Geotechnical talks

It can be differentiated on the basis of following parameters

1. Flexibility:

Gabion: Being highly flexible structure due to its double twists hexagonal mesh, it is not immediately affected by occurrence of any type of settlement in foundation strata, hence suitable for yielding foundation.

Reinforced Cement Concrete: Being rigid construction any settlement of foundation leads to development of cracks and hence suitable only for non-yielding foundation.

2. Permeability:

Gabions: High percentage of voids (30%) makes the structure highly permeable hence no
water pressure develops. There is also no uplift pressure, making structure more
stable. Their ability to combine drainage and retention functions makes them ideal
retaining structures.

Reinforced Cement Concrete: Weep holes provided in structures tend to clog. Subsequently, water pressure develops at the rear of the wall, thereby rendering the structure unstable.

3. Overhead Expenses:

Gabions: Since only stones/rubble is the only fill material required, hence the excess material from rock cutting can be used instead of disposing it in to the valley. Also this doesn't require any stone crusher or batching plant thereby
reducing the overhead expenses.

Reinforced Cement Concrete: Concrete being a mixture of aggregates and cement, the excess material from rock cutting has to be processed through a crusher and batching plant, thereby increasing the overhead expenses.

4. Noise Absorbent:

Gabions: Behavior Porosity of the structure absorbs the sound to a great level (18 – 30 decibels)hence reducing the sound pollution,ensuring environmental friendly
approach.

Reinforced Cement Concrete: Being rigid it does not help in absorbing sounds. The structure reflects sound waves, which may lead to sound pollution.

5. Environmental Friendliness:

Gabions: Structure is eco-friendly. Over a period of time natural cementation takes place in the structure, helping grass & plants to grow on & giving it natural beauty
along with making structure more stable, due to reinforcement with the plant
roots.

Cement concrete construction has proved to be a largely non-eco friendly
technology. Growth of vegetation leads to cracks thereby making the structure
more unstable.

6. Cost Effectiveness:

Gabions: Cost savings by using this solution is of the order ranging from
30% to 50%, since less time is required for execution.

As the work involves cost of cement, aggregates, steel, shuttering, mixers,
vibrators, water etc, it becomes more expensive.

Posted by Sandeep Sahu at 9:39 AM 0 comments  

Labels: Gabions

Project:

Mundra Port Special Economic Zone Limited (MPSEZL), a subsidiary of Adani Group is developing a new port named west port at Mundra, Gujarat. The port will serve the purpose of supplying coal to Tata Power (4000 MW) and Adani Power (4620 MW) located near by. Various infrastructure facilities like jetties, coal stack yard with stacker reclaimer and various storage buildings is being developed in the port.

Soil condition:

The sub soil consists of loose to medium dense sand layer of thickness 6.5 m having SPTN value in the range of 12 to 20, this is followd by medium to dense sand layer having SPTN more than 30.

Solution:

Dry top feed vibro replacement was proposed below the rails of stacker reclaimer (Ref: Fig 1) in order to mitigate liquefaction potential and overcome the problem of differential settlement. The site comes under sesimic zone 5 (AH = 0.36g).

Design Criteria:

Vibro replacement columns of nominal diameter of 600 mm were installed to a depth of 8 meters. An area replacement ratio of 16% was used.

Verification:

Single column routine load test were performed for a loading of 10t/m2. The result was found well within permissible limit.

Posted by Sandeep Sahu at 2:34 AM 0 comments  

Labels: Stone Column

This post is devoted to Karl Terzaghi. Karl Terzaghi who is known as father of geotechnical engineering is among my favorites. His concepts of soil and its behavior had given this world entirely new outlook towards soil mechanics. I would like to post brief history of Karl Terzaghi.

Biography of Karl Terzaghi:
Karl Terzaghi was born in Prague on 2nd October1883. In 1904, he graduated from the Technische Hochschule in Graz, Austria, with an undergraduate degree in mechanical engineering. After his graduation he served one year in the Austrian army. Following his army service, Terzaghi studied one more year, concentrating on geological subjects. In 1908, his first job was as a junior design engineer for the firm Adol Baron Pittle, Vienna. And Karl became involved in the geological problems the firm faced. He went on with great success to an even more chaotic project in St. Petersburg. During the six months in Russia, he developed some novel graphical methods for the design of industrial tanks, which he submitted as a thesis for his doctorate at the University. In January 1912, he received the degree of Doctor of Technical Sciences from his alma mater in Graz. In America, on his own, he undertook an engineering tour of major dam construction sites in the West. This was no ordinary tour, but was his opportunity to gather reports and first-hand knowledge of the problems of many different projects, and he used it to the fullest before returning to Austria in December 1913. When war broke out, he found himself drafted into the army as an officer directing a 250 man engineering battalion. His responsibilities again increased, leading now 1000 men, and he faced combat in Serbia and witnessed the fall of Belgrade. After a short stint managing an airfield, in 1916 he became a professor in the Imperial School of Engineers in Istanbul. He set up a laboratory using only the most rudimentary of equipment, and began his revolution. His measurements and analysis of the force on retaining walls were first published in English in 1919, and was quickly recognized as an important new contribution to the scientific understanding of the fundamental behavior of soils. 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. In 1924 he published much of this in his Magnum Opus, Erdbaumechanik which revolutionized the field to great acclaim. It resulted in a job offer from the Massachusetts Institute of Technology(MIT), which he immediately accepted. 1925-1929 he had done Lectureship at Massachusetts Institute of Technology. One of his first tasks in the USA was to bring his work to the attention of engineers. This he proceeded to do by writing a series of articles for the Engineering News Record, which were published in the winter of 1925, then as a small book in 1926. In 1928 he met the young Harvard doctoral student in geology, Ruth Dogget, and fell deeply in love. In 1929 he accepted a chair at the Vienna Technische Hochshule. He married Ruth, who became his editor and collaborator as well. In 1938 Terzaghi emigrated to the United States and took up a post at Harvard University. Before the end of the war, he consulted on the Chicago Subway system, the New Port News Shipways construction, and raising the Normandie, among others. He became an American citizen in March 1943. He remained as a part-timer at Harvard university until his retirement in 1953 at the mandatory age of 70. In July of the next year, he became the chairman of the Consulting Board for the construction of the Aswan High Dam. He resigned this post in 1959 after coming into conflict with the Russian engineers in charge of the project, but continued to consult on various hydroelectric projects, especially in British Columbia. The American Society Of Civil Engineers established in 1960 the Karl Terzaghi Award to an "author of outstanding contributions to knowledge in the fields of soil mechanics, subsurface and earthwork engineering, and subsurface and earthwork constructionMap of Egypt showing the location of Aswan and Lake Nasser. On October 25, 1963 he died in Winchester, Massachusetts

Books:

Posted by Sandeep Sahu at 12:20 AM 0 comments  

Labels: Evolution of Geotechnical Engineering

Introduction:

Posted by Sandeep Sahu at 11:47 PM 0 comments  

Labels: Stone Column

Posted by Sandeep Sahu at 9:46 PM 0 comments  

Labels: Soil liquefaction

Posted by Sandeep Sahu at 3:59 AM 0 comments  

Labels: Stone Column

Reference:1) Zekkos, D., Manousakis, J., Athanasopoulos, A. (2005), “Geotechnical engineering practice in the Mycenaean Civilization (1600-1100 BC)”, 2nd International Conference “Ancient Greek Technology, 17-21 October 2005, Athens, Greece
2) www.geoengineer.org

Posted by Sandeep Sahu at 1:21 AM 0 comments  

Labels: Evolution of Geotechnical Engineering