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Underwater Bridge Inspection Guidebook for Railway Engineers

Learn the systematic process of underwater bridge inspection for railway engineers according to Indian Railways Bridge Manual. Discover routine, detailed, and special inspection levels along with cleaning methods and reporting guidelines.

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Underwater Bridge Inspection Guidebook for Railway Engineers

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  1. UNDER WATER INSPECTION OF BRIDGES

  2. UNDER WATER INSPECTION OF BRIDGES • References • IRBM • RDSO report no BS-96 on UWI • IRICEN book on “Under Water Inspections” • RDSO report no BS-48 on NDT

  3. KADALUNDI TRAIN MISHAPCalicut – Shoranur Section of Palghat Division on 22-6-2001 due to failure of pile

  4. KADALUNDI TRAIN MISHAP • Br. No. 924 • Span 12X 19.51 m steel girders • Bridge sub structure built in 1861 • Train involved-6602 Manglore – Chennai Exp • Dead 52 • Grievously Injured 105 • Cause • Collapse of screw pile of pier no. 3 • CI pile thickness reduced to 6 mm from original 28 mm • Density reduced to 2.5 from 7.5 gm/cm3

  5. BRIDGE INSPECTION • Systematic observation of condition and behaviour of various components/ parts of a bridge is called bridge inspection • Underwater portion of bridge is also a component to be inspected

  6. Indian Railways Bridge Manual • Clause 102 - AEN to inspect once a year, by a date specified by Chief Engineer after monsoon - this inspection shall include foundation, flooring and substructure • Clause 1107(d) – The substructure of the bridges which are normally under water should be inspected by adopting suitable methods which may include engaging of divers and special equipment. [Old]

  7. Schedule of inspections Para 1107 (d) New as per CS 21 • The sub-structure of the bridges which are normally under water should be inspected by adopting suitable methods which may include engaging of divers and special equipments: (i) Routine/swim by inspection should be done once a year (ii) Detailed inspection should be done once in five years. (iii) Special inspection- as considered necessary” 

  8. Inspection Levels (BS – 96) Routine Inspection or Level I inspection • Visual, tactile inspection. Swim by. Any obvious major damage or deterioration should be detected. • Conducted over 100% exterior surface of each underwater element. • Can indicate the need for detailed inspection • To be done once every year

  9. Routine inspection Visual Inspection or swim by inspection to be done by experienced diver • Water depth sounding and scour around piers and abutments. • Verification of the continuity of the piers in full length. • Registration of spalling. • Registration of corrosion. • Registration of cracks larger than 0.2mm. • Registration of severe damage in general.

  10. Report for Routine inspection • Method and extent of investigation • Background material • Recording of deficiencies/important aspects requiring notice of higher authority • Assign condition rating number of the underwater bridge components. • Need for further inspections (Level II or III) – if required • Photos and video recordings(Not mandatory). • Specific requirement, if any, for photo/video recording should be ascertained by Chief Bridge Engineer of the Railway.

  11. Detailed Inspection or Level II inspection • More detailed and directed towards obtaining limited measurements of damaged or deteriorated areas • Detail Inspection to be done on those structures where problems have been identified/ encountered during Routine or level I Inspection OR Once in five years. • If damage is there, level III inspection may be required • Sectional Sr.DEN/DEN should ascertain the necessity of carrying out Level III inspection

  12. Detailed Inspection • Marine growth needs to be cleaned for surface inspection • Cleaning is restricted to sample areas of the entire underwater structures. • Damage should be measured and the extent and severity of the damage should be documented. • Cleaning for inspections • Bands for cleaning of piers and abutments should be approximately 30 cm wide • Cleaning of the substructure components is to be performed in three different water depths

  13. Detailed Inspection • Cleaning for inspections Contd.. • Bands shall normally be located in the splash zone (low waterline), the mud line (bottom of river) and at construction joints or other structural details. • If no joints exist the area could be placed mid-way between the low waterline and mud line. • Thoroughness of cleaning should be governed by what is necessary to identify the condition of the underlying material. • Water jet cleaning equipment may be used if necessary

  14. Detailed Inspection : Results • Registration of spalling. • Registration of corrosion. • Registration of cracks. • Registration of severe damage in general.

  15. Detailed Inspection : Report • Photos and video recordings to be taken • Method and extent of investigation. • Background material. • Recording of Deficiencies/important aspects requiring notice of higher authority • Assign condition rating number of the underwater bridge components • Need for further inspections (Level III) – if required

  16. Special or Level III Inspection • After unusual floods. • After vessel impact (unless it is obvious that no damage has occurred). • Build-up of debris at piers and abutments (horizontal forces on the structures and scour because of reduced cross section of the river). • Unusual prop wash from vessels. • In case of settlements or other evidence of excessive scour. • As a result of Level I/II inspections

  17. Special or Level III Inspection • Highly detailed inspection to detect hidden or interior damage and loss in cross sectional area. • This involves extensive cleaning, detailed measurements, selected NDT &/or partially destructive techniques. • Basically for a member where extensive repair or possible replacement is contemplated.

  18. Special Inspection • Planned using information from • Drawings, • Previous underwater inspections of this bridge • Underwater inspections of similar bridges • Knowledge and experience • A “hypothesis” concerning the cause of damage, the total damaged area and the condition of the damaged area may be formulated.

  19. Special Inspection • If the test results do not confirm the hypothesis regarding the cause of damage, the hypothesis must be revised. • Perform supplementary tests to confirm the revised hypothesis. • Inspection must be sufficient to determine need for • Speed Restrictions OR • Closure of bridge to traffic and • To assess the Level of effort necessary to repair the damage • Must give section loss, misalignment of members, and loss of foundation support etc

  20. Non –destructive tests • Equipment and calibration different from normal NDT • Ultrasonic Thickness Gauge - Steel • Ultrasonic Testing - Concrete and steel • Cover-meter – Concrete • Schmidt Hammer - Concrete and masonry • Chloride Content - Concrete • Coring Equipment - Concrete and masonry • Evaluation of Concrete Cores – Concrete • Crack Measuring Gauge - Concrete and masonry • Impulse Response Equipment – Concrete • Impact-Echo Equipment - Concrete and masonry • Half-Cell Potential – Concrete

  21. Other issues • Level I and II inspections to be done in presence of AEN and report to be sent to SrDEN • Level III inspections to be done in presence of SrDEN and report to be sent to CBE • List of agencies for Under water Inspections given in Annexure I of the report BS-96 (20 agencies) • Only indicative and can choose other agencies from market also

  22. Limitation of underwater inspection • During heavy scour there is high velocity of water and divers can not operate and when velocity is low, cavity is refilled. • Some underwater portion of structures exposed during some part of year cannot be inspected by the present methods • This is serious limitation specially in case of alluvial soils

  23. What to see in UWI: General • Tilting • Permanent deformations (Settlement/ bulging) • Abnormal vibrations • Material defects

  24. What to see in UWI: Concrete • Spalling • Sulphate Attack • reaction of magnesium sulphate with tricalcium sillicate • Chlorides- attacks steel • Alkali aggregate reaction • Alkali in cement reacts with minerals in certain aggregates • Honeycombing • Effects of Contaminants

  25. What to see in UWI: Steel • Corrosion particularly in low water areas • Cracks • Impact damage • Loose connections etc

  26. What to see in UWI: Masonry • Washout of joints • Cracks in joints • Weathering of masonry • Debonding of bricks/ stone pieces forming cavity • Deterioration of stones/ joints • Impact damage etc

  27. Anaerobic bacterial growth

  28. Spalling

  29. Scaling

  30. Disintegration

  31. Cavitation

  32. Planning an Underwater Inspection • Factors to be considered – • Type of Inspection • Method of underwater inspection • Inspection Level • Qualification of divers Inspectors available • Its possible that different levels may be required at various locations on the same bridge. • Compare inspection results of homogeneous areas • e.g. similar chloride content, depth from water level etc

  33. IMPORTANT POINTS • Divide the periphery into equal intervals– Chainages. • Give notations to the chainages. • Entire surface is divided in equal grids. • Drop a Wire rope with weight as guide line. • Diver descends along the chainage covering each grid. • Distresses shall be located & measured grid wise.

  34. B C A D E H G F Record Keeping and Documentation 1 1 HWL C A B D 2 3 E F G H 4 PIER 5 6 7 LWL 8 9 10 MUD LEVEL WELL

  35. Inspection of a pile in a spiral motion

  36. Methods of Underwater Inspection • Wading Inspection – substructure units and waterway are evaluated using a probing rod, sounding rod, hammers, picks etc. • SCUBA Diving – Self Contained Underwater Breathing Apparatus • Hard Hat Diving – uses a body suit, a hard hat helmet covering the head and a surface supplied air system.

  37. Scuba diving • Weighs about 30 kg • 1 hour at 18 m • 10 minutes at 36 m • As depth increases, diving time decreases • One tank holds about 2m3 of air • At least 3 divers required • No communication with std. Equipment • Communication possible with scuba full mask • Full mask gives protection against cold and contaminated water

  38. Surface Supplied Air Diving or Hard Hat Diving

  39. Surface Supplied Air Diving or Hard Hat Diving • Surface air compressor tank • Suited in adverse conditions • Jack Brown mask • 60 mts at 18 m • 30 mts at 27 m • MK1 mask • 10 mts at 40 m • unlimited up to 18m • Nitrox and heliox gases for longer and deeper dives

  40. Surface supplied air diving • Advantages • Long duration dives • Unlimited air supply • Safety line attached • Better in high velocity/ turbid water • Disadvantages • Large size operation. Boat, air compressor, hoses & lines are reqd.

  41. GENERAL • Most of the Inspection using Touch & Feel. • Most of the assessment through CCTV system • Needs to communicate with diver continuously. • Calls for experience Divers. • Surface Crew needs to be Patient.

  42. Record Keeping and Documentation • On site, recording of all conditions is essential • Sketches in detail • Logs describing the inspection • Tape recording the divers observation when significant damage is observed • Underwater photographs • Underwater Videotapes

  43. Equipment for inspection

  44. Operate in 0 lux light conditions • Self contained unit or one with control and monitor at tope • 5 MPx • 10 x Optical Zoom • Wide lens • Use of clear water box and suitable lighting, if required

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