Note for Ground Improvement Techniques - GIT by Engineering Kings

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Visit : MAHALAKSHMI ENGINEERING COLLEGE TIRUCHIRAPALLI - 621213. QUESTION WITH ANSWERS DEPARTMENT: CIVIL -IV SEMESTER:VII SUB.CODE/ NAME: CE 2033 / Ground Improvement Techniques UNIT 1- INTRODUCTION PART - A (2 marks) 1. What are the major problematic soils? 1. Collapsible soils 2. Liquefiable soils 3. Waste materials 4. Expansive and shrinkage 5. Marshy and soft soils 6. Karst deposits 2 . What is expansive soil? Give one example. Expansive soils are soils that expand when water is added, and shrink when they dry out. This continuous change in soil volume can because homes built on this soil to move unevenly and crack. Ex. Deccan plateau and in some parts of Andhra Pradesh Minimum volume like liquid limit is highest water content in the range of about 100 percent and the shrinkage limit could be as low as 10 percent. 4. What is a collapsible soil? These collapsible soils are nothing but the soils, which have a tendency to collapse upon loading. Many of the reasons such as, the stable or unstable meta structure or capillary structures nullification are some of the reasons for this collapsible nature of the soil. Suppose the soil is partly saturated and when it comes in contact with water, the moment there is a contact with water all the capillary structures are destroyed. Because of this, there is a volume change; it is in fact a reduction in volume and that leads to collapse. 5. What are the difficulties faced with soft clay? When the soft soil is so poor, it is very difficult to construct anything, because the bearing capacity is very low, shear strength is low, consolidation settlements are going to be very high and permeability is very low. These are all very peculiar. So, this needs to be improved. 7. Name the various soil deposits found in India. 1. Black cotton soil 2. Laterites and murmurs 3. Alluvial soil 4. Desert soil 5. Boulder soil Visit :

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Visit : 8. Name any four ground improvement techniques. (AUC MAY/JUNE 2013) 1. Compaction Pile 2.Blasting 3. Pre-Compression 4. Stone Column 5.Vibrofloatation 6.Grouting 7.Electro Osmosis 8.Thermal Treatment 9. What is the need for improving the ground? (AUC MAY/JUNE 2013) Reclamation of unusable land • Betterment of soil properties for improved performance • Cost effective design of foundations 10. Briefly write the role played by ground improvement in foundation engineering. • Improves bearing capacity • Reduces foundation settlements • Enables construction on granular fil s • Provides temporary underpinning • Provides excavation support • Reduction of foundation dimensions • Construction of shallow foundations • Enables dry working conditions for foundation excavations 11. Define ground improvement. (AUC NOV /DEC 2012) Ground improvement technique is the process of improving the geo-technical characteristics of soil used in construction. The soil at a construction site is not always totally suitable for supporting structures such as buildings, bridges, highways and dams. For example, In granular soils, in-situ soil may be very loose and indicate large elastic settlement. Under these conditions, soil needs to be dandified to increase its unit weight and shear strength. 12. What is compaction? When is it adopted? The compaction is process of increasing density of soil means of suitable compaction device . it is predominantly adopted for cohesive soils and also however cohesion less soil can be also compacted by a suitable device . 13. What is dewatering? What are the various methods of dewatering? Dewatering is the process of continuous removal of water to lower the ground water table to the required depth Different methods of dewatering are Sumps and ditches Well point system Deep well system Vacuum dewatering Electro-osmotic dewatering Visit :

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Visit : 14. When is pre-loading adopted as a ground improvement technique? Preloading or pre-compression is the process of placing additional vertical stress on a compressible soil to remove pore water over time The pore water dissipation reduces the total volume causing settlement Surcharging is an economical method for ground improvement 15. What is advantage of using vertical drains along with pre-loading? The main applications of this method are in areas of transportation, highway Embankments, housing projects, hazardous waste remediation and in reducing negative skin friction on pile foundations Vertical drains are nowadays primarily constructed with prefabricated vertical drains 16. How are heating and freezing used to improve ground? Heating soils permanently alters the properties of the soil Depending on the soil, temperatures can range between 300 and 1,000° C The expected property changes are increase in shear strength and modulus of elasticity Its application areas include immobilization of contaminant and soil stabilization Freezing Ground freezing is the use of refrigeration to convert in situ pore water to ice The ice then acts as a cement or glue, bonding together adjacent particles of soil or blocks of rock to increase their combined strength and make them impervious Freezing is mainly adopted for • Temporary underpinning • Support for excavation • Slope stabilization • Contaminant containment • To prevent ground water from entering excavation 17. What is a lime column? Lime column is the process in which soft clays and silts are mixed with dry unslaked lime to form a column of treated soil This process uses a mixing tool that combines the lime with in-situ material during treatment. 18. What is vibro-compaction? In which soils is it adopted? Vibrio-Compaction, sometimes referred to as Vibroflotation, is the rearrangement of soil particles into a denser configuration by the use of powerful depth vibrators It is mainly adopted to reduce settlements, reduce liquefaction hazard and permit construction on granular fills It can be adopted in sands and silty sands with excellent to good results Its applicability is poor in silts and cannot be adopted for clays 19. What is stone column? What are the methods of installing a stone column? The vibro Rig displaces the soil by vibrating a mandrel into the ground to the required depth or refusal, whichever is achieved first Visit :

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Visit : The mandrel Is withdrawn and The subsequent void filled with a clean stone The mandrel is then re-introduced to the in-filled void and taken down close to the base of the previously formed void, displacing the stone laterally into the surrounding soil 20. What are the various methods of grouting? Suspension grouts Solution Grouts Colloidal solution grouts Part –B 1. Explain in detail the role of ground improvement in foundation engineering. Role of GIT in Foundation Engg. • Improves bearing capacity • Reduces foundation settlements • Enables construction on granular fills • Provides temporary underpinning • Provides excavation support • Reduction of foundation dimensions • Construction of shallow foundations • Enables dry working conditions for foundation excavations 2. What are the various geotechnical problems faced with black cotton soil, laterite soil and alluvial soil deposits? (AUC NOV /DEC 2012) (AUC MAY/JUNE 2013) Geotechnical Problems in Soils • Soil is a material which exhibits a very wide range of characteristics that, it led a whole branch of study to understand it better • In this endeavour, man has encountered a wide variety of soils posing problems to his developmental activities • Not all soils are problematic from engineering point of view • Different soils exhibit different levels of difficulty in their handling • Black cotton soil o This is well known group of soils characterized by dark grey to black colour with high clay content Visit :