geotechnical engineering_soil_civil engineering

civil engineer soil mechanics

1. Geotechnical Engineering CEGTEC30 (Soil Formation) Lesson Content: Definition of Geotechnical Engineer and Soil Mechanics. History of Soil Mechanics. The Origin of Soil. Properties of Organic Soil.

2. GEOTECHNICAL ENGG B ranch of civil engineering that involves natural materials close to the surface of the earth I ncludes the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures & earth structures B egan in the 18 th century

3. SOIL MECHANICS B ranch of science that deals w/ study of the physical properties of soil behavior of soil masses subjected to various types of forces. SOIL U ncemented aggregate of mineral grains and decayed organic matter (soil particles) w/ liquid & gases in the empty spaces between the solid particles. U sed as a construction materials in various engineering project S upports structural foundations.

4. HISTORY OF SOIL MECHANICS The art of geotechnical engineering was based on only past experiences through experimentation Many structures were built, some of which have crumbled, while others are still standing without studying the properties of the soil foundation

5. Tower of Pisa in Italy W eighs 15,700 metric tons H as a base with a diameter of 20m 54 m in height and became 5 m out of plumb H as tilted in the past to the east, north west and south 70metric tons of earth were removed to stabilize the foundation

6. Pyramids of Egypt Built as tombs for the country’s Pharaohs Over 138 pyramids have been discovered in Egypt

7. Personalities who have made great contributions to modern soil mechanics Karl Terzaghi father of Modern Soil Mechanics born on Oct. 2, 1883 in Prague, Austria researched on the behavior of soils and settlement of clay Arthur Casagrande Donald Taylor Ralph Peck

8. ROCK CYCLE AND THE ORIGIN OF SOIL Weathering the process of breaking down rocks by mechanical and chemical processes Types of weathering 1. Mechanical weathering – process by which rocks are broken into smaller and smaller pieces by physical forces, including running water, wind, ocean waves, glacier ice, frost and expansion and contraction caused by the gain and loss of heat w/o any change in chemical composition.

9. ROCK CYCLE AND THE ORIGIN OF SOIL Chemical weathering is the process of chemical decomposition of the original rock. rocks break into smaller pieces and the original material may be changed to something entirely different

10. Mechanical erosion due to ocean waves and wind at Yehliu, Taiwan ( Courtesy of Braja M. Das, Henderson, Nevada )

11. Basic types of Rocks Igneous formed by the solidification of molten magma ejected from deep within the earth’s mantle. Sedimentary deposits of gravel, sand, silt, and clay formed by weathering may become compacted by overburden pressure and cemented by agents like iron oxide, calcite, dolomite, and quartz Metamorphic formed by the process of changing the composition and texture of rocks (without melting) by heat and pressure

12. ROCK CYCLE

13. TRANSPORTATION OF WEATHERING PRODUCTS

14. Residual Soils – soils formed by the weathered products at their place of origin Classification of Transported Soil Glacial soils – formed by transportation and deposition of glaciers Alluvial soils – transported by running water and deposited along streams Lacustrine soils – formed by deposition in quiet lakes Marine soils – formed by deposition in the seas Aeolian soils – transported and deposited by wind

15. ORGANIC SOIL A re usually found in low- lying areas where the water table is near or above the ground surface P resence of high water table helps in the growth of aquatic plants that, when decomposed form organic soil U sually encountered in coastal areas

16. Properties of Organic Soil N atural moisture content may range from 200 to 300% H ighly compressible L arge amount of settlement is derived from secondary consolidation

17. SOIL PARTICLES Gravel – pieces of rocks with occasional particles of quartz, feldspar, and other minerals Sand - made of mostly quartz and feldspar Silt – microscopic soil fractions that consist of very fine quartz grains and some flake- shaped particles that are fragments of micaceous minerals. Clays – flake- shaped microscopic and submicroscopic particles of mica clay minerals

18. PARTICLE SIZE CLASSIFICATION Grain size (mm) Name of organization Gravel Sand Silt Clay Massachusetts Institute of Technology (MIT) > 2 2 to 0.06 0.06 to 0.002 < 0.002 U.S. Department of Agriculture > 2 2 to 0.05 0.05 to 0.002 < 0.002 (USDA) American Association of State 76.2 to 2 2 to 0.075 0.075 to 0.002 < 0.002 Highway and Transportation Officials (AASHTO) Unified Soil Classification System 76.2 to 4.75 4.75 to 0.075 Fines (U.S. Army Corps of Engineers, U.S. (i.e., silts and clays) Bureau of Reclamation, and American < 0.075 Society for Testing and Materials) Note: Sieve openings of 4.75 mm are found on a U.S. No. 4 sieve; 2-mm openings on a U.S. No. 10 sieve; 0.075-mm openings on a U.S. No. 200 sieve. See Table 2.5.

19. SOIL- SEPARATE- SIZE LIMIT BY VARIOUS SYSTEMS Massachusetts Institute of Technology U.S. Department of Agriculture American Association of State Highway and Transportation Officials Unified Soil Classification System 100 10 0.01 0.001 1.0 0.1 Grain size (mm) Gravel Sand Silt Silt and clay Clay

20. 🠶 REFERENCE: Das, B.M. (2010) Principles of Geotechnical Engineering. 7 th Ed.

21. End of Presentation