role of textiles in soil erosion control ppt

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  1. 1. Role of Textiles in Soil Erosion Control Submitted to : Prof. AlagiruSamy Submitted by: Ashutosh Shukla
  2. 2. Erosion is a natural process in which soil and rock material is loosened and removed by the action of water, wind, and ice The problem of soil movement due to erosive forces by moving water and/or wind as well as by seeping water is called soil erosion. Soil erosion and sediment controls are measures which are used to reduce the amount of soil particles that are carried off of a land area and deposited in receiving water. Soil Erosion
  3. 3. Geological erosion Includes soil-forming as well as soil-removing, has contributed to the formation of soils and their distribution on the surface of the earth. Man-made erosion Includes the breakdown of soil aggregates and the increased removal of organic and mineral particles; it is caused by clearing, grading, or otherwise altering the land. Erosion of soils that occurs at construction sites Classification
  4. 4. Introduction to the types of erosion Sheet erosion Occurs when thin layers of the top soil are moved by the force of the runoff water, leaving the surface uniformly eroded Rill erosion Caused by runoff water when it creates small, linear depressions in the soil surface Gully erosion Large, wide channels carved by running water
  5. 5. Coarse fragments: - are easily identified - not many erosion issues Fine earth portion: - harder to identify - has higher erosion potential Know your soils
  6. 6. Soil Reinforcement & Errosion control using Geosynthetics Geosynthetics : The membranes used in contact with or within soil are termed as geosynthetics. They are used in subgrade stabilization, soil reinforcement, surface erosion control, subsurface drainage etc. Generally Polymer based - Polypropylene, Polyester, PVC, Polyamide, Polyethylene
  7. 7. The ASTM (1994) defines geotextiles as permeable textile materials used in contact with soil, rock, earth or any other geotechnical related material as an integral part of civil engineering project, structure, or system. Geotextile
  8. 8. Soil Reinforcement by Geotextiles The structural stability of the soil is greatly improved by the tensile strength of the geosynthetic material. This concept is similar to that of reinforcing concrete with steel. Reinforcement function of geotextiles Soil is a structure with high compression strength but with low tensile strength. Geotextiles being high tensile strength materials are ideal to increase soil quality and soil structural stability Geotextile increase load bearing capacity of soil through tensile mechanism.
  9. 9. Erosion Control Mechanism and Role of Geotextiles Erosion is caused by a group of physical and chemical processes by which the soil or rock material is loosened, detached, and transported the geo-textile protects soil surfaces from the tractive forces of moving water or wind and rainfall erosion Geotextiles are also used for temporary protection against erosion on newly seeded slopes. After the slope has been seeded, the geotextile is anchored to the slope holding the soil and seed in-place until the seeds germinate and vegetative cover is established Vegetation can form the best erosion control, but this is often difficult to establish. The use of hydroseeding or seed impregnated fabric can be an effective method to establish vegetation.
  10. 10. Condition of river bank with and without geotextiles Application of erosion control mat (Vishakhapatnam, A.P.)
  11. 11. Different Textile Structures Used For Soil Reinforcement Methods to use textile structures for soil reinforcement Geosynthetics Geotextile wrap-around revetments (GWRs) Fibre reinforced sands
  12. 12. Geosynthetic Structures used for soil reinforcement Biaxially oriented process nets (BOP) Erosion control meshes Erosion control blankets (ECBs) Geogrids
  13. 13. Biaxially oriented process nets Manufactured from polypropylene or polyethylene resins Extremely versatile in that composition, strength, elongation, aperture size and shape, colour and ultraviolet stability Can easily be designed into the product for specific site requirements BOP nets have proven to be so adaptable they are being used to create more complex product Installation of these products is less labor intensive
  14. 14. Biaxially oriented process nets (BOP) Erosion control meshes Erosion control blankets (ECBs) Geogrids
  15. 15. Erosion control meshes A step up from BOP nettings are woven polypropylene geotextile erosion control meshes. Twisted fibre erosion control meshes. Theses high strength polypropylene meshes protect the soil surface from water and wind erosion while accelerating vegetative development. Used for fostering vegetation on geosynthetically reinforced steepened slopes
  16. 16. Biaxially oriented process nets (BOP) Erosion control meshes Erosion control blankets (ECBs) Geogrids
  17. 17. l-2-m wide biodegradable Composed of straw, excelsior, cotton, coconut, polypropylene or blends thereof. Contain UV stabilizers for controlled degradation Applications for the wide variety of blankets range from protection of gradual to steep slopes to low or moderately flowing channels Erosion control blankets (ECBs)
  18. 18. Biaxially oriented process nets (BOP) Erosion control meshes Erosion control blankets (ECBs) Geogrids
  19. 19. Geogrids These are plastic materials formed into a very open grid like configuration with very large apertures. bridge abutments to be constructed where the sill beam rests directly on the Geosynthetic Reinforced Soil (GRS) block. Grid made up of PVA works in textile grid applications to withstand high alkali environments and especially the combination of lime and cement stabilizers PVA grids in cohesive soils where there appears to be a synergistic effect resulting in higher strength and higher resistance to pull out failure
  20. 20. Use of Synthetic Geogrids for Erosion Control of Natural Existing Slopes
  21. 21. Reinforced embankment of unstable foundation soil : Geogrids to avoid reflective cracking in pavements
  22. 22. TERMs versus PERMs At this point an important distinction must be presented regarding the intended use of E & SC materials. For many installations vegetation alone will provide adequate long term erosion protection. Getting vegetation established requires a variety of techniques. Materials of a temporary nature which facilitate vegetative establishment, then degrade, may be termed TERMs (temporary erosion and re-vegetation materials). Basically TERMs consist of degradable natural and/or synthetic components which provide temporary erosion control and facilitate vegetative establishment. These short term materials degrade leaving only vegetation for long term low to medium flow resistance. Site conditions requiring reinforced vegetation or revetment systems will require PERMs (permanent erosion and re-vegetation materials).
  23. 23. Geotextile wrap-around revetments (GWRs) GWRs are sand slopes that are reinforced with a geosynthetic the material is wrapped and encapsulated with geotextiles to create a flexible revetment A layer of geotextile is first placed at the site and sand is placed on top of it to produce a GWR Loose ends of the geotextile are then folded back and inserted into the fill. A second geotextile layer is laid on top and the procedure is repeated until the layers reach to the designed height The structure resists overturning because of its weight Even it resists seaward sliding because of the geosynthetics tensile strength. Advantages They are useful for protection against waves and currents, Other structures can be constructed directly upon them, Total construction and life cycle costs are generally lower than those of hard structures
  24. 24. Recent developments obtained from small-scale model tests The only recorded model tests involving GWR were conducted at the large wave flume at Hannover, Germany (Saathoff and Kohlhase, 1986). Model tests were performed on a three-layer geotextile structure; they were tested with waves up to 1.3m (Fig. left). The GWR structure suffered only slight deformation. Based on those model test results, a GWR was constructed at the island of Sylt in Germany Cross section of model tests at the large wave flume in Hannover and prototype constructed in Sylt, Germany. Previous model test and prototype of wrap-around revetments
  25. 25. Fibre reinforced sands Reinforcing soils using tension resisting elements is an attractive means of improving the performance of soil in a cost effective manner. The use of random discrete flexible fibres mimics the behaviour of plant roots and gives the possibility of improving the strength and the stability of near surface soil layers The discrete fibres are simply added and mixed randomly with soil, much like cement, lime, or other additives Fibres some times used in combination with other admixtures such as cement and fly-ash to increase the shear strength of the soil Classification McGown classified soil reinforcement into two major categories 1. Ideally inextensible- includes high modulus metal strips that strengthens soil and inhibits both internal and boundary deformations. Catastrophic failure and collapse of soil can occur 2. Ideally extensible inclusions- include relatively low modulus natural and/or synthetic fibres, plant roots; and geosynthetics. provide some strengthening but more importantly they present greater extensibility
  26. 26. Fibres used for soil renforcement I. Natural fibres Coconut (coir) fibre Sisal Palm fibres JUTE Flax Bamboo Cane II. Synthetic (man-made) Fibre Polypropylene (PP) fibres Polyethylene (PE) fibres Glass fibres Steel fibres Polyvinyl alcohol (PVA) fibres
  27. 27. Applications of