Soil Improvement Techniques
- 1. Soil Improvement Techniques (Physical Techniques) Professor: Dr. Adel Hanna Presented by: Sadegh Tabatabaei November 2016 1
- 2. Contents: Introduction Different general techniques Physical techniques Application and limitations Conclusion References 2
- 3. Introduction Rapid development of infrastructures with scarcity of useful land forced engineers to improve the properties of soil to bear the load transferred by the infrastructures. The purpose of these techniques to increase bearing capacity and strength of soil reduce the settlement to a considerable extent. Reduce the effects of contaminated soils. The main goal of most soil improvement techniques used for reducing liquefaction hazards is to avoid large increase in pore water pressure during earthquake shacking. This can be achieved by densification of the soil and improvement of its drainage capacity. There are different methods like Physically, Mechanically and chemically modifications. 3
- 5. Surface improvement The surface improvement method enhances the bearing capacity of the ground and prevents unequal settling by mixing, stirring and solidifying the soil from weak ground and the cement-based solidification agent. This method cannot work from approx. 2 m or more below the ground surface. It does not necessitate a dedicated construction machine, this method can be applied to construction sites of any size. 5
- 6. Elaborating Techniques Grouting Soil cement Heating Freezing 6
- 7. Grouting When the adhesives are injected under pressure through a pipe or boreholes into the voids of ground or in between the structure, the process is termed as grouting. Mixing adhesive and special material either in the soil surface or column of soil if required. Natural soil Waste materials Industrial by- products 7
- 8. Ground Underground improvement Foundation construction Sealing pores or cavities By liquid form material 1.Decrease permeability 2.Improve shear strength virtually(cohesion) 8
- 9. Application of Grouting for different outcomes: Control of ground water during construction Void filling to prevent excessive settlement Strengthening adjacent foundation soils to protect them against damage during excavation, Pile driving, etc. Soil Strengthening to reduce lateral support requirements Stabilization of loose sands against Liquefaction Foundation Underpinning 9
- 10. For gravely layers : cement base grout mixes are generally used. For sandy gravel soil : Ultrafine grout mix can be used. Mortar and pastes such as cement to fill in holes or open cracks. Suspensions such as ultra-fine cement to seal and strengthen sand and joints. Solutions such as water glass (silicate). Emulsions such as chemical grout 10
- 12. 12 The use of various grout mixes are very much dependent on the nature of soil and gradation of soil N= (D15)soil / (D65)Grout If N > 24, Grouting is considered feasible If N < 11, Grouting is considered not feasible. (Mitchell and Katti in 1981)
- 13. Jet Grouting ultra high-pressure fluids or binders that are injected into the soils at high velocities. These binders break up the soil structure completely and mix the soil particles in-situ to create a homogeneous mass, which in turn solidifies. This ground modification/ground improvement of the soil plays an important role in the fields of foundation stability, particularly in the treatment of load bearing soils under new and existing buildings; in the in-depth impermeabilization of water bearing soils; in tunnel construction; and to mitigate the movement of impacted soils and groundwater. 13
- 14. Ranges of soil by grouting technology 14
- 15. Soil cement Cement and other admixtures like fly ash ,blast furnace slag has been used in many geotechnical and highway projects to stabilize the soil: 1. Shallow depth stabilization- sub-grade, sub-base and base course of highways and embankment material. 2. Treatment of deep soils like soft soils and peaty soils. benefits can be achieved by this process: 1. Increased strength and stiffness and better volume stability 2. Increased durability 15
- 16. Influenced factors water/ cement(w/c) ratio Method of compaction Time elapsed between mixing and compaction Specimen size and boundary effects Temperature and humidity Length of curing 16
- 17. Heating Due to heating, permanent change in soil properties are observed and the material becomes hard and durable. Settlements of clay under a given applied load increases with increase in temperature The engineering properties of clay changes when it is heated to about 400°C. Heating breaks the soil particle down to form crystal products. Depends on the nature of soil temperature can be varied between 300°C to 1000°C. However the safety of adjacent structures should be ensured while heating 1. Immobilization of radioactive or contaminated soil. 2. Densification and stabilization 17
- 18. Freezing This method is based on conversion of in-situ pore water by use of refrigeration. Ice then acts as a cement or glue, bonding together adjacent particle or blocks of rocks to increase their combined strength resulting in an impervious structure Water expands about 10% by volume ,which does not itself impose any serious stresses and strains on the soil unless the water is confined within a restricted volume. 1. Temporary underpinning 2. Temporary support for an excavation 3. Prevention of groundwater flow into excavated area 4. Temporary slope stabilization 18
- 19. Modification by Addition and Confinement Techniques The one of the method among ground improvement techniques is reinforcing the soil with materials like steel, stainless steel, aluminum, fibers, fiber glass, nylon, polyster, polyamides in the form of other strips or grids and Geotextiles The Primary purpose of reinforcing a soil mass is to improve its stability, increasing its bearing capacity and reduce Settlements and Lateral deformations. Geotextiles and geomembranes, broadly speaking are synthetic fibres used to stabilize structures built on soil. Using reinforcement in the form of fibers, strips, meshes and fabric the soil can be modified 19
- 20. Modification by Confinement techniques Geotextile confined columns (GCC) pile supported embankment Rigid inclusions Micro Piles Reinforcement Soil Nailing 20
- 21. Confinement Methods The role of geosynthetic material varies in different application as it can serve as reinforcement, separation, filtration, protection, containment, fluid transmission and confinement of soil to improve bearing capacity. Geocell reinforcement is a recently developed technique in the area of soil reinforcement It has a three dimensional, polymeric, honeycomb like structure of cells made out of geo-grids inter connected at joints. 21
- 22. Conclusion Ground Improvement Techniques is a technically viable and cost effective solution for soils which are weak in strength and treatment is to be done in order to make them suitable for construction. A suitable and cost effective technique for ground improvement can be designed, keeping in view the following points: 1. Nature and type of soil 2. Intensity of loading and 3. Intended performance Selection processes for ground improvement performs, improved analysis, and knowledge of long term performance and understanding of effects of variability required to develop more efficient designs. Before selecting any ground improvement technique it is important to evaluate the cost of each particular methods and their associated applications. 22
- 23. References Bruce, Donald A. An Introduction to the Deep Soil Mixing Methods as Used in Geotechnical Applications. Publication no. FHWA-RD-99-138, U.S. Department of Transportation, Federal Highway Administration; 2000, 135 pages Deep soil mixing in the UK: geo-environmental research and recent applications Land Contamination & Reclamation, 11 (1) (2003) Welsh, J.P., & Burke, G.K. (2000), ―Advances in grouting technologyǁ, Proceedings of GeoEng 2000. Melbourne. Liu, J. (2003), ―Compensation grouting to reduce settlement of buildings during an adjacent deep excavationǁ, Proc. 3rd Int.Conf. on Grouting and Ground Treatment, Geotechnical Special Publication120, ASCE, New Orleans, Louisiana, 2: 837-844. Varaksin, S.(1981), ―Recent development in soil improvement techniques and their practical applicationsǁ, Solcompact Sols/Soils, Techniques Louis Menard, 15, rue des Sablons, Paris, 38/39-1981. https://www.youtube.com/watch?v=kvtn-27JJ1Y 23
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