Ground Improvement Technology

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November 22, 2022

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Ground Improvement Technology

Why Ground improvement?

Increases shear strength
Reduces permeability, and
Reduces compressibility

Understanding Ground Improvement

Ground improvement includes two parts.

1.First Understand the ground

2.Then find out the most engineered1 solution for improvement

Engineered means most economical, safe and ease of simplicity to adopt

Methods for Soil Improvement?

Ground Reinforcement

Stone Columns
Soil Nails
Deep Soil Nailing
Micro piles (Mini-piles)
Jet Grouting
Ground Anchors
Geosynthetics
Fiber Reinforcement

Ground Improvement
Deep Dynamic Compaction
Drainage/Surcharge
Compaction grouting
Surface Compaction

Ground Treatment
- Soil Cement
- Lime Admixtures
- Fly ash
- Dewatering

Tilting of structure: Overturning

Leaning temple dome, Huma, Orissa, India

A building at the Lotus Riverside complex in Shanghai’s Minhang district collapsed

Sink Holes

Formation of Sink Holes

Frost heave

Overturned apartment complex, Niigata 1964

Why we study geotechnical Structure Failure?

Because we want engineered design of geotechnical structures.
Engineered means
Economical
Safe
Durable
Strong

List of ground improvement techniques

Ground Improvement

Deep Dynamic

Compaction
Drainage/Surcharge
Electro-osmosis
Compaction grouting
Blasting
Surface Compaction
Ground Freezing

Basic Operations:

Increasing soil Density Removing Air Voids, Pore water Changing soil water properties

List of ground improvement techniques

Ground

Improvement

Field Compaction

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.

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.

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.

Equipment (Cont.)

Tamping foot roller
- About 40% coverage
- It is best for compacting fine-

grained soils (silt and clay).

Dynamic Compaction

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
  
  Dynamic compaction was first used in Germany in the mid-1930’s.
  
  Dynamic Compaction
  
  Vibro-Compaction
  
  Vibroflotation
  
  Vibroflotation is a technique for in situ densification of thick layers of loose granular soil deposits.
  
  It was developed in Germany in the 1930s.
  
  Vibroflotation Procedures

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.

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.

Ground Treatment

Soil-Cement stabilization

Stabilization Using cement and other admixtures such as fly ash, blast furnace slag has been adopted in many geotechnical and

highway engineering projects.

Soil Mixing & Deep Soil Mixing

Mixing tools used for different soils

Process of deep soil Mixing

Ground

Reinforcement

Mechanically Stabilized Soil

Elevated Highway,

Grouting

Injection formation

of a slurry or a liquid solution into a soil or rock formation
The grout subsequently hardens – increases the strength and decreases compressibility and permeability.

Stone Column

Stone column consists of crushed coarse aggregates of various sizes
A ground improvement technique to improve the load bearing capacity and reduce the settlement of the soil

INSTALLATION TECHNIQUES

Soil nailing

INTRODUCTION

Soil nailing is the method of reinforcing the soil with steel bars or other material.

CONSTRUCTION SEQUENCE

Excavation of Slope
Drilling Nail Holes
Nail Installation and Grouting
Construction of Temporary Shotcrete Facing
Construction of Subsequent Level
Construction of a Final, Permanent Facing

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.

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.

Geosynthetics

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
  
  Types of Geo-Materials (Geosynthetics family)
  - Geotextile.
  - Geogrid.
  - Geonet.
  - Geo Membrane
  - GeoComposites
  - Geofoam
  - Geocell
  - Geomat
  - Geomesh
  - Geopipe
  - Geospacer
    - Geotextile
      
      Geo Grid
      - Uniaxial (ii) Biaxial
        
        (iii) Bonded (iv) Woven
    - Geonet.
    - Geo Membrane
    - Geo-composites
      - Combination of one or more type of geosynthetics for modified function.
    - Geofoam
Foam like material, provided for functions mentioned below:
Moisture retention.
Erosion protection.
Generally gives temporary solution of the problem.