal due to its interaction with the corroding environment
• Corrosion may take place in either uniform or local forms
• Prevention of corrosion:
  • Protective coatings by painting
  • Metallising - a form of protection by spraying a metal either zinc or Aluminium

Metallising and Epoxy Based Paints

• Metallising:
  • In metallised protection, base metal like zinc or aluminium is lost by atmospheric action, while the base metal (steel) remains unaffected
  • Zinc or aluminium can be sprayed on the surface prepared by grit/sand blasting for giving such protection
• Epoxy based paints:
  • For locations where girders are exposed to corrosive environments, protective coating by way of metallising or by painting with epoxy-based paints may be applied

Painting of Bridges

• The date of painting of steel work should be painted in white on the outside of the left girder of the first span.
• For important girder bridges, the left girder at each end should bear the date of painting.
• The highest flood level line should be painted distinctly by a 25mm broad white line along with the year of its occurrence, in figures 100mm deep.
• The direction of flow should be distinctly marked in white on an abutment or pier.
• Name boards at important bridges should be fixed at either approach at a distance of about 15 metres from the abutment indicating the name of the river and the number and length of spans.

Maintenance of Foundations

• A bridge foundation having less than 2M depth below bed level in case of arch bridges and 1.2M depth below bed level in case of other bridges is termed as shallow foundation.
• Procedure for cement grouting involves drilling holes in the structure, fixing G.I. pipe pieces, sealing cracks and annular space, sluicing with water, injecting cement grout, curing, and providing tell tales.
• Grouting equipment must be cleaned thoroughly after use.

Epoxy Grouting

• Epoxy grout consists of an epoxy resin and a hardener which react chemically when mixed.
• Epoxy resins are thermosetting and can be varied to suit all types of conditions.
• Manufacturer's detailed instructions should be followed for safe handling and processing of epoxy grout.
• Direct skin contact should be avoided, and hand gloves and protective goggles should be used.

Shot Creting / Guniting

• Shotcrete is mortar or concrete conveyed through a hose and pneumatically impinged at high velocity on to the surface to be treated.
• Shotcrete is suitable for repairing spalled concrete surface as well as for strengthening weathered stone or brick masonry.
• Equipment required for shot creting includes a guniting machine, air compressor, placing nozzle with hose, and materials such as ordinary Portland cement, sand, coarse aggregate, water, and admixture.

Protective Coatings by Painting

• Correct surface preparation of the steel to receive the paint is the single most important factor in ensuring good performance.
• Surface preparation methods include manual hand cleaning, cleaning with power driven tools, blast cleaning, and flame cleaning.
• The surface should be clean, dry, and free from contaminants, and rough enough to ensure adhesion of the paint film.

Bridge Bearings

• Phosphor bronze bearings need not be greased as they are corrosion-resistant and retain the smooth surface.
• The tooth bar of the roller assembly should be placed vertically at mean temperature.
• In the case of roller bearings with oil bath, dust covers should be provided to keep the oil free from dirt.
• Inspection of the bearings, after removal of the casings to the extent necessary, should be carried out at least once in 5 years.

Elastomeric Bearings

• Elastomeric bearings are made of natural or synthetic rubber of shore hardness of approximately 50 to 70.
• They are very stiff in resisting volume change but are very flexible when subjected to shear or pure uniaxial tension.
• They are generally reinforced with steel plates in alternate layers to reduce bulging.

This quiz covers the measures taken to maintain waterways within railway limits, including clearing obstructions, guide bunds, and boundary pillars.