I learnt today that Geoff Blight has passed away. I can pay tribute to him best by writing of those times I worked with him. He was a professor at the University of the Witwatersrand. He came in and took over when Professor Jennings died. I never had a lecture from him, so I leave it to others to record his lecture style and teaching abilities–both of which I was told were superb.
My first encounter with him was when I was a lecturer and he was working for a consulting company in Johannesburg–I forget which. He was assigned by Professor Jennings as the “external” examiner to me in the course on soil mechanics that I taught. This involved reviewing the questions I set for the exam and reviewing my marking of papers–particularly of those students just failing. I recall his focus on the details of the examine questions: he would ask me to explain what part of the student’s knowledge I was seeking to test; he would point out potentially ambiguous issues and answers; he demanded that I convince him that I myself knew the answers. When it came to evaluating my failing grade for a marginal student, he would go through the student’s answers with a fine pen. He would grade it himself. He would seek to establish if the student knew more than I gave the student credit for. He was far more generous than me, and many times persuaded me to raise the grade and pass the student. I know he was correct, for many years later I have seen those “marginal” students become great engineers–they owe Geoff a silent thanks.
I left university and joined Steffen, Robertson and Kirsten (now SRK). Oskar called me in one day to tell me that the Chamber of Mines had asked us to consult on dust control from some of those old slimes dams in and around Johannesburg. He told me that Geoff had agreed to help as a specialist consultant on the project. He told me to go meet with Geoff and scope out the work.
We worked together on that project for a long time and achieved much dust suppression. His genius at simplifying a complex problem and formulating a practical engineering solution was key to our success. The first solution was to recommend that we mix cement into the upper surface of the top deck paddocks from which most dust emanated. I had conceived of windrows, silt fences, and other crazy schemes. Geoff pointed out their limited short-term efficacy, and persuaded us that only a good addition of cement would achieve anything like a longer-term efficacy. When I left South Africa some years later the dust was still under control.
Then we set about limiting erosion from the steep slopes of the slimes dams. Geoff came up with the solution that worked. Cut vertical faces and inward-inclined benches. He reasoned that vertical faces got no runoff, hence no erosion; and the inward-inclined benches would trap the water and sediment. This was so contrary to common practice that we had a hard time persuading the “experts.” But we did persuade them; we made the cuts, and as far as I know they worked until the slimes dams were removed to be reworked to retrieve more gold.
Geoff insisted on us building sediment dams–something I had never heard of in my formal education. There was little room for the dam structures. He told me of geotextiles, again something new to me. He sketched a simple dam structure made of geotextiles: a rising series of geotextile bags filled with sand, each successive bag a little smaller than the one it rested on. That was my first geosynthetics in mining design, and I am still proud of those dams we designed and built. I am sure I am the only engineer that ever saw them completed, for they are hidden deep in trash-filled ravines, gullies, and depressions amongst fragrant eucalyptus trees.
I moved to Tucson to design a tailings dam for the Mt. Tolman project in northeast Washington. I bragged to Andy Robertson of the 1,000-ft high structure I conceived of–it would have been a 300-ft high toe of dumped waste rock and then would rise another 700 ft via an embankment of compacted cyclone underflow sand. Andy got a fright, called Geoff, and persuaded him to come to Tucson to help me with the design.
For two glorious weeks I worked with Geoff as he questioned my every data, assumption, calculation, layout detail, and idea. Then one hot Tucson evening, about eight, we went for a run–both of could run then–how fast the strong legs of youth go. As we returned to the offices where Robertson Pincock was housed, we saw Andy standing despondent outside. Andy called us into the foyer and told us that Kay Pincock had sold the company to Harry Winters and that Harry had closed down Robertson Pincock, and that our jobs no longer existed.
I was out of work. Geoff caught a plane back to South Africa a day or two later. The mine never opened and the dam was never built. But I learnt a lot during those two weeks with Geoff.
We never worked together again. I continued to meet him at the occasional conference, read everything he wrote, and dream of the days past.
He was a great person, an inspired engineer, and (I am sure) a great teacher. His writings will survive him and stand as a testament to his kindness and genius.