Under Water Inspection of Bridges

Preface to the Second Edition

Book on Underwater Inspection of Railway Bridges was first published in year 2005. Now the second revised and enlarged edition is being brought out.

Content of the book is thoroughly supplemented with several photographs for better understanding. While revising latest supplements, RDSO publications and recommendations of Bridge Standards Committee have been included.

The second chapter on Underwater Inspection has been revised duly incorporating the cause of damages, growth of aquatic life on underwater structure etc. A new chapter on Underwater Inspection Method is introduced with a section on equipment and apparatus needed.

The chapter on documentation and reporting is supplemented by adding real life case studies on underwater inspection of Railway Bridges on Indian Railway.

It is hoped that this book will fulfil the need and assist the field engineers in bringing awareness about the aspects to be inspected and corrective action to be taken.

Suggestions for improvement may be sent to the undersigned.

Acknowledge to Second Edition

Book on Underwater Inspection of Railway Bridges was first published in Year 2005. Subsequently BS-96 was brought out in year 2008. Underwater Inspection was also discussed during various Bridge Standard Committee meetings.

Underwater Inspection is regularly carried out in Indian Railways; therefore, a need was felt to update the earlier edition. Now the second revised and enlarged edition is being brought out to fulfil the continuous demand for the book.

This book is thoroughly supplemented with several photographs collected from various resources and references to make the topics more clear. Almost all the chapters were revised in terms of content as well as presentations.

Topics related to natural phenomena causing damage to bridges, growth of aquatic life etc. was included in second chapter on Underwater Inspection problems and material defects.

The Chapter on Underwater Inspection methods is bifurcated in two Chapters. In the Underwater Inspection methods, emphasis is given on the various modes of inspections and their related operations, codal provisions etc.

A new Chapter on Underwater Inspection Programme is added which includes the revised guidelines by RDSO issued vide BS-96 (2008) and recommendations of Bridge Standards Committee.

The chapter on Underwater Inspection Procedure is revised duly incorporating various aspects related to diving operations of diving team.

The Chapter on documentation and reporting is supplemented by incorporating two case studies on Underwater Inspection; one bridge is situated on Chalakudi River in Thiruvananthapuram Division of Southern Railway and other bridge is on River Sankaosh in NF Railway.

Efforts have been made by IRICEN faculty and staff to bring out this new edition as more useful guide for the field engineers. In this process the contribution of Shri K. Kurian, SSE/Br./TVC, Shri Harish Trivedi, Shri Praveen Kotkar, Shri V.N. Sohoni and the DTP by Shri Aman Aparadh is most notable. I am grateful to Shri Venkateshwara Rao, Sr. DEN/Co/TVC/S. Rly., for arranging field visit and demo of Underwater Inspection related to the bridge situated in Thiruvananthapuram. I am also thankful to Shri Ashok Kumar, DyCE/Br/HQ/S. Rly., for providing details on rehabilitation of
above bridge.

I am also thankful to Shri C.S.Sharma, Sr. Professor IRICEN and Shri N.K. Khare, Professor, IRICEN for arranging the DTP work and proof checking. I am also thankful to faculty of IRICEN for giving useful suggestions for improving the presentation of this book.

Above all I am grateful to Shri Vishwesh Chaubey, Director IRICEN for his encouragement, regular guidance to bring out the book in its present form.

CHAPTER – 1 UNDERWATER INSPECTION

GENERAL

1.1 Introduction

Bridges that cross waterways often have foundation and substructure elements located in water to provide the most economical total design. It is important that entire bridge is inspected at specified interval not only to ensure safety of the bridge, but also to initiate any repair/rehabilitation work well in time so that the bridge remains functional. Unfortunately, the conditions of substructure and foundation located below waterline is not as easily determined as the condition of parts of the bridge located above waterline. The environment under water is harsher and affects inspecting official’s mobility and visibility. Wherever these elements are continuously submerged, underwater inspection and management techniques must be used to establish their condition so that failures can be avoided.

The underwater inspection of bridges is becoming key activity to be undertaken for maintaining bridge substructure and foundation. Indian Railways Bridge Manual (IRBM) provides for underwater inspection of all bridges whose substructures and foundations are perennially under water.

Underwater inspection has four primary purposes – ensuring public safety, protecting public assets, preventing or reducing facility downtime and initiating proactive maintenance.

In general, the term “underwater inspection” is taken to mean a hands-on inspection requiring underwater breathing apparatus and related diving equipments.

However, it is a more specialised operation than a routine bridge inspection because a fair amount of sophisticated equipments are required as well as a high degree of skill and efforts of both the bridge inspector and a diver. The bridge inspector and the diver must be able to act as a team in relaying the proper information to each other and coordinating the whole inspection procedure. The expense of such inspections necessitates careful consideration of bridges to be selected for inspection.

1.2 Bridge Selection Criteria

Various factors influence the bridge selection criteria.

Factors to consider in establishing the inspection frequency and levels of inspection include:

• Age
• Type of construction material
• Configuration of the substructure
• Adjacent water features such as dams, dikes or marines
• Susceptibility of stream bed materials to scour
• Maintenance history
• Saltwater environment
• Waterway pollution
• Damage due to water borne traffic, debris etc.

1.3 Requried Information

Those bridges, which require underwater inspection must be noted for individual inspection and inventory records as well be compiled in a master list.

For each bridge requiring underwater inspection, the following information should be collected as a minimum and considered while planning its inspection.

• Type and location of the bridge
• Type and frequency of the required inspection
• Location of members to be inspected
• Inspection procedures to be used
• Special equipments requirement
• Dates of previous inspections
• Findings of the last inspection
• Follow up action taken on findings of the last inspection
• Type of foundation
• Bottom of foundation elevation or pile/well tip
  elevation

1.4 Frequency of Inspection

Underwater inspections must be done on every bridge identified for such inspection as per the Indian Railways Bridge Manual (IRBM) provisions. As a minimum, all structures must receive detailed underwater inspection at intervals not to exceed five years. This is the maximum interval at which all underwater elements of a bridge, even if it is in sound condition, must be inspected. More frequent routine and in-depth inspections may be desirable for many structures and necessary for critical structures.

Inspection frequency may be increased in those bridges where deterioration has been noticed during previous inspections. It should be also carried out after any collision with the bridge superstructure or after a major storm so that physical evidence is inspected and recorded.

CONTENTS

1 Underwater Inspection – General.
1.1 Introduction.
1.2 Bridge Selection Criteria.
1.3 Required Information
1.4 Frequency of Inspection.
2 Underwater Problems & Material Defects.
2.1 Introduction.
2.2 Damage Due to Water.
2.3 Scour.
2.4 Growth of Aquatic Life on Underwater Structure.
2.4.1 Types of Marine Fouling.
2.4.2 Growth of Marine Fouling.
2.5 Material Defects.
2.5.1 Plain or Reinforced Concrete Substructure.
2.5.2 Masonry Substructure.
2.5.3 Steel Substructure.
2.5.4 Cast Iron Substructure.
2.6 Deferred Maintenance.
3 Underwater Inspection Methods.
3.1 Introduction.
3.2 Methods of Underwater Inspection.
3.2.1 Wading Inspection.
3.2.2 SCUBA Diving.
3.2.3 Surface Supplied Air Diving.
3.3 Decompression.
3.4 Equipments for Diving.
4 Underwater Inspection Programs.
4.1 Introduction.
4.2 Inspection Type & Frequency.
4.2.1 Level of Inspection.
4.3 Inspection Frequency.
4.3.1 Routine Inspection.
4.3.2 Detail Inspection.
4.3.3 Special Inspection.
5 Underwater Inspection Procedures.
5.1 Introduction.
5.2 Planning an Underwater Inspection
5.3 Preparation.
5.3.1 Review of Available Records.
5.3.2 Availability of Tools and Equipments.
5.3.3 Communication.
5.4 Method Selection Criteria.
5.5 Diving Operation.
5.5.1 Divers.
5.5.2 Divers Qualification.
5.5.3 Signaller (Observer).
5.5.4 Standard Line Signals.
5.5.5 Diving Supervisor.
5.5.6 Divers in a Team.
5.5.7 Safety Precautions.
5.6 Cleaning.
5.7 Scour Investigation.
5.7.1 Divers Investigation.
5.7.2 Sounding/Sensing Devices.
5.8 Inspection of Masonry Substructure.
5.8.1 Inspection Procedure.
5.8.2 Equipments and Tools Required.
5.9 Inspection of Concrete Substructures.
5.9.1 Inspection Procedure.
5.9.2 Equipments & Tools Required.
5.9.3 Level – III Non-Destructive Inspection.
5.10 Inspection of Steel/Cast Iron Substructures.
5.10.1 Inspection Procedure.
5.10.2 Equipments and Tools Required.
5.10.3 Level – III Non-Destructive Inspection.
6 Underwater Non-Destructive Testing.
6.1 Introduction.
6.2 Sounding/Sensing Devices.
6.2.1 Black and White Fathometer.
6.2.2 Dual Frequency and Colour Fathometer.
6.2.3 Fathometer with Theodolite.
6.2.4 Fixed Instrumentation.
6.2.5 Ground Penetration Radar.
6.3 Rebound Hammer.
6.3.1 System Limitations.
6.4 Magnetic Radar locator.
6.4.1 System Limitations.
6.5 Ultrasonic System for Concrete Elements.
6.5.1 System Limitations.
6.6 Ultrasonic Thickness Measurement.
6.7 Underwater Magnetic Particle Testing
6.7.1 Limitations.
6.8 Radiography.
6.8.1 Limitations.
6.9 Dynamic or Vibration tests.
7 Inspection Equipments.
7.1 Access Equipments.
7.2 Diving Equipments.
7.3 Surface Cleaning Tools.
7.4 Inspection Tools.
7.5 Underwater Photography and Video Equipments.
7.5.1 Still Photography Equipments.
7.5.2 Video Equipments.
7.6 Surface Communication.
8 Special Considerations for Underwater
Inspection.
8.1 Introduction.
8.2 Working Environment.
8.3 Dealing with Current
8.4 Dealing with Drift & debris.
8.5 Physical Limitations.
8.6 Decompression Sickness.
8.7 Videography in Turbid Water.
8.7.1 Problems in Turbid Water.
8.7.2 Remidial Measures.
8.7.3 Use of Scattered Lighting.
9 Documentation and Reporting
9.1 Documentation.
9.2 Reporting.
9.3 Case Study – I
9.4 Case Study – II