First textbooks on soil mechanics (1925) and engineering geology (1929)
In 1925 Austrian engineer and geologist Karl Terzaghi published the first textbook on soil mechanics in German, titled Erdbaumechanik (Soil Mechanics), while he was a professeor at Robert College in Constantinople. The appearance of this new branch of engineering knowledge led to an invitation for Terzaghi to serve as a visiting professor at the Massachusettes Institute of Technology between 1925-29, where their new Engineering Building was experiencing severe settlement problems. While he was in Cambridge, MA Terzaghi finished writing his second, and much larger text book, titled Ingenieurgeologie (Engineering Geology), with co-authors Karl A. Redlich and Rudolf Kampe, also in German, and released in 1929.
Failure of the St. Francis Dam (1928)
On the night of March 12/13, 1928 the St. Francis Dam, a 205 ft high curved concrete gravity structure built by the Los Angeles Department of Water & Power between 1924-26 failed catastrophically, killing more than 435 people. The civil engineering profession gained much from the public outcry and notoriety accompanying the St. Francis Dam disaster. Engineering geologic input was all but absent in the 1920s. Engineering geology became more accepted throughout the 1930s, with the Bureau of Reclamation (Frank Nickell) and Army Corps of Engineers (Edward B. Burwell) hiring their first engineering geologists in 1931. The California Division of Water Resources hired Chester Marliave as their chief geologist in 1938. In 1944 the U. S. Geological Survey established an Engineering Geology Branch, with Edwin B. Eckel as its first chief. By the early 1960s the California Department of Water Resources employed 56 engineering geologists; while the Army Corps of Engineers employed 230 geologists, geophysicists, and geographers working in a geotechnical staff of more than 850.
California Bearing Ratio Test (1928)
This was a novel test procedure developed by O. James Porter of the California Division of Highways in the late 1920s, in Sacramento. Porter took subgrade soils from proposed highway alignments and removed the fragments >1/4 inch, then compacted the soil in a cylindrical mold, six inches and diameter and five inches high (1/12th ft3). The samples were then submerged for a known period and then its resistance to a penetrating needle is measured, which is then compared to a “standard resistance” for crushed limestone. The determined resistance was then divided by the standard resistance and multiplied by 100, and referred to as the “California Bearing Ratio” (CBR). It was intended to evaluate subgrade strengths in the investigation of existing pavements and aid in selecting granular subbase beneath pavements.
The empirical test regimen was extrapolated over the succeeding two decades to estimate soil suitability for increasing wheel loads, far beyond what anyone imagined in 1928 [Porter O.J., 1939, The preparation of subgrades: Proc. Highway Res. Bd, Wash., v.18:2, 324-31; and ENR Mar 21, 1946, p.422].
During the Second World War Porter and the Army Corps of Engineers developed a protocol using the CBR test to evaluate subgrade strength for pavement design of airfields (O.J. Porter, 1942, "Foundations for Flexible Pavements," Proceedings, Highway Research Board, Washington, D.C., Dec; O.J. Porter & Co. (1949). Accelerated Traffic Test at Stockton Airfield Stockton, California (Stockton Test No. 2)," Corps of Engineers Sacramento District, Department of the Army).
From 1945 on, this method was used almost exclusively for flexible pavement design by the California Division of Highways and the Army Corps of Engineers because the Corps published simple pavement design correlations based upon the CBR values. These procedures ushered in the modern era of flexible pavement design, making Porter a high visibility figure.
First soil compaction standard (1929)
The first published standard for testing the mechanical compaction of earth was the California State Impact Method, or “California Impact Test.” It is now known as California Test 216 – “Method of Test for Relative Compaction of Untreated and Treated Soils and Aggregates.” It was developed in 1929 by O. James Porter, PE (1901-67) of the California Division of Highways in Sacramento. It presented a procedure for ascertaining the in-place wet density of aggregate baserock or compacted soil, and the preparation of a wet density versus soil moisture content curve (similar to what Proctor later proposed, using dry soil density, described below). The 216 test uses wet density as the measurement standard and has been modified six times since its original adoption in 1929 (see F.N. Hveem, 1958, “Suggested Method of Test for the Moisture-Density Relations of Soils (California Method),” Procedures for Testing Soils, ASTM, Philadelphia, pp. 136-39). The current version of the test used to be referred to as California Test Method No. 216-F, which employs energy input of 37,000 to 44,000 ft-lbs/ft3 of soil.
Committee on Earths and Foundations of ASCE (1929)
This committee of ASCE was formed in 1929 to foster research work in the emerging field of foundation engineering and soil mechanics. Its goal was to establish centers of research in the United States, I cooperation with the hydraulics laboratories at the University of Minnesota and Iowa State then engaged in the extensive flood and navigation improvements being promulgated along the Mississippi River. The principal members were: Lazarus White (of Spencer, White & Prentiss), chairman; George E. Beggs, M.L. Enger, R.J. Fog, Glennon Gilboy of MIT; Harry T. Immerman, Dimetri Krynine of Yale, sanitary engineer Frank A. Marston (Metcalf & Eddy), George Paswell, and Karl Terzaghi. The committee cooperated with Ralph Proctor of LADWP in approving the methodologies employed in developing his compaction tests for the Bouquet Canyon Dams in 1931-33, and with Prof. Gilboy on the hydraulic fill embankments designed by the Corps of Engineers for the Muskingum Project in Ohio in 1934-39, which included construction of the Corps’ first soil mechanics laboratory.
Adoption of engineering registration (1929)
Wyoming was the first state to register engineers, in 1907. A registration act for engineers had been passed by the State Assembly and Senate in Sacramento in 1925, but failed to gain the governor’s approval. Engineers promoting registration then formed the California Engineers Registration Association (CERA) on March 10, 1928, just two days before St. Francis Dam failed. As it turned out, their timing was fortuitous, as the public clamored for “something to be done” to better ensure public welfare and safety in the wake of the dam’s failure, which killed more than 435 people. CERA’s rolls swelled to 600 members by November and politicians were eager to demonstrate to the public that they were making sweeping changes to the status quo.
The Civil Engineers Registration Bill sailed through the state legislature in early July 1929 and became law on August 14th. Right up to its adoption, the act was vigorously opposed by a number of professional organizations, such as the American Institute of Mining Engineers and the American Society of Mechanical Engineers. The new act defined civil engineering as: “that branch of professional engineering which deals with the economics of, the use and design of materials of construction and the determination of their physical qualities; the supervision of the construction of engineering structures; and the investigation of the laws, phenomena and forces of nature; in connection with fixed works for: irrigation, drainage, water power, water supply, flood control, inland waterways, harbors, municipal improvements, railroads, highways, tunnels, airports and airways, purification of water, sewerage, refuse disposal, foundations, framed and homogeneous structures, bridges, and buildings. Furthermore, it included city and regional planning, valuations and appraisals, and surveying, other than land surveying as already defined in Statutes adopted by the legislature in 1891 (the first engineering registration act in the United States) and amended in 1907. It mandated that any person who practices or offers to practice civil engineering in any of its branches must be registered, and created The Board of Registration for Civil Engineers.
The act also directed that civil engineers in state service must be duly registered if they served in a capacity of ‘Assistant Engineer” or higher. The California Supreme Court quickly issued rulings that a contract for engineering services was invalid if the party undertaking to furnish engineering services was not registered and the State’s Appellate Courts ruled that engineers offering expert testimony should be registered, although it left the ultimate decision to the discretion of individual judges because some individuals had previously been qualified as experts, before passage of the registration law.
The act allowed the three-person board to develop standards for applicants over a two year period and to survey registration standards being employed by other states, for purposes of comparison. California made a comprehensive study of procedures practiced in 25 other states and seven Canadian provinces which had laws regulating engineering practice. The standard California adopted required applicants to be at least 25 years old, a legal resident of the state for at least one year (waived for those willing to sit for the examination), and demonstrate more than six years of professional practice, including at least one year of being in “responsible charge.” Applications had be supported by at least four engineers unrelated to the applicants by family or marriage, who could vouch for their character, experience, and technical competence, before they would be eligible to sit for the written examination. The board allowed a college degree in engineering to be the equivalent of four years’ experience, while graduate work in engineering could be credited for up to one year of experience (California did not offer doctorate degrees in civil engineering until sometime later, but this discrepancy has never been amended).
5,700 individuals applied for civil engineering registration during the first year applications were accepted, more than double what the state board had expected. Grandfathering was only allowed for the first 10 months, until June 30, 1930, after which time, applicants would be required to take a written examination. Many of those who applied for grandfathering were asked to appear before the three man board (appointed by the governor) for oral interviews. The basic determinant for “gray area” cases was whether applicants had entered the profession from the labor ranks of construction, this experience was not deemed to be ‘engineering experience.” Of those who applied the first year, 5,035 were accepted, providing the State of California with about one registered engineer for every thousand people then living in the state! It took California the next 25 years to register the next 5,000 civil engineers. Many states followed the examples demonstrated by New York and California. By 1932, 28 states had enacted professional registration for civil engineers. In 1947 Montana became the last state of the original 48 to adopt PE registration.
Over the years, the Board has experienced some major changes under the provisions of the Professional Engineers Act. The number of branches of engineering regulated by the Board has increased, and the status of some of the older branches has changed. When electrical and mechanical engineering were first covered by the registration law in 1947, the law only affected the use of the titles. In 1967, the Act was amended to regulate the practice of those branches, as well as the titles. In the late 1960s and early 1970s, the Act was also amended to give the Board the right to accept additional branches of engineering into the registration program. The additional categories were for the purpose of regulating the use of the titles of those engineering branches. Between 1972 and 1975, the Board expanded the registration program to include nine additional branches of engineering under its jurisdiction. In 1986, at the Board's request, the authority to create new title registration branches was removed from the Act. In the late 1990s and early 2000s, four of the title registration branches were deregulated. In 2009 the Board of Registration for Geology & Geophysics was absorbed into the Board of Registration for Professional Engineers and Land Surveyors (BORPELS). On January 1, 2011 it was renamed the Board for Professional Engineers, Land Surveyors, and Geologists.
California Dam Safety Act of 1929
In the wake of the St. Francis Dam failure, the state passed a much more comprehensive Dam safety Act on August 14, 1929. The Act empowered the State Engineer to review all non-federal dams > 25 feet high or which impound > 50 acre acre-feet of water. The act also allowed the State to employ consultants, as deemed necessary. The State Engineer was given $200,000 and instructed to examine all dams in California within three years and issue recommendations. The State Engineer was given full authority to supervise the maintenance and operation of all non-federal dams (exempting those constructed by the Army Corps of Engineers and the Bureau of Reclamation)
Between August 1929 and November 1931 the State Engineer inspected 827 dams. One third were deemed to exhibit adequate safety, while another third were recommended for further examination, such as borings or subaqueous inspection, before a determination could be made. The remainder, roughly, another third, were ascertained to be in need of alterations, repairs or changes; frequently involving spillway capacity.
After this there followed a six-year program of dam safety inspection, which were concluded in July 1936. During this period 950 dams were inspected; with 588 of these dams being under the State’s jurisdiction. One third of these dams were found in need of repairs. New dam construction was also placed under state observance from August 1929 forward.
Evolution of Porter Soil Samplers (1930-47)
In 1930 Omer James Porter of the California Division of Highways began developing a retractable plug sampler, known as the “Porter Type Soil Sampler.” The device then underwent a series of improvements over the next six years, based on experience. This inexpensive sampler was widely employed over the next 50 years to recover 1-inch to 2-inch diameter samples. The device employed a lockable plug at the foot of the sampler, which remained in place while the sampler rings were driven ahead to the desired depth. When the desired depth interval was reached, the plug was retracted up inside the sample barrel, and the open sample barrel advanced ahead of its starting position, to recover between 18 inches to five feet of relatively undisturbed soil sample (depending on diameter).
The device enjoyed much success because a vacuum was maintained during driving, helping recovery of samples. Porter Samplers came in a variety of diameters and lengths. The one inch diameter samplers were designed for manual operations in soft soils and were limited in their application to depths of up to 60 feet. This sampler employed an outside diameter of just 1.25 inches with 1-inch sampler barrel. The one-inch sampler was usually set up by a three man crew using a portable tripod.
In 1933 Porter introduced a three-inch diameter sampler intended to recover undisturbed two-inch diameter soil samples. The sampler was five feet long, allowing a continuous sample to be taken of that length. Two samplers were normally assigned to each rig so that drilling and sampling operations could be sustained, without interruption. The sampler was fitted with segmented brass liners, 2- inches in diameter and two inches high, which after sampling, were separated using a piano wire saw (see T.E. Stanton, 1936, An Improved Type of Soil Sampler for Explorations of Soil Conditions and Soil Sampling Operations, Proc 1st ICSMFE, Cambridge, v.1, p.13-15).
The two-inch sampler required power equipment and was originally developed for the recovery of undisturbed samples of clay for the San Francisco Oakland Bay Bridge project. Between 1933-36 more than 13,000 lineal feet of samples were taken from 232 borings for the Bay Bridge, as well as other highway projects. These samplers were used to a maximum depth of 232 feet on the Bay Bridge. A larger sampler was also fabricated to recover four-inch diameter samples for those situations that warranted larger diameter samples, for shear strength and consolidation testing.
The two and four-inch samplers were used with truck mounted drilling rigs. For subaqueous sampling beneath San Francisco Bay, the drill rigs were tied to barges and steel well casings was inserted through the waters and driven 7 to 90 feet into the seafloor. The depth of penetration depended on the presence of running sands (ENR, June 4, 1936, p. 804-05). Brass caps were used to seal the individual sample segments upon recovery. The four-inch sampler required heavier equipment to operate, so was only used in situations that justified the additional cost.
During World War II Porter developed “all-in-one” truck-mounted drilling rigs with retractable masts and a suitable array of Porter Samplers. These were intended to provide a more robust system of drilling and recovery of continuous soil samples for the Navy out in the Pacific, where they were having difficulties drilling through porous and cavernous coral, causing loss of drilling circulation. These rigs were equipped with three-foot long samplers, intended to recover continuous two-inch diameter samples using three-foot sampling rounds. The rigs could develop 20,000 pounds force to aid sampling at depth. After the war (1946-47) Porter developed even heavier truck-mounted drilling rigs that could exert pressures of up to 30,000 pounds up or down, which doubled as exploration and foundation drilling rigs, which could be used to drill large diameter caissons (see O.J. Porter, Taking Soil Samples by the Soil Tube Method in November 1947 issue of Roads & Bridges).
In the mid-1950s Porter began marketing a 3-inch diameter sampler capable of recovering 2.5-inch diameter samples, which could be used with 6-inch, 2-inch, or 1-inch high brass rings. This was intended to compete with the Modified California Sampler of Dames & Moore, described later.
First lecture notes in English on soil mechanics (1929-30)
In October 1929 Professor William S. Housel in the Department of Civil Engineering at the University of Michigan prepared a 117 page text titled “A Practical Method for the Selection of Foundations Based on Fundamental Research in Soil Mechanics,” released as University of Michigan Engineering Research Bulletin No. 13 (and published by Waverly Press in Baltimore). This svolume was primarily focused on the determination of soil bearing capacity for spread footings, and resulted from a cooperative project between the university and the Wayne County Road Commission in Detroit, between 1927-29. This book was used by Professor Fred Converse at Caltech when he taught his forst soil mehcanics course in the spring semester of 1934.
In 1930 Glennon Gilboy, Sc.D., an Assistant Professor of Soil Mechanics at MIT, self-published a 62-page monograph titled “Notes on Soil Mechanics: Prepared for Use of Students of the Msssachusetts Institute of Technology,” which he copyrighted as a first edition. Gilboy had been a doctoral student of Professor Karl Terzaghi while he was as a visiting scholar at MIT, from 1925-29. This work was essentially America’s first English volume on the broader spectrum of soil mechanics, which included chapters addressing soil structure, mechanical analysis, permeability, and consolidation theory. It featured detailed ink drawings of the various laboratory tests then in use, along with example calculations, including Gilboy’s doctoral research on consolidation of the clay core of the massive Germantown Dam near Dayton, Ohio, placed using hydraulic fill technology in the early 1920s.
Development and deployment of accelographs (1931)
During the late 1920s John R. Freeman of MIT’s Board of Governors and Romeo R. Martel of Caltech actively corresponded and promoted the idea of developing strong motion sensors, after the damaging earthquakes in Tokyo in 1923 and Santa Barbara in 1925. Freeman’s political clout in Washington, DC eventually secured the necessary funding to see the project approved and funded. This is why Freeman is generally credited as being the father of the modern accelograph.
Frank Wenner of the U.S. Bureau of Standards developed the seismic unit and H.E. McComb and D.L. Parkhurst of the U.S. Coast & Geodetic Survey (USC&GS) developed the recording unit of the world’s first strong motion accelograph, known as the “Montana accelograph,” in 1931. It was based on the design of the Wood-Anderson seismograph developed at the Pasadena Seismological Laboratory of the Carnegie Institution by Harry O. Wood and John Anderson in 1922 (formally absorbed into Caltech in 1931).
Installation of these accelographs began in 1932 by the newly established Seismological Field Survey of the USC&GS, based in California (these activities were transferred to the USGS in 1975). By March 1933, eight units had been installed in California. Three instruments, in Long Beach, Vernon, and Los Angeles, were triggered during the March 10, 1933 M 6.2 Long Beach earthquake, providing the first strong motion records of near field motions, and were important records for many years thereafter, because they emanated from shallow strike-slip faulting, typical of coastal California.
For many years thereafter, Terrametrics of Pasadena was the leading manufacturer of strong motion recorders, because of their proximity to Caltech and the nation’s largest market for such instruments, in the high rise strictures and bridges of the Los Angeles and San Francisco metro areas.
Earthquake Damage and Earthquake Insurance (1932)
Around 1925 John R. Freeman (BSCE 1876, MIT), a nationally prominent waterworks engineer and fire insurance executive (who patented the interior fire sprinkler in 1886), began researching earthquakes when he discovered that nothing was mentioned about them in the structural engineering texts of that era. Freeman was a long-time member of the MIT Board of Trustees, a fellow of the National Academy of Sciences, and the man that brought Karl Terzaghi from Istanbul to MIT in 1925 to solve the foundation settlement problems on the MIT campus. He began corresponding with an array of luminaries who had studied earthquakes, including Professor Tachu Naito in Japan and Romeo R. Martel at Caltech, whom he met face to face at the World Engineering Conference in Tokyo in 1929. Upon his return from this trip he began working on a book that compiled all the known information on earthquake loads on structures, with the desire to summarize how structures such as buildings, could be better designed to resist earthquake loads. He worked non-stop on this project for the next few years, eventually completing the classic tome Earthquake Damage and Earthquake Insurance, which was released shortly before Freeman died, on October 6, 1932. This was about six months before the destructive Long Beach earthquake. His book formed the basis of modern earthquake engineering until the First World Congress on Earthquake Engineering convened in 1953.
Structural Engineer title act (1932)
In September 1932 the California Board of Registration for Civil Engineers begin granting the special title “structural engineer” (S.E.), which required applicants to demonstrate three to five years of responsible charge of structural engineering projects to be eligible to sit for a special examination. But, those individuals who could document more than five years of experience in “responsible charge” were duly grandfathered into the title. The first SE exam wasn’t offered until several years later, in 1934.
In March 1933 the Long Beach earthquake killed 115 people and caused $50 million in damage, mostly to unreinforced masonry structures, such as public school buildings. Within a month of the quake, the California Legislature passed the Field Act (described below), which empowered the Office of the State Architect to undertake whatever measures it deemed appropriate to ensure safe design and construction of public school buildings, which included requirements for plans prepared by a certified architect or structural engineer and set requirements for lateral earthquake loads, which depended on location. The Field Act left a lasting imprint on how structural engineers would be qualified in California; requiring them to demonstrate an understanding of analyses, designs, and consultations involving structural engineering principles associated with the application of seismic loads.
A companion legislation called the Riley Act (described below) was also enacted in 1933, which required local agencies in California to establish their own building and inspection departments (the first Uniform Building Code had appeared in 1927, but only a handful of the state’s largest cities had adopted it). The Riley Act also required all new construction to be designed to withstand an earthquake acceleration of at least 0.02g, but also allowing municipalities the discretion to employ even higher values, as they deemed appropriate.