Introduction to Soil Mechanics types .ppt
- 2. SOIL MECHANICS Soil Mechanics is defined as the branch of engineering science which enables an engineer to know theoretically or experimentally the behaviour of soil under the action of ; 1. Loads (static or dynamic), 2. Gravitational forces, 3. Water and, 4. Temperature. Simply speaking it is the knowledge of engineering science, which deal with properties, behaviour and performance of soil as a construction material or foundation support
- 3. Effects of static loading on soil mass Shear failure of the foundation soil Settlement of structures Stability criteria There should be no shear failure of the foundation soil. The settlement should remain within permissible limits.
- 4. Soil subjected to static load.
- 5. • Impact generation For Design and construction of roads following must be considered COMPACTION CHARATERISTICS MOISTURE VARIATION Effects of dynamic loading on soil mass
- 6. Soil subjected to dynamic load.
- 7. • LANDSLIDES • INSTABILITY OF SLOPES Causes: Major cause is the moisture variation resulting in; Reduction of shear strength Increase of moisture Increase in unit weight Effects of gravitational forces on soil mass
- 8. Landslide of a parking area at the edge of a steep slope, mainly due to increase in moisture content.
- 9. Landslide along the road in a hilly area. The landslide occurred after a heavy rainfall
- 10. Soil subjected to action of water (Erosion).
- 11. Soil subjected to action of water (Erosion).
- 12. • Scouring Causes Increased flow velocity due to obstruction Fineness of riverbed material Stability criteria The foundation of pier must be below the scour depth Effects of river water on soil mass
- 13. Soil under the action of water (Scouring)
- 14. • Reduction Of Shear Strength • Settlement Of Structure In Summer • Lifting Up Of Structure In Winter CAUSES Heaving (due to formation of ice lenses) Increase of moisture due to thawing (MELTING) Effects of frost action on soil mass
- 15. Elevated ground surface due to frost heave Maximum frost heave Original ground surface Frozen soil Ice lenses Unfrozen zone Frost line Depth of frost penetra tion Frost heave Soil subjected to low temperature (Frost action) Ice lenses fed by capillary water from water table. Pavement Original ground surface Frozen soil GWT
- 16. Objectives of soil mechanics Engineering soil surveys Soil sampling devices and methods Soil testing devices and methods Physical properties of soil Evaluation and interpretation of test results Behaviour under loads and forces Soil conservation techniques Sedimentation control of dam reservoirs Design and operation of landfills
- 17. SOIL • The term soil according to engineering view point is defined as the material, by means of which and upon which engineers build their structures FORMATION OF SOIL Soil is generally formed by disintegration and decomposition (weathering) of rocks through the action of physical, mechanical and chemical agents which break them into smaller and smaller particles.
- 18. Top Soil (Highly Organic) Residual Soil (Oldest soil) Completely weathered rock Highly weathered rock (Mostly soil) Moderately weathered rock Slightly weathered rock (Some Fissures in the upper zone) Sound massive rock Different stages of weathering of rocks and formation of soil.
- 19. Different stages of weathering of rocks and formation of soil.
- 20. TYPES OF SOIL • Geological Consideration: 1. Glacial soil: 2. Residual soil: 3. Alluvial soil: 4. Wind blown soil or Aeolian soil 4-a. Dune or Dune Sand: 4-b. Loess 5. Colluvial soil:
- 21. Sand dunes
- 22. Gobi Desert 5 percent of the desert is covered with sand dunes
- 23. Sand dunes Sand dunes tower up to 300 m (1000 ft) high in the Namib-Naukluft Park, Namibia.
- 24. Loess (The dust blown by wind is seen at the top.)
- 25. The Huangtu Gaoyuan (Loess Plateau) in North China is formed by the accumulation of loess, or fine windblown silt
- 26. Engineering consideration: • Clay • Silt • Sand • Gravels • Cobbles or Boulders • Organic Matter TYPES OF SOIL
- 27. Electrical charge on clay particles and inter-particle bonding Particle surface having a net negative charge Particle edges having positive & negative charges. Clay particle (not to scale)
- 28. Nomenclature (Soil Type) Range of Sizes ASTM AASHTO Gravel 75 mm to 4.75 mm (3in Sieve to No. 4 sieve) Larger than 2 mm Coarse Sand 4.75 mm to 2 mm (No. 4 to No. 10 sieve) 2mm to 0.425 mm Medium Sand 2 mm to 0.425 mm (No. 10 to No. 40 sieve) ------------------------- Find Sand 0.425 mm to 0.075 mm (No. 40 to No. 200 sieve) 0.425 mm to 0.075 mm Silt 0.075 mm to 0.005 mm (No. 200 to .005 mm) 0.075 mm to .002 mm Clay Smaller than 0.005 mm Smaller than 0.002 mm Colloids Smaller than 0.001 mm Smaller than 0.001 mm Nomenclature of material (soil type) and range of sizes
- 29. Crib type retaining wall along a highway in mountainous range
- 30. Landslide causing failure of a gravity retaining wall at Kuldana-Murree (August 2002) Road Remnants Colluvium (lean CLAY with gravel) Retaining Wall Diversion Bridge
- 31. Highway passing through a tunnel
Editor's Notes
- #20: Glacial soil is soil that has been deposited by glaciers. It's made up of a mixture of sediments, including rocks, sand, and silt, that glaciers carry and drop as they move. residual soil can be defined as a soil material which is the result of weathering and decomposition of rocks that has not been transported from its original place. Alluvial soil, also known as alluvium, is a loose deposit of sand, silt, clay, or gravel that has been left behind by running water