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Highway and Rail Transit Tunnel Inspection Manual
Table Of Contents
List Of Tables
List Of Figures
In March of 2001, the Federal Highway Administration (FHWA), in conjunction with the Federal Transit Administration (FTA), engaged Gannett Fleming, Inc., to develop the first ever Tunnel Management System to benefit both highway and rail transit tunnel owners throughout the United States and Puerto Rico. Specifically, these federal agencies, acting as ONE DOT, set a common goal to provide uniformity and consistency in assessing the physical condition of the various tunnel components. It is commonly understood that numerous tunnels in the United States are more than 50 years old and are beginning to show signs of considerable deterioration, especially due to water infiltration. In addition, it is desired that good maintenance and rehabilitation practices be presented that would aid tunnel owners in the repair of identified deficiencies. To accomplish these ONE DOT goals, Gannett Fleming, Inc., was tasked to produce an Inspection Manual, a Maintenance and Rehabilitation Manual, and a computerized database wherein all inventory, inspection, and repair data could be collected and stored for historical purposes.
This manual provides specific information for the inspection of both highway and rail transit tunnels. Although several components are similar in both types of tunnels, a few elements are specific to either highway or rail transit tunnels and are defined accordingly. The following paragraphs explain the specific subjects covered along with procedural recommendations that are contained in this manual.
This chapter presents a brief history of the project development and outlines the scope and contents of the Inspection Manual.
Tunnel Construction and Systems
To develop uniformity concerning certain tunnel components and systems, this chapter was developed to define those major systems and describe how they relate to both highway and rail transit tunnels. This chapter is broken down into four sub-chapters, which include: tunnel types, ventilation systems, lighting systems, and other systems/appurtenances.
The tunnel types section covers the different tunnel shapes in existence, liner types that have been used, the two main invert types, the various construction methods used to construct a tunnel, and the multiple different finishes that typically exist in highway tunnels. The ventilation and lighting system sections are self explanatory in that they cover the basic system types and configurations. The other systems/appurtenances section is used to explain tunnel systems that are present in rail transit tunnels, such as: track systems, power systems (third rail/catenary), and signal/communications systems.
Fundamentals of Tunnel Inspection
As can be expected, there are basic steps that must be properly accomplished for the end product of the inspection to be useful to the tunnel owner for planning purposes. These steps include making sure that the inspectors are qualified to properly identify defects and make recommendations about their respective systems within the tunnel. Also, the responsibilities of the individual inspection team members and the tunnel owner are discussed. The next section lists the equipment/tools that may be required to perform the inspections.
A section on preparation for the inspection consists of describing the tasks that should be completed during the mobilization phase of the inspection. Also, a survey control section is given that describes how to record the inspection results with respect to their location within the tunnel. Following that, suggested standard forms are presented that can be used to record the actual structural condition codes assessed during the inspection.
After the preparation section, brief sections on methods of access, which describes equipment that might be necessary to reach the areas that need to be inspected, and safety practices for both highway and rail transit tunnels are included.
Inspection Procedures - General Discussion
This chapter presents recommended frequencies and specific defects to look for in each of the following categories: structural elements, mechanical systems, electrical systems, and other systems/appurtenances.
The structural elements section includes descriptions of defects in concrete, steel, masonry, and timber. Also included in this section is a segment describing the procedures that should be followed in the event that the inspection reveals defects that require immediate repair. Structural conditions codes are detailed on a 0 to 9 scale for the general condition and subsequently for specific tunnel segments for cut-and-cover box tunnels, soft ground tunnel liners, rock tunnel liners, and timber liners. The individual tunnel segment ratings are summarized in a table.
The systems/appurtenances section includes general discussions on track elements, power systems (third rail/catenary), and signal/communication systems. Given the complexity of these systems, only general inspection recommendations are given for the major components.
The final chapter of this manual offers suggestions on how to properly record the results of an in-depth inspection. The field data section describes how to visually record the defects that are found, either on pre-printed forms or through the use of tablet PC's (pen based computers) in to a database. Abbreviations are given for the most common defects that are found on the tunnel structure. Also included are recommendations that are specific to the track structure and any specialized testing reports that were generated during the inspection.
Repair priority definitions are presented so that the individuals writing the inspection report can classify the defects based on definitions for critical, priority, and routine classifications. Finally, a recommended outline for the inspection report is given for guidance as to what information should be included for the tunnel owners' use in determining how to address the items identified during the inspection.
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