Background
In 2016 I retired after fifty years involvement in civil and geotechnical engineering, having witnessed major changes in the techniques available to us and our knowledge of engineering geology and geotechnical phenomena. During that period, I was involved in some very interesting projects that presented us with challenges, often stemming from the geology, that we had to overcome.
In 2018 my wife, Virginia, persuaded me to start writing a book of my reminiscences, and in 2020 I printed it privately and distributed it to a limited number of friends, family and former colleagues as an embargoed publication. Several of those colleagues urged me to publish the book openly, and in November this year Writes Hill Press released an augmented and greatly improved version entitled “Engineering in changing times”
The book deals with both my civil engineering and geotechnical engineering experiences, but this article concentrates on the geotechnical aspects. The book is not intended as a textbook and being recollections is not necessarily an accurate historical account. However, for those interested in the technical details I have referenced 13 geotechnically related papers that I published during my career, and the publisher’s website provides or indicates where copies of those papers can be obtained.
Being recollections, the book focuses on what I saw as the interesting projects and people I worked with and the challenges we faced and overcame. It stresses the team nature of geotechnical engineering and the roles of the engineers, engineering geologists, geophysicists and contractors. And I have named those people who were my mentors and who made significant contributions to projects I was involved in, to emphasise that these were real people. I noted with interest that of the 28 engineering geologists that Don Macfarlane named in his article in the June 2022 edition on engineering geology, and whose names I recognised, I worked with 13 of them, including my engineering geology mentor, the late Brian Paterson.
I enrolled at the Auckland University School of Engineering in 1966 and graduated with a PhD in geotechnical engineering in 1973. I then joined the Ministry of Works and Development where I spent the first four years operating as a general civil engineer, followed by eight years as a specialist geotechnical engineer, and finished with three years managing the Special Projects office, which undertook a wide range of civil engineering projects. I then joined Beca, where I spent 28 years, primarily as a multidisciplinary civil engineering team leader undertaking roading projects, but also with involvement throughout that period in some notable geotechnical projects. In my parallel life in civil engineering, I had to come to terms with the changing requirements of society and the legislation requiring engineers to not just design and build infrastructure, but also to manage the consideration of environmental impacts and consultation with the public.
The book covers the geotechnical aspects of a wide variety of civil engineering projects in a wide range of geological settings, and some of the innovative solutions that were developed to address the challenges we encountered. The following are some of the projects covered in the book:
The 1979 Abbotsford landslide
When I was asked to analyse the 1979 Abbotsford landslide, I had to write a Fortran program to analyse a block slide, because at the time there was no program capable of that available in New Zealand. I also marvelled how the slide had been the result of the presence of a centimetre thick layer of clay with an amazing low residual strength of 6kPa resulting from progressive failure. And the clay layer was only found when 1 metre diameter Calweld shafts were sunk to the base of the slide. Incredibly I went down 10m down those unlined shafts seated on a wooden board between rope strops. And Professor Peter Taylor and the Soil Bureau technicians who recovered the block samples for shear box testing also went down those unlined shafts. Health and safety considerations then were a mile away from those today.
The Ruahihi and Whaeo canal collapses
Then in the 1980’s I was a member of the Ministry of Works committees of inquiry into the Ruahihi and Whaeo canal collapses that brought home to me the challenges of working with volcanic tephra, brown ash and columnar jointed ignimbrite and the frightening ability of water to exploit subtle defects in designs and in the underlying geology.
The Maniototo irrigation scheme
On the Maniototo irrigation scheme a 10m thick fault zone in the schist containing swelling clay minerals evaded our investigation boreholes and affected the tunnel over a 75m length, which took 23 weeks to excavate. And a thin foliation shear in otherwise strong massive quartzo-feldspathic schist caused the sudden failure of a section of the tunnel outlet race batters.
Liquefaction effects
I observed the evolution of our understanding of liquefaction, which was not even mentioned in my undergraduate degree. Because it was only just beginning to be recognised, I was asked in the 1970’s by MWD to write a briefing paper on its recognition, impacts, analysis and treatment. In 1987 I observed first hand many of its manifestations in the Edgecumbe earthquake, and two years later, as part of the Wellington Lifelines Study, presented a briefing to lifeline owners on the expected occurrence of liquefaction in a major earthquake around Wellington and its potential effects on their facilities. And in 2013 I had a brief 30 second slot on TVNZ1 News commenting on the effects of liquefaction in Wellington as a result of the Seddon Earthquake.
Open Cast Coal mining
In the 1980’s large open cast coal mining operations were being initiated, often utilising redundant underground mining managers and staff, with consequent problems with the inefficient recovery of the coal and unacceptable environmental impacts from the disposal of overburden. I was involved in a study of overburden disposal options at the Island Block mine where side-cast overburden had formed an unstable slope in the head of a valley and deposits of quicksand had accumulated on the river terraces. Then at Ohai we had to find means of constructing 100m high mine pit walls above coal seams that contained voids from previous underground workings, StateCoal being concerned that any slope failures could admit air to the old workings and set off spontaneous combustion fires that would be difficult to put out.
Manawatu Gorge
I had involvement with projects and studies associated with Manawatu Gorge over a 25-year period and saw first-hand the challenges of dealing with unstable colluvium and highly fractured greywacke rock, both during early, largely unsuccessful, attempts to improve the road alignment by cutting back spurs, and later during attempts to clear the massive slips that eventually led to the abandonment of the route. It was interesting to see how difficult the stereoscopic mapping and rock slope stabilising techniques developed overseas were to use with the highly fractured greywacke and argillite in the gorge.
The Pitteau experience
And when the National Roads Board engaged a Canadian engineering geologist, Doug Pitteau, to give a course on rock slope engineering, he was dismayed when I took him on a tiki tour to show him natural and cut greywacke and papa slopes. His reaction was that the techniques that he would be presenting had been largely developed for use in geological settings with regular widely spaced jointing in hard rocks, such as the granite of the Fraser Canyon in British Columbia, and he could see that there were problems with their application to the chaotic tectonic induced fractures in our greywacke.
The Tunnels
In addition to the design of the Maniototo irrigation tunnel and some modifications to existing road and rail tunnels, I had involvement in a number of preliminary studies associated with rail tunnels including public transport tunnels beneath Auckland Harbour, the Auckland City Rail Loop and a rail tunnel north of Wellington between Paekakariki and Pukerua Bay. All of them involved input from international consultant partners, and in all cases I experienced problems, either with getting timely input or with their experts not being able to come to grips with the variability of our geology as a consequence of our turbulent tectonic history. The experience of the reviewer for the Paekakariki to Pukerua Bay tunnel seemed to be largely in Sydney’s Hawkesbury Sandstone, and he found it hard to accept that I was predicting materials ranging from highly weathered crush zones that could be excavated with a spade, through to greywacke sandstone with an unconfined compressive strength of 200 MPa.
Some challenging bridge foundations
For the foundations of the Ewen Bridge over the Hutt River we had to develop innovative grouting techniques to prevent artesian water leaking up the outside of the piles, and for the construction of the 4m diameter piles for the Otira Viaduct the contractor, Albert Smith, had to build a circular secant pile coffer dam within the incredibly hard and abrasive blocky greywacke debris from the rockfall that blocked the valley 2000 years ago, and included individual blocks at least 12 metres in size. We also saw first-hand that earthquakes still periodically release large rocks from 700m above the valley floor and this had to be allowed for in the viaduct design.
The Ngauranga Flyover abutment – the first major Reinforced Earth wall on the State Highway Network. The author was a member of the design team and, with Brian Prendergast, published a paper on its design at the 3rd Australia New Zealand Geomechanics Conference in 1980.
The replacement Ewen Bridge at Lower Hutt. The foundations extend through an aquiclude into the Waiwhetu Gravels, an artesian aquifer that provided 25% of Wellington’s water supply. An innovative grouting technique had to be developed by the author to prevent escape of the artesian pressures up the outside of the pile casings. The paper on the pile design, construction, and grouting, which appeared in the 1995 IPENZ Transactions, was awarded the IPENZ Fulton Downer Gold Medal, the NZ Concrete Society Freysinett Award and the NZ Geotechnical Society Award.
Otira Viaduct. The author was responsible for the investigations and design of the 4m diameter piles. With Richard Holyoake, the Beca engineer who supervised the construction, he published a a paper on the foundation design and construction at the ISRM’s International Symposium in Melbourne in 2000. Beca photo / John McCombe
The challenge of geotechnical investigations in a geothermal field
My final significant geotechnical role was as the technical project manager for investigations at Wairakei and Tauhara in geothermal conditions to establish the stratigraphy and recover undisturbed samples in materials ranging from the consistency of toothpaste to moderately strong rock, and from depths up to 800m. In the end we drilled 9 holes totalling 4390 metres in length with almost continuous core recovery and recovered 269 undisturbed samples. To recover the undisturbed samples, we adapted a standard triple tube sampler by replacing part of the splits with a tube. We engaged Mel Griffiths to advise us on both the drilling and sample recovery methods.
The laboratory testing aimed at producing deformation properties for the subsidence analyses was undertaken by Professor Mick Pender at Auckland University using a triaxial cell very similar to one I designed for my PhD in 1972 to undertake slow drained stress-path tests. Apart from the reinforcement of the cell for the very high pressures required to replicate the stresses at depths of hundreds of metres, the major changes were the replacement of the data loggers, valves, gauges and analogue devices I used in 1972 by a single laptop on a trolley which recorded the results and drove servo-controlled valves to follow the required stress path. And in 1972 to slowly increase pressures and maintain drained conditions I used a standard valve turned one revolution every 24 hours by a small motor and gearbox.
The Evolution
At the beginning of my career computers were not yet used in practice, and the importance of engineering geology to geotechnical engineers was not taught or really appreciated. Engineering was a male dominated profession and I observed first-hand the barriers that some early women engineers faced. Our understanding of phenomena such as liquefaction and seismicity was rudimentary and during my career grew out of all recognition.
I saw the influence of the arrival of word processors, email and evolving printing technology through my roles on the Society’s management committee as publications officer in the 1980’s, and as an editor for the 1980 and 2015 ANZ Conferences, and for the 1992 International Symposium on Landslides which the society organised. I saw huge strides in our ability to communicate with authors, the standards of presentation expected, the requirements for peer reviewing, and the evolution from paper to electronic USB stick or DVD proceedings.
In addition to the massive technological developments during my career, I experienced the profound impacts in the restructuring of the profession as a consequence of Rogernomics, and in particular the transformation of the Ministry of Works and Development (MWD) into a commercial consultancy and New Zealand Geological Survey (NZGS) into a Crown Research Institute. In both cases the roles of the former organisations in training staff, undertaking R&D, and preparing guidelines for use throughout the consulting industry were largely lost. A number of prominent overseas engineers and geologists I met in the 1980’s commented on the value of the roles of MWD and NZGS, and the collaboration they had with academia and the private consulting industry, which allowed rapid dissemination of knowledge and new ideas – something they lamented did not occur in their own countries.
On the training front MWD sent a number of engineers to Imperial College London to do an MSC in geotechnical engineering, and they all returned with the latest practical knowledge.
The MWDs role in preparing Technical Guidelines
In terms of technical guidelines, while at MWD I personally undertook the preparation of a Code of Practice for Falsework which, because of my own background, contained a section on foundation design which was far more comprehensive than was necessary. I also prepared the section on foundations for the 1980’s NZ National Society of Earthquake Engineering’s guide for Seismic Design of Storage Tanks. I was involved in or oversaw the preparation of the MWD Reinforced Earth Retaining Wall Design Notes, the MWD Pile Design Notes and the MWD Guide for Site Investigations. These guidelines were prepared to standardise practice across the MWD and also as a resource for private consultants, though some saw them as waste of government money. And the MWD Guide for Site Investigations provided some of the material for the later first edition of the NZ Geomechanics Society’s Field Guide to the Description of Soils and Rocks.
The Guide for Site Investigations drew heavily on an unpublished in-house NZGS manual and brought me into contact with Les Oborn, the head of the Engineering Geological Section, who was very highly regarded within MWD, and can be considered as one of the fathers of engineering geology in NZ. I understood that the reluctance of NZGS to release their draft manual arose from the existence of a vigorous debate on how clays should be identified and classified in the field, and in particular the extent to which it should be based on a visual-mechanical assessment or a field assessment of plasticity. At MWD we felt that to hold up the issuing of the guidelines to await resolution of the debate was unnecessary and undesirable, as it would lead to the remaining 95% of urgently required guidance being unavailable. And I understand that the debate on how to describe and classify clays in the field is still alive and well.
The loss of the MWD approach to R&D
A major advantage of the MWD approach in the research and development area was that it had the ability to decide what needed to be done and was not dependent on obtaining research funding from another body. This advantage was demonstrated some 10 years later at Beca, when one of my staff, Alexei Murashev, undertook research and prepared reports on mechanically stabilised earth with research funding from Transfund. This work largely superseded the early 1980’s MWD design notes, but the final phase of Alexei’s work went uncompleted at that time, because the final tranche of funding was not granted and Beca, as a private consultant, was not in the business of funding research. In MWD days the whole programme would have been completed.
The career change
The effects of the corporatisation on MWD led me to leave it and join Beca, a consultancy tracing its roots back to a practice founded by my great-uncle Arthur Gray in 1920. That move led to a change in the direction of my career, to largely leading multidisciplinary teams engaged on roading design projects, with geotechnical engineering as a secondary role. And, while I had been heavily involved in tunnel related work in MWD and had been New Zealand’s representative on International Tunnelling Association working groups for 6 years, after I joined Beca it was 15 years before I had any further involvement in tunnelling work.
The book
Ron Carter, one of the founders of the modern Beca firm, urged me to publish the book, and he has provided a foreword that explains the difference between the science of engineering, which can be taught, and the art of engineering which lets us design and build safe structures, despite the limitations of the science and the uncertainties that geological conditions present. And Ron sees the value of the book in it being about the art of engineering and my experiences in dealing with the challenges in the geology arising from New Zealand’s turbulent tectonic, glacial and volcanic history.
For those interested in reading more about my experiences, copies are available for purchase on-line from my publisher at writeshillpress.co.nz. Alternatively, you can ask your public library whether they have a copy and, if not, suggest they buy a copy for you to borrow.
