The GeoInstitute has chosen to feature George Goble’s Terzaghi Lecture, it’s here:
He covers the waterfront (complete with a major marine project) on the WEAP/CAPWAP method of pile dynamics. The methods he and his colleagues pioneered have become standard in driven pile practice. I have a few comments on the lecture as follows:
- He brings up the Case Method. I really think that he and Frank Rausche had high hopes for this, but ultimately it has been superseded by CAPWAP. The key problem, as George pointed out, was determining the Case damping constant. Had the Case Method worked out as hoped, dynamic monitoring and the interpretation of the results would have been much easier to “sell” to the geotechnical community. (I should mention that I used the Case Method as a teaching tool for pile dynamics.)
- One long standing problem with CAPWAP has been the lack of transparency on how it really works. George didn’t address that in the lecture; however, a good deal of that has been resolved with Rausche, F., Likins, G. E., Liang, L., and Hussein, M.H. (2010). “Static and Dynamic Models for CAPWAP Signal Matching.” The Art of Foundation Engineering Practice, American Society of Civil Engineers, Reston, VA, 534-553, which came after this lecture.
- His comment that he wasn’t the best of friends with Tom Davisson was probably diplomatic; at one time their methodologies were competitive with each other. Had Tom had a better feel for the structure of the industry and the skill in commercialising what he was doing, it could have been a contest. But getting new methodologies approved in our complicated acceptance system isn’t a simple business. George was surprised after visiting Texas A&M that the wave equation method had not obtained wider acceptance outside of the offshore oil industry; subsequently he showed he had the patience and grit to get through the system, which is about as important as having a good method to start with. It’s a good example of how science doesn’t always move in a straight line and forward the way we would like it to.
- One thing he did agree with Tom on was the Davisson Method for static (and dynamic) load testing acceptance, and for the same reason as it is the preferred method in the U.S. today: it is reproducible from one analyst to the next. The offset yield concept was well established in metallurgy and its adaptation to static load testing was an advance. George would have been well advised to adopt some of Tom’s thinking on semi-infinite piles and impedance, which would have “tightened” his technical narrative.
- One surprising thing towards the end was the George didn’t characterise himself as a geotechincal engineer. I think that anyone who specialises in pile dynamics at any level finds themselves in a different world that most geotechs do, and that adds to the communication problem which has further complicated acceptance of wave mechanics in piling. It’s interesting that this is a Terzaghi Lecture; the great man himself tackled the problem without really adding much to the solution. I discussed in my post An Industry Gets Restless: Terzaghi’s 1929 Paper on Dynamic Formulae and the Response:
Terzaghi’s strength was in his deep understanding of the behaviour of soils, an understanding which resulted both from experimental and experiential practice and the application of the proper theory to the actual behaviour. That combination revolutionised geotechnical engineering, and secured his place in the profession.
Most soils behaviour is slow except if something bad happens. Pile dynamics at any level, however, involves the rapid movement of pile and soil alike, plastic soil displacement and remoulding. Such a problem is more the province of the mechanical engineer than the civil, which is why progress in the field has been difficult: it is beyond the skill set of most civil engineers, let alone geotechnical ones. It took Raymond’s Chief Mechanical Engineer E.A.L. Smith and computer power to break the logjam and put pile dynamics on a more scientific basis, and much of the progress before and since has been due to the involvement of people more skilled in dynamic phenomena.
To make a major contribution to a problem that even Terzaghi couldn’t quite get ahead of is major, and that ultimately is the legacy of George Goble.
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