3. Understanding Ground Improvement • Ground improvement includes two parts. 1.First Understand the ground 2.Then find out the most engineered1 solution for improvement 1. Engineered means most economical , safe and ease of simplicity to adopt
5. Tilting of structure : Overturning Leaning temple dome, Huma, Orissa, India A building at the Lotus Riverside complex in Shanghai’s Minhang district collapsed
10. Why we study geotechnical Structure Failure? • Because we want engineered design of geotechnical structures. • Engineered means Economical Safe Durable Strong
11. List of ground improvement techniques Ground Improvement Basic Operations: Increasing soil Density Removing Air Voids, Pore water Changing soil water properties • Deep Dynamic Compaction • Drainage/Surcharge • Electro-osmosis • Compaction grouting • Blasting • Surface Compaction • Ground Freezing
12. List of ground improvement techniques Ground Treatment • Soil Cement • Lime Admixtures • Fly ash • Soil Mixing • Deep Soil Mixing Basic Operations: Changing soil Properties by Adding Soil, fly ash, slag, cement Chemicals (admixtures) etc. It means that the modified property represents the property of mixture and not soil as an Independent element
13. List of ground improvement techniques Ground Reinforcement • Stone Columns • Soil Nails • Deep Soil Nailing • Micro piles (Mini-piles) • Jet Grouting • Geosynthetics • Fiber Reinforcement • Lime Columns • Vibro-Concrete Column • Mechanically Stabilized Earth Basic Operations: Soil and Reinforcing material act as a structure in which takes reinforcing elements majority of load
16. Equipment Smooth-wheel roller (drum) • 100% coverage under the wheel • Can be used on all soil types except for rocky soils. • The most common use of large smooth wheel rollers is for proof- rolling subgrades and compacting asphalt pavement. • Now a days Vertical vibrator is also attached to smooth wheel rollers.
17. Equipment (Cont.) Pneumatic (or rubber-tired) roller • 80% coverage under the wheel • Can be used for both granular and fine-grained soils. • Can be used for highway fills or earth dam construction.
18. Equipment (Cont.) Sheepsfoot rollers • Has many round or rectangular shaped protrusions or “feet” attached to a steel drum • 8% ~ 12 % coverage • It is best suited for clayed soils.
19. Equipment (Cont.) T amping foot roller • About 40% coverage • It is best for compacting fine- grained soils (silt and clay).
20. • When • Existing surface or near-surface soil is poor with regard to foundation support • For which soil? • Both cohesive and cohesionless soils • How • Drop a very heavy (2~20 tons) weight onto the soil from a relatively great height (20 ~ 100 ft) • Dropping weight randomly? a closely spaced grid pattern is selected. Dynamic Compaction
21. Dynamic Compaction Dynamic compaction was first used in Germany in the mid-1930’s.
23. Vibroflotation From Das, 1998 Vibroflotation is a technique for in situ densification of thick layers of loose granular soil deposits. It was developed in Germany in the 1930s. Vibro-Compaction
24. Vibroflotation-Procedures From Das, 1998 Stage1: The jet at the bottom of the Vibroflot is turned on and lowered into the ground Stage2: The water jet creates a quick condition in the soil. It allows the vibrating unit to sink into the ground Stage 3: Granular material is poured from the top of the hole. The water from the lower jet is transferred to the jet at the top of the vibrating unit. This water carries the granular material down the hole Stage 4: The vibrating unit is gradually raised in about 0.3-m lifts and held vibrating for about 30 seconds at each lift. This process compacts the soil to the desired unit weight.
25. Pre-loading: Vertical Drains Prefabricated Vertical Drains (PVDs) are composed of a plastic core encased by a geotextile for the purpose of expediting consolidation of slow draining soils.
27. Soil-Cement stabilization Stabilization ash, blast using furnace and cement and other slag has admixtures such as fly in many been adopted geotechnical highway engineering projects.
34. Grouting • Injection formation of a slurry or a liquid solution into a soil or rock • The grout subsequently hardens – increases the strength and decreases compressibility and permeability.
35. MODES OF GROUTING A. Penetration- Grout flows into soil voids freely with minimal effect B. Compaction or Controlled displacement- Grout remains more or less intact as a mass C. Hydraulic Fracturing or Uncontrolled displacement- Grout rapidly penetrates into a fractured zone created when the grout pressure is greater A B C
36. Stone Column A ground improvement technique to improve the load bearing capacity and reduce the settlement of the soil Stone column consists of crushed coarse aggregates of various sizes
37. INSTALLATION TECHNIQUES BORED RAMMED SYSTEM VIBRO REPLACEMENT METHOD
38. Procedure Penetration Stone Feeding Compaction Finishing
39. Soil nailing INTRODUCTION Soil nailing is the method of reinforcing the soil with steel bars or other material.
40. CONSTRUCTION SEQUENCE Excavation of Slope Drilling Nail Holes Nail Installation and Grouting Construction Shotcrete Fa Construction Construction Facing of Temporary cing of Subsequent Level of a Final, Permanent
41. COMPONENTS OF THE SYSTEM Figure:- Component of Soil Nail Wall
42. Gabions What are Gabions? • The term gabion refers to a modular containment system that enables rock, stone or other inert materials to be used as a construction material.
43. Micro piles • A micropile is a small-diameter (typically less than 300 mm), drilled and grouted replacement pile that is typically (up to 20% As/Ac) reinforced. • A micropile is constructed by drilling a borehole, placing reinforcement, and grouting the hole. • Micropiles can withstand axial and/or lateral loads.
44. What is a Geosynthetic ? • Natural or artificial product that is used along with soil in geotechnical constructions. • Natural: coir , jute, hemp, etc. • Artificial: polymeric or metallic Geosynthetics
