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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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    <item>
      <title>FINANCE AND SAFETY</title>
      <link>https://trid.trb.org/View/635095</link>
      <description><![CDATA[In this article, the author proposes that tunnel engineers, clients, and financiers should consider the best ways of establishing the status of tunnelling and ensuring that it can contribute fully to improving the quality of life. It focuses on the key aspects of finance and safety, both of which are often misunderstood by the general public and by politicians, and sometimes even by clients and tunnelling engineers. Money supply is not the problem of financing tunnels, which are exceptionally expensive to construct; the relevant questions are who will pay the money back to the lenders, how, and on what terms. A few decades ago, the UK Government financed large projects from public funds, but, since Autumn 1993, the UK has played a leading part in developing private finance for public services worldwide. Bankers should be made fully aware of project costs, spending sequence, areas of risk, and especially the management of those risks. No mode of transport is totally safe, and safety standards have ranged from very safe to rather debatable. The public accepts railways as a convenient and safe method of travel, but has a partially justified feeling that investment in safety is sometimes reduced. Tunnellers should have a key objective of improving their understanding of safety in tunnels.]]></description>
      <pubDate>Fri, 18 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/635095</guid>
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      <title>URBAN TUNNELLING CONSEQUENCES</title>
      <link>https://trid.trb.org/View/635097</link>
      <description><![CDATA[This article discusses some of the issues involved in urban tunnelling, which must be considered as five-dimensional, involving politics as well as time and space. Its political issues are more complex than in rural areas, and quality is especially important. The issues concern the advantages and disadvantages of using one tunnelling technique rather than another, and the consequences of a decision about which method to use. Relevant issues include: (1) public and political support for a tunnelling project; (2) its costs and sources of funding; (3) assessing the risk of each technique, in relation to the tunnel's alignment and expected ground conditions; (4) the project's impact on the tunnelling industry in the region; and (5) the political risks of budget and schedule overrun. The questions confronting tunnellers are social and human rather than technical, such as what people are willing to pay to avoid unwanted environmental impacts. Taxpayers are not always made aware of all the possible options. From a social viewpoint, a bored tunnel is usually the preferred option for new routes through urban areas; this principle is illustrated by several examples. Relevant factors include design, costs, incentives, risk, safety, durability, maintenance, and legal and contractual aspects.]]></description>
      <pubDate>Fri, 18 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/635097</guid>
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      <title>DIFFERING SITE CONDITIONS</title>
      <link>https://trid.trb.org/View/635098</link>
      <description><![CDATA[The article discusses the Differing Site Condition (DSC) clause in US construction law, which has created some problems that it was intended to solve. For example, claims for extras have become routine, and contractors often choose this tool as the most convenient way to justify cost overruns or obtain more profits. Owners and engineers have often been reluctant to compensate contractors for legitimate claims arising from unforeseen costs. The clause was introduced to reduce the construction price by removing a contractor's cost for contingencies; in return, contractors were protected against unexpected site conditions from the owner. In preparing a differing site condition claim, a contractor must effectively address the concerns of the engineer while he is reviewing the claim document. To arrive at a difference in conditions, it is necessary to compare 'reasonable' anticipated conditions with actual site conditions. To determine the difference between anticipated and encountered conditions, it is necessary to establish 'reasonable' anticipated performance, which must satisfy several conditions. The issue of 'cause and effect', assoicated with construction in natural materials, must be addressed properly. It is also necessary to fulfil the requirements of the contract.]]></description>
      <pubDate>Fri, 18 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/635098</guid>
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      <title>TUNNEL COLLAPSES: ARE THEY UNAVOIDABLE?</title>
      <link>https://trid.trb.org/View/635094</link>
      <description><![CDATA[The paper discusses the causes and repair of collapses during tunnel construction, and recommends how to make them less likely. Collapses for geological reasons occur whatever construction method is used. A few of them are due to meeting an unforeseeable geohydrological or geotechnical situation. Most of them are the result of similar situations, that could be foreseen but are not recognised for various reasons. Collapses occur because of the following types of tunnel instability: (1) in the face; (2) beyond the face, for example in the pilot tunnel; (3) a stretch of excavated but not yet supported tunnel; (4) a stretch of excavated but not yet supported face; (5) during excavation of the invert; and (6) near other intersecting tunnels. The repair of tunnel collapses consists of stabilisation and reconstruction, according to a defined procedure, approved before construction starts and integrated with the monitoring plan and design review and control; it has five stages. Although tunnel design should not assume that the most extreme conditions will occur, it should allow for such conditions by simulating the results of possible collapses, integrating ground investigations with design, predefining a monitoring plan, and defining technical criteria for intervention, and administrative responsibilities and procedures.]]></description>
      <pubDate>Fri, 18 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/635094</guid>
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      <title>SUBWAY CONSTRUCTION IN LOS ANGELES - A NEW SET OF CHALLENGES</title>
      <link>https://trid.trb.org/View/635096</link>
      <description><![CDATA[This article outlines progress in the development of the Los Angeles metro, and discusses the new set of challenges faced by its tunnellers. It is forecast that 467 new route miles will be operating in Los Angeles by 2000, and its next stage will be the construction of the East Line Extension, whose design is nearly complete. A realistic design method for seismic input to underground structures was developed originally for this metro. It views seismic input as distortions to be superimposed on static loads, rather than pseudo-static loads as is done for structures above ground. Its two design levels are: (1) an operating ground level, under which structures would only be cracked and soon return to service, with occurrence probability about 40%; and (2) maximum level, under which structures would not collapse but might need major repair, with occurrence probability about 4%. This design approach was tested as successful in the 1994 Northridge earthquake in Southern California. Challenges from underground gas include those from methane and hydrogen sulphide. Because the East Extension passes under about 250 buildings and other structures, its tunnellers are required to use closed pressure-face (earth pressure balance or slurry) machines and one-pass lining systems, using precast concrete segments.]]></description>
      <pubDate>Fri, 18 Sep 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/635096</guid>
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      <title>UNDERPINNING SOUTH STATION</title>
      <link>https://trid.trb.org/View/486577</link>
      <description><![CDATA[Various road and other construction activity has transformed Boston's business district into one of the world's most complex construction sites. The tunnelling work there is tricky at best. It requires immersed tubes, box jacking, cut and cover, shield and hand mining, and all types of ground treatment, to facilitate excavation in alluvial soil and the notoriously soft Boston clay. This article describes one of the more difficult construction manoeuvres to be undertaken, the passage of the north carriageway of the I-93 highway under the Metro Red Line at South Station. At this point, the railway itself passes under a major road junction, and both rail and road traffic had to be kept moving without interruption. Sophisticated underpinning was required, with total length 98ft; the opening for the passage of the I-93 had to be 64ft wide. An internal height of 42ft was required for the underpinning, to allow a minimum clearance of 4ft below the foundations of South Station and ensure that the new structure's base was safely into bedrock. Dense sand and gravel aquifer was found, so that use of the New Austrian Tunnelling Method (NATM) was rejected in favour of stacked headings and pits to form the excavation's walls and interlocking horizontal connecting drives to form its roof. Completion is scheduled for January 1999.]]></description>
      <pubDate>Fri, 26 Jun 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/486577</guid>
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      <title>UNIQUE SOLUTIONS AT RICHMOND</title>
      <link>https://trid.trb.org/View/486576</link>
      <description><![CDATA[This article describes the construction of two adjoining combined sewage overflow tunnels in the City of Richmond, VA, USA. CSO 1 is a combination of open cut at the eastern diffuser area, with a tunnel from a common shaft with two portals. CSO 2 is an open cut, running parallel to railway tracks from the terminus of CSO 1 to Reedy Creek. CSO 1 is located near a boundary between crystalline rock, mostly granite, and sedimentary rock. A Robbins model 1101-198 tunnel boring machine (TBM) was used for the excavated section. An excavation shaft was built between March and July 1996, and the TBM was placed in the shaft and began work in mid-July. Drilling proceeded at variable rates, sometimes slowly when very hard rock was encountered. In mid-January 1997, it stopped when serious ingress of ground water occurred. Shortly after drilling resumed in early March, serious flooding occurred; within a short time, the whole tunnel and shaft were filled with water to a depth of 30ft. By the end of April, repair work was completed, and drilling resumed again, with a cofferdam in place and dewatered. Other difficulties included breakdowns to the TBM, due to water and rock, and the need to support an old stone wall that was encountered. In December 1997, the TBM was recovered intact, after it had finished its work.]]></description>
      <pubDate>Fri, 26 Jun 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/486576</guid>
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      <title>CONNECTING BERLIN</title>
      <link>https://trid.trb.org/View/486575</link>
      <description><![CDATA[This article describes the extensive project for building new transport links across the centre of Berlin, and especially its tunnel construction operations. 3.8km of tunnels are being built for the new railway between the northern and southern main termini, Lehrter and Papestrasse, 4km for the new extensions to the U-Bahn and S-Bahn metros, and 2.5km for the B96 expressway. Their routes are shown in a map, and cross the River Spree and the Tiergarten Park. For environmental reasons, construction has to be underground in cut-and-cover, sunk-caisson, or bored tunnels. Much of the tunnelling is through water-bearing sand and clay, with a water table about 3m below ground level. Two Herrenknecht 8.9m diameter slurry Mixshields are excavating the bored sections of the railway tunnels. In 2002, Lehrter Station will become the main railway hub for Berlin, with links to all parts of Europe and interchanges to U-Bahn, S-Bahn, and road transport. Its structure was built using slurry diaphragm walls and top-down excavation, and has several levels. Its concrete base was poured under water. New structures are also being built at Potsdamer Platz station and Papestrasse Station. The B96 expressway is being built in a cut-and-cover tunnel, from near the Lehrter Station to the Landwehr Canal south of Potsdamer Platz.]]></description>
      <pubDate>Fri, 26 Jun 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/486575</guid>
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    <item>
      <title>FIRE, SAFETY AND VENTILATION</title>
      <link>https://trid.trb.org/View/486578</link>
      <description><![CDATA[The risk of serious fires in road tunnels is rising, due to increasing traffic density and higher speeds, and in rail tunnels, because of longer lengths and faster travel. Causes of tunnel fires include vehicles carrying hazardous goods, traffic accidents, electrical faults, vandalism, and sabotage. The EUREKA FIRETUN project in Europe has investigated the causes of tunnel fires and possible measures to prevent them. It has been shown that damage to vehicles and tunnel structures is least when the vehicle is made of steel rather than aluminium or plastic. In modern railway carriages, furnishings used based on phenol resin are much more flame-resistant than those made from fibre-glass reinforced unsaturated polyester. Temperatures during fires range from 400-500 degrees C during car fires through 700-800 degrees C for bus and lorry fires and 800-1000 degrees C for railway carriage fires to 1000-1350 degrees C for heavy vehicles with burning goods. There are various causes of fires during tunnel construction, and there are European Safety Standards for tunnel construction equipment. This article gives details of products and equipment, and design and other services, provided by companies concerned with: (1) safety and rescue; (2) fire and flame protection; (3) special materials; (4) hydraulic fluids; and (5) tunnel ventilation.]]></description>
      <pubDate>Fri, 26 Jun 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/486578</guid>
    </item>
    <item>
      <title>SHOTCRETE ESSENTIALS</title>
      <link>https://trid.trb.org/View/477150</link>
      <description><![CDATA[Shotcreting, by spraying concrete onto a tunnel lining's perimeter, may be used to prevent weathering, provide local support, or reduce water ingress. More importantly, often combined with additional reinforcement, shotcrete may support and line a tunnel, either as part of the New Austrian Tunnelling Method (NATM), or by constructing a sprayed concrete lining (SCL). Both NATM and SCL are used successfully in relatively short tunnels, where the cost of machine boring cannot be justified, ground conditions do not favour boring, or cross-sections are not circular. NATM beneficially alters the stress pattern around an underground opening under construction, by coordinating its excavation and support. SCL uses a rigorous design, with confirmation by monitoring and, if necessary, predetermined strengthening procedures. This article gives details of the essential components of successful tunnel design and construction using sprayed concrete: (1) experienced and competent consultants and contractors; (2) accurate instruments for measuring and monitoring; (3) efficient concrete spraying equipment and materials; and (4) well designed lattice girders. The addresses and fax numbers of the companies involved are listed.]]></description>
      <pubDate>Tue, 28 Apr 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/477150</guid>
    </item>
    <item>
      <title>CHANGING BUNYARD FOR THE BETTER</title>
      <link>https://trid.trb.org/View/477149</link>
      <description><![CDATA[This article describes the design and construction of the Bunyard Tunnel in Arkansas, USA. It will carry part of the relocated limited access Highway 71 through the Ozark mountains. It was decided to tunnel, as the alternative was a long, very deep and wide cutting which would have destroyed the local scenery. There will be two parallel reinforced concrete lined, mined rock tunnels. Each will be about 1375ft long, and run nearly 200ft below Bunyard Ridge; it will accommodate two 12ft traffic lanes and two shoulders within a 38ft wide roadway, and require an excavation approach 45ft wide and 29ft high. The preliminary design was conducted in 1992, and used subsurface excavation borings to 300ft deep. The rocks include limestone, sandstone and shale, and there is a thin surface layer of clayey silt with sandstone cobbles. As originally presented, the construction project was to use the New Austrian Tunnelling Method (NATM) in four classes of ground. The contract was awarded to J.F. Shea and excavation at the south portal began in April 1996. The excavation procedure was changed from NATM's multiple heading drift and bench system to a full steel support system with a full top heading. Bench excavation began in both tunnels in March 1997. The project is due to be completed on time, on budget, and with an excellent safety record.]]></description>
      <pubDate>Tue, 28 Apr 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/477149</guid>
    </item>
    <item>
      <title>NATM DESIGN FOR SOFT GROUND</title>
      <link>https://trid.trb.org/View/476731</link>
      <description><![CDATA[This article aims to progress the UK debate on the initial design of New Austrian Tunnelling Method (NATM) and sprayed-concrete-lined (SCL) tunnels, and provides practical guidance on methods of analysis. After the collapse of an NATM tunnel under London Heathrow Airport in 1994, some tunnelling engineers tended to discard using the term 'NATM' to describe tunnels with sprayed concrete linings (SCLs). Actually, 'NATM' relates to a construction philosophy that requires a controlled deformation of the ground before the permanent tunnel lining is constructed. Not all SCLs are made using this philosophy. In 1996, the Institution of Civil Engineers (ICE) published a design and practice guide for SCLs for tunnels in soft ground. The guide briefly describes and discusses the methods of analysis for SCLs and the primary support for NATM tunnels. It provides a reasonable survey of analysis methods for primary lining support design. The present paper discusses some design considerations of the more traditional design approaches, and presents a methodology for the detailed design of the primary and secondary linings of an NATM tunnel. If properly executed, this approach can be used to design a demonstrably safe and secure initial NATM lining. Finite element and finite difference techniques are especially appropriate here.]]></description>
      <pubDate>Fri, 17 Apr 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/476731</guid>
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    <item>
      <title>ADVANCES IN GROUTING TECHNOLOGY</title>
      <link>https://trid.trb.org/View/476732</link>
      <description><![CDATA['Grouting' may be defined as the injection of pumpable materials into a rock or soil formation to change its physical characteristics. It is a viable method of controlling groundwater and stabilising soil in preparation for tunnelling in soft ground; it very effectively improves conditions in various situations. Compaction and compensation grouting are reactive processes with an element of risk. Chemical and jet grouting reduce the risk by proceeding ahead of the tunnel excavation and verifying that grouting is installed to the required quality. The advantages of chemical grouting include its ability to change the support capability of granular soils without disturbing them, and its ability to be less disruptive. However, it can be applied to only some soil types. Jet grouting provides a valuable solution to a wide range of problems, when conventional injection methods are unsuitable, unsafe, or too expensive. It can treat a wide range of soils by means of simple cement grouts, and has many other advantages; it is the fastest growing grouting technique. Two examples of its use in US metro tunnels are described; in one of the projects, it was used to control settlement. The development of sophisticated high-quality grouting techniques has kept up with tunnelling and subsurface construction advances.]]></description>
      <pubDate>Fri, 17 Apr 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/476732</guid>
    </item>
    <item>
      <title>OERESUND CROSSING</title>
      <link>https://trid.trb.org/View/476321</link>
      <description><![CDATA[Construction of the Oeresund Crossing between Denmark and Sweden began in 1995, and is due to be completed in 2000. Its main components are: (1) a road and railway between Copenhagen, Kastrup Airport, and the Danish coast; (2) a 430m-long peninsula from the Danish coast, constructed from dredged material; (3) a 4050m-long tunnel, including 3510m of immersed tube, under the Drogden shipping channel; (4) the 4055-long Peberholm island, constructed from dredged material; (5) approach bridges with abutments on Peberholm Island and on Lernacken on the Swedish coast, 3014m and 3739m long, respectively; (6) a central 1092m-long cable-stayed elevated span across the Flinte shipping channel; (7) a road and railway from Lernacken to Malmo in Sweden; and (8) a terminal area, toll station, and main control area in Lernacken.  This article lists the main consultants, contractors, and manufacturers in the project, and describes the design and construction of the tunnels and bridges. Tunnelling work included casting and laying of immersed tubes, cut-and-cover, formwork, and concreting.  Dredging work included building artificial islands, cutting navigation and immersed tube tunnels, and compensation dredging.  The foundations, piers and pylons of the three-span two-level rail and road bridge are made of reinforced concrete.]]></description>
      <pubDate>Tue, 24 Mar 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/476321</guid>
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    <item>
      <title>DIRECT ACCESS TO PORT RAMSGATE</title>
      <link>https://trid.trb.org/View/474402</link>
      <description><![CDATA[The present access road to Ramsgate Harbour in Kent, England has become unacceptable. In 1994, a new 2.2km-long road was proposed, to link the harbour with the A28 and A253 trunk roads. It will include a 570m-long cutting, 240m of cut-and-cover tunnel, and 540m of driven tunnel. This article describes the ground investigations for the road and the design of its engineering works. The dominant rock in the area is Upper Chalk, which is usually suitable for tunnelling. Both preliminary and detailed ground investigations were conducted. Boreholes were drilled during Autumn 1994. Additional boreholes, shallow pits, and dynamic probes were used early in 1996, and on-site permeability measurements were made. Larger drillings were then made. The selected tunnel alignment was found to pass through very soft to medium-hard chalk. The cutting will descend to a depth of 14m. The cut-and-cover tunnel will be 1.3m to 6.8m below the ground. The tunnel will have two curved sections and one straight section, with cover between 6.8m and 13.0m. The carriageway will be 7.3m wide, with 1.2m-wide footways. Gullies and channels will drain water from the tunnel into soak-aways or into the sea after treatment for oil removal. The scheme is awaiting funding, but it is hoped that construction will begin very early in 1998.]]></description>
      <pubDate>Mon, 29 Dec 1997 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/474402</guid>
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