"On the surface of the matter, nothing seems more poorly adapted to a scientific
study than earth, commonly known as dirt."
-F.E. Schmitt, Editor of Engineering News-Record, 1936.
Man's study of the soil is older than civilization. Over ten thousand years ago, long before the invention of writing or use of metal tools, the invention of agriculture and construction of vast irrigation systems brought our prehistoric forebears into contact — often conflict — with the complexities of the engineering behavior of soils for the first time. Knowledge of the earth and its properties became, and remains, a matter of practical necessity.
By the third and second millennia B.C., monumental construction in Egypt, Mesopotamia, India, and China presented new soils-related engineering and architectural challenges, especially pertaining to foundations. Towering pyramids and ziggurats, city walls of huge dimensions, columned temples, obelisks, pagodas and other structures arose as tributes to man's growing ability to master the earth. In the following centuries, by the beginning of the Christian era, Greek and Roman mastery of bridges, paved roads, aqueducts, sewage and drainage systems, retaining walls, earthen dams and other structures had familiarized ancient engineers, at least in a general sense, with almost all aspects of geotechnical engineering. Even the rudimentary beginnings of earthquake engineering date from ancient Greece and Sung China.1 Yet despite its substantial lineage, geotechnical engineering as an independent, quantitative discipline, a science as well as an art, is one of the most recent branches of engineering to emerge. Its real origins date only from the second quarter of this century.
Prior to the rise of modern geotechnology, all civil engineering and architectural triumphs (and failures) derived essentially from empirical knowledge: knowledge and practice derived from experience, trial and error, or experiment in the field rather than theory or systematized analysis. Results were often wasteful and in many cases disastrous; the successors of all ancient civilizations are built on their ruins. Earlier societies clearly understood certain mathematical relationships as fundamental to construction, but appear to have based their actual engineering practice strictly on observation and precedent. The Egyptians, for example, built the great pyramid of Khufu without knowing the number π, while the Greeks (among others) attributed supernatural powers to stones, soil, and other inorganic matter, a superstition commonly held until the Enlightenment of the eighteenth century. Magnificent Romanesque and soaring Gothic cathedrals of the Middle Ages, imposing castles, and even the revival of classical styles in the Renaissance were likewise not founded on known theoretical or quantitative premises. Jean Kérisel, in a noted essay on early geotechnology, lamented that up until 1700 historians still "searched in vain for any mathematical equations or soil mechanics formulae."2
The mere recognition of soil mechanics as an independent study dates only from the late seventeenth century. Then, French military engineers such as the great Sebástian le Prestre de Vauban produced a succession of analyses of earth pressures on retaining walls and of earth slopes to improve the design of fortifications. These calculations sprang from need. Whereas before the seventeenth century earth pressure problems were not recognized as being particularly important in construction, the great increase in building roads, canals, and sophisticated artillery-proof fortifications required a more systematic approach.3 Vauban consequently had by 1687 compiled tables for the design of retaining walls of from six to eighty feet in height. These provided practical data but "hardly constituted a theory of earth pressure since Vauban did not account for the properties of the soil."4
France continued to lead through the eighteenth century. In 1720 the French government created the famous "Corps des ingénieurs des ponts et chaussées" (Corps of engineers of bridges and roads) — the first state-sponsored organization dedicated to civil engineering. A further state-supported "Ecole des ponts et chaussées" was founded in 1747. The "Ingénieurs des ponts et chaussées" produced there, by virtue of rigorous mathematical training, systematically attempted to use exact methods of geometry and statics to predetermine the proper dimensions of structures, especially retaining walls, which involved soil mechanics. By the mid-eighteenth century, papers on lateral earth pressures began to appear in Italian, Dutch, and Swedish scientific publications, indicating that soil studies were no longer exclusively French.5 Still, empiricism was dominant.
The presentation of Charles Augustin Coulomb's "Essai sur une application des règles de maximis et minimis à quelques problèmes de Statique relatifs à l'architecture" (Essay for the application of the rules of maximums and minimums to certain problems of statics relative to architecture) as a paper to the French Academie des Sciences in 1773 was a milestone. ("Coulomb's Essay" was not published until three years later, causing some confusion in dating.) Karl Terzaghi, the universally acknowledged father of twentieth century soil mechanics, considered Coulomb's work of such magnitude that in 1948 he stated that "Soil mechanics started with the publication of Coulomb's theory of earth pressure on retaining walls.... This was a brilliant beginning."6
Coulomb's theory of earth pressure on lateral supports was founded on the assumption that "failure of a laterally supported bank occurs as a result of the shearing resistance of the earth being exceeded along a surface of sliding." From this he derived the first mathematical formula intended to predict soil behavior in a theoretical framework.
"Coulomb's Law" held that:
s = c + p tan φ
in which s is the shearing resistance of the soil (the strength of the soil to resist failure), c is the cohesion, p is the unit pressure on the surface of sliding, and φ the angle of internal friction. This modest equation, still an integral part of every fledgling civil engineer's education, contained the elemental ingredients of many earth-pressure problems: shearing strength, cohesion, pressure, and internal friction. Coulomb's conclusions soon gained general acceptance, although they were severely limited in that they applied to computing pressures only for dry, clean, cohesionless soil (particularly sand) on the back of retaining walls. Clays were particularly exempt from calculation.7
Erstwhile soil mechanics pioneers made few great advances in the nineteenth century, in part because of their persistence in attempting to apply Coulomb's equation to field conditions which he had specifically excluded. In 1846 Alexandre Collin published Recherches expérimentales sur les glissements spontanés des terraines argileux, accompagnées de considérations sur quelques principes de la mécanique terrestre (Experimental research on spontaneous slides of clay terrain, accompanied by considerations of some principles of soil mechanics). It was the first comprehensive work on the stability of clay slopes, but after publication it remained virtually unknown for almost seventy years.8 Of some consolation was the fact that Collin gave the first name to his subject — "mécanique terrestre" — "terrestrial mechanics," though that term was superseded by the more accurate "mécanique des sols" by the end of the nineteenth century.9 Thomas Tel-ford in the meantime built his success in canal, lock, and bridge construction by determining soil conditions through borings and trial pits.10
Easily the most imposing figure in the nineteenth century English-speaking engineering world was W.J.M. Rankine, author of over 150 scientific papers. Of these only one, "On the Stability of Loose Earth," published in 1853, dealt exclusively with soil mechanics, presenting an alternative to Coulomb's earth-pressure equation for retaining walls.11 Rankine's authority tended to prevail despite criticisms, so that the works of other researchers received little more than passing attention. One critic of Rankine's "angle of repose" miscalculation surmised that "The long survival of Rankine's methods may have been due to their suitability as material for examination questions."12 Another noted British engineer, Sir Benjamin Baker, in a widely read paper published in 1881 stated that existing soil mechanics theory was based on "calculations that disregard the most vital elements existent in fact."13 Terzaghi noted that by the late nineteenth century "Theories of earth pressure and bearing capacity existed for more than a century, but their influence on engineering practice was almost nil."14 Even as late as 1920 the editors of Engineering News-Record concluded that "No two men agree on a method of soil testing," and that "Established earth pressure theory has long been discredited."15
Disaster was the mother of reconsideration. In the first decade of the twentieth century, geotechnical studies reached their nadir in relation to other engineering and architectural fields, especially structural engineering. A succession of catastrophes accentuated the widening gap, sometimes spectacularly. These included railway slides in Sweden, slope failures on the Panama Canal, wall failures on the Kiel Canal in Germany, numerous dam failures, and foundation settlements of large buildings. Finally, in the period before World War I, engineers in both Europe and America tentatively made the commitment to geotechnical progress. As in the prehistoric past, knowledge of the soil and its behavior had become a matter of practical necessity. And despite the efforts of ten thousand years, according to Terzaghi, twentieth-century investigators practically "had to start from scratch."16
Sweden took the lead. Extremely bad soil conditions existed there due to deep deposits of clay of very low shear strength and high compressibility. Railroad construction was particularly treacherous and landslides common. Consequently, in 1908 the Swedish State Railways appointed a special committee of three engineers and one geologist to study the problem of landslides. Among the engineers was the influential Wolmar Fellenius.
The committee's statement that it was still impossible to predict the bearing capacity of embankment loadings or the resistance of earth to sliding in most cases reflected the primitive state of knowledge concerning slope stability. A major slide in 1913, in which almost two hundred meters of railway embankment tumbled into a lake, led to the creation of a full-time Geotechnical Commission. Thus the Swedes used the term "geotechnical" in a civil engineering context for the first time. The commission employed three full-time engineers and two geologists, with numerous others assisting part-time. It also established an active laboratory for analyzing soil samples in Stockholm which was apparently the first of its kind. By 1921 researchers there had tested over two thousand samples, mostly from boring tests and trial pits.17 Work in Sweden attracted the interest of engineers in other Scandinavian countries, so that by the early 1920s Stockholm drew researchers and students from the entire region.
Independently of the railway Geotechnical Commission, the Swedish chemist-agriculturist Albert M. Atterberg started his soils research career in 1900 at the age of fifty-four. Rather than focusing on the problems of engineering design and calculation, Atterberg devoted the final sixteen years of his life to the study of soil classification. He investigated a large number of clays — the most complex and unpredictable of soils — with different water contents. Eventually he established simple tests to determine the plasticity and liquid limit of clays, with indexes employed by every soils engineer in practice to this day.18
Atterberg's work, like that of the Swedish Geotechnical Commission, found an international audience. In 1913 a Berlin conference of soil researchers accepted his classifications of soil particles as an international standard. Two years later a U.S. Bureau of Standards report stated that Atterberg's method was as "as simple a one as could be devised, and...it is well that we should become familiar with it."19
Simultaneously, a succession of bank failures on the Kiel Canal in Germany stimulated research there. H.F.B. Müller-Breslau pioneered studies of earth pressure on canal retaining walls. However, of particular note, Hans-Detlef Krey in 1910 was put in charge of the Versuchsanstalt für Wasserbau und Schiffbau (Experiment Station for Hydraulic Structures and Shipbuilding) in Berlin. The institution had only recently been established and its entire staff consisted of an elderly public works engineer, two clerks, a foreman, and a few workmen. Funds were almost non-existent. In these modest circumstances Krey conducted some of the earliest systematic investigations in soil mechanics, especially dealing with sheet pilings and subterranean and underwater engineering. In the process, he developed one of the first effective direct shear devices of a type that numerous laboratories in Germany adopted in the 1920s.20
In the United States, research was even more sporadic. Many agencies involved in construction — such as the U.S. Army Corps of Engineers — had long dealt with soils phenomena in erecting fortifications, jetties, and other structures. Studies of riverine behavior, especially in the Mississippi River Valley, had also led the Corps to perform rudimentary studies in sedimentation. The Reclamation Service (later U.S. Bureau of Reclamation) attempted some soils classification and testing in the early twentieth century, primarily for use in the design and construction of earthen dams for irrigation purposes. Within the Department of Agriculture, the Bureau of Public Roads also began soils testing because of the ongoing revolution in road building. Even in 1921, though, the bureau acknowledged that inadequate progress had been made, as "only two or three Europeans and the Agriculture Department's Bureau of Soils had examined soils."21
By 1913, the year of the creation of the Swedish Geotechnical Commission, sufficient interest in soils problems led to the appointment by the American Society of Civil Engineers (ASCE) of a "Special Committee to Codify Present Practice on the Bearing Value of Soils for Foundations, and report upon the Physical Characteristics of Soils, in their relation to Engineering Structures." Chaired by Robert A. Cummings of Pittsburgh, the committee contributed little despite its formidable title.22 Cummings in 1916 made the revealing statement that as to both practical and scientific phases of soil mechanics, the committee knew "practically nothing."23
The publication of Karl Terzaghi's Erdbaumechanik auf bodenphysikalischer Grundlage (Fundamental Principles of Earth Mechanics) in 1925 was the landmark of twentieth-century soil mechanics.24 For nearly the next four decades, until his death in 1963, Terzaghi towered over his associates, disciples, and competitors. Seldom has an individual so thoroughly dominated a field. In tribute, four of the leading figures in the world of geotechnical engineering in 1960 — Arthur Casagrande, Laurits Bjerrum, Ralph B. Peck, and A.W. Skempton — collectively stated that "Few men in a lifetime have exerted an influence on their profession to compare with that of Karl Terzaghi on Civil Engineering and Engineering Geology."25
Terzaghi was born in Prague in 1883, the son of an Austrian cavalry officer.26 In 1904 he graduated from the Technische Hochschule (Technical University) in Graz, Austria, with a degree in mechanical engineering. However, he spent much of his time at the university attending courses in geology, philosophy, and astronomy. At one point he was nearly expelled for "excessive indulgence in academic freedom." He supplemented his formal education with prodigious and diverse reading; one of his professors even suggested that he become a professional writer. A true Renaissance man, Terzaghi's favorite sport as a collegian was mountain climbing, a passion he carried into his seventies. He also bore scars from dueling.
Terzaghi's early professional experiences carried him from the Austro-Hungarian Empire to Czarist Russia. In these travels he witnessed the striking discrepancies between engineering "forecast and reality," and became particularly concerned at the lack of knowledge regarding earthworks and foundations. By 1910 he had decided to abandon the field of structural engineering and to dedicate the rest of his long life to the advancement of soil mechanics.
In 1912 Terzaghi began the first of four sojourns in the United States, where he hoped to find insight into a scientific approach to soils engineering. Activities of the Reclamation Service, especially its earthen dam projects, attracted his interest. For two years at his own expense, occasionally even working as a common laborer, Terzaghi traveled the length and breadth of the United States investigating Reclamation Service projects in the Southwest and Pacific Northwest. He also toured the Mississippi delta. His observations brought more disappointment than discovery, and on his return to Europe in 1914 he was convinced that meaningful work in geotechnology had scarcely begun.
Terzaghi's American odyssey had barely ended before World War I broke out in August 1914. After brief service with the Austrian Army on the Serbian front, he was transferred to the Austrian air force, spending two years as commanding officer of an aeronautical testing station near Vienna. In 1916 he relocated to Turkey, where the Austrians were helping the Turkish government establish modern engineering education. At the age of thirty-three Terzaghi became Professor of Foundation Engineering at the Imperial School of Engineering, Constantinople. Thus began a ten-year stint in Constantinople (Istanbul after 1923) during which he formulated his basic philosophy of soil mechanics: there a science was born.
At the university Terzaghi began a systematic experimentation with soils, starting with sands. Because almost no testing instruments were available, he borrowed measuring devices and constructed his own out of cigar boxes and other odds and ends. Simultaneously, his reading expanded to include practically every major civil engineering publication of the nineteenth and early twentieth centuries in a variety of languages.
In 1918, at the end of the World War I, Turkish institutions dismissed members of teaching staffs from the defeated nations, including Austria. Terzaghi then accepted a position at the American Robert College in Constantinople, teaching courses in thermodynamics and mechanical engineering. In his minimal spare time he constructed a testing laboratory, again using whatever materials were available, including many items from the college dump. Beans sometimes served as a surface of backfilling on experimental retaining walls and clay from the shores of the Bosporus provided samples that he used for the rest of his life. With primitive equipment and limited funds, he began to lay the foundations of his discipline. In doing so Terzaghi had absolute confidence in himself and his genius. With a profound sense of destiny, he became convinced that the time had arrived for a revolution in soils engineering and that, indeed, he was the instrument through which this revolution would unfold. The future would bear him out.27
The behavior of clays subjected to pressure, among the most unpredictable phenomena in soil mechanics, consumed Terzaghi's immediate post-War interest. Fabricating necessary apparatus, he made a simple consolidometer out of a metal ring with two sand filters sandwiching a clay sample and keeping it saturated with water. He subjected circular disks of clay about 3.4 inches in diameter and 0.4 inches thick to pressure under conditions that theoretically closely replicated those existing in the heart of a mass of moist clay below the groundwater table. While applying a constant load to the sample he took observations of the resulting compression at frequent intervals. Plotted readings produced compression curves for various clays under different loads over differing lengths of time. From these simple experiments Terzaghi rightly concluded that compressibility and permeability were the determining factors in settlement of clays and that these might vary greatly even in soils with identical grain size.
These and other investigations in Constantinople led Terzaghi to formulate his first and most fundamental contribution to soil mechanics theory: the principle of effective stress. Coordinating the influences of grain size, soil type, and water content into an integrated whole, effective stress provided the most accurate and comprehensive method for predicting soil failures and settlements.
Terzaghi's work slowly attracted wider attention. In 1920 the influential Engineering News-Record published Terzaghi's article "Old Earth-Pressure Theories and New Test Results" with a favorable review. This was his first exposure to an American audience.28 In 1924 he read a paper on his theory of the consolidation of clay at an international conference on applied mechanics in Delft, Holland, and received an enthusiastic response. All of this was a mere preliminary to his publication of Erdbaumechanik in 1925.
The year 1925 was a turning point in the history of geotechnical engineering as well as in Terzaghi's life. He was forty-two and his career was at a crossroads. The publication of Erdbaumechanik had attracted international attention, but his reputation and influence were still limited, partly because of his self-imposed "exile" in Constantinople for almost a decade. Concurrent research, especially in Germany, Holland, and Sweden, was considered paramount. Then again, America beckoned.
In 1916 the Massachusetts Institute of Technology (MIT) moved its campus, amid great fanfare and celebration, from the Back Bay of Boston across the Charles River to Cambridge. The noted engineer John R. Freeman played a major role in designing the new campus, which was called the "New Technology." Engineers and builders for the New Technology expected minimal settlements, but almost immediately the new buildings began to sink at an alarming rate. Cracks appeared and stories circulated that MIT students would someday enter on the second floor. Because MIT was one of the premier engineering institutions in the United States, such a failure was particularly embarrassing. It also emphasized the poor state of existing knowledge of soils and foundation engineering.
Erdbaumechanik had attracted Freeman's attention despite his lack of proficiency in German; he bought a number of copies and distributed them. Professor Charles M. Spofford, Head of the Department of Civil and Sanitary Engineering at MIT, was also familiar with Terzaghi's work, possibly through Freeman. On learning that Terzaghi had received a one-year leave of absence from Robert College in Istanbul, Freeman and Spofford recommended to MIT President Samuel Stratton that Terzaghi be offered a temporary position as a lecturer and research associate. They apparently wished to invite Terzaghi not only to teach but also to evaluate problems related to the settlement of the New Technology.29 Terzaghi accepted the position at a salary of $2,000, arriving in Boston in the fall of 1925. He did not return to Europe until 1929. In the four year interim, soil mechanics emerged as an accepted branch of engineering in the United States, with Terzaghi as its acknowledged father.
Terzaghi, on his second arrival in the United States, moved quickly to enhance further his American reputation. By the end of 1925 he had authored a series of eight articles for Engineering News-Record collectively titled "Principles of Soil Mechanics." His first works in English since 1920, they contributed greatly to his prominence among American engineers and scientists.30 The following year the Bureau of Public Roads engaged him as a research consultant, and he published a further series of seminal articles for that organization that introduced the new discipline of soil mechanics to the field of road construction.31 Simultaneously, through the influence of Freeman, a past president of the ASCE and of the American Society of Mechanical Engineers (ASME), he addressed professional engineering societies in Boston and New York and was introduced into their inner circles.32
Not all of the reaction, as could be expected in the case of any iconoclast, was favorable. In a "Letter to the Editor" of Engineering News-Record in November 1925, the Chief Engineer, Board of Water Supply of New York City, blasted Terzaghi's recently published articles, stating that the theories presented therein "appeal strongly to the imagination but...leave the mind adrift in a sea of wonder and amazement," and further that the "fragmentary evidence presented and the inconclusive argument advanced is a severe test for the native credulity of the initiated." Terzaghi's equally terse response noted sarcastically that his papers were not apt to be clear to "the unprepared mind."33
Meanwhile, at MIT Freeman and Spofford had become even more impressed with Terzaghi's work; Freeman was convinced that Terzaghi was a genius. Both Freeman and Spofford appealed to Stratton in 1926 to retain Terzaghi at the institute permanently and to provide him with the space and apparatuses for a laboratory. Stratton again accepted their recommendation despite his view of Terzaghi as a "prima donna" and admonished that "I can assure you that it is my intention to give Dr. Terzaghi an opportunity to demonstrate whether or not he is a genius."34
Stratton made good on his word. MIT established the laboratory facilities Terzaghi requested and provided him with research assistants, several of whom became his most ardent disciples. Now adequately supported in his efforts for the first time, Terzaghi supervised the improvement of his original, primitive testing methods and tools and invented new ones. He also developed classroom lecture techniques that set the standard, a particularly noteworthy achievement in that no texts for soil mechanics courses existed until the 1940s. And in addition to his work at MIT, the indefatigable Austrian continued to publish regularly, to address professional societies, to engage in private consulting work with the Bureau of Public Roads, and to act as a consultant in Latin America, including work for the Corps of Engineers in Panama.
By 1929 Terzaghi had borne out Freeman's supposition of genius: he was recognized not only as preeminent in his field, but as its founder. Further, laboratory research had shifted from a predominantly European focus to an impressive American body of work, with MIT as its nucleus. Had Terzaghi remained in Europe, the United States may well have lagged for decades in soils research.
Reflecting increased national interest in soil mechanics, in 1930 the ASCE appointed a Special Committee on Earths and Foundations, chaired by New York engineer Lazarus White. Terzaghi was nominally a member, but his input was indirect as he had returned temporarily to Vienna. Most actual research was performed at MIT under the auspices of Terzaghi's former students, notably Glennon Gilboy, Spencer J. Buchanan, Arthur Casagrande, and Leo Jürgenson. The committee's lengthy reports, published in 1933 and 1934, signified the ASCE's acceptance of Terzaghi's methods — quite an accomplishment considering their relative lack of recognition only a few years earlier.35
Terzaghi hardly spent all of his time at MIT at work. Sylvia Plath, author of The Bell Jar, was a gifted and accomplished writer before her suicide in 1963. Coincidentally, in the summer of 1927, A.S. Plath, mother of Sylvia Plath, had worked as a student assistant for Terzaghi at MIT. In 1978 A.S. Plath collected and published nearly seven hundred of her daughter's letters as Letters Home: Correspondence, 1950-1963. In her foreword to the book, A.S. Plath stated of Terzaghi:
I listened, fascinated, to his accounts of travel and colorful adventures, fully realizing that I was in the presence of a true genius in both the arts and sciences. I came away with my notebook filled with reading lists that led me to Greek drama, Russian literature, the works of Hermann Hesse, the poems of Rainer Maria Rilke, as well as the writings of the great world philosophers. That experience was to affect me the rest of my life, for I realized how narrow my world had been and that self-education could and should be an exciting lifelong adventure. It was the beginning of my dream.36
He was to make many such impressions during his life, both personally and professionally.
At the end of 1929 Terzaghi returned to Europe, first to the Soviet Union where he prepared a report on the locks of the Don-Volga Canal, then lectured in Moscow. In 1930 he accepted a professorship at the prestigious Technische Hochschule in Vienna, indeed a triumphant return to his homeland. Vienna for the next eight years was a mecca for European engineers interested in soil mechanics, and Terzaghi attracted students from as far away as Australia. Among his compatriots was M. Juul Hvorslev, later an employee of the Waterways Experiment Station, who began his research on the shearing resistance of clay in Vienna in 1933.37
Although Terzaghi did not return to the United States until 1936, former students maintained his tradition at MIT. Gilboy, Terzaghi's first research assistant in 1925 and 1926, assumed primary responsibility for continuing laboratory and classroom work in Terzaghi's absence, first as an assistant professor from 1929 to 1932, then as an associate professor from 1932 to 1937. He then went into private practice. In 1930 Gilboy typed his instructional notes, derived primarily from Terzaghi's lectures, and reproduced them with data and illustrations for use by MIT students. This represented the first crude text for soil mechanics instruction in the United States. Donald W. Taylor, who had joined the MIT faculty in 1932, expanded and revised Gilboy's notes in 1938 and again in 1939.38 (Taylor remained at MIT until his death in 1955.39) Buchanan, a Texas A&M graduate, was another prominent Terzaghi apprentice who remained in Cambridge until 1933. Of greatest long-term influence, however, was Casagrande's arrival in 1926.
Casagrande, like Terzaghi, was a native of Austria.40 Born in 1902, he received a civil engineering degree from the Vienna Technische Hochschule in 1924, then took a position in the university's hydraulics laboratory. However, low pay and the lack of opportunity in post-war Austria convinced Casagrande to risk moving to the United States, a decision that dismayed his family and colleagues. Jobless and with little money, he arrived in New York in April 1926, where he wrote to Spofford at MIT describing his Vienna experiences. Spofford forthwith invited Casagrande to Cambridge for an interview, and there Casagrande met Terzaghi. Intrigued by his fellow countryman, Terzaghi offered Casagrande a position as a research assistant. Thus began a partnership that lasted literally until Terzaghi's death in 1963. Terzaghi also got the twenty-four-year-old Casagrande a concurrent job as a consultant with the Bureau of Public Roads, a post he held until 1932. And like Terzaghi, Casagrande profoundly influenced that organization.41
Casagrande accompanied Terzaghi on his return to Europe in 1929, setting up Terzaghi's laboratory in Vienna while Terzaghi was in the Soviet Union. In 1929 and 1930 Casagrande, in addition to tending to responsibilities in Vienna, toured soils laboratories all over Europe. Hence, on his return to MIT in 1930, he had first-hand knowledge not only of the state of the art in soil mechanics in the United States, but also of the latest international developments.
In 1932 Harvard University lured Casagrande away from MIT to accept a lectureship. There in Pierce Hall he taught a two-semester course in soil mechanics, a course in foundation engineering, and in 1933 a course in soil testing. Harvard touted these as the first full-scale courses of their type, though much of the "groundwork" had already been done by Terzaghi, Gilboy, and others at MIT. In 1933 Casagrande also received a doctoral degree from the Vienna Hochschule based on his research and publications in the United States, and in 1934 Harvard elevated him to an assistant professorship. Only eight years had passed since his less-than-auspicious arrival in New York.
The year 1936 was another milestone in the history of geotechnical studies. Casagrande in 1935 had suggested to Harvard President James B. Conant that the university host an international conference on soil mechanics the following year to coincide with the tricentennial celebration of the founding of the university. Terzaghi, in Vienna, expressed doubt that such an undertaking would arouse sufficient interest. At Casagrande's insistence, however, Conant agreed to commit university funds and facilities, setting a June 1936 date. Casagrande then persuaded Terzaghi to lecture at Harvard during the spring term of 1936 and to preside over the proposed International Conference on Soil Mechanics and Foundation Engineering. Although Terzaghi's presence ensured instant credibility, Harvard anxiously awaited responses to invitations from engineering societies around the world.42
The success of the International Conference far exceeded the hopes of its planners. On 22 June 1936, 206 participants met at Pierce Hall to hear the thirty-four-year-old Casagrande's opening address. In triumph, he welcomed engineers from twenty-two countries, mostly Terzaghi's Soil Mechanics Laboratory, Vienna Technical University, 1935 European, but including delegations from China, Egypt, the Dutch East Indies, and Cuba. An additional 181 absentee members from such diverse locales as India, Japan, Palestine, Siam (now Thailand), and the Soviet Union paid dues but were unable to attend.43 For five days participants presented scholarly papers, attended discussions, disseminated reports, and viewed films. In addition to technical articles, conference literature included reports on the facilities, equipment, and personnel of soils laboratories globally. So substantive were these publications that Terzaghi later stated that the Proceedings of the [First] International Conference on Soil Mechanics and Foundation Engineering alone contained "a greater amount of quantitative information regarding soils and foundations than the entire engineering literature prior to 1910."44 On a more personal level, dinners, tours, and other social activities brought many internationally prominent individuals in soil mechanics together for the first time.
At various informal occasions, conference participants suggested that the membership form a permanent organization. Consequently, at the conference's conclusion, the membership passed resolutions providing for a permanent International Conference on Soil Mechanics and Foundation Engineering and for the election of an International Committee. Preliminary plans for a second meeting of the membership four years later were also discussed. The group elected Terzaghi president of the fledgling organization with Casa-grande as secretary. Philip Rutledge, also of Harvard, served as treasurer.45
Not all of the conference participants came from internationally prominent academic or engineering institutions. Among the luminaries at the conference, for example, two American participants — Spencer J. Buchanan and Lee H. Johnson, Jr. — represented a little-known facility on the outskirts of Vicksburg, Mississippi: the U.S. Army Corps of Engineers Waterways Experiment Station.
Although scientific study of the soil and its practical applications — soil mechanics — was relatively recent in origin, by 1936 the new discipline was ready to take its place among the major fields of engineering application. Remarkable changes, most of which dated from the beginning of the twentieth century, often little known even within the scientific community, had revolutionized the prospects for the study of soil mechanics. Its founders and disciples, men such as Atterberg, Terzaghi, Casagrande, Gilboy, and others, had established the theories, the methods, and the instrumentation of their discipline as integral elements in the engineering community. America demonstrated its new primacy by hosting the first great international conference of soil mechanics practitioners. Global in context, soil mechanics now stood on the brink of a new technological revolution, one in which it would emerge as an increasingly diverse and comprehensive field.