Principles of soil densification – Properties of Compacted soil, Compaction control tests, Specification of compaction requirements, Blasting, Vibrocompaction, Dynamic Tamping and Compaction piles.

1. UNIT-2
Mechanical
modifications

2. ➢ Mechanical modifications :
In mechanical modifications, the soil density is increased
by the application of mechanical force,including
compaction of surface layers by static vibratories.
This increase the density of soil and rocks by removal of
air voids through mechanical energy application is
known as densification.

3. Insite
ground
improvement
techniques
compaction
preloading
Thermal
treatment

4. compaction
dynamic
vibratory
static

5. DEEP COMPACTION TECHNIQUES:
➢ Densification of deep soil deposits is achieved by the following techniques:
1) Vibro compaction
1) Vibro-Displacement compaction
1) Dynamic compaction
blasting
Vibratory probe
Vibratory compactors
Displacement piles
Vibro flotation
Sand compaction piles

6. Vibro
compaction:
a) Blasting:
INSTALATION OF EXPLOSIVES
▪ In this technique a certain amount of amount of explosive is buried at
certain depth of a cohesionless soil, and is then detonated.

7. b) Vibratory
probe:
▪ Vibratory probe is also called as Terra probe.
▪ It is mainly used in offshore locations.
▪ It is efficient when ground water is 2 to 3m of surface.

8. c) Vibratory compactor
▪ These compactors are available as vibrating drums, vibrating pneumatic
tires, vibrating plate equipment.
▪ They have limited depth of effectiveness.
▪ Heaviest vibratory rollers can densify above 2m depth.

9. DENSITY Vs DEPTH GRAPH FOR DIFFERENT NO. OF ROLLERS PASSES

10. 2) Vibro-Displacement Compaction:
This is a method to improve the density of
cohesion less granular soils.
a) Displacement piles:
▪ Natural ground and existing
fill cannot be compacted in
layers.
▪ The simplest method
among the vibro
displacement technique is
driving piles which is very
effective in densifying
cohesionless sands upto
some depth.
▪ Such piles are called as
displacement or
compaction piles.

11. b) Vibroflotation:
▪ It is an effective technique for densifying cohesionless soils with
simultaneous vibration and saturation.
▪ This equipment consist of vibroflot probe, power supply, water pump,
crane, front end loader.
▪ The results are effective which depends on;
a) Equipment capacity
b) Probe spacing and pattern
c) Type of soil to be compacted
d) Backfill material
e) Workmanship

12. c) Sand compaction piles:
▪ In this method a hollow steel pipe with detachable bottom plate is
driven to desirable depth.
▪ Sand is introduced in lifts with each lift compacted with the
withdrawl of pipe pile.
▪ It is also called as vibro composer method.
▪ This method economical for moderate depths upto 15m.

13. 3) Dynamic compaction:
▪ Dynamic compaction is a technique which was used long ago.
▪ In this heavy weight is dropped from a height of 15 to 40m to fall freely back
down to ground.
▪ This process is repeated either at same location or over other that to be
stabilized at 5m to 10m spacing.
▪ The soil at the shallow depth from the surface will be in great distributed
condition.
▪ As soft soils are susceptible for disturbance due to heavy impact, a very
careful evaluation is required in clayey soils.

14. DYNAMIC COMPACTION EQUIPMENT

15. INSITU DENSIFICATION OF COHESIVE
SOILS:
INSITU
DENSIFICATION
METHODS
PRELOADING VERTICAL
DRAINS
STONE
COLUMNS

16. PRELOADING
HEAPING OF FILL
MATERIAL
EMBANKMENT
LOADING
LOWERING WATER
TABLE
INUNDATION OR
PREPONDING
VACUUME
PRELOADING METHOD
JACKING
VACUUME PRELOADING
METHOD