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Soil Stabilization

Soil Stabilization. Prof. Mayur M Maske Head Department of Civil Engineering RIT, Rajaramnagar. Soil Stabilization. improving the engineering properties of soils by use of mechanical or chemical methods.

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Soil Stabilization

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  1. Soil Stabilization Prof. Mayur M Maske Head Department of Civil Engineering RIT, Rajaramnagar

  2. Soil Stabilization improving the engineering properties of soils by use of mechanical or chemical methods. Soil stabilization aims at improving soil strength and increasing resistance to softening by water through bonding the soil particles together, water proofing the particles or combination of the two (Sherwood, 1993) Mayur M Maske

  3. Soil stabilization methods Mayur M Maske

  4. Mechanical Stabilization Soil stabilization can be achieved through physical process by alteringthe structure of native soil particles by either induced vibration or compaction or by using other physical properties such as barriers and nailing. Mayur M Maske

  5. Factors Affecting Mechanical Stabilization Mayur M Maske

  6. Mechanical Strength When the soil is used in small proportion to fill up the voids the crushing strength of aggregates is important Gradation A well graded aggregate soil mix results in a mix with high dry density and stability values Properties of soil A mix with Plasticity Index, results poor stability under soaking conditions. Hence it is desirable to limit the plasticity index of the soil Mayur M Maske

  7. Presence of Chemicals Presence of Salts like Sulphates and mica is undesirable while Presence of Calcium Chloride is Beneficial Compaction Effective Compaction is desirable to produce high density and stability mix Mayur M Maske

  8. Field Compaction Smooth Wheeled Roller Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts) Mayur M Maske

  9. Field Compaction Vibrating Plates • for compacting very small areas • effective for granular soils Mayur M Maske

  10. Field Compaction Sheepsfoot Roller • Provides kneading action; “walks out” after compaction • Very effective on clays Mayur M Maske

  11. Field Compaction Impact Roller • Provides deeper (2-3m) compaction. e.g., air field Mayur M Maske

  12. solution cavities in limestone Pounder (Tamper) Crater created by the impact Dynamic Compaction - pounding the ground by a heavy weight Suitable for granular soils, land fills and karst terrain with sink holes. (to be backfilled) Mayur M Maske

  13. Pounder (Tamper)Mass = 5-30 tonneDrop = 10-30 m Dynamic Compaction Mayur M Maske

  14. Vibroflot (vibrating unit)Length = 2 – 3 mDiameter = 0.3 – 0.5 mMass = 2 tonnes Vibroflotation Suitable for granular soils • Practiced in several forms: • vibro–compaction • stone columns • vibro-replacement (lowered into the ground and vibrated) Mayur M Maske

  15. Stone Columns vibrator makes a hole in the weak ground ..and compacted Densely compacted stone column hole backfilled Mayur M Maske

  16. Vibroflotation Mayur M Maske

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  18. Chemical Stabilization Chemical soil stabilization depends mainly on chemical reactions between stabilizer (cementitious material) and soil minerals (pozzolanic materials) to achieve the desired effect. Mayur M Maske

  19. Methods of Chemical Stabilization • Soil Cement Stabilization • Soil Lime Stabilization • Soil Bitumen Stabilization • Lime Fly ash Stabilization • Lime Fly ash Bound Macadam. Mayur M Maske

  20. Selection of the appropriate additive • Soil consistency and gradation • Soil mineralogy and composition • Desired engineering properties • Purpose of treatment • Mechanisms of stabilization • Environmental conditions and engineering economics Mayur M Maske

  21. Soil Cement Stabilization Soil Cement is an intimate mix of soil, cement and water, compacted to form a strong base course A cement-modified soil (CMS) is a soil material that has been treated with a relatively small proportion of Portland cement. Mayur M Maske

  22. Soil Cement Stabilization Cement stabilization is ideally suited for well graded aggregates with a sufficient amount of fines to effectively fill the available voids space and float the coarse aggregate particles. Mayur M Maske

  23. General guidelines for stabilization are, For coarse-grained soils IP should be less than 30. For fine-grained soils, the IP should be less than 20 and the liquid limit (LL) should be less than 40 in order to ensure proper mixing. Mayur M Maske

  24. Results of Using Portland Cement: • Reduction in plasticity characteristics as measured by Plasticity Index (PI) • Reduction in the amount of silt and clay size particles • Increase in the California Bearing Ratio (CBR) • Increase in shearing strength • Decrease in volume-change properties Mayur M Maske

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  28. In-place mixing of Cement with existing base Mayur M Maske

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  30. Lime Lime has been found to react successfully with medium, moderately fine and fine grained soils. It causes a decrease in plasticity and swell potential of expansive soils. Lime increases workability and strength properties of the soils. Lime can be used to treat soils in order to improve their load-bearing characteristics in a number of situations. Mayur M Maske

  31. Lime Quicklime is frequently used to dry wet soils at construction sites providing an improved working surface. An more significant use of lime is in the modification and stabilization of soil beneath road and similar construction projects. Use of lime can substantially increase the stability, impermeability, and load-bearing capacity of the subgrade. Mayur M Maske

  32. Factors affecting Properties of Soil-Lime Lime Content Generally increase in lime content causes slight change in liquid limit and considerable increase in Plasticity index. The rate of increase is first rapid and then decreases beyond a certain limit. The point is often termed as lime fixation point This is considered as design lime content. Mayur M Maske

  33. Type of Lime Quick lime has been found more effective than Hydrated lime. Calcium Carbonate must be heated at higher temperature to form Quick lime calcium oxide( CaO) Calcium oxide must be slaked ( by the addition of water) to form Hydrated lime. Mayur M Maske

  34. Compaction Compaction is done at OMC and maximum dry density. Mayur M Maske

  35. Curing The strength of soil-lime increases with curingperiod up to several years. The rate of increase is rapid during initialperiod. The humidity of the surroundings also affects the strength Mayur M Maske

  36. Additives Sodium metasilicate, Sodium hydroxide and Sodium Sulphate are also found useful additives Mayur M Maske

  37. Soil- Bituminous Stabilization The Basic Principles of this stabilization are Water Proofing and Binding By Water Proofing inherent strength and other properties could be retained. Mayur M Maske

  38. Soil- Bituminous Stabilization Most Commonly used materials are Cutback and Emulsion Bitumen Stabilized layer may be used as Sub-base or base course for all the roads Mayur M Maske

  39. Soil- Bituminous Stabilization Mayur M Maske

  40. Factors affecting properties of soil-bitumen Soil The particle size, shape and gradation of the soil influence the properties of the soil-bitumen mix. Mayur M Maske

  41. Factors affecting properties of soil-bitumen Types of Bitumen Cutbacks of higher grade should be preferred, Emulsions generally gives slightly inferior results than Cutback. Mayur M Maske

  42. Amount of Mixing Increasing proportion of bitumen causes a decrease in dry density but increases the stability after a certain bitumen content The optimum bitumen content for maximum stability generally ranges from 4 to 6% Mayur M Maske

  43. Mixing Improved type of mixing with low mixing period may be selected . Mayur M Maske

  44. Compaction Effective Compaction results higher stability and resistance to absorb water. Mayur M Maske

  45. Additives Anti stripping and reactive chemical additives have been tried to improve the properties of the mixes Portland cement can also be used along with the soil bitumen Mayur M Maske

  46. Soil stabilization method selection Mayur M Maske

  47. Soil stabilization method selection Mayur M Maske

  48. California Bearing Ratio (CBR) The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and base courses. It was developed by the California Department of Transportation. Mayur M Maske

  49. The test is performed by measuring the pressure required to penetrate a soil sample with a plunger of standard area. The measured pressure is then divided by the pressure required to achieve an equal penetration on a standard crushed rock material. Mayur M Maske

  50. Take load readings at penetrations of: “the result” 0.025” ……………70 psi 0.05”……………...115 psi 0.1”……………….220 psi 0.2”……………….300 psi 0.4”……………….320 psi California Bearing Ratio (CBR) 6” mold Penetrations of 0.05” per minute Mayur M Maske

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