This document discusses ground improvement technologies including stone column and band drain technologies. Stone columns involve compacting aggregates into vertical columns to improve soil conditions and increase load capacity. Band drains involve installing prefabricated vertical drains to accelerate consolidation of loose, saturated clays by providing lateral drainage pathways. A case study describes a highway project in India where both stone columns and band drains were used over 10km to improve ground conditions.

1. GROUND IMPROVEMENT TECHNOLOGY
- STONE COLUMN TECHNOLOGY
- BAND DRAIN TECHNOLOGY
Sravan MV
Engineer

2. ALTERNATIVES FOR INADEQUATE GROUND?
 Abandon the site and locate the structure
elsewhere
 Design deep foundations to carry the weight of
the structure to competent stratum
 Redesign the structure according to the ground
conditions
 Improve the properties of the ground prior to
construction

3. BASIC PRINCIPLE OF GROUND IMPROVEMENT
Ground improvement is the modification of
the ground properties in order to achieve the
required ground conditions for the particular use
of the ground.
 Densification of the ground , E.g.: Compaction
 Accelerate the consolidation, E.g.: Vertical drains
 Usage of geo synthetics, E.g.: Geotextiles
 Usage of admixtures, E.g.: Cement stabilization
 Preloading
 Mechanical Stabilization

4. STONE COLUMN TECHNOLOGY

5. STONE COLUMN TECHNOLOGY
 It is also known as Vibro replacement or Vibro
displacement
 Compacted aggregates form as a vertical
columns to improve the soil conditions.
 Resulting in considerable increase in vertical
load capacity and to an extent contribute to as
drains to dissipate pore water pressure.

6. STONE COLUMN TECHNOLOGY
Two methods of stone columns:
 Wet / Top Feed Method
 Dry / Bottom Feed Method

7. STONE COLUMN : WET / TOP FEED METHOD
Vibro Probe
 Step 1 : Penetration of probe
 Step 2 : Backfilling of aggregate and compacting
 Step 3 : Consolidation of granular fill and
finishing the column

8. STONE COLUMN : DRY / BOTTOM FEED METHOD
 Step 1 : Penetration of probe
 Step 2 : Installation of aggregate through separate duct
along the vibro probe
 Step 3 : Consolidation of granular fill and finishing the
column

9. STONE COLUMN : ADVANTAGES
 Technically and potentially economical
alternative for deep compaction.
 Alternative for dynamic compaction, deep
blasting etc.,
 Quicker than preloading the site
 It increases the bearing capacity, reduces the
settlements, liquefaction potential.

11. CASE STUDY:
Four Lane National Highway Connectivity to ICTT –
Vallarpadam, Kochi
 Connects NH - 47 and NH - 17.
 Project cost was revised from 329.46 cr to 571.20 cr due
to ground improvement, bridges and retaining walls.
 Road Length – 17.2km, total length of bridges – 2.93km.
 Ground improvement works – 10km.
 Wet /Top method of installation was used.
 Stone columns where installed in 15 locations between
Ch, 0.245 and 16.210

12. CASE STUDY: INSTALLATION

13. CASE STUDY : INSTALLATION

14. CASE STUDY :STONE COLUMN
 Quantity of stone aggregate used : 28,774 cum.
 Geo grid consumed: 35,536. 12 sq.m
 Bulk density considered : 1.8 MT/m3
 App. Quantity of aggregate for one column : 35MT
 Total number of stone columns : 22,166 no's
 Time required for each stone column : 60 min
 No. of stone columns installed per day : 15 no's
 Total running meter of all the columns : 91,641 Rm

15. BAND DRAIN TECHNOLOGY

16. BAND DRAIN TECHNOLOGY - PVD
 Used in loose, compressible and water
saturated clay and silty clays.
 Soils are characterized by very loose skeleton
and a large pore sizes filled with water
 Requires about ten or more years to
consolidate on preload.
PVD – Prefabricated Vertical Drain.

17. WHAT IS VERTICAL DRAIN?
 Consolidation takes place in only
one direction
 Vertical drainage path may be
substantially longer
 It may take 10+ years to
consolidate
 Pore water will flow laterally
 Pore water pressure dissipates as
the layer drains and water is
conveyed through vertical drains
 It takes only about 6months or so
to consolidate

18. COMPONENTS OF PVD?
Core
 Core : It is called drained body
corrugated, flexible and made of
polypropylene, designed to provide
high discharge capacity, high tensile
and compressive strength.
 Filter Jacket: Non – woven ,thermically
Filter
bonded polypropylene wrapped
around the core. Acts as the filter to
allow ground water to the core.

19. ADVANTAGES OF BAND DRAIN TECHNOLOGY:
 Minimum disturbance to the soil layers during
installation
 High water discharge capacity
 High tensile strength prevents the collapse of
flow path.
 Fast and easy installation
 Deep installation up to 40m.

20. CASE STUDY:
Four Lane National Highway Connectivity to ICTT –
Vallarpadam, Kochi
 Connects NH- 47 and NH – 17.
 Project cost was revised from 329.46 cr to 571.20 cr due
to ground improvement, bridges and retaining walls.
 Road Length – 17.2km, total length of bridges – 2.93km.
 Ground improvement works – 10km.
 PVD were installed in 8 locations between Chainage 8.400
– 15.000

21. CASE STUDY: INSTALLATION EQUIPMENT
 Hydraulic Stitcher
 Mandrel
 Base Hydraulic Machine

22. CASE STUDY: BAND DRAIN INSTALLATION

23. CASE STUDY: BAND DRAIN INSTALLATION

24. CASE STUDY: BAND DRAIN TECHNOLOGY
 Total length of band drains : 56,21,780 Rm
 Total Granular blanket : 1,23,386 Cum
 Total Geotextiles used : 3,90,714 sq.m
 Time taken for install one band drain of 25m : 1min
 Time taken for splicing the wick : 1 min

25. CASE STUDY: BAND DRAIN TECHNOLOGY
After the installation of band
drains, Casagrande peizometer and plate type
settlement recorders where installed in order to
check the settlements

26. CASE STUDY: BAND DRAIN TECHNOLOGY
Description Values
Cumulative Heights Stage 1 : 3.0m ( i.e., 1.0m above the top of
reclamation)
Stage 2 : 5.5m ( includes 1.5m of
additional surcharge)
Waiting period of each stage Stage 1 : 6.0 months
Stage 2 : 6.0 months
The water coming out of the vertical drains is collected
in temporary ditch. The water collected is regularly
dewatered to the adjoining area.

27. THANK YOU!