The Power of Education

April 8, 2008 pukul 10:53 am | Ditulis dalam Uncategorized | Tinggalkan komentar

I believe in the power of science and knowledge, but I believe more in education (tarbiyyah),” Qutb

“Subsurface engineering is an art; soil mechanics is an engineering science……We would do well recall and examine the attributes necessary for the successful practice of subsurface engineering. There are at least three : knowledge of precedents, familiarity with soil mechanics and a working knowledge of geology…”(Peck, 1962)

Geotechnical Engineering— A Historical Perspective III

Oktober 23, 2008 pukul 6:35 am | Ditulis dalam Kuliah Geoteknik | Tinggalkan komentar
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4. Modern Geotechnical Engineering, after 1927
The publication of Erdbaumechanik auf Bodenphysikalisher Grundlage by Karl Terzaghi in 1925 gave birth to a 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, which was then the capital of theAustrian province of Bohemia. In 1904 he graduated from the Technische Hochschule in Graz, Austria, with an undergraduate degree in mechanical engineering. After graduation he served one year in the Austrian army. Following his army service, Terzaghi studied one more year, concentrating on geological subjects. In January 1912, he received the degree of Doctor of Technical Sciences from his alma mater in Graz. In 1916, he accepted a teaching position at the Imperial School of Engineers in Istanbul. After the end of World War I, he accepted a lectureship at the American Robert College in Istanbul (1918–1925). There he began his research work on the behavior of soils and settlement of clays and on the failure due to piping in sand under dams. The publication Erdbaumechanik is primarily the result of this research.

In 1925, Terzaghi accepted a visiting lectureship at Massachusetts Institute ofTechnology, 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 to 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. The first conference of the International Society of Soil Mechanics and Foundation Engineering (ISSMFE) was held at Harvard University in 1936 with Karl Terzaghi presiding. 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 penetrometer, centrifuge testing, consolidation settlement, elastic stress distribution, preloading for soil improvement, frost action, expansive clays, arching theory of earth pressure, 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. To that effect, in 1985, Ralph Peck wrote
that “few people during Terzaghi’s lifetime would have disagreed that he was not only the guiding spirit in soil mechanics, but that he was the clearing house for research and application throughout the world. Within the next few years he would be engaged on projects on every continent save Australia and Antarctica.” Peck continued with, “Hence, even today, one can hardly improve on his contemporary assessments of the state of soil mechanics as expressed in his summary papers and presidential addresses.” In 1939, Terzaghi delivered the 45th James Forrest Lecture at the Institution of Civil Engineers, London. His lecture was entitled “Soil Mechanics— A New Chapter in Engineering Science.”


Geotechnical Engineering— A Historical Perspective II

Oktober 23, 2008 pukul 6:21 am | Ditulis dalam Kuliah Geoteknik | Tinggalkan komentar
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1.Preclassical 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 semiempirical 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 natural slope is what we now refer to as the angle of repose. According to this study, the natural slope of clean dry sand and ordinary earth were 31 and 45, respectively. Also, the unit weight of clean dry sand and ordinary earthwere recommended to be 18.1kN/m3 (115 lb/ft3) and 13.4kN/m3 (85 lb/ft3), respectively. No test results on clay were reported. In 1729, Bernard Forest de Belidor (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 that was a follow-up to Gautier’s (1717) original study.

The first laboratory model test results on a 76-mm-high ( 3 in.) retaining wall built with sand backfill were reported in 1746 by a French engineer, Francois Gadroy (1705–1759), who observed the existence of slip planes in the soil at failure. ) Gadroy’s study was later summarized by J. J. Mayniel in 1808.

2. Classical Soil Mechanics—Phase I (1776 –1856)
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 earth 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 this analysis, Coulomb used the laws of friction and cohesion for solid bodies. In 1820, special cases of Coulomb’s work were studied by French engineer Jacques Frederic
Francais (1775–1833) and by French applied mechanics professor Claude Louis Marie Henri Navier (1785–1836). These special cases related to inclined backfills and backfills supporting surcharge. In 1840, Jean 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 f for soil friction angle.
He also provided the first ultimate bearing-capacity theory for shallow foundations. In 1846 Alexandre Collin (1808–1890), an engineer, provided the details for deep slips in clay slopes, cutting, and embankments .
Collin theorized that in all cases the failure takes place when the mobilized cohesion exceeds the existing cohesion of the soil. He also observed that the actual failure surfaces could be approximated as arcs of cycloids.
The end of Phase I of the 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. This study provided a notable theory on earth pressure and equilibrium of earth masses.

Rankine’s theory is a simplification of Coulomb’s theory.

3. Classical Soil Mechanics—Phase II (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 Henri Philibert Gaspard Darcy (1803–1858). In 1856, he published a study on the permeability of sand filters (see Chapter 6). Based on those tests, Darcy defined the term coefficient of permeability (or hydraulic conductivity) of soil, a very
useful parameter in geotechnical engineering to this day.
Sir George Howard Darwin (1845–1912), a professor of astronomy, conducted laboratory tests to determine the overturning moment on a hingedwall 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, semiinfinite, elastic, and isotropic medium (see Chapter 9). In 1887, Osborne Reynolds (1842–1912) demonstrated the phenomenon of dilatency in sand.

Geotechnical Engineering— A Historical Perspective I

Oktober 22, 2008 pukul 2:23 am | Ditulis dalam Kuliah Geoteknik | Tinggalkan komentar
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Recorded history tells us that ancient civilizations flourished along the banks of rivers, such as the Nile (Egypt), the Tigris and Euphrates (Mesopotamia), the Huang Ho(YellowRiver, 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 (in what became Pakistan after 1947). During the Chan dynasty in China (1120 B.C. to249B.C.) 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 (Kerisel,1985). Ancient Greek civilization used isolated pad footings and strip-and-raft foundations for building structures. Beginning around 2750 B.C., the five most important pyramids were built in Egypt in a period of less than a century (Saqqarah, Meidum, Dahshur South and North, and Cheops). This posed formidable challenges regarding foundations, stability of slopes, and construction of underground chambers. With the arrival of Buddhism in China during the Eastern Han dynasty in 68 A.D., thousands of pagodas were built. Many of these structures were constructed on silt and
soft clay 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 of problems related to soil-bearing capacity in the construction of structures prior to the 18th century is the Leaning Tower of Pisa in Italy. (See Figure 1.1.) Construction of the tower began in 1173 A.D. when the Republic of Pisa was flourishing and continued in various stages for over 200 years. The structure weighs about 15,700 metric tons and is supported by a circular base having a diameter of 20 m (66 ft). Recent investigations showed that a weak clay layer exists at a depth of about 11m(36 ft) belowthe ground surface compression, which caused the tower to tilt. It became more than 5 m ( 16.5 ft) out of plumb with the 54 m ( 179 ft) height. The tower was closed in 1990 because it was feared that it would either fall over or collapse. It recently has been stabilized by excavating soil from under the north side of the tower. About 70 metric tons of earth were removed in 41 separate extractions that spanned the width of the tower. As the ground gradually settled to fill the resulting space, the tilt of the tower eased. The tower now leans 5 degrees. The half-degree change is not noticeable, but it makes the structure considerably more stable.

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 to 1776 A.D.)
2. Classical soil mechanics—Phase I (1776 to 1856 A.D.)
3. Classical soil mechanics—Phase II (1856 to 1910 A.D.)
4. Modern soil mechanics (1910 to 1927 A.D.)


Oktober 17, 2008 pukul 6:18 am | Ditulis dalam Kuliah Geoteknik | 1 Komentar
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Apakah yang dimaksud dengan tanah?
Definisi tentang tanah yang dipergunakan oleh seorang insinyur sipil agak berbeda degan definisi yang digunakan oleh seorang ahli geologi, soil scientist ataupun orang awam. Seorang insinyur sipil menganggap tanah termasuk semua bahan organik dan anorganik yang ada diatas bedrock. Terdapat banyak perbedaan dasar dalam terminologi dan definisi yang digunakan mengklasifikasikan dan menjelaskan perlikau tanah secara fisika dan kimia.

Sifat-sifat teknis tanah pada dasarnya merupakan fungsi dari siafat-sifat kimia dan fisika dari bahan induknya, tipe pelapukan yang telah membentuk tanah, apakah deposit berupa tanah residual atau tanah tertransport, cara trasportasi dan deposisinya, sejarah tegangan dari tanah deposit. sejarah kimia dari tanah air pori dan sejarah dari water tablenya.

For engineering purposes, soil is defined as the uncemented aggregate of mineral grains and decayed organic matter (solid 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 engineers 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 mechanics is the branch of science that deals with the study of the physical properties of soil and the behavior of soil masses subjected to various types of forces. Soils 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.

Berdasarkan asalnya, tanah dapat dibagi secara luas menjadi tanah organik dan tanah anorganik. Tanah organik adalah campuran yang mengandung bagian-bagian yang cukup berarti berasal dari lapukan dan sisa tanaman dan kadang-kadang dari kumpulan kerangka dan kulit organisma kecil. Tanah anorganik berasal dari pelapukan batuan secara kimia ataupun fisika.

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