Mind map

Ground Improvement Techniques

Daisy Ronn English

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Why
- Fit for engineering purpose
  - Avoid cracking
  - effective loads
  - behaviour of soil
What can we change
- Strength
  - Extend to which soil resists deformation in response to an applied force
  - Shear box test
  - Triaxial test
- Compressibility
  - Volume decreases
  - Settlement
- Hydraulic properties
  - Change the rate of flow of water
- Problematic Behaviour
  - Excessive swelling/shrinkage
    - London clay
- Effects the ecosystem
- Factors effecting choice
  - Economics
  - Soil type
  - Area, depth and location
  - Desired soil properties
  - Availability of materials
  - Environmental concerns
  - Time
  - Experience and skill
Non-intrusive
- without addition of material
  - EK
    - electrode array
      - electroosmotic array
        anodes = reinforcement array
        cathodes = drainage array
    - geosynethetic types
      - geotextile
      - geodrains
      - electrokinetic geosynethetic
      - geonets
      - geocomposites
      - geogrids
      - geocells
      - geomats
      - geospacers
      - geostrips
      - geofoam
      - fibres
      - geomembranes
      - synthetic clay liners
      - geopipes
      - functions
        barrier
        drainage
        filtration
        protection
        reinforcement
        seperation
        erosion control
  - Microbial remediation
  - surface compaction
  - thermal treatment
Intrusive
- without adding material
  - shallow densifaction
    - smooth vibrating drum roller
    - sheepsfoot
    - Pneumatic tyre roller
    - combination rollers
    - grid rollers
    - impact rollers
    - small portable compactors
  - deep densifaction
    - blasting
      - explosive compaction
    - vibro-densifaction
      - vibro-compaction
        water
      - vibro-replacement
        water
      - vibro-displacement
        air
      - vibro-concrete columns
    - deep dynamic compaction
    - rapid impact compaction
- adding external material
  - stone columns
  - grouting
    - compensation
      - control or reverse settlement
      - cement
      - expands fractures
      - TAM
    - corrective
      - Physical method
      - Placing infill into subsurface voids
    - permeation grouting
      - chemical method
      - solidify granular ground so that it can carry an increased load
      - control water flow
        disposal of hazardous waste
        landfill
        tunnel through water bearing granular material
  - lime stabilisation
    - reactive
      - reaction occurs immeditely
    - 2-8% lime added
    - double diffused layer
      - flocculated
        higher compressibility
        higher peak strength
        less ductile
        less swell potential
    - methods
      - surface mixing
      - deep mixing
      - lime slurry pressure injection
      - lime piles
  - tar
    - physical process
      - binding asphalt and soil
  - cement
    - acts as a binder
      - ideal for well graded soils
      - ineffective in cohesive soils
      - offers
        increased compressive strength
        increased shear strength
        increase tensile strength
        increased stiffness
        resistance against freeze/thaw
        expansive soils
- providing reinforcement
  - ground anchors
  - soil nailing
    - benefits
      - 20-50%
      - suited to sloping terrian
      - immune to earthquakes
      - sustainable
    - Element facing
    - Full height facing face
    - Wrap around facing
    - construction
      - reinforcement in line with compressive plane causes failure
      - creep
    - failure modes
      - overall slope instability
      - sliding failure
      - overturning failure
      - rupture of connections
      - rupture of facing element
      - rupture/pullout of reinforcement
      - sliding between planes
      - sliding along reinforcement
  - reinforced geosynthetics
methods
- Mechanical
  - physical manipulation of the earth materials to increase soil density
  - short term external forces
  - surface compaction
  - deep compaction
- Physical/Chemical
  - thermal treatment
    - Heat
      - not used today
      - burning petroleum products
      - high temp causes drying effects by evaporation of water
      - cause physical reaction in clay
      - decreases compressibilty
      - reduces plasticity
      - reduces swelling potential
      - increases strength
    - Ground Freezing
      - temporary measure
      - unpleasant work
      - dangerous
      - expensive
      - convert pore water pressure to ice
        ice acts as a glue to bond together soil blocks
        increase bearing capacity and strength
      - all soils with sufficient water can be frozen
      - types
        open system
        expandable refrigerant system
        liquid nitrogen passed through copper tubes
        rapid freezing
        costly as coolant is lost
        closed system
        circulating coolant system
        cool brine
        5-10 times slower freezing
        cheaper
      - problems
        stress strain properties
        long term stability
        increased soil volume
        large displacements
        comprehensive modelling required
        safety
  - mixing additives
  - bio-stabilization
- hydraulic modification
  - lowing the water table
    - deep excavations
    - shallow water table
    - dry working space
    - lower lateral earth pressures
    - lower upwards force - seepage
      - reduce seepage to prevent erosion
  - Passive: Drains
    - slope stability
    - roadways
  - Active: Pumps
  - filtering
    - stop groundwater carrying away particles
    - geotextile
- Reinforcement
  - Improve tensile strength
  - Soil nailing
  - Vegetation

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Description: Mind Map on Ground Improvement Techniques, created by Daisy Ronn on 14/01/2018.
Created by: Daisy Ronn
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Ground Improvement Techniques

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