Geotechnical Quotes from Karl von Terzaghi, the father of soil mechanics

Karl von Terzaghi (October 2, 1883 – October 25, 1963) was an Austrian civil engineer and geologist, called the father of soil mechanics. Here are some of his quotes.

“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”