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Highway and Rail Transit Tunnel Inspection Manual
2005 Edition
Chapter 3: Fundamentals Of Tunnel Inspection
A. Inspector Qualifications
The inspection should be accomplished with teams consisting of a minimum of two individuals; all team members should meet certain minimum qualifications as defined below. Aside from these general qualifications and the specific qualifications listed for each discipline, a tunnel owner may require that all tunnel inspection team members be certified to ensure that these qualifications are met. This certification would need to be performed by the tunnel owner, since currently there is no national tunnel inspection certification program. These inspection team members are classified as a Team Leader and Team Member(s). All individuals who will perform inspection work should be knowledgeable of tunnel components and understand how they function. The inspection team should meet the following general qualifications:
- Be able to climb and/or use equipment to access the higher regions of the structures.
- Be able to evaluate and determine types of equipment or testing required to fully define a deficiency.
- Be able to print legibly and to draw understandable sketches.
- Be able to read and interpret drawings.
- Be able to use tablet PC's for data collection.
Specific qualifications of the Team Leader and Team Member(s) for the various components to be inspected include:
1. Civil/Structural
a) Team Leader
- Be a registered professional engineer or
- Have design experience in tunnels using the same materials and
- Have a minimum of five years inspection experience with the ability to identify and evaluate defects that pose a threat to the integrity of a structural member.
- Be able to assess the degree of deterioration for concrete, steel, masonry, and timber members.
b) Team Member(s)
- Be trained in general tunnel inspection requirements.
- Have a minimum of one year inspection experience in concrete, steel, timber, and masonry structures.
2. Mechanical
a) Team Leader
- Be a registered professional engineer or
- Have design experience or be familiar with the type of mechanical systems installed in the tunnel. Examples of these systems are, but not limited to:
- Tunnel Ventilation
- Air Conditioning
- Heating
- Controls
- Plumbing
- Tunnel Drainage Systems (e.g., sump pumps)
- Fire Protection
- Wells/Septic.
- Have a minimum of three years inspection experience with the ability to evaluate the physical condition as well as the operational condition of equipment.
- Be aware of applicable codes and guidelines for tunnel construction and operation pertaining to mechanical features.
b) Team Member(s)
- Be trained in general inspection requirements.
- Have a minimum of one year inspection experience with mechanical and plumbing systems.
3. Electrical
4. Track, Third Rail, Catenary, Signals, and Communications
a) Team Leader
- Be a registered professional engineer or
- Have design experience in the system components being inspected.
- Have a minimum of three years inspection experience with the ability to identify and evaluate the condition of the components being inspected.
- Be familiar with specialized testing equipment to assess a particular component's operational viability.
b) Team Member(s)
- Be trained in general inspection requirements.
- Have a minimum of one year inspection experience with track, third rail, catenary, signals and communications systems.
B. Responsibilities
Each member of the inspection team must fulfill certain duties for work to be accomplished in an efficient manner. The Team Leader is responsible for coordination with appropriate tunnel and supervisory staff for access into the tunnels, for scheduling equipment, for determining the degree of inspection required, for evaluating all deficiencies, for ensuring that all inspection forms are thoroughly completed and legible (if using paper forms), and for notifying appropriate tunnel staff of any potentially dangerous condition. The other Team Member will assist the team leader in the inspection. Such duties may include performing portions of the inspection, carrying the equipment and inspection forms, taking photographs, and making sketches.
The tunnel owner is responsible for closing down the tunnel for inspection access and for responding to any critical actions that are identified by the inspectors.
C. Equipment/Tools
Below is a suggested list of equipment and tools commonly used for tunnel inspections:
- Aerial Bucket Truck or High Lift - Used to lift the inspector to areas inaccessible by foot or ladders.
- Hi-Rail Vehicle - Used atop the track to gain access to the rail transit tunnel structure or catenary power system. The tunnel owner may supply such vehicles.
- Awl/Boring Tool - Used to determine extent of deterioration in timber.
- Calipers - Used to measure steel plate thicknesses.
- Camera (35mm or digital) with Flash - Used to take photographs for documentation of the inspection.
- Chalk, Keel, or Markers - Used to make reference marks on tunnel surfaces.
- Chipping Hammer - Used to sound concrete (see Chapter 4, Section A, Part 2 - What to Look For).
- Clip Board - Used to take notes and fill out paper inspection forms during the inspection.
- Crack Comparator Gauge - Used to measure crack widths in inches.
- D-Meter - Used to measure the thickness of steel.
- Extension Cord - Used to get electricity to inspection area.
- Field Forms - Used to document the findings, take notes, and draw sketches for the various structures.
- Flashlights - Used in dark areas to help see during inspection.
- Ladders - Used in lieu of a lifting system to access areas not visible from the ground.
- Light Meter - Used to measure the brightness in the tunnel.
- Halogen Lights - Used where tunnel lighting is inadequate during inspection.
- Pencil
- Plumb Bob - Used to check plumbness of columns and wall faces.
- Pocket Knife - Used to examine loose material and other items.
- Sample Bottles - Used to obtain liquid samples.
- Scraper - Used to determine extent of corrosion and concrete deterioration.
- Screw Driver - Used to probe weep holes to check for clogs.
- Wire Brush or Brooms - Used to clean debris from surfaces to be inspected.
- Tablet PC - Used to take notes or draw sketches onto screens that would be synonymous with paper forms.
- Tapes
- Pocket Tapes and Folding Rules - Used to measure dimensions of defects.
- 30 m (100 ft) Tape (Non Metallic) - Used to measure anything beyond the reach of pocket tapes and folding rules.
Safety equipment meeting the most current OSHA Standards should be available for the inspection team's use and may include:
- Appropriate devices for traffic control
- First aid kit
- Flashlights
- Hardhats
- Leather work gloves
- Appropriate safety vests
- Protective eye wear
- Knee pads
- Safety belts or harnesses
- Work boots
- Protective breathing masks if soot and dirt buildup is prevalent on the tunnel surfaces
- Air quality monitoring equipment.
For the confined spaces, the appropriate equipment designated by the field safety officer should be employed. This equipment includes respirators, tie off ropes, radios, and instruments to measure gas levels. It is especially important to monitor gas levels in areas of known ground contamination by deleterious materials.
D. Preparation
1. Mobilization
Prior to conducting tunnel inspections, a mobilization period of planning and organizing for the inspection is a must for the inspection to be performed as efficiently as possible. If the inspection is to be conducted by a consultant, the consultant will need to coordinate carefully with the tunnel owner to determine available access times for inspecting within the road or track area, where vehicles can be parked, communication procedures for shutting off and locking out fans during the inspection, timing for shutting down electrical systems for testing, discussion of known problem areas, etc.
A vital part of the mobilization phase is the receipt and study of available tunnel drawings or previous inspection reports. It is crucial to minimize tunnel closures; therefore, forms should be developed on paper or on computer screens during the mobilization period prior to entering the field. The forms should also contain the necessary fields of information to be supplied as part of the computerized database. It is also critical that all health and safety plans, where confined space entry is deemed necessary, be completed and inspectors be knowledgeable of their responsibilities.
In summary, the planning and scheduling of the inspection during the mobilization phase should lead to an efficiently run inspection effort that benefits both the inspection team and the tunnel owner/operator.
2. Survey Control
It is necessary to establish a system by which the location of a defect can be recorded and understood in reference to where the defect is observed. Establishing such a system will allow the inspections to be referenced historically for future monitoring of the condition of a particular defect and will increase the efficiency of the overall inspection process.
Most highway and rail transit tunnels already have a baseline or stationing system established throughout the tunnel. This allows defects to be recorded using the station where they occur. Some tunnel owners have defined panels that are of a given length and sequentially numbered. Joints in the lining material are used to delineate these panels. To tie the panels into the baseline system, the station of the beginning and end of each panel can be established and a defect can be located relative to its distance from either end of the panel, which can subsequently be converted into a specific station or distance from the end of the tunnel.
In addition to locating a defect by panel number and station, it is necessary to note the defect's position within the tunnel cross-section. Figures 3.1 to 3.5 show a typical tunnel layout plan along with the designations for typical tunnel cross-sections. Defects in circular tunnels without air ducts or structural slabs can be located using a clock system with 12:00 being at the top. Horseshoe, rectangular, and other circular tunnels can be broken down into the cross-sectional elements that are shown on the following pages.
Figure 3.01 - Tunnel Inspection Layout Plan
Figure 3.02 - Circular Tunnel Clock System Designations
Figure 3.03 - Circular Tunnel Label System Designations
Figure 3.04 - Rectangular Tunnel Label System Designations
Figure 3.05 - Horseshoe Tunnel Label System Designations
3. Inspection Forms
To properly gather and record structural inspection data for historical purposes, it is necessary to develop forms that are clearly understood and easily entered into a database. These forms can be on pre-printed sheets and then scanned into the database or transferred manually. Another option would be to make use of tablet PC's, which can be pre-programmed to correspond to the main database. This option allows the data to be downloaded directly into the structural database for future use.
The forms to be used fall into two main categories: documentation forms and defect location forms. The documentation forms are discussed in this section along with examples of forms to be used for both highway and rail transit tunnels. Examples of the defect location forms that apply to the components of main tunnel segments or panels as well as auxiliary spaces such as portal buildings, control rooms, stations, etc., are provided in Chapter 5, Section A.
Below are general instructions for proper completion of the subsequent example documentation forms:
a) Highway Forms
(1) Condition Code Form
- Tunnel Name: Enter the name typically assigned to the tunnel.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present, enter the predetermined panel number for the segment for which this form is being completed (e.g., 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
Table 3.01 - Liner Type Acronyms
| Acronym | Description |
|---|
| UR | Unlined Rock |
| CIPNR | Cast-In-Place Concrete, No Reinforcement |
| CIPR | Cast-In-Place Concrete, Reinforced |
| SG | Shotcrete/Gunite |
| PCLS | Precast Concrete Liner Segments |
| SILP | Steel/Iron Liner Plate |
| M | Masonry |
| T | Timber |
| SCB | Steel Columns and Beams, Jackarches |
| RMPS | Rock-fall Mesh Pinned to Surface |
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Condition Codes: Assign each element a numerical rating in accordance with the rating schedules given in Chapter 4, Section A, Part 4. Enter a dash (-) for all elements that are not present in the tunnel segment.
- Comments: Add any pertinent comments as necessary for properly explaining the tunnel segment's condition codes.
(2) Supplemental Tunnel Segment Sketches
- Tunnel Name: Enter the name typically assigned to the tunnel.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present, enter the predetermined panel number for the segment for which this form is being completed (e.g. 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Sketches: Provide detailed sketches of defects found in areas of the tunnel or auxiliary spaces that is not covered by the standard forms that are provided in Chapter 5, Section A.
(3) Tunnel Segment Photo Log Sheet
- Tunnel Name: Enter the name typically assigned to the tunnel.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present, enter the predetermined panel number for the segment for which this form is being completed (e.g., 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Photos: Provide relevant information for any photos that are taken within that tunnel segment. Include as much detail as possible within the description section. It would be helpful to take photographs of the same conditions or defects as previous inspections, so that the rate of deterioration can be ascertained.
b) Rail Transit Forms
(1) Condition Code Form
- Line: Enter the given name of the system line that is being inspected (e.g., A, Blue, Market Street, etc.).
- Track: Enter directional description of track being inspected (e.g., inbound, outbound, north, east, south, west, etc.).
- Name of Station Ahead: Enter name of station (subway or ground) that is next along direction of train traffic.
- Name of Station Behind: Enter name of station (subway or ground) that is next in opposite direction of train traffic.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present, enter the predetermined panel number for the segment for which this form is being completed (e.g., 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Condition Codes: Assign each element a numerical rating in accordance with the rating schedules given in Chapter 4, Section A, Part 4. Enter a dash (-) for all elements that are not present in the tunnel segment.
- Comments: Add any pertinent comments as necessary for properly explaining the tunnel segment's condition codes.
(2) Supplemental Tunnel Segment Sketches
- Line: Enter the given name of the system line that is being inspected (e.g., A, Blue, Market Street, etc.).
- Track: Enter directional description of track being inspected (e.g., inbound, outbound, north, east, south, west, etc.).
- Name of Station Ahead: Enter name of station (subway or ground) that is next along direction of train traffic.
- Name of Station Behind: Enter name of station (subway or ground) that is next in opposite direction of train traffic.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present, enter the predetermined panel number for the segment for which this form is being completed (e.g., 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Sketches: Provide detailed sketches of defects found in areas of the tunnel or auxiliary spaces that is not covered by the standard forms that are provided in Chapter 5, Section A.
(3) Tunnel Segment Photo Log Sheet
- Line: Enter the given name of the system line that is being inspected (e.g., A, Blue, Market Street, etc.).
- Track: Enter directional description of track being inspected (e.g., inbound, outbound, north, east, south, west, etc.).
- Name of Station Ahead: Enter name of station (subway or ground) that is next along direction of train traffic.
- Name of Station Behind: Enter name of station (subway or ground) that is next in opposite direction of train traffic.
- Begin Station: Enter the beginning station of the tunnel segment for which this form is being completed (e.g., Sta. 70+00.00).
- End Station: Enter the ending station of the tunnel segment for which this form is being completed (e.g., Sta. 72+00.00).
- Panel Number: If present enter the predetermined panel number for the segment for which this form is being completed (e.g., 101).
- Year Built: Enter the year during which construction of the tunnel was completed.
- Liner Type: Enter the appropriate acronym from Table 3.1.
- Date of Inspection: Enter the month, day, and year the inspection is performed.
- Inspector(s): Enter the inspector(s) first initial and last name.
- Photos: Provide relevant information for any photos that are taken within that tunnel segment. Include as much detail as possible within the description section. It would be helpful to take photographs of the same conditions or defects as previous inspections, so that the rate of deterioration can be ascertained.
TUNNEL AGENCY NAME
HIGHWAY TUNNEL FIELD INSPECTION FORM
TUNNEL SEGMENT CONDITION CODES
| General Information |
|---|
| Tunnel Name | |
|---|
| Begin Station | | End Station | |
|---|
| Or |
| Panel Number | |
|---|
| Year Built | | Liner Type | |
|---|
| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
|---|
| Condition Codes |
|---|
| Upper Plenum (if present) | Rating | Roadway | Rating |
|---|
| Underside of Roof | | Underside of Ceiling/Roof Slab | |
| Top of Ceiling Slab | | Top of Invert | |
| Right Wall (if applicable) | | Right Wall | |
| Left Wall (if applicable) | | Left Wall | |
| Lower Plenum (if present) | | Miscellaneous Appurtenances | |
|---|
| Underside of Invert | | Safety Walks | |
| Bottom of Plenum | | Railings | |
| Right Wall (if applicable) | | Utility/CCTV Supports | |
| Left Wall (if applicable) | | Finishes
Excellent ___ Good ___ Fair ___ Poor ___ |
| Comments |
|---|
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TUNNEL AGENCY NAME
HIGHWAY TUNNEL FIELD INSPECTION FORM
SUPPLEMENTAL TUNNEL SEGMENT SKETCHES
| General Information |
|---|
| Tunnel Name | |
|---|
| Begin Station | | End Station | |
|---|
| Or |
| Panel Number | |
|---|
| Year Built | | Liner Type | |
|---|
| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
|---|
| This Space To Be Used For Supplemental Sketches, And/Or Comments |
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TUNNEL AGENCY NAME
HIGHWAY TUNNEL FIELD INSPECTION FORM
TUNNEL SEGMENT PHOTO LOG SHEET
| General Information |
|---|
| Tunnel Name | |
|---|
| Begin Station | | End Station | |
|---|
| Or |
| Panel Number | |
|---|
| Year Built | | Liner Type | |
|---|
| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
|---|
| Roll No. | Counter No. | Description |
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TUNNEL AGENCY NAME
RAIL TRANSIT TUNNEL FIELD INSPECTION FORM
TUNNEL SEGMENT CONDITION CODES
| General Information |
|---|
| Line | | Track | |
|---|
| Name of Station Ahead | |
|---|
| Name of Station Behind | |
|---|
| Begin Station | | End Station | |
|---|
| Or |
| Panel Number | |
|---|
| Year Built | | Liner Type | |
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| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
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| Condition Codes |
|---|
| Track Area | Rating | Miscellaneous Appurtenances | Rating |
|---|
| Underside of Roof | | Safety Walks | |
| Concrete Track Supports | | Railings | |
| Right Wall | | Utility Supports | |
| Left Wall | | | |
| Comments |
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TUNNEL AGENCY NAME
RAIL TRANSIT TUNNEL FIELD INSPECTION FORM
SUPPLEMENTAL TUNNEL SEGMENT SKETCHES
| General Information |
|---|
| Line | | Track | |
|---|
| Name of Station Ahead | |
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| Name of Station Behind | |
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| Begin Station | | End Station | |
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| Or |
| Panel Number | |
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| Year Built | | Liner Type | |
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| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
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| This Space To Be Used For Supplemental Sketches, And/Or Comments |
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TUNNEL AGENCY NAME
RAIL TRANSIT TUNNEL FIELD INSPECTION FORM
TUNNEL SEGMENT PHOTO LOG SHEET
| General Information |
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| Line | | Track | |
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| Name of Station Ahead | |
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| Name of Station Behind | |
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| Begin Station | | End Station | |
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| Or |
| Panel Number | |
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| Year Built | | Liner Type | |
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| Date of Inspection | _____ / _____ / _____ | Inspector(s) | |
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| Roll No. | Counter No. | Description |
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E. Methods Of Access
To access the various structural elements for up-close visual inspection requires that additional equipment be used. A man-lift truck, a rail-mounted vehicle, ladders, and/or removable scaffolding is required.
These types of equipment will permit the inspectors to gain an up-close, hands-on view of most of the structural elements. Binoculars can also be used to locate surface defects from nearby manlifts or ladders, where up-close access is difficult to achieve. It is preferred, however, that up-close, non-destructive testing be used on all tunnel surfaces.
F. Safety Practices
Another significant duty of the inspection team is to ensure that safety practices are followed at all times. Along with the safety of inspection personnel, the inspection teams should use caution when inspecting to prevent danger to the public, to tunnel personnel, and to members of the inspection team. If possible, it is best to have the owner close the tunnel when inspections are being conducted. Also, all inspectors should wear reflective vests. Other safety practices that are more specific to highway and transit tunnels are discussed below.
1. Highway
For highway tunnels, appropriate protective devices and vehicles should be properly positioned when using lifts and ladders, and where deemed necessary to warn that equipment is in the roadway. All traffic control devices should conform to and be positioned as directed by the Manual on Uniform Traffic Control Devices (MUTCD). This document is endorsed by the Federal Highway Administration (FHWA) and is published by the American Traffic Safety Services Association (ATSSA), the Institute of Transportation Engineers (ITE), and the American Association of State Highway and Transportation Officials (AASHTO). Also, the Manual for Work Zone Traffic Control Devices should be reviewed. It should be noted that some local jurisdictions might require the presence of the local or state police in the event of a tunnel closure or partial closure. This would be to help ensure the safety of the inspection team and the motorist that typically would be using the tunnel.
2. Rail Transit
For rail transit tunnels, inspectors should take extra precaution to avoid contact with the third rail or catenary system. If possible, the third rail or catenary system should be de-energized in the area where the inspection is taking place. This can be accomplished during pre-planning coordination with the tunnel owner. Lock-outs and tags must be used to engage the switch to ensure that the power does not inadvertently re-energize while the inspection is occurring. If the power cannot be de-energized, it is suggested that the tunnel owner provide appropriate personnel to remain with the inspection team during the inspection period. In addition, most rail transit agencies will require that a flagman be present when conducting inspections in the track area.
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