For engineering purposes, soil is defined as the uncemented aggregate of mineral grains and decayed organic matter (soil particles) with liquid and gas in the empty spaces between the solid particles. Soil is used as a construction material in various civil engineering projects, and it supports structural foundations. Thus, civil engineer must study the properties of soil, such as its origin, grain-size distribution, ability to drain water, compressibility, shear strength, and load-bearing capacity. Soil engineering is the application of the principles of soil mechanics to practical problems. Geotechnical engineering is the subdiscipline of civil engineering that involves natural materials found close to the surface of the earth. It includes the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures, and earth structures.

1.1   Geotechnical engineering prior to the 18^th century

Recorded history tells that ancient civilizations flourished along the banks of rivers, such as the Nile (Egypt), the Tigris and Euphrates (Mesopotamia), the Yellow River (China), and the Indus(India). Dykes dating back to about 2000 B.C. were built in the basin of the Indus to protect the town of Mohenjo Dara(it became Pakistan after 1947). During Han Dynasty in China, many dykes were built for irrigation purposes. There is no evidence that measures were taken to stabilize the foundations or check erosion caused by floods. Ancient Greek civilization used isolated pad footings and strip-raft foundations for building structures. With the arrival of Buddhism in China during the Easter Han Dynasty in 68 A.D., thousands of pagodas were built. Many of these structures were constructed on silt and soft layers. In some cases, the foundation pressure exceeded the load-bearing capacity of the soil and thereby caused extensive structural damage.

One of the most famous examples off problems related to soil-bearing capacity in the construction of structures prior to the 18^th century is the Leaning Tower of Pisa in Italy. After encountering several foundation-related problems during construction over centuries past, engineers and scientists began to address the properties and behavior of soils in a more methodical manner starting in the early part of the 18^th century. Based on the emphasis and the nature of study in the area of geotechnical engineering, the time span extending from 1700 to 1927 can be divided into four major periods (Skempton, 1985):

1.       Pre-classical(1700-1776);

2.       Ⅰ(1776 to 1856 A.D.);Classical soil mechanics-Phase

3.       Ⅱ(1856 to 1910 A.D.);Classical soil mechanics-Phase

4.       Modern soil mechanics (1910 to 1927 A.D.)

1.2   Pre-classical period of soil mechanics (1700-1776)

This period concentrated on studies relating to natural slope and unit weights of various types of soils as well as the semi-empirical earth pressure theories. In 1717 a French royal engineer, Henri Gautier (1660-1737), studied the natural slopes of soils when tipped in a heap for formulating the design procedures of retaining walls. The According to this study, the natural slopes of clean dry sand and ordinary earth were 31° and 45°,respectively. Also, the unit weights of clean dry sand and ordinary earth were recommended to be 18.1kN/m³ and 13.4kN/m³, respectively. In 1729, Bernard Forest de Beldor (1671-1761) published a textbook for military and civil engineers in France. In the book, he proposed a theory for lateral earth pressure on retaining walls, he also specified a soil classification system.

The first laboratory model test results on a 76-mm-high retaining wall built with sand backfill were reported in 1746 by a French engineer, Francois Gadroy(1705-1759), who observed the existence of a slip planes in the soil at failure.

1.3   Ⅰ(1776 to 1856 A.D.)Classical Soil Mechanics-Phase

During this period, most of the developments in the area of geotechnical engineering came from engineers and scientists in France. In the preclassical period, practically all theoretical considerations used in calculating lateral pressure on retaining walls were based on an arbitrarily based failure surface in soil. In his famous paper presented in 1776, French scientist Charles Augustin Coulomb (1736-1806) used the principles of calculus for maxima and minima to determine the true position of the sliding surface in soil behind a retaining wall. In his analysis, Coulomb used the laws of friction and cohesion for slid bodies. In 1820, special cases of Coulomb’s work were studied by French engineer Jacques Frederic Francais and by French applied mechanics professor Henri Navier. These special cases related to inclined backfills and backfills supporting surcharge. In 1840, Victor Poncelet(1788-1867), an army engineer and professor of mechanics, extended Coulomb’s theory by providing a graphical method for determining the magnitude of lateral earth pressure on vertical and inclined retaining walls with arbitrarily broken polygonal ground surfaces. Poncelet was also the first to use the symbol φfor soil friction angle. He also provided the first ultimate bearing-capacity theory for shallow foundations.

The end of PhaseⅠof classical soil mechanics period is generally marked by the year 1857 of the first publication by William John Macquorn Rankine (1820-1872), a professor of civil engineering at the University of Glasgow, Rankine’s theory is a simplification of Coulomb’s theory.

1.4 Classical soil mechanics-PhaseⅡ(1856-1910)

Several experimental results from laboratory tests on sand appeared in the literature in this phase. One of the earliest and most important publications is one by French engineer Darcy (1803-1858). In 1856, he published a study on the permeability of sand filters. Based on those tests, Darcy define the term coefficient of permeability (or hydraulic conductivity) of soil, a very useful parameter in geotechnical engineering to this day.

Table 1 Important studies on clays (1910-1927)

Sir George Howard Darwin (1845-1912), a professor of astronomy, conducted laboratory tests to determine the overturning moment on a hinged wall retaining sand in loose and dense states of compaction. Another noteworthy contribution, which was published in 1885 by Joseph Valentin Boussinesq (1842-1929), was the development of the theory of stress distribution under loaded bearing areas in a homogeneous, semi-infinite, elastic, and isotropic medium. In 1887, Osborne Reynolds demonstrated the phenomenon of dilatancy in sand.

1.5   Modern soil mechanics

In this period, results of research conducted on clays were published in which the fundamental properties and parameters of clays were established. The most natable publications are given in Table 1.

 

1.6 Geotechnical Engineering after 1927

The publication of Erdbaumechanik Auf Bodenphysikalisher Grundlage by Karl Terzaghi in 1925 gave birth to new era in the development of soil mechanics. Karl Terzaghi is known as the father of modern soil mechanics, and rightfully so. Terzaghi was born on October 2, 1883 in Prague, in 1904, he graduated from the Technische Hochschule in Graz, Austria, with an undergraduate degree in mechanical engineering. After his one-year service in the Austrian army, Terzaghi studied one more year concentrating on geological subjects. In January 1912, he received the degree of Doctor of Technical Science in Graz. In 1916, he accepted a teaching position at the Imperial School of Engineers in Istanbul. In 1925, Terzaghi accepted a visiting lectureship at Massachusetts Institute of Technology, where he worked until 1929. During that time, he became recognized as the leader of the new branch of civil engineering called soil mechanics. In October 1929, he returned Europe to accept a professorship at the Technical university of Vienna, which soon became the nucleus for civil engineers interested in soil mechanics. In 1939, he returned to the United States to become a professor at Harvard University.

Terzaghi presided the first conference of the International Society of Soil Mechanics held at Harvard University in 1936. It was through the inspiration and guidance of Terzaghi over the preceding quarter-century that papers were brought to that conference covering a wide range of topics, such as shear strength, effective stress, in-situ testing, Dutch cone penetration, centrifuge testing, consolidation settlement, elastic stress distribution, preloading for soil improvement, frost action, expansive clays, arching theory of earth pressure, and soil dynamics and earthquakes. For the next quarter-century, Terzaghi was the guiding spirit in the development of soil mechanics and geotechnical engineering throughout the world.

Following are some highlights in the development of soil mechanics and geotechnical engineering that evolved after the first conference of the ISSMFE in 1936:

·Publication of the book Theoretical Soil Mechanics by Karl Terzaghi in 1943(Wiley, New York);

·Publication of the book Soil Mechanics in Engineering Practice by Karl Terzaghi in 1948(Wiley, New York);

·Publication of the book Fundamentals of Soil Mechanics by Donald W.Taylor in 1948(Wiley, New York);

·Start of the publication of Geotechnique, the international journal of soil mechanics in 1948 in England;

·Presentation of the paper on φ=0 concept for clays by A.W.Skempton in 1948;

·Publication of the book The Measurement of Soil Properties in the Triaxial Test by A.W. Bishop and B.J.Henkel in 1957.

Since the first conference in 1936, except for a brief interruption during World War Ⅱ,the ISSMFE conferences have been held at four-year intervals. In 1997, the ISSMFE was changed to ISSMGE(International Society of Soil Mechanics and Geotechnical Engineering) to reflect its true scope. Table 1.2 gives the location and year in which each conference of ISSMFE/ISSMGE held and the presidents of the society.