Nothing happens in underground infrastructure development if a number of elements are not in place, and highly effective logistical support is one of them – especially on longer, and/or deeper, tunnels.
A report looking at those supporting concerns for long and deep tunnels was last year published, with that name, by the International Tunnelling and Underground Space Association (ITA-AITES). The report – No.31 from ITA – was the outcome of extensive investigation by Working Group 17 (WG17), which is focused on all aspect of long tunnels and great depth.
Coming in at 92 pages long, the lefty report is organised with the first half discussing the various aspects of the topic before turning over to the latter half which has appendices and guidelines but is dominated by a database on logistical aspects from the perspective of Owners. The last, large, section begins with tables of general overview details in a list of specific projects but those are followed by multi-page spotlights on each of those same projects, in turn, such as: Brenner Base Tunnel (Austria/Italy); Terzo Valico Tunnel (Italy); Hakkoda Tunnel (Japan); Sunkoshi Marin Diversion Project (Nepal); Follo Project (Norway); Pajares Tunnels (Spain); Stockholm Bypass Project (Sweden); Ceneri Base Tunnel (Switzerland); and more.
It is an excellent discussion and reference. The report is well populated with more than 60 images (photos/ graphics) and tables across the numerous sections of information that are spread and arranged well throughout its chapters and appendices.
SETTING THE SCENE
What sparked a major report on logistics?
In the Introduction, the report points to a lack of literature on the specific needs of organising logistics for such long and deep tunnels – despite importance that cannot be underestimated for the success of such construction endeavours, and their contractual arrangements. WG17, therefore, set out to develop recommendations for Owners and Designers, to enable logistical needs and benefits – or problems, otherwise – to be recognised early on, and addressed before the project gets close to approaching the milestones of the procurement and construction phases.
Another dimension of de-risking a project, in a way.
Following the Introduction, the report discusses (over 18 pages) key logistical aspects that should be anticipated well before construction commences; only then does it proceed to discuss the main challenges of such in construction (across 17 pages).
Key guidelines are summarised in a table in Appendix 1 (in 4 pages). The points of focus in the guidelines include: getting the project accepted locally, and authorized, and meeting environmental needs in doing so; final disposal arrangements for muck; agreeable placement of site camps; transport outside as well as into the project boundary areas; access to and excavation of adits and portals; potential for temporary use of space that will be created for the operational phase of the infrastructure asset; health & safety; traffic and movements management underground; spoil management from generation to final disposal; concrete production and transport; power, comms, water, effluent, ventilation and cooling systems; and more.
After that brief listing comes the extensive international database (in 41 pages) that highlights with project examples different Owners’ points of view on logistics, as Appendix 2.
It begins with a large table of general characteristics of the selected projects, such as: Owner; service sector (road, rail, water/hydropower); number of tubes and their broad specification (length, diameter); civil works cost (at time of construction starting); current project status (study phase, or construction, operation, etc); and, procurement type.
Then the table gives an overview of the project logistical aspects to the following categories: number of access points; muck disposal sites (number, volume of deposit material, total excavated volume); number of contractor camps; arrangements of energy, water & comms; excavation methods; and, examples of selected logistics solutions.
Some of the selected projects that are discussed in the report are shown in the box ‘Long and deep tunnels: project spotlights on logistics’, on the next page.
LONG AND DEEP TUNNELS: PROJECT SPOTLIGHTS ON LOGISTICS
The WG17 logistics report on long and deep tunnels spotlights a number of projects as case studies. They are discussed in the report using the same structure and questions: the main characteristics, including timeline; type of contract, including remuneration of logistic structures; fit of activities into the community and landscape (access, camps, disposal, services, etc); and, logistical aspects. Below, a selection of the projects is listed in alphabetical order, by nation, as in the report. Their logistical aspects are briefly summarised.
Brenner Base Rail Tunnel (Austria/Italy): main logistical constraints are spoil transport below and above ground, and disposal, plus placement of construction and concreting sites. Belt conveyors were used, feeding to the surface via key adit junctions (logistics ‘nodes’). For conventional excavations, support is by wheeled transport, while TBMs have rail-mounted support plus multi-functional services vehicles (MSVs).
Agua Negra Road Tunnel (Argentina/Chile): main logistical constraints are twofold – very high, cold altitudes in Andes mountains, especially in winter conditions; and, extremely remote project location. Tunnel slope allows gravity drainage to the Chilean portal (west) but pumping will be necessary up to the Argentine portal (east).
Los Condores Hydro project (Chile): High mountains and remoteness have been among the key logistics challenges, especially in winter. Further challenges includes environmental constraints, sourcing suitable gravel for concrete, camps located away from project area, and transport speed limitations.
Frejus Road Tunnel (France/Italy): cold winter conditions were a logistics limitation that required construction site installations to be protected, such as for concreting. Further restrictions on permissions/access had one precasting plant far removed, and it plus another required much transportation support to the tunnel sites. A logistics adit was also built.
Terzo Valico Tunnel (Italy): With a focus on the Valico long and deep tunnel on the multi-tunnel rail project, one of the key logistical challenges was geology containing asbestos mineral fibres. Technical, safety and environmental measures (including disposal) were extensive for the zones where the mineral was encountered.
Hida Road Tunnel (Japan): Built over 1993-2008, the entire project, excavations saw highly variable geology and topographical challenges that saw many planning changes for tunnelling method and use of adits, plus a parallel ventilation tunnel in advance, plus work back to open up more logistical support spaces, including for TBM cutterhead repair. Deep boreholes tried to help inform about ground variability to suit TBM or not. Above ground, winter snow management was needed, where possible; sometimes work was suspended. Groundwater was utilised – in small hydro to support site power, and seepage also helped to melt snow.
Hakkoda High-Speed Rail Tunnel (Japan): With tunnel excavation undertaken over 1999-2005, the main logistical challenges for the project were transport and disposal of spoil, some of which contained mineralised altered rock, requiring extra handling. Electrical transmission infrastructure was also needed to support some feeds from the grid to the constructions sites.
Blix Tunnel in Follo Rail Project (Norway): As the main underground section of the Follo project, the 20km-long double-tube Blix Tunnel was constructed mostly by hard rock TBMs, except for at the ends. The principle logistical aspects were to have: access adits; sufficient space (rig areas) for a multitude of supporting activities, including segment production; use of MSVs for flexibility, instead of rail transport after contractor proposal; and, water treatment.
Pajares High-Speed Tunnels (Spain): Excavations for the twin tunnels were performed during the first decade of 21st Century. Logistical challenges included handling high groundwater inflows due to the geology and alignment slope; surface space for segment casting and storage; and, lack of available existing power supply for part of the project. Use of conveyors was required for spoil removal; intermediate access switched some shafts to a gallery, plus phase/type of an adit use.
Guadarrama Tunnel (Spain): Water supply pipelines and power lines were constructed. Spoil transport was a constraint with long conveyor belts specified to run on the surface from the portals. Surface storage for TBM support was led, to be higher, by specification of double-shield TBMs for tunnelling. Working time restrictions were in place at some construction sites.
Stockholm Road Bypass (Sweden): Logistically, as the project is in a major urban setting in a country with high environment standards, the challenges came early – such as in geological exploration and various access and preparatory works. Then there were limitations to location of work sites during construction, need for spoil transport by conveyor and boat – but rock crushing underground helped the process.
PRIOR ITA WG17 REPORTS ON LONG AND DEEP TUNNELS
ITA’s Working Group 17 (WG17) – looking at Long Tunnels at Great Depth – has issued four reports, the most recent in 2023 and the prior reports in 2017, 2013 and 2010, respectively.
The first report, in 2010, was also ITA’s own Report No4. It was an overview report by the name of the WG itself – ‘Long Tunnels at Great Depth’. The 32-page report is well illustrated across 10 main chapters, top and tailed by the Introduction and References. As such, the chapters are relatively short but do highlight ground conditions, safety and the environment, design, construction, risk management, plus three chapters that spotlight special conditions for functional tunnels – rail, road and water (hydraulic).
As noted briefly in that report, logistical concerns were ‘special constructed-related needs’ that were strongly related to site conditions as well as the length and depth of a tunnel, covering matters such as equipment for ventilation, colling, de-gassing and also groundwater management, mucking out and materials transport. Additionally, logistical constraints limit drive lengths, which and a project may require combinations of intermediate adits, as inclined galleries and/or vertical shafts, and potentially restrictions on access. Above ground, to reliably reach the portals and adits, there might be need for long access roads, and again there may be accessibility permission issues, and more.
Following on three years later, the next report from WG17, in 2013, put more focus on adits. While it is a much shorter report (only 12 pages), for this aspect of developing long and deep tunnels the document places its consideration upon three main areas:
- functionality (discussed per phase of life – design, construction, operation);
- design (locations, gallery -v- shaft, spacing, crosssections, and construction); and,
- safety during construction (braking on inclines, rescue team access, ventilation, vertical shafts, and more).
It then adds brief points under topics of risk, and also special issues for adits, such as how to assess if they are needed and, if so, where, what range of use, when, and procurement arrangements; much depends on the status of planning and design development, and those in turn rely on sufficiency of geological knowledge for the project.
Specifically, on logistics, the report has a sub-section that notes that adits often require excavation of caverns, which would be mostly at junctions with other adits or main tunnels, for large vehicle movements, or space at junctures to thread through equipment, materials or muck transportation, including jumbos and other vehicles manoeuvring, or sheer vastness to support the assembly/ disassembly of tunnel boring machines (TBMs) at their launch/reception.
For the most part they are underground corridors supporting the construction of the main works with much that needs to go in, including air, power, comms, cooling and materials and equipment, and that which needs removed (muck) – and in emergencies, people, as the adits enable evacuation.
Not mentioned, some adits occasionally are permanent service access routes after construction; and, before main construction, some can help facilitate exploratory phases of project to help determine geology, though their own excavations as well as enabling launch of pilot tunnels (which themselves may come to be service tunnels).
In 2017, the third report from WG17 considered TBM boring on long and deep tunnels under difficult rock conditions. At 64 pages, the report was the longest yet – double the length of the first report (2010) and more than five times the length of the adit report (2013). It is well illustrated and packed with project-related information gathered from jobs underway during the prior 20 years.
In fact, the appendix (annex database) with project profiles takes up about two-thirds of the entire document.
Upfront in the report, given its focus on difficult rock conditions, the two primary chapters focus, first, on geological hazard scenarios, and then, second, those related to TBM tunnelling and mitigation measures. Those sections are preceded and followed by the Introduction and the Conclusion and References, respectively.
As those chapters explain, the report – in considering primarily long TBM drives under high overburden and geological uncertainty – introduces a common technical language, analyses the influence and consequences of such ground hazards, and provides recommendations for TBM selection and design and also mitigation measures. In that regard, matters of logistics have little mention as, the report says, it does not look at non-geological hazards.
