Good presentation on Dynamic Compaction

1. Dynamic compaction

2. Need of ground improvement(few reasons)

3. Ground improvement techniques are of 3 types(basic
operations)
1. Ground improvement(current topic falls here):increasing soil
density by removing air voids , pore water & changing soil water
properties
2. Ground treatment : modification using additional materials(fly ash,
slag,…) to achieve required results.
3. Ground reinforcement: reinforcing materials acting as structure and
take majority of load.

4. Dynamic compaction
• Method was invented in late 60’s by Menard company
• This method is used for various soil conditions and variety of
application such as: roads , airports , large halls

5. Dynamic compaction has been successfully used to improve
many types of weak ground deposits including:
• Loose naturally occurring soils such as alluvial, flood plain.
• Landfill deposits both recent and old.
• Building rubble and construction debris deposits.
• Partially saturated clay fill deposits that are elevated above
the water table.
• Collapsible soils including loess.
• Loose sands and silts to reduce liquefaction potential.
Most suitable for :granular soils
Unfavorable for :Saturated or nearly saturated impervious
soils

6. Dynamic compaction
• Technique involves repeated dropping of heavy weights(generally
metal plates) from a crane.
• Weight ranges from 6-172 tons
• Drop height varies from 10m to 40m
• Can densify loose sands up to a depth of 3-12m using 6-30ton weight
• Can be done in either rectangular or triangular pattern in phases
• Spacing between impact depends upon :
Depth of compressible layer
Permeability of soil
Location of water table
• Deep layers are compacted at wider grid spacing whereas upper layer
is compacted using lower grid spacing

7. • Deep layers are compacted at wider grid spacing whereas upper layer
is compacted using lower grid spacing

8. • Spacing between impact depends upon :
Depth of compressible layer
Permeability of soil
Location of water table
• Deep layers are compacted at wider grid spacing whereas upper layer
is compacted using lower grid spacing

9. • Deep crates are formed and can be filled using sand after each pass
• Heaving around crater is small as they are compressible layers.
Things to be taken care of
• Ground water table should be kept below 2m
• Through soil exploration must be done in order to act accordingly
• After completion of the treatment we should check whether its giving us
required results or not by :
deep penetration tests like standard penetration resistance
cone penetration resistance.

12. Advantages
• Reduces post construction settlements.
• Increased bearing capacity ,in-situ density and voids are collapsed.
• Reduces volume of landfill waste.
• In many cases may prove economical as piling may be more costly.

13. Limitations
• Expensive and time consuming
• Shock waves may affect underground facilities and adjacent
constructed area
• Causes pollution by making vibrations, noise and gusts of air.
Thank you