Discussion of “D. W. Taylor and the Foundations of Modern Soil Mechanics” by John T. Christian and Gregory B. Baecher

Abstract

The “D.W. Taylor and the Foundations of Modern Soil Mechanics” Forum paper by Christian and Baecher (2015) is a useful contribution to the history of modern soil mechanics. One valuable piece of historical information in the paper is that it connects Taylor soil mechanics to Terzaghi soil mechanics, and the important role that Glennon Gilboy (1902–1958) played in it. According to the Forum paper, starting in 1926 Gilboy became Terzaghi’s doctoral student at the Massachusetts Institute of Technology (MIT), and he served as Terzaghi’s assistant through 1929. In 1930 Gilboy prepared instructional notes based largely on Terzaghi’s lectures, and reproduced them for use by his students. Donald Wood Taylor began graduate study at MIT in 1931 and earned a M.Sc. degree in soil mechanics under the direction of Gilboy. Taylor expanded and revised the Gilboy notes in 1938 and 1939, and ultimately the expanded and revised Terzaghi lectures became the basis of Fundamentals of Soil Mechanics, published in 1948, the same year Soil Mechanics in Engineering Practice by Terzaghi and Peck was published. Thus, there lies one explanation of the mystery about the Taylor-Terzaghi and Peck controversy. Because the Forum papers are characterized as “opinion pieces : : : sometimes containing speculation” my first instinct was to consider it unnecessary to venture a comment on the paper’s account of the MIT connection to the Newmark sliding block method. However, on second thought, the following is a brief alternative history. I have previously reported (Mesri 2009) that Ralph Peck was a consultant on Portage Mountain Dam in British Columbia. Peck consulted his colleague at the University of Illinois, Nathan M. Newmark, on the effect of earthquakes on dams and embankments. The sliding block idea was developed by Newmark in 1960 (e.g., Davis and associates 1960) to evaluate seismic deformation of Portage Mountain Dam. I have explained in my written and oral contributions to the 2001 symposium honoring Charles Cushing Ladd III (Mesri 2001) that it was Donald Taylor who, through meticulous consolidation tests and interpretation (Taylor 1942), initiated the question posed later in terms of hypothesis A versus hypothesis B (Ladd et al. 1977). Unfortunately, in referring to the ongoing debate, frequently the two hypotheses are incorrectly defined. Both hypotheses A and B accept the contribution of compressibility-with-time during primary consolidation. However, whereas hypothesis A, based on the observed interrelationship between compressibility-with-time and compressibility-with-effective-stress, proposes an end-ofprimary (EOP) vertical strain independent of the duration of primary consolidation, hypothesis B predicts an increase in EOP vertical strain with the increase in duration of primary consolidation (Mesri and Feng 2014). Hypothesis B originated mainly from theoretical analyses of consolidation (e.g., Taylor and Merchant 1940), whereas hypothesis A is based on laboratory tests and field observations (e.g., Mesri and Funk 2015). In 1948, and for a generation of soil engineers, Fundamentals of Soil Mechanics by Taylor was an excellent textbook, and it remains a useful reference on certain topics in soil mechanics. Christian and Baecher only in passing mention the third edition of Soil Mechanics in Engineering Practice (Terzaghi et al. 1996) and neglected to include it in the reference list. Donald Taylor would have appreciated, as for example did Charles Ladd (personal communication), the advances in fundamentals of soil mechanics and soil behavior in practice, chronicled in terms of the observed behavior of natural soil deposits, in the third edition of Soil Mechanics in Engineering Practice.