Benoit Jones suggests in his preface that hitherto, there has been no comprehensive textbook available to cover the design of tunnels in soft ground. I would agree, although I was always taught from the start of my engineering career to refer to Tunnel Engineering Handbook by Bickel, Kuesel & King, a book that includes a chapter on soft ground tunnelling. With regard to design, Jones’ book is more comprehensive..
Based on the author’s teaching for the MSc in Tunnelling and Underground Space at the University of Warwick, and with an objective to concentrate on design due to available texts on construction methods, the book is an excellent read.
The target audience is set: students, graduate and experienced engineers. However, I would suggest that a few others (design managers, third party consultants etc) involved in such projects wanting to know aspects of the design would also find this a useful read – in part. If the author was encouraged to prepare a second edition, I would be keen to see an introduction on design aspects that covers expectations of the level of design and detail that is expected to be produced during the lifecycle of a project, from say, concept, through preliminary and detail, and beyond into construction and handover.
However, the author does clarify what is covered and, noting the constraints of space, lists a number of aspects not covered. Perhaps a Volume 2 might be worthy, which could be extended to include the design interface with other key parties; design aspects with temporary works could also be added.
Nevertheless, the book is structured well and covers a range of design subjects from the basics to building damage assessment. The emphasis on the author’s three principal themes of stability, prediction of ground movements and structural design of tunnel lining defines the content. And illustrated by worked examples, this works well.
Chapter 1 explains the design objective of ensuring an analysis model reflects the tunnel structure’s behaviour with the ground. The explanation of understanding reality before undertaking modelling is a useful lesson. The author’s style of stating the key points addressed in the chapter, at the start, is useful to the reader. Especially the reader who is ‘dipping’ in and out of the text, investigating a particular design aspect or just wanting a precise overview of tunnel behaviour when considering open- and closed-face working. The explanation on stability and the consequences of instability are aptly framed around photos and case studies. The account of the Heathrow Express Terminal 4 Station concourse tunnel case history, at the end of this chapter, is useful from a ground stress and monitoring point of view.
Chapters two to five cover aspects associated with stability, including shaft stability and a comparison with Eurocodes. The author explains the differences between undrained and drained stability, especially in the geometry associated with failure and the preparation of the design calculation. The relationship of permeability and whether a soil will behave in an undrained or drained manner during the timescale of a typical tunnel construction, is explained.
Each design aspect of undrained stability is explored by considering tunnel heading stability in clay, in a variety of situations, and carefully demonstrated by a range of appropriate worked examples. This is followed by advice in terms of blow-out failures in clay, with worked examples. When moving to drained stability, the author covers this without seepage, applying it to closed-face tunnel boring machines and blow-out failures in drained soils, all in a similar manner with carefully selected worked examples.
The next chapter starts by suggesting that unlike a tunnel heading, when at the base of a shaft, gravity assists. However, we are then warned that seepage forces or constrained water pressures cause instability, as well as heave pressures arising from swelling clay. Again, the chapter is laid out with explanations of the various aspects which a design engineer needs to consider, illustrated by worked examples.
This is then followed by stability in terms of the Eurocode 7, where the design engineer is warned that although a specific section on the design of tunnels is missing, it is suggested that perhaps a future edition of this Eurocode may correct this. Once this chapter has been covered, an understanding is obtained on how Eurocode 7 ensures stability through the use of characteristic values and partial factors; and how the design engineer should select characteristic values of parameters; also incorporated here is the use of statistics and probability theory in geotechnical design.
Chapters six and seven cover design with regards to analytical methods and numerical modelling. The design engineer will note from Chapter six on design using analytical solutions, the limitations of such on tunnel design, the relative importance of soil stiffness, lining stiffness and limiting flexibility to the forces and moments set up. Chapter seven compares this when designing using numerical modelling. Here, the design engineer will understand the principles of numerical modelling in 2D and 3D, the limitations, the boundary effects on the model, as well as how groundwater should be modelled.
The next chapters (eight to ten) cover lining materials and their behaviours, segmental lining design, and finally designing for loadings during transportation, delivery and storage of the tunnel segments. The chapter on lining design allows the design engineer to understand in better detail the flat and curved joints and the effect of packers, contact stress concentrations set up by geometrical inaccuracies, and how analysis can incorporate joint rotation behaviour. The chapter on segment design for transient loads will assist the design engineer in determining the main load cases that apply to the segment, from casting in the factory to installation within the tunnel. It also covers the jacking loads set up by the tunnel boring machine, as well as grouting pressures and longitudinal bending of the tunnel lining.
Chapter 11 covers sprayed concrete lining design and starts with a comparison with segmental linings. Primary and secondary linings are explained via various configurations, layers and passes before progressing to designing the profile and dividing the face. Here full-face, top heading – invert, top heading-bench invert, as well as single or twin sidewall drift and pilot tunnels are covered before the variations in cavern geometry are described. This chapter gives guidance on numerical modelling but is ‘lighter’ with regards to worked examples.
The final two chapters describe estimating ground movements followed by estimating building damage. The former will give an understanding of settlements in various soil types, volume loss, short- and long-term settlements, as well as those movements set up by shaft excavation. The latter covers the limiting of tensile strain and its correlation to building damage categories; idealisation of a building as a simple beam and how this helps estimate maximum strains; the stages of building damage assessment; and a ‘toe into the water’ that is detailed Stage 3 assessments. Here, the consideration can be detailed from record search, structural investigation to open up and confirm as-built structural detail, to then analyse with stiffness and strength associated with the building structure that is being effected by the movements set up by the tunnelling below.
In summary, this book is essential for the tunnel design engineer, of varying experience and maturity, with clear worked examples and referencing to assist throughout. It is a must for design organisations engaged within the tunnelling sector, irrespective of whether the project is in an urban or rural location, in the UK or overseas. This book should be available to design engineers whether in an in-house client section, a consulting engineering practice or a contractor-based team. And a copy is essential for all libraries, whether professional, academic or personal. I commend this book to readers and congratulate the author on his work.
