INTRODUCTION
An excellent, 66-page report on ‘Selection of Shaft Construction Method’ was issued for the tunnelling industry last year by ITA-AITES. It emphasises that proper method selection is integral to successful tunnelling projects and as such gives briefings on water management, ground conditioning, options for excavation and lining, and mucking out – and pulls it all together decision trees and charts.
After the briefing, though, it does emphasise that the report does not replace the value of direct experience with the design and management of shaft construction.
REPORT STRUCTURE
The contents are presented with the appearance of a journal paper although the guidance is, in effect, a short book – one that that is exceedingly clear in its well-structured information, effectively illustrated with graphics, photos and some tables, and is well referenced.
The look of a journal paper comes from how the information was first published (See box panel 2).
The contents emerged from collaborative work by Working Group 23 (WG23) of ITA-AITES (The International Tunnelling and Underground Space Association, or Association Internationale des Tunnels et de L’Espace Souterrain). It is Report 36, issued in July 2025.
As such, however, this short technical book is without a Contents page to easily map the structure of the information that will be presented – in chapter sections and their sub-sections, respectively. The limited labelling can leave it difficult to readily determine location in the body of the book.
Neither is there an Index. While such is not common in reports, the specialist briefing here of such length as to be akin to a short reference book would perhaps be served with such a helpful and practical bookend.
CONTENTS
The covers plus the explanation of relationship to the TUST paper takes up three pages, leaving the bulk of the book to present its main information over 63-pages, in eight chapter sections, replicating the journal presentation. The chapter sections and their lengths are noted below, and clearly the majority of information relates to lining and excavation options, respectively, followed in pagination total by water management. The guidance has numerous illustrations, supporting the various points of briefing and discussion.
1 – General Considerations – 15 short sub-sections; pp1-4
Topics include: table of ‘essential factors’ for selecting the shaft construction method then brief discussions of each, which are – future use, shape, size, depth, inclination, location, ground conditions, hydrogeology, environmental impact, existing loads, regulatory and permit requirements, safety and risk, contractor experience, and time & cost.
2 – Water Management Options – nine sub-sections of varied lengths; pp4-14
Topics include: discussion of the different techniques – open pumping (within shaft), pre-drainage by external pumped wells, in-shaft wells, pumping methods used in combination with support systems/water stopping methods, permeation/fissure grouting for water stopping, and jet grouting. There is very little coverage of the, albeit less common, method of artificial ground freezing (AGF). The discussion adopts this methodology – describe method, its applicability to shafts, suitability geotechnically, advantages and disadvantages, and design and construction considerations.
3 – Ground Conditioning and Improvement Options – three sub-sections; pp 14-19
Topics include: the same methodology is used again, considering the following – description, applicability, suitability geotechnically, advantages and disadvantages, and some options have discussion of and design and construction considerations. The techniques covered are – compaction grouting, deep soil mixing, and this time AGF has more coverage.
4 – Lining Options – three sub-sections, but with further sub-divisions; pp 19-40
Topics include: initial discussion on temporary versus permanent lining, then each is explored in the following pages through different methods, following the same methodology as before. Methods discussed includes: for soft ground – piles (tangent, secant), sheet piling, trenched/diaphragm walls, caisson (open, pneumatic), segmental underpinning, ribs & boards & liner plates; and, for rock – bolts, shotcrete, steel ribs & mesh, cast insitu concrete, and steel segmental lining. Note is made of the emerging trend, for final lining design and construction, of using spray-applied waterproofing membranes.
5 – Excavation Options – ; pp40-48
Topics include: boring & raise boring, roadheader, and vertical shaft sinking machines (also for soft ground), and drill & blast. Discussion includes use of techniques in mining as well as applicability to civil engineering tunnels. Note that some excavations options will have crossover with lining methods, such as piling, D-Walls, caisson, and segmental.
6 – Mucking and Hoisting – two sub-sections; pp48-53
Topics include: methods discussed are primarily grabs and crane systems.
7 – Decision Chart and Diagrams
One sub-section; pp53-62
8 – Summary – very brief; pp62
References; pp62-63
ILLUSTRATIONS AND CHARTS
The chapter sections are very well illustrated; the images are highly effective additions to support the well-structured information. In total, there are 77 figures, including a few large tables.
Although there is less labelling than may be preferable for a book-style focus on a subject, the information structure has a repeated pattern which helps to negotiate the narrative flow. The similarities in such labelling can though, without beneficial numbering, require some extra checks on location within the report. The arrangement supports dipping into the report as a ready reference to brief, specific areas. Fuller, closer reading throughout is, like most reports, likely only to be closer for early or initial familiarisation with the information, in full, and which of course will help later navigation.
The report concludes with, in journal style, 1.5-pages of References. As noted, there is no Index, but certainly having a series of extensive flow charts on shaft selection – albeit from case study examples, and while noting they have specific data – is a constructive way to bring the ideas discussed together. As listed above they are gathered together and constitute chapter section 7 – which is over 10 pages, and is dominated by its six large flow charts and two large tables.
The principal other table in the report is in the chapter section 6, immediately before, and provides a general approach and recommendations for selecting the shaft construction method.
Thereafter, the tables in the report work with the flow charts to focus on application to two case studies discussed – a sewer tunnel and a transport tunnel, respectively, both from the US Pacific North West. They are:
Case 1: West side combined sewer overflow (CSO) tunnel project in Portland, Oregon.
Case 2: Sound Transit’s Northgate Link Extension project, in Seattle, Washington.
The first case study is discussed with four flow charts, the second case using two flow charts and two large tables.
CONCLUSION
The report emphasises that shaft construction is an integral part of tunnelling works to develop different kinds of underground spaces. Yet, being so important it “remains under-developed” for the most part, it says, and “Hence, proper selection of the construction method is critical”.
As such, the reports points to the value of decision trees and charts as “valuable tools” to negotiate the information matrix in a structured way and so “improve the selection process” for shaft construction methods.
“Therefore, integrating these tools into the planning and execution phases of shaft construction is highly recommended for any engineering team,” it says.
The summary cautions, though, that the guidance “does not replace direct experience with the design and management of shaft construction.” It points to the uniqueness of each project and, consequently, discussions required on management and allocation of risk, of ‘What If’ scenarios, the contents of the risk register, and value engineering.
The look of a journal paper comes from how the information was first published. Although the contents originate from work undertaken within ITA-AITES by WG23, the information came out first elsewhere – as a long paper in the Elsevier journal Tunnelling and Underground Space Technology (TUST), under an open access facility.
Inside, the ITA-AITES report presents the information as a reproduction of the TUST journal’s long paper, as permitted under the particular open access facility. For citation purposes, ITA-AITES points to the TUST publication – as below * – but it labels its own version of the guidance as Report 36, issued in July 2025, from WG23.
*For citation, the details are: TUST 164 (2025) 106654, and https://doi.org/10.1016/j. tust.2025.106654.
