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As pointed out by McDonald and Skempton (1),3 the phenomenon of consolidation in clays has been understood qualitatively for a long time. Around 1810 Telford preloaded the 55-ft bed of soft clay on which the eastern sea-lock of the Caledonian canal was to be founded, by building an embankment and allowing it to settle “for the purpose of squeezing out the water and consolidating the clay,” before constructing the lock (2). According to the writings of Sooy Smith (3), engineers in Chicago realized before the turn of the 20th century that the settlements of their tall buildings were due to the consolidation of clay beneath the foundations. However, it was not until 1923 that a quantitative approach first became possible, as a result of the publication of Terzaghi's one-dimensional consolidation equation (4). In connection with the development of his theory, Terzaghi (5) designed an apparatus for measuring the consolidation of clay (called an oedometer) which, in its essential features, is paralleled by the modern one-dimensional consolidometer. While the effects of remolding on the properties of clays were recognized before 1916 (6),4 and while Terzaghi was fully cognizant of the need for obtaining undisturbed samples before 1927 (7,8), the significance of this phenomenon was not fully realized until 1932, when Casagrande published his classic paper on the structure of clay (9). Although settlement estimates of structures were being made sporadically in the late 1920's (10,11,12 13,14),5 it was not until 1933, when the ASCE Committee on Earths and Foundations published its report giving descriptions of calculation procedures (15), that settlement analyses for structures on clay based on (a) the Boussinesq stress distribution theory, (b) the Terzaghi theory of consolidation, and (c) oedometer tests on undisturbed samples may be said to have entered the field of engineering practice (1).
Leonards, G. A.
Professor of Soil Mechanics, Purdue University, Lafayette, Ind.
Ramiah, B. K.
Engineer, Am. Testing and Engineering Corp., Indianapolis, Ind.