PREFABRICATED VERTICAL
DRAINS (PVD)
In construction of various structures
on compressible, saturated soils
like soft clay, excessive settlement
is a common problem to deal with.
The ground improvement technique
using prefabricated vertical drains
(PVD) is one of the most suitable
methods to overcome this problem.
The sole purpose of vertical drain
system is to shorten the drainage
path of the pore water from a low
permeable layer to free water surface
or to pre-installed drainage
layer, thereby accelerating the rate
of primary consolidation or the process
of settlement. Application of
ground improvement method using
prefabricated vertical drains (PVD)
coupled with surcharge or preloading
can significantly shorten the
period of primary settlement.
SEAFCO
144 Prayasuren Road, Bangchan, Khlong Sam Wah, Bangkok 10510. Tel. (662) 919 0090-7, Fax. (662) 919 0098
EQUIPMENT
PVD installation equipment can be developed to suit the soil
condition, installation depth, specified scope of work and required
production rate. Technical data of typical medium-sized
PVD installation equipment and accessories are shown below.
Installation Rig
Type of Base Machine : Excavator of suitable model
CAT EL200B or larger model
Size (CAT EL200B) : 3.18m x 4.45m
Weight (CAT EL200B) : 20 ton
Pushing Force : 5.5 – 20 ton
Mandrel Lifting and Pushing : Hydraulic gear drive
Mast Height : 8m
Typical Mandrel Dimensions
Weight of Guide and Mandrel : 1.5 to 4 ton
Length of Mandrel : 12 to 20m
Cross-sectional Area of Mandrel : 60 to 70 cm2
Maximum Installation Depth : 11 to 19m
CHARACTERISTICS OF PVD
PVD is a prefabricated material
consisting of a plastic core covered
by synthetic geotextile “filter jacket”.
Two main components of PVD
serve the following functions;
• Core serves as a longitudinal
flow path along the drain
• Filter jacket allows water to
pass into the core while restricting
intrusion of soil particles
Time settlement curve of soft clay showing significant
time reduction achieved by applying PVD with
surcharge loading
TYPICAL APPLICATIONS
PVDs with surcharge as pre-loading
method has been successfully applied
in various projects. PVDs are
typically used as ground improvement
system in -
• Construction of road, railway,
embankment, airport and ports
• Industrial projects
• Land reclamation projects
Application of PVD with surcharge loading for ground improvement
work of road embankment
Time
Settlement
without PVD
PVD w ithout surcharge
required settlement PVD with surcharge
Surcharge
Final R oad Level
Dra inage S and Blanket P um p in g W e ll
SO F T C L AY P V D
Close-up view of
PVD installation
144 Prayasuren Road, Bangchan, Khlong Sam Wah, Bangkok 10510. Tel. (662) 919 0090-7, Fax. (662) 919 0098
SEAFCO
Reference:
• Hansbo, S. (1993), “Band Drains”, Ground Improvement, Blackie Academic Professional, U.K
• Center for Civil Engineering Research and Code (1996), Building on Soft Soils, A.A. Balkema, Rotterdam, The
Netherlands
All rights reserved. No part of this publication may be reproduced in any form or by any means, without
the prior written permission of SEAFCO PUBLIC CO., LTD.
QUALITY CONTROL IN
INSTALLATION
• Use appropriate size of
Mandrel and anchor plate
to minimize soil disturbance
• Use Mandrel with adequate
stiffness to maintain verticality
• Apply appropriate penetration
rate to avoid significant
bending
• Check verticality during installation
LAYOUT CONFIGURATION AND DRAIN INFLUENCE ZONE
PVDs are installed in either square or triangular patterns. A square
pattern is more simple for setting out in the field. Triangular pattern
however provides more uniform consolidation between drains.
Relationship of drain influence zone (D) to drain spacing (S) can be
expressed by;
For square pattern D = 1.13 S
For triangular pattern D = 1.05 S PVD equipment in operation
QUALITY CONTROL TEST
FOR PVD MATERIAL
• Apparent opening size
• Puncture resistance
• Burst strength
• Trapezoidal tear strength
• Grab tensile strength
• Discharge capacity (plain
and triaxial)
• Density of filter fabric
Installation sequence
Typical PVD layouts and drainage influence
Anchor
Plate
Position equipment and
anchor plate installation
Mandrel driving Mandrel extraction PVD cutting
D = 1.05 S D = 1.13 S
Triangular Pattern Square Pattern
PVD
PVD
DRAINS (PVD)
In construction of various structures
on compressible, saturated soils
like soft clay, excessive settlement
is a common problem to deal with.
The ground improvement technique
using prefabricated vertical drains
(PVD) is one of the most suitable
methods to overcome this problem.
The sole purpose of vertical drain
system is to shorten the drainage
path of the pore water from a low
permeable layer to free water surface
or to pre-installed drainage
layer, thereby accelerating the rate
of primary consolidation or the process
of settlement. Application of
ground improvement method using
prefabricated vertical drains (PVD)
coupled with surcharge or preloading
can significantly shorten the
period of primary settlement.
SEAFCO
144 Prayasuren Road, Bangchan, Khlong Sam Wah, Bangkok 10510. Tel. (662) 919 0090-7, Fax. (662) 919 0098
EQUIPMENT
PVD installation equipment can be developed to suit the soil
condition, installation depth, specified scope of work and required
production rate. Technical data of typical medium-sized
PVD installation equipment and accessories are shown below.
Installation Rig
Type of Base Machine : Excavator of suitable model
CAT EL200B or larger model
Size (CAT EL200B) : 3.18m x 4.45m
Weight (CAT EL200B) : 20 ton
Pushing Force : 5.5 – 20 ton
Mandrel Lifting and Pushing : Hydraulic gear drive
Mast Height : 8m
Typical Mandrel Dimensions
Weight of Guide and Mandrel : 1.5 to 4 ton
Length of Mandrel : 12 to 20m
Cross-sectional Area of Mandrel : 60 to 70 cm2
Maximum Installation Depth : 11 to 19m
CHARACTERISTICS OF PVD
PVD is a prefabricated material
consisting of a plastic core covered
by synthetic geotextile “filter jacket”.
Two main components of PVD
serve the following functions;
• Core serves as a longitudinal
flow path along the drain
• Filter jacket allows water to
pass into the core while restricting
intrusion of soil particles
Time settlement curve of soft clay showing significant
time reduction achieved by applying PVD with
surcharge loading
TYPICAL APPLICATIONS
PVDs with surcharge as pre-loading
method has been successfully applied
in various projects. PVDs are
typically used as ground improvement
system in -
• Construction of road, railway,
embankment, airport and ports
• Industrial projects
• Land reclamation projects
Application of PVD with surcharge loading for ground improvement
work of road embankment
Time
Settlement
without PVD
PVD w ithout surcharge
required settlement PVD with surcharge
Surcharge
Final R oad Level
Dra inage S and Blanket P um p in g W e ll
SO F T C L AY P V D
Close-up view of
PVD installation
144 Prayasuren Road, Bangchan, Khlong Sam Wah, Bangkok 10510. Tel. (662) 919 0090-7, Fax. (662) 919 0098
SEAFCO
Reference:
• Hansbo, S. (1993), “Band Drains”, Ground Improvement, Blackie Academic Professional, U.K
• Center for Civil Engineering Research and Code (1996), Building on Soft Soils, A.A. Balkema, Rotterdam, The
Netherlands
All rights reserved. No part of this publication may be reproduced in any form or by any means, without
the prior written permission of SEAFCO PUBLIC CO., LTD.
QUALITY CONTROL IN
INSTALLATION
• Use appropriate size of
Mandrel and anchor plate
to minimize soil disturbance
• Use Mandrel with adequate
stiffness to maintain verticality
• Apply appropriate penetration
rate to avoid significant
bending
• Check verticality during installation
LAYOUT CONFIGURATION AND DRAIN INFLUENCE ZONE
PVDs are installed in either square or triangular patterns. A square
pattern is more simple for setting out in the field. Triangular pattern
however provides more uniform consolidation between drains.
Relationship of drain influence zone (D) to drain spacing (S) can be
expressed by;
For square pattern D = 1.13 S
For triangular pattern D = 1.05 S PVD equipment in operation
QUALITY CONTROL TEST
FOR PVD MATERIAL
• Apparent opening size
• Puncture resistance
• Burst strength
• Trapezoidal tear strength
• Grab tensile strength
• Discharge capacity (plain
and triaxial)
• Density of filter fabric
Installation sequence
Typical PVD layouts and drainage influence
Anchor
Plate
Position equipment and
anchor plate installation
Mandrel driving Mandrel extraction PVD cutting
D = 1.05 S D = 1.13 S
Triangular Pattern Square Pattern
PVD
PVD
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