All Prefabricated Vertical Drains (PVD) will be installed in the same manner, unless otherwise specified by CLIENT. This method statement describes all steps in the process of installing the Prefabricated Vertical Drains.

1. 1.1 Method of Installation of PVD/Wick Drain
The drains will be installed to depths and at spacing as per approved working drawings.
Approval will be obtained for complete plan for installation of the drains along with the
particulars and test results from the manufacturer conformance to the specifications. The
equipment and the methodology for installation of the drains will conform to the specified
requirement of prescribed degree of consolidation and the time for achieving the same.
1.1.1 Method of Transportation and Storage
 The vertical drain material will be labeled or tagged for sample identification and other
quality control purposes.
 Each roll will be identified by individual roll number, date of manufacture and product
identification.
 During transportation and storage the drain will be wrapped in heavy paper, opaque
plastic or other or similar heavy duty protection covering.
 The drain will be protected from sunlight, mud, dirt, dust, debris and other detrimental
substances during transportation and storage on site.
1.1.2 Quality Control and Testing
 The acceptance will be based on verified physical dimensions; manufacturer’s drain
designation /stamp on drain or package, and manufacturer's certification of properties.
1.1.3 Equipment
 Prefabricated Vertical Drain (PVD) will be installed with approved hydraulic stitcher
which will cause a minimum of disturbance to the soil during installation and maintain
the mandrel in a vertical position.
 The PVD's will be installed using a mandrel or sleeve that will be advanced through the
compressible soils to the required depth using constant load, or constant rate of
advancement.
 The mandrel will protect the PVD material from tears, cuts and abrasion during
installation and will be withdrawn after the installation of the drain.
 The drain will be provided with an anchor plate or rod at the bottom of the mandrel to
cover the mandrel end and prevent soil from entering the mandrel during installation.
 The anchor plate or rod will be sufficient to anchor the drain at the required depth
during mandrel removal.
 The mandrel will be shaped to minimize disturbance to the soil, having a uniform and
smooth exterior shape, without projections of any kind.

2. 1.1.4 Approval
• Prior to the beginning of PVD installation, approval will be obtained for materials and
equipment, sequence and method proposed for PVD installation.
• Geotechnical Investigations/tests will be conducted to identify the required locations
where prefabricated vertical drains will be installed.
• Detaildesign,drawings willbe prepared and approval willbe obtained for the installation
of prefabricated vertical drains prior to execution of the work.
1.2 Preparation of Working Platform
Placement of earth fills of 1.0 m thickness or sufficient for working of installation machinery
will be done prior to actual installation. The unsuitable materials below the existing ground
Level will be removed up to 500 mm to 1000 mm or as per instruction of the Engineer and will
be refilled with suitable embankment soil in layer for preparation of working platform and
moving the PVD equipment. The embankment will be constructed as per Drawing or as
directed by the Engineer in charge.
1.2.1 Installation Method:
PVD Materials will be transported to work location and stock piled under a shed on elevated
platform
 Bench mark will be established, Layout will be given according to approved drawing by
numbering the PVD.
 Precautions will be taken to protect the bench marks & other.
 The installed location of the PVDs will not vary by more than 150 mm from the plan
locations designated on the drawings.
 PVDs will be installed from the working surface to the approved design depth.
 PVD will be terminated if refusal is encountered at a depth less than design depth.
 The refusal length of each drain will vary based on the derived geological formations
encountered over the site.
 Refusal of PVD will be defined as installation of the drain to the non-compressible layer
(stiff clay) underlying the compressible layer (soft clay) which will be consolidated.
 The compressible layer versus the non-compressible layer will be defined by testing of
soil log collected from the designated treatment areas.
 Refusal will be identified when the mandrel meets resistance and stops or slows at the
certain depth of the non-compressible layer.
 Depth of installationwillbe marked on mandrel by paint mark for determining the depth
of the advancing drain at any given time and the length of the drain installed at each
location.
 The drain material will be cut neatly at its upper end with 300 mm protruding above the
working surface.
 Whenever the PVD is required to connect to prefabricated horizontal drainage system,
sufficient PVD material will be left to make the connection.

3.  A summary of the total quantity of PVD installed at the end of each working day will be
maintained with due signatures of Employer/Engineer representatives.
 Equipment for installing PVD will be aligned & plumbed to testify the verticality of the
mandrel prior to installing each drain and will not deviate from the vertical more than 1
in 50 during installation of any drain.
 The installation will be performed without any damage to the drain during advancement
or retraction/withdrawal of the mandrel.
 Alternate raising or lowering of the mandrel during advancement will not be done.
 Raising of the mandrel will be done after completion of a drain installation.
 Installation of the drains will be coordinated with the placement of geotechnical
instrumentation.
 Due care will be taken to installing drains in such a manner so as not to disturb
instrumentation already in place.
1.2.2 Splicing of PVD Material
 Splicing of the PVD drain material will be done by stapling in a workmanlike manner so
as to ensure structural and hydraulic continuity of the drain. At the splice, the jacket that
passes through the installationrig firstwillbe external to the trailing portion. A maximum
of one splice per drain will be permitted without specific permission from the Employer
/Engineer -in-charge. The jacket and core will be overlapped a minimum of 100 mm at
any splice.
2.1 Drainage Sand Blanket:
2.1.1 Sand Blanket:
 After bed preparation a sand blanket of medium to coarse sand of 500 mm compacted
thickness will be laid over the top of compacted formation and will project 2.0m on all
sides.
 The blanket will spread over the entire area of treatment as per drawing and design.
 The blanket will be laid in layers of 150mm (maximum compacted thickness) and
compacted by means of vibratory rollers.
2.1.2 Drainage System:
 To remove the water from consolidating system, proper drainage arrangement including
pits, channels and pumping arrangement will be constructed.

4. 2.1.3 Protection of Non- woven Geotextile during high wind:
 If wind is prevalent, fabric installation will be started at the upwind side of the project
and will be continued towards down wind.
 The leading edge of the fabric will be secured at all times with sandbags or other means
sufficient to hold it down during high winds.
 Sandbags or rubber tires will be used as required to hold the fabric in position during
installation.
 Materials, equipment or other items will not be dragged across the fabric or be allowed
to slide down slopes on the fabric.
 If the fabric is damaged during any step of the installation, the damaged section will be
repaired by covering it with a piece of fabric.
 Installed Geo-textile will be immediately covered by sand blanket and preloading fill of
required height
2.1.4 Drainage of Ground Water
The water that discharges through the prefabricated vertical drains will be accumulated at
temporary ditches to be dug at nearby areas and the accumulated water will be dewatered
regularly from the ditches to the outfalls as instructed by the Engineer.
2.1.5 Instrumentation and Monitoring
• The Contractor will develop an Instrumentation and Monitoring Plan (IMP) to monitor
the embankment performance and settlements during construction and the
maintenance period.
• The plan will detail the nature of the instrumentation, locations and positions within the
ground where they will be installed, the frequency of survey, and provide justifications
for their use, and the design objectives they will clarify.
• The plan will detail the methods of interpretation of monitoring data, and specify how
this information will enable the Contractor to verify the compliance of the embankment
to the design criteria.
• The plan will detail the methods of maintaining the existing and proposed embankment
at design elevations during construction, and the trigger which initiates this need for
maintenance.
• This will be correlated with the design criteria, the tolerance for rail operation and the
proposed frequency of maintenance.
The IMP will detail the activities that are proposed to be undertaken as part of the
monitoring program. This includes:
• Baseline surveys and measurements within 4 weeks of the completion of construction of
each section of the embankment;
• Survey measurements at 50 m intervals along the existing and proposed road
embankment, and at 20 m intervals within 100 m of bridge/culvert abutments, and at
all locations where settlement is predicted to be maximum;

5. • Using the results of the monitoring program to assess the need for remedial works, and
in the design of any necessary remedial works; and
• Production of inspection reports, interpreted instrumentation monitoring reports and
remedial works reports.
2.1.6 Monitoring the Build-up and Dissipation of Pore Pressure:
 Vibrating wire piezometer will be used for the measurement of changes in pore
pressure.
 The type of tip will be chosen to suit the expected maximum groundwater pressure and
the characteristics of the surrounding ground.
 The combined accuracy of instrument and readout device will be within ±1.0 % of the
true pressure;
 All piezometers will be tested before installation by submergence in still clean water to
a series of depths appropriate to the anticipated pressure range of operation in order to
verify the calibration and accuracy of the instrument;
 The tip of each piezometer will be air free and the porous stone of the tip will be fully
saturated by submergence in clean de-aired water for a period of at least 24 hours prior
to installation.
 Complete de-airing of the porous stone will be confirmed by periodic weighing;
 The piezometer will be installed in 100 mm diameter boreholes, at depths instructed by
the Engineer;
 Drilling to the required depth will be carried out without the use of air flush, in the
vicinity of the tip position.
 Casing will be used to stabilize the hole through unstable ground;
 Complete installation will be carried out as soon as practicable, and no later than 24
hours, after drilling to minimize the amount of deterioration or alteration of the ground
at the location of the piezometer tip;
 The hole will be flushed until it is filled with clean water.
 The piezometer tip will then be inserted under water and backfilled with clean sand to
form a sand cell. The sand cell will be of 1.0m height with the piezometer located in its
center; and
 Piezometers will be installed at locations shown on the Working drawings or as
instructed by the Engineer
2.1.7 Monitoring the lateral movement of foundation soils with Toe-monuments
 The lateral movement of foundation soils due to embankment loading will be measured
by the inclinometers.
 They willconsistof a 10 mm diasteel rod which is installedin the ground to the required
depth.
 During the placing of the surcharge and compaction, the Contractor will take utmost
care so that the monitoring instruments are not damaged.

6.  Where the Engineer determines that the monitoring instruments are damaged or non-
functional, they willbe immediately replaced by the Contractor to the satisfactionofthe
Engineer.
 Compaction by small vibratory rollers will be done for 1.5 m around the monitoring
instruments and bigger rollers will not be used near the monitoring instruments.
Similarly care will be taken that movement of dumpers does not damage the monitoring
instruments.
2.1.8 Frequency of Observations
 The readings of the piezometers, toe-monuments and the settlement gauges will be
recorded at the frequency shown on the Working drawings or as instructed by the
Engineer.
 All data will be recorded in a register and maintained accurately to a format approved
by the Engineer.
 The observation data will be recorded during construction and for the duration of the
maintenance period thereafter, unless otherwise instructed by the Engineer.
 It is therefore essential that the instruments are not tampered with and/or stolen.
Suitable precautions will be taken in this regard by the Contractor.
2.1.9 Staged Construction of Embankment
 Pre-consolidation by surcharging and/or staged construction of embankments will be
carried out where and as indicated on the Working drawings or as instructed by the
Engineer.
 The staged construction of embankment fill and subgrade material will be placed over
the geotextile layer, in layers, up to the height and to the sequence shown on the
working drawings.
 The addition of surcharge material will be placed as and where shown on the working
drawings.
 The surcharge, where required, willbe kept in place for a period as shown on the working
drawings to achieve desired degree of consolidation.
 The surcharge material will meet the requirements of the subgrade material defined.
 After ascertaining that the desired degree of consolidation is achieved, the surcharge,
where specified, which is not forming part of permanent works embankment will be
removed to the required line and level as per the working drawings.
 If the consecutive 3 results of consolidation remains same after staged Construction of
embankment for 3 months the Engineer-In-Charge may instruct the contractor to
proceed further activities over the surcharge.
 Records of the instruments will be done twice a week during the active filling stage of
the embankment, whereas the survey may be taken once in a week during hold periods.