NEWS: In Honor of Father’s Day – The Father of Geotechnical Engineering – Karl von Terzaghi
Excerpts from the article published in the October 2002, GEO-STRATA magazine of the ASCE and written by Professor Richard Goodman.
Karl Terzaghi’s legacy in Geotechnical Engineering
Karl Terzaghi (1883-1963) was the first to elaborate a comprehensive mechanics of soils with his publication of Erdbaumechanik in 1925. Terzaghi disseminated advances in soils engineering that influenced the entire civil engineering world.
His recognition and formulation of the effective stress principle and its influence on settlement analysis, strength, permeability and erosion of soils was his most prodigious contribution. But Terzaghi also pioneered a great range of methods and procedures for investigation, analysis, testing, instrumentation, and practice that defined much of the field we currently know as geotechnical engineering.
Karl Terzaghi expressed his personal beliefs about the practice of engineering to others which included:
- Assume the worst configuration of properties and boundary conditions consistent with data from site investigations.
- Follow through on every angle and every subtask.
- Don’t oversimplify the site model, its properties, or its response.
- Take responsibility as an engineer, even beyond the specifics of one’s own specific assignment.
- Learn continuously from experience, personal and vicarious, and publish meaningful experiences for the betterment of the profession.
The following describes some key facets of Terzaghi’s Methodology in reviewing projects.
- He reported relevant case histories, from his own experience or about which he had learned from conversations with engineers, or reading, both of which he pursued diligently.
- In the beginning, and throughout the course of a job, Terzaghi demanded a great deal of data and was usually persistent in obtaining most of the specifics he needed. He often questioned the results of prior soil investigations, sometimes rejecting their conclusions outright and beginning a new.
- He generally tried to unravel a site’s geological history, then used it to develop a list of questions that the investigations should attempt to address. He applied this history, and geological logic, to infer a foundation’s geometric and material properties.
- He tried to develop and explain simplified procedures or apparatus that the client could adopt to carry out the recommendations without undue inconvenience.
- When criticizing previous work, he was courteous and careful to explain the nature of his disagreement, yet firm in his resolve.
- In completing a study he tried to cover all the essential bases – engineering geology, geotechnical engineering, structural engineering, sometimes even hydraulics – so as not to leave the client hanging by overspecialization.
- He attached as much interest to the construction procedures as to the design itself, with full expectation that the design would be appropriately modified during construction, as the true conditions were unveiled through observations and measurements.
- He provided very definite and explicit recommendations in a way that was immediately useful to his clients. He stated his recommendations convincingly, sometimes almost threateningly, warning the reader, in the sternest, absolute terms, that the difference between success and failure, safety and catastrophe, resided in absolute adherence to his word.
- He was always conscious of the need to be efficient, if not optimal, in approach to excavation and design of any work within the constraints of assured safety. He often recommended staged design, awaiting the results of measurements, in order to avoid overdesign.
(found in the excellent biography of Karl Terzaghi, authored by Professor D. Goodman, titled “Karl Terzagi, the engineer as artist”, published by the ASCE):
“Theory is the language by means of which lessons of experience can be clearly expressed.”
“Theory -and even very rigorous theory- is required for training and developing our capacity for correctly interpreting what we observe; but at the same time, with theory alone we could not accomplish anything at all in the field of earthwork engineering, an the more plain facts we can accumulate, the better. I always lose my temper with people who think they have grasped the very core of the substance after they have succeeded in representing some artificially simplified phase of it by means of complicated triple integrals; while at the same time, they have forgotten how the soil really looks. Keen observation is at least as necessary as penetrating analysis”
“Unfortunately, soils are made by nature and not by man, and the products of nature are always complex… As soon as we pass from steel and concrete to earth, the omnipotence of theory ceases to exist. Natural soil is never uniform. Its properties change from point to point while our knowledge of its properties are limited to those few spots at which the samples have been collected. In soil mechanics the accuracy of computed results never exceeds that of a crude estimate, and the principal function of theory consists in teaching us what and how to observe in the field.”
“When utilizing past experience in the design of a new structure we proceed by analogy and no conclusion by analogy can be considered valid unless all the vital factors involved in the cases subject to comparison are practically identical. Experience does not tell us anything about the nature of these factors and many engineers who are proud of their experience do not even suspect the conditions required for the validity of their mental operations. Hence our practical experience can be very misleading unless it combines with it a fairly accurate conception of the mechanics of the phenomena under consideration.”
“I produced my theories and made my experiments for the purpose of establishing an aid in forming a correct opinion and I realized with dismay that they are still considered by the majority as a substitute for common sense and experience.”