Formation and development of ground.pptx

Ground Improvement techniques

1. Formation and Development of ground Module - 1 Aswathy C M Assistant Professor SJEC Ground improvement techniques

2. The materials that constitute Earth’s crust Rock is a material strongly bonded of minerals Soil is an assemblage of solid particles formed by disintegration of rocks.

3. Weathering Mechanical/Physical weathering Breakdown of larger rocks into smaller rocks – without any chemical reaction Chemical weathering Chemical reactions occur in rock to dissolve and form new substances Biological weathering Rock disintegration due to plant/animal actions

4. Soils in India

5. Alluvial soils are formed mainly due to silt deposited by Indo-Gangetic Brahmaputra rivers. In coastal regions some alluvial deposits are formed due to wave action - Sandy and clayey soil The parent material for most of the black soil are the volcanic rocks that were formed in the Deccan Plateau (Deccan and the Rajmahal trap) – low fertile, moisture retention Red soils along with its minor groups form the largest soil group of India – sand to clay – Tamilnadu, Karnataka, Maharashtra Laterite soils are mostly the end products of weathering – Laterite means brick in latin – harden due to moisture loss – res in colour – Maharashtra, Karnataka Forest-mountain soils are mainly heterogeneous soils found on the hill slopes covered by forests – Himalayan, western and eastern ghats The desert soils consist of Aeolian sand (90 to 95 per cent) and clay (5 to 10 per cent) - presence of sand inhibits soil growth. In Saline and Alkaline Soils, the top soil is impregnated (soak or saturate with a substance) with saline and alkaline efflorescences (become covered with salt particles). Peaty –Marshy are soils with large amount of organic matter and considerable amount of soluble salts. • The most humid regions have this type of soil. • They are black, heavy and highly acidic.

6. Sedimentary soils

7. Problems Of Indian Soils Soil erosion (Himalayan region, Chambal ravines etc.) Deficiency in fertility (red, lateritic and other soils), Desertification (around thar desert, rain-shadow regions like parts of Karnataka, Telangana etc.) Waterlogging (Punjab-Haryana plain) Salinity and alkalinity (excessively irrigated regions of Punjab, Haryana, Karnataka etc.) Over exploitation of soils due to an increase in population and rise in living standards and encroachment of agricultural land due to urban and transport development.

8. O-Horizon U pper layer of topsoil. O rganic materials like dried leaves, grasses, and dead plants. Small rocks, twigs, and surface organisms are also found here. Fallen trees and decomposed organic matter contribute to this layer. Its colour is often black, brown, or dark brown due to its organic content. A-Horizon R ich in organic material and is called the humus layer. M ix of organic matter and decomposed materials. S oft and porous, allowing for air and water retention. Seed germination occurs here - leading to new root growth and plant development. Microorganisms like earthworms, fungi, and bacteria are present in this layer.

9. B- Horizon The subsoil is below the topsoil and above the bedrock. It's harder and denser than topsoil, with less organic matter and humus. Certain minerals and metal salts like iron oxide are deposited here. It holds more water and appears lighter brown due to clay content. When fields are ploughed, subsoil and topsoil often mix. C- Horizon This layer is devoid of any organic matter and is made up of broken bedrock. This layer is also known as saprolite. The geological material present in this zone is cemented.

10. Ground improvement potential The soil and rock conditions can be placed under categories. 1. Hazardous 2. Poor 3. Favourable • So as to identify the ground condition which will enable the engineer to decide a proper treatment approach and or design approach

11. 1. HAZARDOUS GROUND CONDITIONS It is a regional or local field condition such that a regular design approach or an economical treatment is not feasible. Construction in such location may result in ultimate disaster. Such locations should be avoided. E.g. : Site located close to faults (particularly in seismically active region), Loose to medium dense sand may easily be susceptible to quicksand condition leading to liquefaction, Active mines, Flood plains 2. POOR It is a regional or local field condition which may require special design or special treatment E.g.: Expansive soils , very soft to firm soils, organic soils 3. FAVOURABLE It is a regional or local field conditions for which normal design and ground treatments are suitable E.g.: Cohesive granular soils such as sandy- clay mixture, Cohesive granular soils such as medium dense to dense sands and sand gravel mixture , Shallow rock without any discontinuities

12. Alterations of the ground after formation Effect of seasonal moisture variation Effect of water seepage and surface tension Effect of construction operation Effect of vegetation Effect of temperature variation Effect of vibration Effect of mining subsidence and pumping

13. Reclaimed soils The term reclaimed soil comprises all materials deposited on a site using various methods for different purposes. Need for reclamation • Industrial & commercial development of urban areas • Development of navigation channels for ports & other water front structures. • Disposal of garbage, industrial wastes etc

14. Generally, reclamation followed by ground treatment is preferable and economical than designing deep foundations Types of reclamation materials 1. Hydraulic fills of dredged soil 2. Sanitary fill 3. Paper sludge 4. Fly ash and slag 5. Rubbish & Debris