Terzaghi文稿 | 土力学—工程科学的新篇章
“Soil Mechanics arrived at the borderline between science and art. I use the term “art” to indicate mental processes leading to satisfactory results without the assistance of step-for-step logical reasoning…To acquire competence in the field of earthwork engineering one must live with the soil. One must love it and observe its performance not only in the laboratory but also in the field, to become familiar with those of its manifold properties that are not disclosed by boring records…”Karl-Terzaghi-The-Engineer-as-Artist
This page includes some of my favorite Karl Terzaghi (1883-1963) sayings. These can be found in the excellent biography of Karl Terzaghi, authored by Professor D. Goodman, titled “Karl Terzagi, the engineer as artist”, published by the ASCE. I consider the book essential reading for every geotechnical engineer, especially for young Geotechnical Engineers. I found it inspiring and learned many lessons that will be valuable in my career.
Dimitris P. Zekkos
“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.”
“…once a theory appears on the question sheet of a college examination, it turns into something to be feared and believed, and many of the engineers who were benefited by a college education applied the theories without even suspecting the narrow limits of their validity.”
“… Any attempt to stop the settlement without making the proposed preliminary investigation would be an irresponsible gamble. Since I have witnessed many gambles of this kind I can state from personal experience that the savings associate with inadequate preliminary investigations are entirely out of proportion to the financial risks.”
“These government organizations have a great reluctance to carry responsibilities; they always want to be covered by something, and a factor of safety-that is something tangible. So when the general asks the captain: ”How about the factor of safety of the dam?-“1.51” [is the answer] and then he is happy”
“The one thing an engineer should be afraid of is the development of conditions on the job which he has not anticipated. The construction drawings are no more than a wish dream. I have the impression that the great majority of dam failures were due to negligent construction and not to faulty design.”
“Soil Mechanics arrived at the borderline between science and art. I use the term “art” to indicate mental processes leading to satisfactory results without the assistance of step-for-step logical reasoning…To acquire competence in the field of earthwork engineering one must live with the soil. One must love it and observe its performance not only in the laboratory but also in the field, to become familiar with those of its manifold properties that are not disclosed by boring records…”
4th International Congress on Soil Mechanics, England , 1957
“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.”
When Yves Lacroix asked Terzaghi how much time he ought to spend on writing his report, he got the following advice:
“Spend on it as much time as necessary to inform the reader with as few words as practicable about all the significant findings and about the essential features of the construction operations which have been performed”
“Proving the old adage that results depend not on the perfection of the equipment but on the truth of the proposition… The simper and cheaper the apparatus, the better it expresses the purpose and accordingly one can gain insight into a process being investigated, approving or rejecting and postulating anew, without wasting time and money. Costly, sensitive instruments belong to the situation where one already has a clear hold of the natural phenomena and where there is value in obtaining refined numbers. When one begins experiments with costly apparatus, he becomes a slave to that apparatus and the experiment, rather than serving to establish the truthfulness of a valuable idea, serves merely to establish a fact-but never to establish a law.”
“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”
This article was published in the October 2002, GEO-STRATA magazine of the ASCE and was writen by Professor Richard Goodman. We have considered that the article was very interesting and should be read by all geotechs and we requested to host the article in the Geoengineer website. Permission for its use was granted by ASCE on November 19th. For more information about the publications of the ASCE you can click here and for information about the GEOINSTITUTE click here
Karl Terzaghi’s legacy in Geotechnical Engineering
By Richard E. Goodman*
Karl Terzaghi (1883-1963) was the first to elaborate a comprehensive mechanics of soils with his publication of Erdbaumechanik in 1925. 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.
Among Terzaghi’s publications, reports and lectures, one finds seminal contributions across a wide terrain, including: classification methods for soils and rocks; capillary phenomena in soils; the theory and documentation of consolidation and settlement; piping and its prevention; design and construction of earth, rock and concrete dams on all kinds of foundations; anchorages for suspension bridges in soils; field and laboratory measurement of pore pressures and soil properties; use of flow nets in two and three dimensions; design of drainage wells and tunnels; design to avoid scour of river and waterfront structures; earth pressure variations on walls and bulkheads; engineering in terrain underlain by permafrost; pile foundations; soil improvement by compaction, pile-driving, grouting and incorporation of geotextiles; soil and rock tunneling; engineering geology; sinkhole formation and collapse; regional subsidence due to oil-field operations; and landslides.
He was the great professor of geotechnical engineering of his day, with regular appointments first in Istanbul, then at MIT, Vienna, and Harvard, as well as courses of lectures in Berlin, Texas and Illinois. Through hisvoluminous correspondence with engineers and scientists, his lifelong devotion to publishing both research findings and practical experiences, his numerous public lectures, and his authorship of clear and complete procedures in many engineering reports, Terzaghi disseminated advances in soils engineering that influenced the entire civil engineering world.
Ironically, although he was a great educator, Terzaghi grew to entertain a suspicion of formal education, which he thought had the capacity to obscure observation of new phenomena. He reserved his greater admiration for “self-
made men” who learned from their open eyes and minds.
TERZAGHI’S PERSONALITY AND INTERESTS
In reviewing the range of accomplishments and his domination of the field, it is interesting to examine Terzaghi’s background and interests as well as his philosophy and methods of working. His upbringing and education combined Austrian rigor and military training and a passion for observation of natural science and the contemplative beauty of nature. His attractions ranged widely: construction, geology, mathematics, philosophy and ethics, architecture, flowers, swimming, conversation, travel, literature, music, art, women, men and writing.
He was certainly a remarkable listener as well as a reader and an observer. He was also an exceptionally faithful diarist and prolific correspondent, and through his correspondence he revealed a penchant for classifying almost everything in his experience; people, ideas, objects and of course, rocks and soils. Terzaghi could be a severe critic, especially of those who tended to be blinded by their own theories, or worse, those utterly devoid of theories. He accused some of hiding inarticulately, behind a pensive exterior.
Terzaghi’s goals, which were set like sails to drive his life, changed dramatically at about age 43 (1926). As a younger man he had striven t formulate a rational analytical or empirical methodology, properly embracing geological constraints, for designing works founded on soils (and, to a lesser extent, rocks). But as a mature man, having achieved his first target, he pursued the practice of engineering passionately to test and temper the emerging methods by physical realities.
In this he became increasingly concerned wit the difficulty or knowing enough of a site’s morphology and properties to determine a design solution before construction had started. This worry committed him ever further to the observation of soil and structural response throughout the construction period in order to inform a constant updating of the designs, transforming him into a proponent and practitioner (with coworker Ralph Peck) of the “observational method”. Thus, despite Terzaghi’s considerable achievement in advancing the theory of soil mechanics, he repeatedly counseled the profession to stay connected with the behavior of the actual soil in engineering practice.
TERZAGHI’S PRAGMATIC PHILOSOPHY AND METHOD
As his own method of accomplishment became formed, Karl Terzaghi expressed his personal beliefs about the practice of engineering to others. The key components included the following points:
- Take on only what one’s own competence allows him or her to handle personally. Terzaghi had such confidence in his own core resources as to seek out the most challenging (some would say “adventurous”) projects.
- 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.
These items from Terzaghi’s personal creed colored his attitude as an engineering consultant, the methods he adopted in working with others to solve engineering problems, and the way he wrote his own engineering reports. The following describes some key facets of his system.
- 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.
- In sleuthing failures, he tried to obtain old records, photos, and eyewitness accounts and worked to identify and resolve inconsistencies among these data.
- In writing his reports, he chose his words so as t make his thought process visible, being careful to expose the logic that led to certain simplifications and/or correlations observations.
- His calculations were tempered by judgments concerning imperfections in sampling and testing and variability in the morphology and properties of different layers.
- 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.
- He reviewed any specific design with a checklist of possible defects related to the interaction of geological and engineering factors and then meticulously examined each, point by point. He then computed or judged the capacity of the design to overcome the specific obstacles and, if warranted, suggested refinements or reworkings in the design, which were accompanied by detailed sketches and drawings as well as pertinent case histories.
- 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 used hydrologic measurements from weirs to piezometers, together with analysis to compare the response of homogeneous materials with that of the actual site. Anomalies thus identified focused the investigations on critical locations.
- 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 insisted on obtaining, and often helped recruit, highly qualified people to conduct the sensitive construction jobs, whether engineering measurement, excavation supervision, or tunnel foreman, and he argued for the employment of engineering geologists.
- He invariably required measurements to be made on the site, with sufficient lead time to establish behavior before, during and after construction. He warned of the implications of not making the required 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.
- He was entirely committed to sticking with a project to its completion, even in the face of changes in management such that he no longer had a client to fund his involvement.
- He was consistently aware of his ethical responsibility as an engineer and did not hesitate to indicate problems in a part of a job even if it lay outside his specific charge.
Karl Terzaghi was a remarkable mad and an impassioned engineer. As he put it himself, “All the modest achievements which I have to my credit can be described by a simple formula… Guided by common sense and casual observations, I recognized weak points in traditional procedures and tried to make them less weak. Sometimes I failed, but usually I succeeded.”
*Richard Goodman, M.ASCE, a member of the National Academy of Engineering, is Cahill Professor Emeritus in Geotechnical Engineering at the University ofCalifornia, Berkeley, and a regular visiting Professor in the Technical University of Graz, Austria. His research in applied rock mechanics led to development of the joint element for finite element analysis (with Robert Taylor), introduction of the base friction model test, and the development of block theory (with Gen hua Shi). He is the author of five books, including Karl Terzaghi, the Engineer as Artist available through ASCE. He can be reached at firstname.lastname@example.org.