VIETNAM OIL AND GAS GROUP
SOUTHWEST PIPELINE OPERATING COMPANY
PROJECT
BLOCK B – O MON GAS PIPELINE
PACKAGE
DETAILED DESIGN FOR THE ENTIRE PROJECT, PROCUREMENT,
CONSTRUCTION AND INSTALLATION OF ONSHORE PIPELINE,
STATIONS AND COMMISSIONING FOR THE ENTIRE PROJECT (EPC)
TECHNICAL SPECIFICATION
FOR SOIL IMPROVEMENT FOR ALL STATIONS
0
30/09/24
Issued for Approval
Rev.
Date
Purpose
EPC CONTRACTOR:
CONTRACTOR
SUBCONTRACTOR:
COMPANY
Document No:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Total of Pages: 49
PTSC-LILAMA18 CONSORTIUM
GEOVIETNAM - CCU
(Including this page)
This DOCUMENT is the property of SWPOC and PTSC-LILAMA18 Consortium. Therefore, it shall not be released to any third party
without the permission of authorized personnel of SWPOC and PTSC-LILAMA18 Consortium.
VIETNAM OIL AND GAS GROUP
SOUTHWEST PIPELINE OPERATING COMPANY
PROJECT
BLOCK B – O MON GAS PIPELINE
PACKAGE
DETAILED DESIGN FOR THE ENTIRE PROJECT, PROCUREMENT,
CONSTRUCTION AND INSTALLATION OF ONSHORE PIPELINE,
STATIONS AND COMMISSIONING FOR THE ENTIRE PROJECT (EPC)
TECHNICAL SPECIFICATION
FOR SOIL IMPROVEMENT FOR ALL STATIONS
0
30/09/24
Issued for Approval
PNB
PMT/NQV
PHD/NTS
TDT
Rev.
Date
Purpose
Prepared
Checked
Reviewed
Approved
EPC CONTRACTOR:
SUBCONTRACTOR:
Document No:
SWG-PTSCL18-EPC-00-CI-SPC-0001
PTSC-LILAMA18 CONSORTIUM
GEOVIETNAM - CCU
BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
REVISION HISTORY
No
Page
Content
1
All
Issued for Approval
Revision Date
Revision No.
30/09/24
0
Note
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BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
TABLE OF CONTENT
1.
PROJECT INTRODUCTION .................................................................................... 6
1.1.
Project overview ........................................................................................................... 6
1.2.
Project description ....................................................................................................... 6
2.
GENERAL INFORMATION ..................................................................................... 7
2.1.
Purpose of Document................................................................................................... 7
2.2.
Definitions and Abbreviations .................................................................................... 7
2.3.
Codes and Standards ................................................................................................... 8
2.4.
Reference Documents ................................................................................................ 10
3.
TECHNICAL SPECIFICATION FOR LEVELING ............................................. 11
3.1.
Construction sequence ............................................................................................... 11
3.2.
Preparation ................................................................................................................. 11
3.3.
Construction of Standard Benchmark ..................................................................... 12
3.4.
Organic removal and leveling before spreading of separation geotextile ............ 12
3.5.
Spreading of separation geotextile ........................................................................... 13
3.6.
Construction of leveling............................................................................................. 15
3.7.
Inspection and acceptance......................................................................................... 17
3.8.
Monitoring work ........................................................................................................ 18
4.
SOIL IMPROVEMENT WORK BY PVP METHOD ........................................... 19
4.1.
Construction sequence ............................................................................................... 19
4.2.
Technical requirements of construction works ....................................................... 21
4.3.
Installation PVD ......................................................................................................... 21
4.4.
Construction of sealing wall ...................................................................................... 24
4.5.
Horizontal drainage pipe system construction work .............................................. 27
4.6.
Geotextile .................................................................................................................... 28
4.7.
Geomembrane ............................................................................................................ 28
4.8.
Vacuum Pump Installation ....................................................................................... 30
4.9.
Compensation sand filling ......................................................................................... 31
4.10.
Removal of vacuum system ....................................................................................... 32
4.11.
Drainage water ........................................................................................................... 32
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IMPROVEMENT FOR ALL STATIONS
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Revision No.: 0
4.12.
Monitoring work ........................................................................................................ 33
4.13.
Soil investigation to re-evaluation of Soil improvement work............................... 40
5.
SOIL IMPROVEMENT WORK BY CDM METHOD ......................................... 40
5.1.
Technical requirements for construction ................................................................ 40
5.2.
Requirements of material and equipment .............................................................. 43
5.3.
Quality inspection and acceptance of CDM columns ............................................. 46
6.
SAFETY AND ENVIRONMENTAL SANITATION WORK .............................. 47
6.1.
Environmental sanitation work:............................................................................... 47
6.2.
Occupational safety work .......................................................................................... 47
6.3.
Fire and explosion prevention work: ....................................................................... 48
6.4.
Electrical safety work: ............................................................................................... 48
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BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
1.
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
PROJECT INTRODUCTION
1.1. Project overview
Southwest Pipeline Operating Company (SWPOC) hereafter referred to as COMPANY
is responsible for development of Block B – O Mon Gas Pipeline to transport natural
gas from Block B, 48/95 & 52/97 located in Southwest Sea of Vietnam to supply gas
to the power plants at O Mon, Kien Giang Power Centre, supplement gas for Ca Mau
Gas – Power – Fertilizer Complex and other customers at Southwest area. Block B – O
Mon pipeline landfall points are at An Minh, Kien Giang & Mui Tram, Ca Mau. The
overall project includes about 432 km of offshore and onshore gas pipelines passing
through 03 provinces/cities: Ca Mau, Kien Giang and Can Tho.
1.2. Project description
The Block B-O Mon Gas Pipeline Project includes the following facilities:
 The offshore pipeline has a total length of 330.69 km, of which:
 Approximately 292.24 km of 28-inch offshore pipeline from Subsea Isolation
Valve (SSIV) downstream flange to An Minh Landfall Station (LFS) at Kien
Giang province.
 Approximately 38.45 km of 18-inch spur offshore pipeline from KP 206.9 to
approach Mui Tram Landfall Station (LFS) at Ca Mau province.
Figure 1. Location of Project’s facilities
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 The onshore pipeline has a total length of 102.8 km, of which:
 Approximately 7 km of 28-inch onshore pipeline from An Minh Landfall Point
(LFP) to An Minh Landfall Station (LFS) at Kien Giang province.
 Approximately 94 km of 30-inch onshore pipeline from An Minh Landfall
Station to O Mon Gas Distribution Center (GDC) at Can Tho Province;
 Approximately 0.4 km of 18-inch onshore pipeline from Mui Tram LFP to Mui
Tram LFS at Ca Mau province.
 Two (02) LFS’s at An Minh and Mui Tram, six (06) Line Block Valve Stations
(LBV), one (01) O Mon GDC.
2.
GENERAL INFORMATION
2.1. Purpose of Document
This document presents the Techinical specifications for Soil improvement work for
An Minh LFS and Mui Tram LFS, including 02 types as follows:
 Prefabricated vertical drain combined with Vacuum Pump (PVP)
 Cement deep mixing method (CDM)
2.2. Definitions and Abbreviations
2.2.1. Definitions
The following definitions and abbreviations are used in this document:
PROJECT
Block B – O Mon Gas Pipeline;
OWNER
PVN (28.7%), PV Gas (51%), MSPL (15.12%) and PTTEP
(5.18%);
COMPANY
Southwest Pipeline Operating Company – Representative of
OWNER;
CONTRACTOR/
PURCHASER
PTSC-LILAMA18 Consortium;
SUBCONTRACTOR GEOVIETNAM-CCU
2.2.2. Abbreviations
LFS
Landfall Station
PVP
Prefabricated Vertical Drain combined with Vacuum Pump
CDM
Cement deep mixing method
SI
Soil improvement
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IMPROVEMENT FOR ALL STATIONS
Document No.:
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Revision No.: 0
2.3. Codes and Standards
The Standard and Codes for Design
TCVN 9355:2013
Ground improvement by prefabricated vertical drain (PVD)
– Design, Construction and Acceptance
TCVN 9403:2012
Stabilization of soft soil – The soil cement column method
(CDM);
TCVN 4447: 2012
Earth work. Codes for construction, check and acceptance;
TCVN 9360:2012
Technical process of settlement monitoring of civil and
industrial building by geometrical levelling.
22TCN 262: 2000
Procedure for Investigation and Design of Road
Embankment on Weak Soil
TCCS 41:
2022/TCĐBVN
Specification for Survey and Design of Highway
Embankment on Soft Ground
The Standard and Codes for Material tests
22 TCN 259-2000
Practice for soil investigation.
TCVN 4198:2014
Soils – Laboratory methods for particle - size analysis
TCVN 8729:2012
Soils for hydraulic engineering construction - Field test method
for determination of volumetric weight of soils
TCVN 4200-2012
Soil-Laboratory method of determination of compressibility.
TCVN 6016:2011
Cement - Test methods - Determination of strength.
TCVN 6017-1995
Cements - Test methods - Determination of setting time and
soundness.
TCVN 6260-2009
Portland blended cement - Specifications
TCVN 2682- 1999
Portland cemant - Technical requirements
TCVN 141-2008
Portland cement - Methods of chemical analysis
TCVN 4030:2003
Cement – Test method for determination of fineness
TCVN 4316-2007
Portland blast furnace slag cement
TCVN 4056:2012
Water for concretes and mortars – Technical requirements
TCVN 8220:2009
Geotextile – Test method for determination of normal thickness
TCVN 8221:2009
Geotextile - Test method for determination of mass per unit area
TCVN 88711÷6:2011
Geotextile – Standard Test method
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TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
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Revision No.: 0
TCVN 8042:2009
Testitles-Fabrics - Test methods for mass per unit area (weight).
ASTM D1587
Sampling of soil.
ASSHTO T88,
ADTM D2487
Standard of soil classification.
ASHTO T90
Standard specification for determining the relationship of
moisture- gravity of soil.
ASTM D4318
Standard Test Method for liquid limit, plastic limit and
plasticity index.
ASTM D4253,
ASTM D4254
Standard Test Method for minimum index density and unit
weight of soil and calculation.
ASTM D1856-84
Test Method for laboratory Compaction characteristic of soil.
ASTM D2435
Oedometer test.
ASTM D2850
Standard Test Method for Unconsolidated Undrained Tri-axial
Compressive Test on Cohesive soil.
ASTM D4767
Standard Test Method for Consolidated Undrained Tri-axial
Compression Test for Cohesive soil.
ASTM D2166
Standard Test Method for Unconfined Compression Strength of
Cohesive soil.
ASTM D2216
Standard Test Method for Laboratory Determination of Water
(Moisture) Content of Soil and Rock by Mass.
ASTM D2573
Standard test method for Field Vane Shear test in cohesive Soil.
ASTM D5778
Standard Test Method for Electronic for Friction Cone &
Piezocone Penetration Testing of soil.
ASTM D1586
Standard Test Method for Penetration Test and Split Barrel
Sampling of soil.
ASTM D1556-90
Density and unit weight in-situ test of soil by sand cone method.
ASTM D2487
Filling materials.
The Standard and Codes for Construction
TCVN 9842:2013
Vacuum consolidation method with sealed membrane for
soft ground improvement in transport – Construction and
acceptance
TCVN 9361:2012
Foundation works - Check and acceptance
TCVN 5308:1991
Code of Practice for bulding safety technique.
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IMPROVEMENT FOR ALL STATIONS
Document No.:
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Revision No.: 0
22 TCN 259-2000
Borings of Site investigation.
TCVN 4447:2012
Earth works - Construction, check and acceptance
2.4. Reference Documents
 Report on Geotechnical Investigation Work for FEED of Pipeline section from
LBV2 to Kien Giang GDS station and Kien Giang GDS station, carried out by PVE
on dated 05/2017: SWG-PVE-LPK-FE-SV-60-PL-REP-001;
 Report on Onshore topographical survey for FEED, carried out by PVE on dated
05/2017: SWG-PVE&LPK-FEED-70-SV-REP-001;
 Assessment and Selection of Soil improvement Method for All stations, carried out
by PVE on dated: 11/2017: SWG-WPPVE-FEED-00-CI-CAL-0002;
 Assess Road Calculation for All stations, carried out by PVE on dated: 09/2017:
SWG-WPPVE-FEED-00-CI-CAL-0003;
 Report for Soil Investigation for Detail Design of Landfall stations (LFS), carried by
VSP-PVC-PTSC on dated 05/2010: BB.G-VSP-PVE-SV-20-CI-REP-001;
 Basis of Design: SWG-PTSCL18-EPC-00-PM-BOD-0001;
 Technical Specification for Soil Improvement for All Station: SWG-PTSCL18-EPC00-CI-SPC-0001;
 Assessment Report for Soil Improvement Method for An Minh, Mui Tram LFS:
SWG-PTSCL18-EPC-00-CI–REP-0001;
 Report for Soil Investigation of Onshore Gas Pipeline for Detail Design – Station
and Access Road to the Station, carried by PTSC-Lilama 18 on dated 05/2024: SWGPTSC18-EPC-70-SV-REP-0002;
 Soil Improvement Calculation Report, Mui Tram LFS: SWG-PTSC18-EPC-50-CICAL-0001;
 Soil Improvement Calculation Report, An Minh LFS: SWG-PTSC18-EPC-20-CICAL-0001;
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BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
3.
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
TECHNICAL SPECIFICATION FOR LEVELING
3.1. Construction sequence
The sequence for leveling the construction site on the basis of Detailed design
documentations is as follows:
Preparation
(Acceptance of coordinates and elevations of the project
landmarks; establishment of coordinate network and
construction elevation; construction of standard benchmark)
Site clearance
Organic removal, measurement of elevation network as a basis
for acceptance of organic removal work
Spreading of sepration geotextile; Spreading of reinforcement
geotextile at project’s boundary; Construction of protection
dike; Installation of surface settlement plates
Construction of additional filling to design elevation of
+2.0m and simultaneously perform the monitoring work
Measurement and analysis of monitoring data; determination
of compensation thickness of leveling work
Acceptance and Handover
Figure 2. Construction sequence for leveling
3.2. Preparation
 Acceptance of leveling area. Determination and acceptance of elevation and
coordinates of project’s landmark. Locating project.
 Establishment of a square grid of 20m x 20m as a basis of measuring elevation of
leveling area and estimating actual construction volume to ensure payment and
completion at the end of leveling work.
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IMPROVEMENT FOR ALL STATIONS
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Revision No.: 0
3.3. Construction of Standard Benchmark
The Standard Benchmark of Project must be A level and meet the regulations in
Vietnamese standard TCVN 9360:2012” Technical process of settlement monitoring of
civil and industrial building by geometrical leveling”. This Standard Benchmark is
using as the basis of monitoring work during construction of leveling.
Sequence of construction of Standard Benchmark is as follows:
 Determining the location of Standard Benchmark on the site;
 Using rotary drilling machine to drill a borehole with diameter D110 to the depth of
sandy or gravel soil. The depth is approximately 70 ~ 80 m. Use bentonite to stabilize
the borehole wall;
 Installing a casing of PVC D90 to the end of borehole and washing the casing.
 Installing a stainless galvanized steel pipe D60 into the casing. Note that the steel
pipe needs to be threaded to ensure pipe quality;
 Pumping non-shrink cement motar into the space between the steel pipe and casing.
 Building the protection box for Standard Benchmark.
Transmitting landmarks from National Benchmark into the project's Standard
Benchmark:
 The process of transmitting landmarks from National Benchmark is carried out using
the class IV transmission line network, following the current standards (referred to
QCVN11: 2008/BTNMT - National technical regulation on establisment of leveling
network).
3.4. Site clearance
After construction of Standard Benchmark, all areas of the site specific or marked in
the drawings for clearance or from which material is to be excavated or upon which
filling is to be deposited shall be cleared.
3.5. Organic removal and leveling before spreading of separation geotextile
 In general, it is needed to remove the organic layer (grass and tree roots) with an
estimated thickness of 0.3÷0.5m. Refer to TCVN 4447:2012, in the tree area with
the filling depth smaller than 1.5m, root shall be removed as least 50cm below
ground. Following the result of topographic survey, the thickness of topsoil
excavation considers averagely as below:
o At An Minh LFS, thickness of removal organic layer is 30cm.
o At Mui Tram LFS, thickness of removal organic layer is 50cm.
The actual removal thickness of organic layer shall be confirmed at site.
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TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
Document No.:
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Revision No.: 0
 At canal locations, all mud and organic material must be dredged. The volume of
organic material removal is estimated based on an average thickness of 0.5m. This
volume may change according to actual construction requirements.
 Flatten the surface in preparation for spreading geotextile layer on the ground.
 At canal locations (if any), sand needs to be pumped to the elevation of organic
removal to create a ground surface for spreading the geotextile layer.
 Measure and check the elevation of the natural ground surface after organic removal
according to the designed grid. The technical requirements for the sand used for
leveling the canals must match those of sand used for leveling the construction site.
 All mud and soil mixed with vegetation from the canals must be transported out of
the construction site. The treatment and dumping of waste during organic removal
must follow the regulations of environmental sanitation.
 The organic removal work is not carried out outsite the leveling boundary to enhance
the stability of the slope at the leveling boundary (acting as a natural counterweight).
 Acceptance of the elevation after organic removal based on the actual coordinate grid
on the site.
3.6. Border earth dyke
 Filling for dykes surrounding the construction sites shall be carried out to the lines
and grade shown on the Drawings.
 The construction of dykes must be suitable to prevent seepage line across the dyke
embankment and to avoid affecting the daily life and cultivation of the population in
the region.
3.7. Spreading of separation geotextile
3.7.1. Requirements for geotextile layer for separation and slope protection
 The geotextile used for separation and protection must meet following technical
specifications:
 Separation geotextile layer must be a needle-punched non-woven type with
continuous long fibers, made from 100% virgin polypropylene.
 The high-strength geotextile layer for slope protection must be a high-strength
composite woven fabric consisting of polyester load-bearing fiber bundles sewn
onto a needle-punched non-woven fabric made from 100% polypropylene
material.
 The geotextile layer manufacturer must provide their quality certificate and an
independent quality certificate from a laboratory to ensure that the geotextile
layer supplied to the site fully meets the above technical specifications.
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Document No.:
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Revision No.: 0
 The technical specifications of the geotextile is provided in the following table:
Table 1. Technical specification of separation geotextile layer
Criteria (Unit)
Value
Testing
methods
Class 1
Class 2
eg < 50% eg ≥ 50% eg < 50% eg ≥ 50%
Tensile strength (N)
≥ 1400
≥ 900
≥ 1100
≥ 700 TCVN 8871-1
Puncture resistance (N)
≥ 500
≥ 350
≥ 400
≥ 250 TCVN 8871-4
Tear strength (N)
≥ 500
≥ 350
≥ 400
≥ 250 TCVN 8871-2
Bursting strength (N)
≥ 3500 ≥ 1700 ≥ 2700 ≥ 1300 TCVN 8871-5
Tensile strength at joint (N) ≥ 1260
≥ 810
≥ 990
≥ 630 TCVN 8871-1
-1
Permittivity (s )
≤ 0.50 for soil with d15 > 0.075mm
≤ 0.20 for soil with d50 ≥ 0.075mm ≥ d15 ASTM D4491
≤ 0.10 for soil with d50 < 0.075mm
Apparent opening size O95
≤ 0.43 for soil with d15 > 0.075mm
(mm)
≤ 0.25 for soil with d50 ≥ 0.075mm ≥ d15 TCVN 8871-6
≤ 0.075 for soil with d50 < 0.075mm
Note:  eg is elongation at break according to TCVN 8871-1
 d15 is maximum diameter of soil particle whose accumulative content is 15%
 d50 is maximum diameter of soil particle whose accumulative content is 50%
 Testing frequence: 10000 m2/sample or 3 samples/1 container.
3.7.2. Geotextile storage work
 During storage outside the construction site, geotextile rolls must be wrapped and
kept elevated above damp ground. Adequate covering measures should be
implemented to prevent damage from site-related activities, UV radiation, chemicals,
fire, or any other environmental conditions that could affect the physical properties
of the geotextile layer.
3.7.3. Spreading work
 The spreading of geotextile layers for separation and slope protection must comply
with TCVN 9844-2013: Requirements for design, construction, and acceptance
testing of geotextile fabrics in construction on weak ground.
 Establish the fabric sewing machine's work layout under the principle of minimizing
the total length of sewing line.
 Prepare the construction site surface:
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Revision No.: 0
 If there is stagnant water, the water pumping or drainage must be conducted to
ensure the entire area where geotextile fabric spread is flat and dry.
 Remove all tree roots, debris, and any objects taller than 100mm above the
ground surface.
 At canal locations, it is needed to fill sand up to the elevation of organic removal.
 Level the ground surface and compact sand slopes (at embankment locations) before
spreading the geotextile layer.
 Spread the geotextile layer directly on the prepared ground. Two layers will be joined
by sewing. The overlap width should average 15 cm.
3.7.4. Sewing work
 The work of spreading and joining the geotextile layers is performed after preparing
the ground surface.
 Geotextile layer joining must be done using specialized sewing machines with
double stitching. The stitching line should be 5cm from the edge and 10cm apart.
The sewing thread used must be synthetic, such as polypropylene, polyamide, or
polyester.
 Inspection of the joints: The joint inspection must be carried out following TCVN
9138:2012 "Geotextiles - Determination of tensile strength of seams". It is noted that:
 For separation geotextiles: The tensile strength of the seam (tested according to
ASTM D 4884) must be equal to or greater than 50% of the tensile strength of
the geotextile (tested according to ASTM D 4595).
 For reinforcement geotextiles (slope protection): The tensile strength of the seam
must not be less than 50% of the tensile strength of the geotextile in the width
direction and not less than 70% in the roll direction (tested according to ASTM
D 4595).
 Testing quantity: not less than 5 samples
3.8. Construction of leveling
3.8.1. Technical requirement
 The leveling work with fill sand is performed along with daily daily settlement
monitoring until meed the design elevation of +2.0m. The technical requirement of
leveling primarily follows the TCVN 4447-2012 - Earthwork - Construction
Standards and Acceptance Testing.
 After spreading the geotextile layer on the natural ground after organic removal, the
construction of sandfill is carried out in layers not exceeding 0.5m thick (the actual
thickness of each layer is determined by the compaction capability of the contractor).
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Revision No.: 0
 Compaction requirement: Minimum compaction degree must achieve k ≥ 0.90 for
each layer of fill sand (with each layer not exceeding 0.5m thickness).
 During the leveling, it is needed to prevent settlement plates from damage or
displacement.
3.8.2. Material Requirements for Fill Sand (additional filling and compensation)
 Fill sand material used for the project is fine-grained sand. This material is capable
of high mechanical construction (pumping from barges), less affected by weather
conditions (rain, high humidity), allowing for shortened construction schedules.
 The fine-grained fill sand used for leveling must meet the following minimum
criteria (according to TCVN 7570-2006 for fine-grained sand):
Table 2. Technical requirements for Fill sand
No.
Testing criteria
1 Organic content
2 Particles size smaller than 0.075mm
3 Compaction degree (wet density > 1.7T/m3)
Table 3. Frequency of quality testing for sand
No.
Testing criteria
Testing the quality of sand quarry
1
Particle composition testing
2
Organic content
On-site quality control testing
3
Particle composition testing
4
Organic content
5
Standard compaction testing
Checking the compaction degree
6
during construction
Technical requirements
≤ 5%
≤ 15%
K ≥ 0.9
Quantity
3 samples/mine
3 samples/mine
1000 m3/sample or 1 barge/ sample
10000 m3/sample
10000 m3/sample
1000 m3/3 samples/1 layer
3.9. Construction of sand blanket (drainage fill)
 Drainage fill comprises well graded coarse granular material which allows free
drainage of water. The drainage layer is placed as the initial working platform layer
for PVD installation to receive and disperse ground water from PVD. The drainage
material shall be hydraulically connected to the vertical wick drains for this purpose.
 Drainage fill shall comply with the minimum requirements and grading of select fill.
Details are as follows:
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(1) Grain size distribution

d>0.25mm
>50% (TCVN 4198)

d<0.14mm
<10%
(2) Permeability coefficient more than 1.0 x10-4 cm/s
(3) Organic content: <5%
 Note: Depend on the actual conditions at site, the SIW Contractor may proposed
alternative methods to provide the sufficient drainage of water from PVD during the
Construction stage.
3.10. Slope protection work
 With an average fill thickness ranging from natural ground level of 1.5m to 2m, to
protect the slopes surrounding the project area, it is necessary to reinforce the slopes
using earth dyke surrounding the construction sites.
 The surface water drainage system must be constructed surrounding the construction
sites to avoid affecting the daily life and cultivation of the population in the region.
3.11. Inspection and acceptance
3.11.1.Inspection plan
 The inspection activities are conducted regularly throughout the construction
process. The inspection scope includes (but is not limited to) the following tasks:
 Inspection of installation of signs within at the construction area according to
regulations.
 Inspection of materials and equipment used for construction.
 Inspection of plans for materials, equipment at the construction site, electrical
and water works, and other services to support construction activities.
 Inspection of fire and explosion safety measures, safety for personnel and
equipment during construction.
 Verification of compliance with procedures of leveling.
 Monitoring progress of construction activities for each category and phase.
 Checking the Construction diary.
 Examination of acceptance records for work volume and confirmation of any
additional work volumes if applicable.
 Assessment of factors influencing the leveling process.
 For procurement of materials, supplies, and equipment, inspections are conducted
immediately after they arrival at the construction site and before installation. The
inspection includes:
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 Type, specifications, and technical parameters meeting design
specifications.
 Certificates, technical documentation, quality inspection certificates, or
material testing certificates provided by the contractor.
3.11.2.Acceptance stages
 Acceptance work includes organic removal, spreading of separation geotextile, and
lelving to the designed elevation. Acceptance testing must comply with the current
regulations of construction law and the guidelines of the regulatory authority.
 Acceptance forms will be applied according to categories and stages, following
current regulations.
 Tolerances for surface levels compared to the designated elevation in landfilling are
0 to +5 cm. Other tolerances complying with the provisions of TCVN 4447-2012.
3.12. Monitoring work
3.12.1.Technical requirements of monitoring work
 Settlement monitoring must be conducted continuously during the leveling work to
determine both immediate settlement and consolidation settlement under the sandfill
load.
 Monitoring frequency: During the sand pumping phase, measurements are taken
once per day. After completion of pumping, measurements are taken once every 7
days. If the settlement rate exceeds 10 mm/day-night and there are signs of soil
subsidence, the filling speed must be reduced or performing alternative measures to
ensure stability of the weak soil layer beneath the fill layer.
 Settlement monitoring method: The technical requirements, data handling, and
reporting of settlement measurements must be carried out according to TCXDVN
9360:2012 "Technical procedure for determining settlement of civil and industrial
structures using geometric height measurement method."
3.12.2.Monitoring settlement equipments
 Use standard leveling instruments with high accuracy such as Ni 004, Wild N3, Ni
002, Na 3003, H1, H2, H3, NAK2, KONi007, and similar instruments with the
following main technical features:
 Magnification of the lens not less than 24 times.
 Graduation value on the stadia rod not exceeding 12 inches/2 mm, with water
bubbles visible in the device (for Ni030, Ni004 models).
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 The graduation value on the vernier scale for fine readings is 0.05 mm or 0.10
mm.
 The leveling staff (mia) used includes invar rods with lengths of 1m, 1.7m, 2m, or
3m, and wooden rods with a length of 3m. Graduation values on these rods are
typically 5mm or 10mm. The rods are equipped with a circular water tube with a
graduation value smaller than 5'/2mm.
 All the equipment have to have certificate and valid verification.
4.
SOIL IMPROVEMENT WORK BY PVP METHOD
4.1. Construction sequence
Construction work of PVP method is summarized into following steps:
 Step 1: Site preparation that consists of acceptance of elevation and coordination
of located key points of improving areas and flattern the ground surface;
 Step 2: PVDs installation and construction of sealing wall;
 Step 3: Installation of monitoring system and vacuum system (pump, drainage
system);
 Step 4: Spreading of the first geotextile layer and geomembrane layer and
setting up vacuum system;
 Step 5: Vacuum system testing and check the airtight condition;
 Step 6: Spreading the second geotextile layer; Vacuum system operation and
data analysis and report;
 Step 7: Construction of 1st stage of compensation filling;
 Step 8: Vacuum loading removal, post-construction geology investigation;
 Step 9: Additional compensation backfills (if any) to meet handover elevation
 Step 10: Ground clearance and handover the site.
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Acceptance of elevations, coordinatates of SIW area
Flatten the ground surface
PVDs installation
Installation of monitoring instruments and vacuum system (pump, drainage systems)
Sealing wall
Construction of horizontal drainage systems
st
Spreading of 1 geotextle layer
Spreading of geomembrane layer
Installation of vacuum system
Installation of surface settlement plates gauges
Collection of monitoring data before operation of vacuum system
Vacuum system operation testing
Spreading of 2
nd
geotextle layer
Construction of 1st compensation. Vacuum loading
Removal of vacuum loading, compensation filling
Post geotechnical investigation
Inspection and Acceptance
Figure 3. Construction sequence for SI by PVP
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Monitoring,
analysis
data and
report
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4.2. Technical requirements of construction works
 Acceptance of boundary coordinates, elevation, and soil improvement area
 Before construction begins, it is necessary to conduct measurements and
acceptance of the boundary lines, coordinate markers, and elevation markers of the
soil improvement area that have been handed over.
 Acceptance of the current elevation of the sand leveling layer should be conducted
according to a 20m x 20m control grid.
4.3. Installation PVD
 PVD are arranged in an equilateral square grid pattern of 1.0m x 1.0m across the
entire treatment area. The depth of PVD varies depending on the specific area of
soil improvement, as detailed in the design documents. The installation of PVD
must meet the following technical requirements:
4.3.1. Material requirements:
 The material for the vertical drains must comply with TCVN 9842-2013 as follows:
Table 4. Technical specification of PVD
Property
Requirement
Code
Core:
Thickness, mm, not less than
4
TCVN 8220
Strength at break, kN, greater than
1,6
ASTM D4595
Elongation at break (*), %, greater than
20
ASTM D4595
Elongation at tensile force 0.5 kn, %, less than
10
TCVN 8871-1
Discharge capacity at pressure of 10 kn/m2; gradient
(80÷140)x 10-6 ASTM D4716
i = 0.5, m3/s
Discharge capacity at pressure of 300 kpa and
(60÷80) x 10-6 ASTM D4716
3
gradient i = 0.5, m /s
Filter:
Trapezoidal strength at break, n, greater than
100
TCVN 8871-2
Pressure of tear resistance, kpa, greater than
900
TCVN 8871-5
Pressure of puncture resistance, n, greater than
100
TCVN 8871-4
-4
Permeability, m/s, not less than
1,4 x 10
ASTM D4491
Apparent size, mm, not greater than
0,075
TCVN 8871-6
Note: *) Elongation at break at the maximum tensile force.
*Testing frequence: 10,000m/ 1 sample or 3 samples/ 1 container.
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 Before use, PVD must be stored in a warehouse, avoiding direct exposure to
sunlight and rain, which can cause them to degrade.
 The type of vertical drains must be approved by the Owner before being used for
SI work. When the PVD are delivered from the factory, they must come with a
certificate of origin from the supplier. Before mass construction, samples of the
PVD must be tested to ensure they meet the specified technical requirements.
4.3.2. Equipment and Manpower for Construction:
a) Equipment requirement:
 Use of crawler-type installation machine: The machine must have valid inspection
certificates and be capable of installing vertical drains to the designed depth.
 The installation machine should have a data reading system to determine the depth
of the vertical drain, oil pressure, and be equipped with devices (such as a level
gauge and inclinometer) to regularly check the vertical alignment of the drains
during installation.
 The machine must ensure stability and reliable operation under all weather
conditions, including rain and wind.
b) Manpower requirement:
 The personnel operating the PVD installation equipment must possess the
necessary technical skills and have sufficient experience in installing PVD. They
must also have all the required safety certificates in accordance with the general
regulations of the project.
4.3.3. Trial installation PVD:
 The vertical drains are designed to be installed to the full depth of the weak soil
layer. Before mass construction, it is necessary to first conduct trial installations of
5 to 10 PVDs on the site to verify the installation depth for each area. During the
trial installations, it is essential to accurately record all parameters such as
installation speed, installation depth, and the level of vibration. This data will be
used to make any necessary adjustments and serve as the basis for the mass
construction.
4.3.4. Mass installation of PVD
 Checking the coordinates of PVD installation points: According to the survey,
establish control points and set up control posts as required, marking the positions
of PVD and plastic strings as reference points.
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 Setting Up the PVD Installation Machine: Ensure the verticality of the probe rod
for PVD installation using a plumb line or a roller device mounted on the machine
frame. The allowable deviation in verticality is less than 1.5% (according to TCVN
9355:2013). Efforts should be made during installation to minimize this deviation.
 PVD Installation:
 During installation, ensure to check the verticality of the mandrel. Ensure the
incline of the mandrel is less than 1.5%. When the mandrel reaches the design
depth, stop the mandrel and withdraw the mandrel upwards.
 Attach a steel anchor plate to the PVD with a minimum folded length of 20 cm,
secured with steel staples. Typically, the dimensions of the steel anchor plate
are 85 × 150 mm × 0.5 mm.
 After withdraw the mandrel from the ground, cut the PVD with a sharp cutter
to leave at least 0.20m of extended length above the sand blanket.
 Ensure the PVD are installed to the design depth according to design document.
If the geological conditions prevent adherence to design requirements, promptly
contact the supervising engineer for approval before adjusting the installation
depth.
 During PVD installation, ensure the PVD filter and that the PVD are not broken,
folded, or twisted together, to prevent soil and clay from entering the PVD core.
 PVD may be connected by overlapping with a minimum overlap length of 30
cm. Before installation, design and inspect the joints as per TCVN 9842:2013.
 In case of obstacles preventing PVD installation to the design depth, alternative
PVD must be installed at the closest postion.
4.3.5. Acceptance of PVD installation:
 Acceptance of PVD is based on grid dimensions, the number of insertion points,
and the PVD joints (if any).
 Position on the surface: According to the grid positioning, the positional deviation
should be less than 30 mm.
 Insertion depth of PVD: PVD are installed to the designed depth, monitored by the
depth of the insertion mandrel (deviation ≤ ±0.2m). In case of encountering
obstructions preventing insertion to the designed depth, a supplementary
installation solution is required.
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4.4.
Document No.:
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Revision No.: 0
Construction of sealing wall
 The sealing wall system is constructed around soil improvement area to isolate and
maintain pressure within SI area.
4.4.1. Equipment requirements
 Mobilization of sealing wall construction machine:
 The sealing wall construction machine is brought to the site. The sealing wall's
position is determined using a level and a total station. The position points are
marked with stakes on the ground.
 The sealing wall construction machine is structured with two rows of mixing
columns. The columns are created by two mixing blades with a diameter of 700
mm, overlapping by about 200 mm, resulting in an sealing wall width of 1.2 m.
 The sealing wall construction machine uses twin drill bits to break up and
loosen the soil structure. During the drilling and extraction process, a clay slurry
is pumped and continuously mixed with the soil at the mixing location to form
clay columns meeting the specified technical requirements.
4.4.2. Material requirements
 Clay is to be extracted from a clay storage area that has been authorized for
extraction by the local government.
 Material requirements:
 Clay content: ≥ 15%.
 Permeability of the sealing wall: ≤ 10-5cm/s
 The clay material must be free of significant organic matter, shells, and sharp
objects.
 Sample Testing:
 At the mine: Minimum of 5 samples.
 On-Site: 500 m³/1 sample.
4.4.3. Construction sequence
Before construction of the sealing wall, it is necessary to locate the control points along
the centerline of the sealing wall and mark the sections for trial construction using a
total station or RTK. The construction of the sealing wall proceeds through the
following stages:
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a) Preparation of clay solution:
 The clay material is transported to the construction site by barge or truck to the
storage area near the construction site. The clay is then mixed into a slurry using a
mixing system and filtered through a fine wire mesh to remove coarse particles,
roots, and other sharp objects.
 A mixer is used to stir the clay and water until a homogeneous mixture is formed.
During the mixing process, qualified engineers will supervise the quality of the
clay slurry. The clay slurry is then stored in a temporary pit, dug near the mixing
area. The bottom of the pit is covered with a thin plastic film on top of a geotextile
layer to prevent the solution from washing away.
b) Trial construction:
 Before mass construction, conduct a trial construction (approximately 5m to 10m)
to determine the appropriate grout flow rate and mixing cycle. The quality of the
trial sealing wall will be tested (for permeability and clay particle content). The test
results will serve as the basis for controlling the mix ratio between clay and water,
and the amount of clay grout pumped into each clay wall pile. The trial mixing
construction process is outlined as follows:
 Step 1: Before construction of the sealing wall, a guide trench approximately
1.0m to 1.5m deep is dug along the location of the sealing wall. Clay slurry is
then poured into the trench to prevent slurry spillage during the mixing process.
 Step 2: Conduct the drilling and mixing using a specialized mixing drill
according to the following procedure:
 To ensure the quality of the sealing wall, the construction process needs
to be performed in two cycles: drilling down and retracting.
 During the drilling down cycle, simultaneously drill and pump the clay
slurry. Upon reaching the design depth, raise the drill head while
continuing to pump grout. When the drill is 50cm from the surface or at
the design elevation, stop the grout pump and mix evenly for 30 seconds
to ensure uniformity.
 For highly permeable soil layers (clayey sand, silt, high organic content),
reduce the drilling and mixing speed and perform multiple mixes to ensure
the quality of the clay wall.
 Perform at least three trial mixes with different grout flow rates (volume
of clay slurry per meter of pile length). Each flow rate will be trialed over
a minimum length of 3m. The specific grout flow details will depend on
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the slurry quality and will be submitted by the contractor prior to the trial
construction.
 Step 3: Quality Testing of the Clay Sealing Wall
 Arrange test locations along the clay wall (the positions may vary as per
the supervising consultant's requirements). At each test location, collect
samples from different depths:
 For clay walls passing through sand layers, sample every 2m in depth.
 For clay walls passing through clay layers, sample every 3m to 5m in
depth.
 Conduct laboratory tests on the samples to ensure the clay particle content
is ≥ 15% and the permeability coefficient k is ≤ 10-5 cm/s.
 Step 4: Based on the test results, determine the required clay grout flow rate and
perform mass construction.
c) Mass construction
 After the trial construction, the following parameters will be determined: grout
pump flow rate and mixing drill speed
 Due to the presence of thick sand layers in the project area, it is necessary to control
the construction process safely.
 The quality of the sealing wall will be verified during the vacuum operation,
ensuring it meets the design pressure requirements.
4.4.4. Acceptance of sealing wall
 The average deviation for each position of the sealing wall piles is controlled within
±70mm horizontally and ±1.5% vertically.
 The width of the sealing wall (including both rows of mixed piles) is approximately
1.2 meters. The depth of construction of the sealing wall is based on the approved
design but may be adjusted on-site with the consent of all parties involved.
 Quality inspection of the sealing wall: On the ground surface, at intervals of 50
meters (as per the design documents or as may be varied upon request), select a
location where:
 Sampling at varying depths: within the sand layer of the sealing wall, the
sampling distance is 2m depth / sample, and for the clay layer, it ranges from 3
÷ 5m depth / sample.
 Testing frequence: 250m3/ sample
 Sample testing requirements: clay particle content ≥ 15%, permeability
coefficient of the sample ensures k ≤ 10-5 cm/s.
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4.5. Horizontal drainage pipe system construction work
4.5.1. Material requirement
 The vacuum suction pipe system consists of two main types of pipes:
 Main pipes: These are pressure-supply pipes from the vacuum pumps, designed
to withstand a minimum vacuum pressure of 500 kPa. The diameter of these
main pipes should not be less than Φ 63 mm.
 Branch pipes (Secondary pipes): These are drainage pipes, designed with a
diameter of Φ 50 mm. On the walls of the branch pipes, drill holes with a
diameter of 6 mm, spaced 80 mm apart in a staggered pattern (like a flower
pattern). The exterior of these pipes should be wrapped with a layer of nonwoven geotextile fabric.
 Testing frequence: 10000m/1 sample or 3 samples/ 1 batch.
4.5.2. Technical requirement for construction:
 Before installing horizontal drainage pipes and vacuum suction pipes, conduct a
preliminary check to ensure the pipes are not crushed, deformed, or blocked.
 The horizontal drainage pipes are installed after PVD installation. The system of
horizontal pipes consists of two types of pipes the main pipes and the filter pipes:
 The filter pipes: with diameter of 50 mm is used for water drainage purpose.
The filter pipes are alternatively perforated and wrapped by nonwoven filter
geotextile in order to prevent sand getting inside the pipe.
 The main pipes: with diameter of 63 mm, the pipe connect vacuum pumps with
the filter pipes system. The pipe shall be stiff enought to against the vacuum
pressure and pressure generated by sandfill.
 Excavate a trench approximately 20 cm deep along the designated grid to ensure
that the horizontal water suction pipes are positioned within the sand layer. The
entire vacuum suction pipe network must be buried beneath the sand layer, ensuring
a burial depth of ≥ 10 cm.
 The drainage pipe system should be interconnected in a fishbone pattern. At
intersections, use T-joints or cross-joints (4-way joints) to connect the pipes. The
joints are sealed with glue, and if necessary, secure them tightly with flexible ties
to prevent displacement during construction. The length of each joint should not be
less than 100 mm.
 During installation of drainage pipes, ensure no materials enter the interior of the
pipe system, which could cause blockages during pumping and suction operations.
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4.6. Geotextile
 Using two layers of geotextile to protect the geomembrane, which is a non-woven
type. The 1st geotextile layer under the geomembrane is placed on a sand layer used
to protect the geomembrane during the operation of the vacuum system. The 2nd
geotextile layer above the geomembrane is to protect the membrane during the
construction of the sand layer. The geotextile sheets are sewn together with a single
seam using a sewing machine with overlapping sections of 5 cm to 10 cm.
 Before the construction of the 1st geotextile layer, the surface must be leveled, and
all hard and sharp objects that could puncture the geotextile and geomembrane
must be removed. Record the surface settlement measurements.
 The second layer of geotextile fabric is installed after the vacuum pump system has
been tested, any holes in the geomembrane have been patched, and the vacuum
pressure has stabilized according to the design.
Table 5. Technical specifications of geotextiles
Parameter
Unit
Testing
Under
standard
layer
2
Unit Weight
g/m
TCVN 8221
≥ 150
Thickness
mm
TCVN 8220
≥ 1.5
Tensile strength
kN/m
ASTM D4595
≥ 6.5
Elongation at break
%
ASTM D4595
≥ 50
Trapezoidal tear strength
kN
TCVN 8871-2
≥ 0.1
CBR puncture force
kN
TCVN 8871-3
≥ 0.6
2
Testing frequence: 10,000m /1sample or 3 samples/ container.
Upper
layer
≥ 300
≥ 2.2
≥ 9.5
≥ 50
≥ 0.24
≥ 1.5
Table 6. Technical specifications of geotextile for protecting drainage system
Parameter
Unit Test standard
Value
2
Unit weight
g/m
TCVN 8221
≥ 200
Apparent size of hole
mm
TCVN 8871-6
≤ 0.08
Permeability coefficient
m/s
ASTM D4491 ≥ 2x10-4
* Sampling frequency are similar to geotextile layers protect geomembrane layers
4.7. Geomembrane
4.7.1. Material requirements:
Based on the requirements of geomembrane materials specified in TCVN9842-2013
standard, the geomembrane layer must meet the technical requirements as shown in
table below:
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Table 7. Technical specification of geomembrane
No.
Property
Unit
Code
1
Tensile strength (longitudinal/cross)
MPa ASTM D-882
2
Elongation at break (longitudinal/cross)
%
ASTM D-882
3
Minimum right angle tearing strength
kN/m ASTM-D624
4
Thickness
mm
ASTM 5199
5
Permeability under static pressure of
ASTM –
cm/s
100 kpa
D5048
6
Anti-permeability strength or
ASTM
kPa
hydrostatic pressure resistance
D5385
2
*Sampling Frequency: 10,000m /1sample or 3 samples/ container.
Value
≥ 15/13
≥ 220/200
≥ 40
0.14
≤ 10-11
≥ 150
4.7.2. Construction and Acceptance Requirements
 The geomembrane layers is placed between two geotextile layers. The
geomembrane is pre-bonded at the factory into a continuous sheet that covers the
entire area requiring soil improvement, with an overlap of at least 15 mm. The
dimensions of the geomembrane must be larger than the area to be treated to ensure
complete coverage.
 The outer edge of the geomembrane should extend beyond the airtight wall by more
than 1.5 meters. The geomembrane must be anchored into the sealing wall to a
depth of more than 1.2 meters, using clay-filled bages for securing. The contractor
must calculate the area of the geomembrane to ensure adequate coverage,
accounting for any loss due to overlaps and folds during installation.
4.7.3. Technical Requirements for Patching Holes (if any)
 During the trial run of the vacuum pumping system, it is essential to promptly
detect and seal any holes that appear on the geomembrane. If holes are detected,
they must be promptly patched using the appropriate adhesive methods to ensure
the system remains airtight. The patching procedure should follow the construction
and acceptance standards outlined in TCVN 9842-2013:
 Depending on the size of the tear or hole, choose a patch of appropriate size.
 The minimum size for the patch is 50 x 50 mm (for square patches) or a diameter
of 50 mm (for circular patches).
 The safety margin from the edge of the patch to the edge of the hole should be
at least 50 mm.
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 The patch should be made from the same type of geomembrane, ensuring
similar technical properties.
 The edges of the tear should be cleaned and dried, and a layer of glue should be
applied. Place the patch over the hole, ensuring the hole is centered under the
patch. Use a hand roller to press the patch until the adhesive dries and achieves
the required bond strength.
 Mark the patched area with a bright color paint for easy monitoring.
4.8. Vacuum Pump Installation
 Utilize a water-injected vacuum pump with a capacity greater than 7.5 kW. During
operation, the vacuum pressure must reach at least 95 kPa and be able to maintain
a pressure above 70 kPa over an area of 1000 m² to 1100 m².
 To monitor and control the vacuum pressure, it is advisable to use a pump placed
on land, equipped with a tank and a vacuum pressure gauge attached to the pump
to regularly check the vacuum pressure. Additionally, a shut-off valve should be
installed between the main pipe and the pump to allow for pressure checks and
pump replacement without causing pressure drops.
 The main vacuum pipe is connected to the pump through a steel wire pipe and valve
connection, ensuring that the membrane connection points are secure and airtight
to maintain pressure. To prevent pump failures, it is necessary to have reserve
pumps arranged to ensure that at least 80% of the pumps are operational at all times.
4.8.1. Installation of the Vacuum Pump System:
 The vacuum pump connection must be buried within the sand layer to protect the
geomembrane.
 The pump must be installed in accordance with the designed position and ensure a
stable power supply.
 During operation, the vacuum pump system must maintain continuous power
supply and have backup generators prepared near the pumps on-site to ensure
continuous operation in case of power outage.
4.8.2. Vacuum test
 After completing the construction of the two layers of vacuum membranes, the
vacuum pump system must undergo a test run until achieving stable pressure of 70
kPa. During the test run, comprehensive inspections within the reinforced area are
necessary to detect any holes or leaks in the membrane and promptly repair them.
Typically, the vacuum pumping process is conducted according to table below.
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Table 8. Vacuum pump loading process
Time (day)
1st -2nd
2nd -3rd
3 rd -4th
5th -8 th
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Vacuum pressure
10 kPa ~ 20 kPa
20 kPa ~ 40 kPa
40 kPa ~ 60 kPa
60kPa ~ 70 kPa
 During operation, once the vacuum pressure reaches 70 kPa, ensure that the pumps
operate continuously for at least 80% of the time.
 Monitoring activities must be carried out continuously and promptly, based on
monitoring data to assess and analyze, thereby proposing appropriate measures in
case of any abnormal incidents.
 If the vacuum pressure within the system fails to reach the design pressure of 70
kPa, the contractor must propose suitable solutions (e.g., adding more vacuum
pumps), ensuring compliance with technical requirements and project schedule,
and obtaining approval from the investor and relevant parties.
4.9. Compensation sand filling
4.9.1. Construction requirements:
 After the vacuum pressure reaches a stable value of 70 kPa, spreading 2nd geotextile
layer and performing construction of 1st compensation layer to ensure the SI load
and loading time. The total thickness of the fill layer and the prescribed time must
follow the design documents.
 The sand fill will be executed in incremental steps for each layer, with each layer
not exceeding 0.5m in thickness, depending on the compaction capabilities of the
construction equipment.
 Once a specific area is filled with sand to the desired layer thickness, allow
sufficient time for the surface to dry before mobilizing graders and rollers to level
and compact the surface thoroughly. Before compaction, sharp stones, shells, and
other materials should be removed to prevent puncturing the geomembrane.
4.9.2. Material Requirements:
 The sand used for the 1st compensation must comply with the technical
specifications for fill sand as specified in the leveling.
4.9.3. Acceptance Criteria:
 The settlement compensation layer will undergo acceptance testing based on
elevation control grids measuring 20m x 20m. Specifically, the construction
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elevation of the final layer must ensure a tolerance range from 0m to +5cm, while
other tolerances must comply with TCVN 4447-2012 regulations.
 After vacuum removal, in areas where the ground elevation after vacuum removal
is lower than the required elevation, fill and compact the settlement compensation
to the required compacation degree.
4.10. Removal of vacuum system
 When the following conditions are met, vacuum preloading removal can be
considered:
 The consolidation degree of the ground, determined by the ASAOKA method
through monitoring results, is ≥ 90%.
* Note: The vacuum preloading time is based on the design document.
However, the actual vacuum preloading duration is determined based on real-time
monitoring data at the site, especially surface settlement measurements. Specifically:
 If the vacuum preloading time has not exceeded the designated period, but the
criteria for consolidation and settlement rate have met the requirements, the
vacuum preloading can be considered to stop.
 If within the designated vacuum preloading period, the requirements for
vacuum removal not been achieved, the contractor needs to propose appropriate
solutions such as extending the vacuum preloading time, increasing vacuum
pressure (adding pumps), etc. This proposal must be approved by the
owner/design consultant and relevant parties.
 If during the vacuum preloading period, the settlement of the ground has not
reached the predicted values, but the settlement and consolidation degree
obtained from monitoring meet the requirements, the vacuum removal can be
considered.
4.11. Drainage water
 When leveling the ground surface during filling, it's essential to control the slope,
ensuring higher elevation on the sides and lower in the middle. This formation
helps create drainage channels and low points outside the construction site to
facilitate water runoff in case of rainfall during the filling process. These channels
and low points serve as outlets for water to drain away from the construction area.
 During the initial phase of vacuum preloading for soil improvement, especially
when applying the vacuum load, the vacuum equipment may extract a significant
amount of relatively large water volume. This water is typically discharged into a
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temporary drainage ditch serving the entire project. In cases where water cannot
drain fast enough, additional backup water pumps may be needed.
4.12. Monitoring work
4.12.1.Monitoring purposes
 The monitoring work is recommended as part of the design in order to:
 Assess the variability of settlement: instruments are used to verify the design
assumptions, and check the prediction during performance.
 Determine the remaining settlement both due to primary and secondary
consolidation settlement;
 Validate the strength gain which assumed in stability design;
 Check the slope stability to provent the construction from excessive movements
which are able to lead to structural failures.
 The initial assumptions and predictions may be revised based on the review of the
monitoring data which shall be undertaken during construction (placement of fill
and surcharge), consolidation period, after completion of construction, and start up
of the terminal operations.
 The interaction between design and monitoring process is presented in Figure 5.
Commencemet of
Construction
Prediction
Before
Construction
Prediction
During
Construction
Construction
- Modification of Design & Procedure
- Countermeasure Work
NG
Comparision &
Analysis between
Monitoring
Prediction and
Monitoring Data
OK
Completion of
Construction
Prediction
After
Construction
Figure 4. Flow Chart for the Observational Construction Method
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4.12.2.Monitoring Plan and Details
 The monitoring layout and details are shown in relevant drawings. The instruments
consists of:
1. Settlement plate
2. Observation well
3. Piezometer
4. Extensometer
5. Inclinometer
 The instruments should be protected and maintained in good working condition by
providing the visible barriers at a distance of 750mm around each instrument.
Compaction equipment, trucks should not approach within 1.5m of instruments.
 The sequence of installation is as follows:
 Settlement plates shall be installed first. During the installation of PVD, if the
GS pipe and PVC protecting tube are above ground level, it shall be cut off for
PVD installation.
 Extensometers, inclinometers and piezometers shall be installed after PVD or
CDM/pile installations to avoid from instruments damaged during PVD or
CDM installation.
a) Detail of surface settlement plate:
 The surface settlement plate consists of a guide steel rod inside a plastic tube to
seperate from sandfill so that the plate can move freely with surface settlement.
The guide steel rod is welded to a 5mm steel plate at base. guide steel rod can be
extended by bolting with others, each segment should be from 0.5m to 1m, length
1m above ground connection. Displacement of the guide steel rod is compared with
the benchmark elevation and is determined by the average hydro with accuracy is
less than ± 2 mm. During analysis of loading removal the accuracy of measurement
should be less than 0.1mm.
Table 9. Detail of surface settlement plate
Structure
Steel base plate
Guide rod
Protection tupe
Description
Length x Width: 0.5 m x 0.5 m
Thickness: 5 mm
Diameter:  = 27
Diameter:  = 140
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Figure 5. Detail of Surface settlement plate
b) Detail of Vacuum gause:
 The vacuum gauges are arranged overall improving area. Location of vacuum
gauge sensor must be penetrated below geomembrane and connect to filter pipes.
The capacity of vacuum gauge should be larger than 80 kPa, error should be less
than ± 2 kPa.
 When vacuum system is operating, the vacuum pressure is supplied from the pump,
propagates in the main pipe system and transmitted to the filter pipe. Then, vacuum
pressure will be transmitted to PVDs. Vacuum pressure gauges will measure
vacuum pressure maintained in D50 pipe system.
c) Detail of Extensometer:
 Drilling bored holes with diameter of 130 mm to the stable soil layers - about over
35 m deep from the sandmat elevation (based on geology investigation).
 Then the temporary casing 110 mm PVC pipe casing down to the design depth
 The casing diameter of 38 mm equiped with spider magnets attached togethers are
installed inside the 110 mm PVC pipe.
 Gradually and slowly pulled out the temporary casing of 110mm to avoid
influences on the magnets along the inside casing.
 Insert cement mixing with sand at the gap between the 38mm casing and soil.
 Notes: At the position where the casing pass through them membrane, the sealing
shall be reinforced to keep air-tight condition.
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Table 10. Detail of Extensometer:
Description
Range
Manufactory
Depth of
measurement
Sensor
Casing diameter
Accuracy
Specification
50 m
ACE-Korea
50m
Sensing ring type
38 mm
±1% FSR
d) Detail of Piezometer:
 Drill a bored hole and insert a PVD casing to the design depth.
 Piezometer is then inserted to the design depth. Coarsed grain sand is then poured
into the casing (about 1m).
 Bentonite balls (bentonite bouder mixing with lean water) are then put into the
casing.
 Bentonite mixed with sand and cement is then poured into the hole.
 Notes: All the work is carfully conducted to protect the signal caple. At the position
where signal cable and casing pass through the membrane vacuum, cable is wound
into bundles and then sealed with two layers of membrane to avoid puncturing the
membrane and loss of vacuum pressure.
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Table 11. Detail of Piezometer:
Description
Probe
Range
Accuracy
Readout type
Manufactory
Specification
VW Type-Push-in piezometer
3.5 bar
0.1% F.S.R
VW Data logger, stainless steel
Korea
Figure 6. Installation method of piezometer (Push in type)
e) Detail of Inclinometer:
 Inclinometers are installed to measure the lateral movement during vacuum
loading. 01 point of inclinometer is installed at or near the edge of the surcharge
embankment.
 Thus, the vertical displacements caused by consolidation and lateral displacement
can be differentiated. Inclinometers should be anchored at hard strata where there
is no lateral movement, about 30-35 m.
 Firstly, borehole of diameter 110 mm - 130 mm shall be drilled from top ground to
designed elevation. Then the series casings of inclinometer shall be connected and
placed into the borehole. The gap between casing of inclinometer and borehole if
any shall be filled up with cement - bentonite grout. According to the instruction
of manufacturer, the proportion of the Portland cement: Bentonite: water shoud be
in range 100%: 30~40%: 650%.
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 The ABS or PVC pipe with high accurate dimension should be used. The outer
diameter is of 70 ± 2 mm, and inter diameter is of 59 ± 2 mm. The pipe wall
requires to be smooth, and to not contain cracks to ensure the accuracy during
measurement. The inclination degree of the casing is less than 1.5 %.
Table 12. Detail of Inclinometer:
Description
Inclinometer probe
Data acquisor
Manufactor
Diameter of casing
Range
Resolution
Accuracy
Specification
Digitilt Inclinometer Probe
Digitilt Datamate Readout
ACE instruments - Korea
70 mm
300 (theo phương đứng / in vertical direction)
0.005mm/5m
±2mm/25m
a. Casing pipe
c. Readout data
b. Inclinometer probe
Figure 7. Inclinometer instrument
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4.12.3.Monitoring Frequency
 Data monitoring, analysis, and reporting should be done on a weekly and monthly
basis throughout the soil improvement process.
 To obtain accurate data for evaluating the ground improvement, the stability of the
ground must be monitored during the filling process up to the maximum surcharge
height and during the waiting period for settlement with a monitoring frequency as
shown in table below:
Table 13. Frequence of monitoring work:
Parameter
Monitoring frequency
Before
During
activation
vacuum
of vacuum system test
system
(7 days)
Settlement
plates
Multi layers
settlement
(extensometers)
Banking
period
03 times
1 time / day 1 time / day
03 times
1 time / day 1 time / day
Inclinometer
03 times
1 time / day 1 time / day
Piezomerters
03 times
1 time / day 1 time / day
03 times
1 time / day 1 time / day
03 times
1 time / day 1 time / day
Water table
observation
well
Vacuum
gauges
Preloading
period
Every 3
days
30 days
before
removing
vacuum
Every 3
days
1 time /
day
4.12.4.Report of monitoring work
 The monitoring report includes following material:
 Drawing of installing monitoring equipment
 Summarized table of recording data
 Chart of relationship between monitoring values
 Analyzing data and comparing to accepted limitation value, given out the
warning if each measurement data is over limitation value.
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 Monitoring data reports are submitted to the Owner and Supervising Consultant on
a monthly basis and before remove vacuum loading. If any abnormal conditions
occur, that information must be reported to the Owner and Supervising Consultant
within one day.
4.13. Soil investigation to re-evaluation of Soil improvement work
 After completing the soil improvement work, a minimum of three boreholes must
be surveyed through sample drilling (within the weak soil layer at 2m intervals per
sample) for both laboratory and field tests. The required tests include:
 Field tests: Survey drilling combined with sampling to a depth of approximately
30m, with soil samples taken every 2m for Standard Penetration Tests (SPT).
Additionally, perform field shear vane tests (VST) and Cone Penetration Tests
(CPTu) within the weak soil layer.
 Laboratory tests: Determine 09 fundamental geotechnical parameters (bulk
density, moisture content, specific gravity, liquid limit, plastic limit, void ratio,
compression index, modulus of deformation, ...).
 Quantity of borehole: at least 3 boreholes.The boreholes shall be located near
the boreholes conducted before SIW.
 After completing the soil investigation, based on the monitoring data and soil
investigation after soil improvement, the SIW Contractor shall provide a report to
validate quality of the soil improvement which include but is not limited to
following informations:
 Construction schedule to which meets design criteria;
 Monitoring data (settlement, porewater pressure, layer settlment, etc), the
consolidation degree, residual settlement in conformity with the design criteria.
 Soil properties before and after soil improvement, based on the soil data after
soil improvement, the contractor shall provide calculation to confirm the
bearing capacity and residual settlement as per requested by design criteria.
5.
SOIL IMPROVEMENT WORK BY CDM METHOD
5.1. Technical requirements for construction
5.1.1. Mixing samples in the laboratory
 Based on the design process, to determine the optimal cement content necessary to
achieve the design strength during the construction of cement soil piles, soil
samples from the site must first be taken and mixed with cement at various cement
contents to determine the optimal mixing ratio. These trial samples will undergo
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unconfined compresion test to determine the compressive strength after 28 days of
mixing (for wet mixing method).
 The trial construction of cement soil piles will proceed with cement contents
ranging from 200, 220, 240, 260, 280,... kg/m3 of cement soil pile.
 This systematic approach ensures that the cement content selected for mass
construction is optimized to meet the required design strength, verified through
practical trials and testing Trial CDM column construction.
 Based on the test results in laboratory, optimal cement content will be proposed,
which will then guide the on-site mixing for construction. The preliminary
construction of cement soil pile trials must be conducted before large-scale
deployment for the following purposes:
 To verify the operation and adaptation of construction equipment such as
drilling machines, mixing heads, equipment for supplying and spraying cement
slurry, and automated measuring devices. This includes establishing a rational
construction process for parameters like mixing head rotation speed,
penetration rate, withdrawal speed, cement slurry spraying rate, spraying
pressure, and cement usage.
 To conduct laboratory and on-site experiments to verify compliance with design
specifications regarding the compressive strength in radial expansion (qu),
modulus of deformation (E) of cement soil piles at 14 and 28 days of age. This
process allows for adjustments to the design as necessary before large-scale
construction.
 To realistically assess the environmental impacts (noise, vibration,
deformation, etc.) on the surrounding environment.
5.1.2. Mass construction of CDM
 After completing the trial construction phase and establishing the parameters for
cement content, water-to-cement ratio, mixer rotation speed, drilling speed, cement
slurry injection rate, injection pressure, and cement consumption, the large-scale
construction phase of CDM column proceeds as follows:
 Locating the column Position:
 Use a theodolite or total station to locate the column position. Mark the column
position with wooden or bamboo stakes.
 Moving and Preparing the Drilling and Injection Equipment:
 Move the drilling and injection machine to the construction site.
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




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 Align the drill bit with the column position, ensuring the machine is balanced,
and adjust the verticality of the drilling rod.
Preparing and Checking the Reinforcement Material: Check and replenish the
reinforcement material in the machine's reservoir.
Drilling and Cement Slurry Injection:
 Drill and inject cement slurry to form the column. The drilling machine rotates
the drill bit into the ground while injecting cement slurry through compressed
air via holes in the mixing head.
 The mixing head blades blend the cement slurry with the soil, which has been
pre-loosened.
 Operational parameters such as mixing head rotation speed, drilling rod
withdrawal speed, injection pressure, and injection volume must be maintained
stable and monitored electronically.
Completion of Construction and Equipment Movement:
 Once the drill reaches the designed depth, reverse the rotation and retract the
drill bit.
 Move the drilling machine to a new column construction location.
Management of Waiting Time and Other Activities:
 Allow simultaneous construction of new columns adjacent to recently
completed columns without requiring waiting time.
 During the first 3 days after construction, prohibit other equipment (such as
cars, graders) from moving and operating on top of the column to avoid
impacting column strength.
 After the column reaches a minimum age of 7 days, allow excavation of the
column head to inspect quality (if necessary).
Recording and Reporting:
 Record details of the drilling machine type, cement type and quantity used,
drilling and cement slurry injection times, critical technical parameters, and any
encountered anomalies during construction.
 Measure drilling depth, cement slurry injection length, and amount of cement
injected per meter (automatically recorded by monitoring equipment during
construction).
 Note permissible tolerances during cement soil column construction, such as
positional errors in column positioning, height deviations, and allowable
inclinations.
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 Allowing simultaneous construction of new columns adjacent to recently
completed columns without requiring waiting time. During the first 3 days after
completion, prohibit other construction equipment (such as cars, graders) from
moving or operating on top of the column. After this initial period, other equipment
may move, provided they do not create vibrations or impacts that could affect the
strength development of the column. Once the column reaches a minimum age of
7 days, excavation of the column head can begin to inspect the quality of the
completed columns (if necessary).
 During the construction process, the following information must be recorded:
 Type of cement soil column drilling machine
 Type and dosage of cement used
 Drilling and cement injection time, injection pressure, rotation speed, and
withdrawal speed
 Any anomalies encountered during column creation: encountering obstacles
during drilling, machinery malfunctions
 Inclination of the drilling rod (column inclination)
 Drilling depth, cement injection length, and amount of cement injected per
meter (automatically recorded by monitoring equipment during construction)
 Height of column tip, column head, and ground level during construction
 All the above information is comcolumnd into a report for each column, confirmed
by the Investor's Supervisor and Consulting Supervisor.
 Permissible tolerances during cement soil column construction include:
 Positional error of column positioning in all directions: 10cm
 Height deviation of column tip: ± 0.10m
 Permissible inclination: 1%
 Error in the amount of cement injected into the soil: ± 5% per meter length
5.2. Requirements of material and equipment
5.2.1. Cement
 The cement used for testing concrete drilled columns is Portland cement following
standard TCVN 6260:2009 or stable soil cement. Cement quality is tested
according to TCVN 6016-2011 and ISO 679-2009 standards. The test results must
meet the technical requirements set by the design agency and are evaluated based
on the following criteria:
 Compressive strength (TCVN 6016-2011): not less than 400 kg/cm² (R28
days).
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 Setting time (TCVN 6017-2015 / ISO 9597-2008):
o Initial setting time: not less than 45 minutes.
o Final setting time: not less than 170 minutes.
 Volume stability measured by LeChatelier method: ≤ 10 mm.
 SO3 content (TCVN 141-2008): not greater than 3.5%.
 Cement must not be lumpy or stored for more than 3 months. Each batch of cement
delivered to the site must undergo full testing before use.
5.2.2. Water
 The water used for mixing cement grout must meet the technical requirements
specified in TCXDVN 302-2012 standards, according to the following criteria:
 Water must be free from grease and oil.
 Organic impurities must not exceed 15 mg/l.
 pH level should be between 6.5 and 12.5.
 Dissolved salt content (TDS) should be ≤ 10 g/l.
 SO4 content should be ≤ 2.7 g/l.
 Cl- ion content should be ≤ 3.5 g/l.
 Suspended solids content should be ≤ 0.3 g/l.
 Test frequency: 3 samples / 1 supplier
5.2.3. Geogrid and crushed stone
 Choose geosynthetic grid that works bidirectionally (biaxial grid), with a minimum
tensile strength of 50 kN/m. Geosynthetic grids can be selected from polypropylene
(PP) or polyester (PE) materials.
 For the crushed stone subbase:
 Use crushed stone material with particle diameters ranging from 5 to 20 mm.
 Sampling frequency should not exceed 10,000 m² per sample.
5.2.4. Equipments
 All machines and equipment must be ensure quantity, dimensions of CDM and
progress of the project.
 All machines and equipment must be approved by EPC Contractor/Owner before
mobilization to the site.
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 The equipment for mixing shall be provided with blades, storage tanks for cement,
mixing blade rotation and facility to control withdrawal speeds.
 The ejector type of mixing equipment shall be used. Cement slurry shall be
discharged to secure the desired mixing quality for small particle clay
predominantly encountered in Vietnamese ground.
 The equipment shall be durable to rotate the mixing blade at a speed of not less
than 60 rpm.
 The withdrawal speed during mixing shall be established in the field after the
experience gained from the construction of the trial cement column.
 The number of blade rotation, which is defined as the number of rotation of the
mixing blades in a soil-stabilizer mixture in a given 1-m-long section while the
blades are raised and lowered, shall be computed as follows.
T = M x {(Nd/Vd) + (Nu/Vu)}
 Where (for injection during penetration)
T:
number of blade rotation (n/m)
∑M: total number of mixing blades
Nd: rotation speed of the blades during penetration (rpm)
Vd: mixing blade penetration velocity (m/min)
Nu: rotational speed of the blades during withdrawal (rpm)
Vu: mixing blade withdrawal velocity (m/min)
 The number of blade rotation as defined shall not be less than 350 rpm. The mixing
blade shall be designed to ensure homogeneous mixture of the soil and the
stabilizing agent. The diameter of the mixing blade shall range from 800 which
shall not be less than the column diameter to be constructed as shown on the
Drawings. Tolerance of deviation of the mixing blade diameter shall not be more
than 5%.
 The mixing rod with the mixing blades shall be of the double type to ensure high
quality mixture.
 The control of the mixing process shall be computerized to assure the best quality
of mixture. After the placement of each of the column, one printout result shall be
generated from the computer showing the column number, time, depth of the
column, content of cement slurry used in the mixing process and the number of
rotation. The process must be recorded and submitted for all the columns to be
installed for the checking of the integrity and quality of the end products.
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5.3. Quality inspection and acceptance of CDM columns
5.3.1. Quality inspection of CDM column
a) Sampling drilling
 When the 28-day-old CDM column are sampled, it is done to assess their quality
and uniformity. The sampling operation follows the Procedure for Geological
Exploration Drilling of Construction 22TCN 259-2000. Suitable diameter drill bits
and double-wall sample tubes are used to maximize sample length, ensuring
samples have a minimum diameter of 70mm. Sampling occurs at the center of the
concrete drilled column.
 During drilling, detailed descriptions of the samples are recorded, including length
statistics arranged sequentially by depth, and comprehensive photographs of each
sample are taken.
 Test samples are kept intact in sample tubes until testing according to TCVN 26831991 standards.
 The number column are selected for sampling and testing approximately 0.5% of
the total number of columns. The locations for sampling are randomly chosen by
the Owner's Representative from all construction columns
b) Unconfine compression tests
 CDM columns samples are performed unconfined compression tests to determine
compressive strength (qu) and shear strength (Su).
 The unconfined compression test is conducted according to ASTM D2166
standards.
5.3.2. Acceptance of CDM
 The soil improvement by CDM must acceptance according to state regulations, as
per the design documents and completion dossier prepared by the executing unit.
The quality acceptance standards for the CDM work are implemented in stages,
with the specific inspection criteria outlined in the following table:
Table 14. Technical requirements for CDM columns
Item
The coordinates of
the column axis
compared to the
design coordinates
Quality
standards and
allowable errors
Testing frequency
Testing method
10 cm in all
directions
Inspection over a
representative area
and when there are
suspicions
Measured using a
surveying
instrument
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BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
Item
Quality
standards and
allowable errors
Length of column
±10 cm
Inclination angle
of column
1%
The amount of
cement grout
injected into the
column body.
Unconfined
compressive
strength qu at 28
days old.
Deformation
modulus
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
Testing
frequency
100% columns
Random
inspection
Testing method
Measured using
drilling equipment
Measured using
drilling equipment
±5%/ m
100% columns
Measured using
automatic
quantitative
equipment of the
machine.Monitoring
the amount of
cement consumed.
5kg/cm2
On drilled
columns
Unconfined
compression test
187.5kg/cm2
On drilled
columns
Unconfined
compression test
6.
SAFETY AND ENVIRONMENTAL SANITATION WORK
6.1. Environmental sanitation work:
 Environmental sanitation work must be carried out rigorously without adversely
affecting the surrounding environment:
 Oil and grease spills from construction machinery must be cleaned up and disposed
of properly according to regulations.
 Waste generated during construction must be cleaned up and gathered at designated
locations.
 Given the relatively large construction area, sanitary facilities should be
strategically located to serve technical staff and construction workers effectively.
6.2. Occupational safety work
 All technical staff and workers involved in construction, as well as construction
management, must undergo occupational safety training as stipulated by the
project.
Page 47 of 48
BLOCK B – O MON GAS PIPELINE PROJECT
TECHNICAL SPECIFICATION FOR SOIL
IMPROVEMENT FOR ALL STATIONS
Document No.:
SWG-PTSCL18-EPC-00-CI-SPC-0001
Revision No.: 0
 During construction, strict adherence to safety principles is mandatory. Workers
should only perform tasks within their designated scope of work and refrain from
undertaking tasks outside of their responsibilities.
 All technical staff and construction workers must be equipped with complete
personal protective equipment (PPE) such as protective clothing, steel-toe boots,
rain boots, gloves, and helmets.
6.3. Fire and explosion prevention work:
 Emergency fire extinguishers must be strategically placed on-site, especially in fuel
storage areas, material warehouses, and on construction machinery...
 Combustible materials must be stored separately from other materials, especially
away from electrical sources and potential ignition points.
 Regular inspections are conducted to detect and promptly resolve any arising
incidents.
6.4. Electrical safety work:
 Electrical sources must be positioned at rational locations, convenient for
construction operations while ensuring safety.
 Circuit breakers (Aptomat) should be installed at electrical terminals, and
grounding should be provided for machinery and electrical equipment.
 Electrical cables must meet requirements for power capacity and current intensity
of the equipment.
 Electrical cables should be suspended high to prevent direct contact with ground
and water.
 Workers operating machinery and electrical equipment must be equipped with
complete safety gear such as rubber gloves and insulated boot.
Page 48 of 48