06 4 ok CW2C VCM

CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 SOFT SOIL IMPROVEMENT MEASURES 1/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 METHOD STATEMENT OF VACUUM CONSOLIDATION METHOD (V.C.M) 2/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 TABLE OF CONTENTS INTRODUCTION RELEVANT SPECIFICATIONS, STANDARDS AND DOCUMENTS SITE ORGANIZATION CONSTRUCTION PROCEDURE RESOURCES TO BE USED QUALITY CONTROL OCCUPATIONAL HEALTH AND SAFETY CONTROL ENVIRONMENTAL CONTROL 3/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 INTRODUCTION All works must comply with regulations of Section 03500 “Soft Soil Improvement Measures” and Section 03600 “Vacuum Consolidation Method” of the Specifications Construction of VCM shall be carried out in accordance with the method statement approved by the Engineer, and the recommendations of the Contractor’s VCM specialist Regarding requirements for construction using VCM, reference is made to MOT Decision 384/QD-BGTVT of February 2013 Temporary regulations on vacuum treatment method using membrane method In principle construction using VCM should comply with the requirements of Decision 384, however the Contractor is permitted subject to the Engineer’s approval to apply methods meeting alternative requirements based on the technical recommendation of their specialist VCM contractor, or if compliance with Decision 384 would lead to breach by the Contractor of another firm’s patents Construction of other elements such as PVD installation, sand blanket, construction of embankment, and subgrade preparation shall be in accordance with the relevant sections of this Specification Applied vacuum depressurization shall be 65 kPa (minimum) measured at mid-depth of the PVD throughout the consolidation period and a minimum of 80 kPa prior to the installation of the fill The piezometric pressure reduction shall be measured by an electrical piezometer installed within a PVD at middepth along with a reference groundwater level measured by an observation well in a non-improved area An adequate number of vacuum pumps shall be provided to ensure that there is continuous application of vacuum throughout the consolidation period It should be emphasized that continuous depressurization is essential in controlling the stability of the embankment Vacuum pressure shall be maintained through the required period day and night Vacuum depressurization may and where necessary shall be applied prior to placing of embankment and surcharge and may and where necessary shall be applied simultaneously with the loading applied by the weight of embankment and surcharge fill The height of the surcharge fill, duration of vacuum application, and duration of surcharging are as shown on the Drawings Unless stated otherwise on the Drawings, or unless agreed 4/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 otherwise by the Engineer, the duration of vacuum application shall be the total duration of the “filling time” (embankment construction time) plus the “waiting time” (consolidation time) as shown on the Drawings VCM shall be implemented by zones VCM shall be terminated when the criteria for acceptance are satisfied for the whole of the relevant zone The Contractor may propose the zoning system The criteria for acceptance is that the specified piezometric pressure reduction together with the specified height of surcharge fill have been achieved and maintained for the duration specified on the Drawings for that zone Surcharge fill as shown on the drawings shall be placed over the net improvement area at an acceptable filling rate The side slope shall not be greater than (V): (H) If failure to maintain the required vacuum pressure leads to a requirement to increase the surcharge fill height or filling rate, the Contractor is required to provide calculations on stability of the embankment for approval by the Engineer At interfaces between VCM method and non-VCM sections, in principle the VCM treatment should be carried out first, in order that embankment construction and surcharge filling may take place uniformly across the transition At the site of pipe or box culverts, the VCM treatment and any surcharging required shall be carried out first and settlement criteria achieved prior to pipe or box culvert construction, in order that uniform ground improvement can be achieved over the culvert and its approaches During implementation of VCM, existing drainage shall be routed in temporary drainage pipes through the zone of VCM and fill, or diverted by pumping 1.1 WORK SCOPE This method statement includes the following work scopes: (i) PVDs Installation (ii) Vacuum system installation and trial running (iii) Placing Geo- membrane and Protecting geotextile 1.2 WORKING DRAWING Prior to commence the work each area, Working Drawings will be submitted for the Engineer separately Designated areas for the works will be shown in Working Drawing separately submitted in due course Typical 5/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 cross section drawings are attached to provide general view RELEVANT SPECIFICATIONS, STANDARDS AND DOCUMENTS RELEVANT SPECIFICATIONS AND STANDARDS ASTM D 1621 Standard Test Method for Compressive Properties of Rigid Cellular Plastics ASTM D3776 Standard Test Methods for Mass Per Unit Area (Weight) of Fabric ASTM D3786 Bursting Strength Standard of Test Method for Textile Fabrics—Diaphragm Bursting Strength Tester Method ASTM D 4491 Standard Test Method for Water Permeability of Geotextiles by the Permittivity method ASTM D 4533 Test Method for Trapezoid Tearing Strength of Geotextiles ASTM D 4632 Test Method for Breaking Load and Elongation of Geotextiles (Grab Method) ASTM D 4716 Test Method for Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using Constant Head ASTM D4751 Standard Test Method for Determining Apparent Opening Size of a Geotextile ASTM D 4833 Test Method for Index Puncture Resistance of Geotextiles, Geomembranes, and Related Products ASTM D 5101 Measuring the Soil-Geotextile System Clogging Potential (By the Gradient Ratio) ASTM D 5321 Standard Test Method for Determining the Coefficient of Soil and Geosynthetic or Geosynthetic and Geosynthetic Friction by the Direct Shear Method  ASTM D 5567 Hydraulic Conductivity Ratio (HCR) Testing of Soil/Geotextile Systems  MOT Decision 384/QD-BGTVT of February 2013 Temporary regulations on vacuum treatment method using membrane method 6/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 SITE ORGANIZATION Site organization for this project is shown below Project Manager QC Manager Construction Manager Environment & Safety Engineer Site Engineer Team for PVD work Team for VCM work CONSTRUCTION PROCEDURE 4.1WORK FLOW-CHART Construction procedure for soil improvement work by vacuum preloading method is 7/ 27 shown in Flow chart for construction as below: PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Construction preparation Set monitoring equipment Install PVD Drainage ditch construction Set up filtration and main pipe Laying geotextile (first layer) and geo-membrane (2 layers) Monitoring Information Set outerway of vacuum and bury geo-membrane Installation pumps Set up settlement plates Vacuum operation Laying the second geotextile layer Sand filling Test and Acceptance 4.2 WORK PROCEDURE The work procedure is described as follows (1) Site preparation - The soil surface shall be leveled and then temporary facilities will be set up for construction - Preparation of utilities including electricity, water and light at required positions will be implemented - Prepare machineries maintenance, labor allocation, site layout, material storage, temporary facilities, fire alarms and drainages - 8/ 27 Products and semi-products are tidily stored in warehouses and PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE Marking of PVD CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 separated by tags or signs Trial penetration of PVD Miscellaneous materials such as hardware and welding supplies shall be stored in the warehouses and managed by a material staff Machine, equipment and material should be ensured in good quality Mass construction of PVD installation and supply on time - (2) Installation of Prefabricated Vertical Drains (PVDs) The construction flow of PVD is shown as below: Prefabricated vertical drains (PVDs) shall be installed throughout the soft soil layers; Table 4.1 shows the main properties of PVD material to be used 9/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Table 4.1 Required characteritics of PVD matterial according to “Technical specification for soil improvementTechnical design documents” Properties Test Designati Requireme nts VN standard 22 TCN 262 on Apparent Opening Size (AOS) O95, ASTM D 2000 Less than 75 Less than 75 Greater than Greater than 4751 μm Grab Tensile Strength, kN (longitudinally only) Discharge Capacity (m3/yr) at day, ASTM D 4632 ASTM D 4716 Greater than 500 Applied pressure of 350kPa 200kPa and hydraulic gradient i of Permeability of filter, m/sec ASTM D 4491 Width of filter Greater than Greater than x x 10-4 Unrestricted 10-4 100mm Catalogue of PVD material shall be submitted for approval before purchasing and supplying for installation in soil improvement areas with spacing and penetration depth according to the Technical Design  Technical requirements for PVD installation  PVD material shall be stored in the warehouses to protect from rains, sunshine and ruins PVDs with any defects are strictly not allowed to use  Extension of PVD shall be implemented by opening the filter cover and overlapping (≥300 mm) the core, then wrap and staple to ends  Tags shall be used to locate the installation points  PVD installation is presented as below: - Use ruler or marked line to measure the spacing and points with deviation of ±100 mm 10/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450  Cut and Record When casing pipe will be set back to original position, the plastic band drain shall be cut by knife Vertical Drain shall be remained at least 300 mm from the platform Then, Anchor plate shall be arranged again At the same time, the length of each vertical drain shall be recorded to the monitoring format Total vertical drain length will be calculated each day, cumulated and presented every day as a daily progress report (3) Setup Horizontal Drain  Requirement of Materials MOT Decision 384/QD-BGTVT of February 2013 Temporary regulations on vacuum treatment method using membrane method The horizontal drainage system includes a main pipe and filter pipes Filter pipes are placed at a spacing as shown in working drawing The main pipes are splacing along the road,  Placement of horizontal drain - One main pipe will be placed along the centre line of road Other sub pipes will be placed overlap the row of PVD with spacing as shown in working drawing The distance between boundary of treatment and the end of pipe that is 10 – 15cm - Position of the filter pipes Use shovels to excavate ditches The ditches can be rectangular cross-section (15-20 cm wide and 15 cm deep) or triangular cross-section (15 opening and 20 cm deep) - Install pipes into the ditches, which are connected by four-way joint to filter pipes Recheck the performance of the pipes before the placement, e.g., the ruins of the filter, the broken of the pipes - The connection joints shall be wrapped and wired by geotextiles to prevent from the intrusion of sand particles - PVD will be rolled around the filter pipe and then belted by plastic belt - Fill sand into the ditches after completion of placement pipes - The main pipe are connected to the UPVC pipe without holes by three – way joint and connected to the pump, placing along the road  Attention - The excavation depth of the ditches shall be guaranteed - Check the appearance and ruin of the filter membrane and pipe body 13/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 - The joints shall be firmly connected to the filters and wrapped by geotextiles 14/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 (4) Placement of Geomembrance Laying the first geotextile layer Transported geomembrane to site Laying first layer of geomembrane Check and patch first layer of geomembrane Laying second layer of geomembrane Check and patch second layer of geomembrane Bury geomembrane Laying the second geotextile layer Installation vacuum system 15/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 The installation of Geo-membrane must meet the following  requirements Geo-membrane is keyed into anchor trenches which are filled with clay grout for air tightness Geo-membrane should be sustainable, flexible and anti- punch airtight materials Prior to the placement of the geo-membranes, the jobsite shall be leveled and cleared Rigid and sharp materials (e.g., gravels and chunks) shall be cleared Meanwhile, a protection layer of non-fabric geotextile shall be placed below the geo-membranes The size of the geo-membranes shall be pre-determined in accordance with the treatment scope by manufacturer The size shall also account for the embedment into the cut-off wall An overlapping between 02 sheets of geomembrane is joined by glue, it shall not be less than 20 cm During the test of the vacuum preloading, the overlapping shall be carefully inspected The geo-membranes strips shall be firstly mobilized by excavators to the center of the jobsite and unpacked two-ways During mobilization, the geo-membranes shall not be ruined by the excavators The placement of the geo-membranes shall proceed daytime with less than force wind power Two geo-membranes are placed independently Each placement will be followed by careful checks and repairs of ruins After installation of geomembrane, sand bags shall be put on geomembrane In the course of geo-membranes placement, the persons shall wear soft shoes Each placement will be followed by careful checks and repairs of ruins or openings In the course of geo-membranes placement, the geo-membranes shall not be pulled excessively A length of geo-membrane shall be reserved at the sides of each treatment unit An opening can be repaired using a small size geo-membrane Firstly, clear the surface of the opening and the geo-membrane Then, daub the binder around the opening When the binder is felt non-cohesive, place the small geomembrane onto the opening, without leaving air bubbles between the contact surfaces When position the settlement measurements on the geo-membranes, geotextiles, soft mats or geo-membranes shall be placed beneath the measurements Weight shall also be placed on the base Check the geo-membranes very carefully prior to the vacuum operation Assess the leaking potentials based on the vacuum meter, vision and hearing Any 16/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 opening or ruin shall be repaired immediately Geo-membranes shall be backed up on-site for at least operations of two units When ruins or vacuum leaking is identified after surcharge is loaded, it is hard to correctly identify the points of ruins  Attention - Adequate persons and geo-membranes Complete the placement in one time - Careful check the appearance of the geo-membrane following the first placement, and repair ruins - The geo-membrane placement shall last around hours That is, placement under high temperature shall be avoided - Gloves shall be worn to prevent from ruins - Geo-membranes binding works shall be completed by skilled persons - Geo-membranes shall be embedded into the impervious soil for at least 50 cm - Miscellaneous materials shall be immediately cleared from the ditches  Edge Treatment After the Airtight sheet arrangement, Edge Treatment shall be executed by Excavator for excavation and backfilling work Airtight sheet shall be embedded into the cohesive material at least 50 cm to prevent air 17/ 27 leak PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 (5) Placement of Geotextile Two (2) layers of geo-textile shall be installed before and after laying geomembrane layers to protect both the lower and upper sides of the geomembrane Proposed geotextiles shall be subject to prior approval by the Engineer Control testing shall be carried out for each batch of geotextile in accordance with the Geotextile Supplier’s quality system In addition to the manufacturer's product certification and quality testing, independent testing shall be arranged by the Contractor at an approved laboratory with testing frequencies at a rate of one suite of testing per 10,000m2 of geotextile Each suite of tests shall include measurement of material thickness and weight, tensile strength and puncture resistance Unless otherwise shown on the Drawings or instructed by the Engineer, the 18/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 materials to be used shall be as follows: Separation Geotextile: Non-woven - Non-woven geo-textile sheets shall be UV-stabilized, made of 100% polypropylene yarns which may be mechanically or thermally bonded from continuous filament - It shall have the following requirements: Property Min Strip Tensile Strength Required Values Test Method 12 ASTM D4595 Min Permittivity /s ASTM D 4491 Max Pore Size of Geotextile, 125 ASTM D 4751 kN/m O95 (μm) High Strength Geotextile: Woven - The geotextile sheets shall be UV-stabilized and made of polyester yarns - The ultimate tensile strength to ASTM D 4595 shall be more than 200 kN/m in the longitudinal direction and 50 kN/m in the lateral direction at breaking elongation of not more than 20% Separation Geotextile: Woven - Woven geo-textile when installed below the pavement structure shall be UV-stabilized, made of 100% polypropylene yarns, and shall have the following requirements: Property Required Test Method Values Min Strip Tensile Strength 25 ASTM D4595 Min CBR Puncture Strength N 2250 ASTM D6241 Min Permittivity /s 0.02 ASTM D 4491 kN/m  Construction procedure - The jobsite shall be completely cleared prior to the placement of 19/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 geotextiles, in particular, the removal of garbage, sharp or rigid chunks - Each reel of geotextiles has the dimension of 6m  100m Carts are employed to mobilize the geotextiles to the correct work site - The geotextiles are placed by humans A reservoir for deformation or twist is accounted for - An overlapping not less than 30cm is needed, and sewed by portable or special sewers - The performance of geotextiles shall be supervised by a special person - As the geotextile gains weight if damped or soaked, the placement shall be placed by preventing from rainfalls and water (6) Construction vacuum system The construction of vacuum system is shown as following 20/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Installation vacuum system Installation vacuum pumps Connecting pipe to the pump Cable set Checking system Vacuum operation Laying the second geotextile layer Backfill  Electricity Supply of Vacuum System - The jobsite is able to access the electricity The electricity is transmitted to the worksite through alumina cable of 3150 An electric closet is equipped adjacent to the worksite Copper cables of 34 are used to further transmit the power from the closet to each vacuum pump Every 18-20 sets of vacuum pumps are powered by a closet Each power line for a vacuum pump is controlled by a switch, which enables the independence and safety of the power supplies - Additional, in case of emergency: to generators will be rent Each vacuum pump is equipped auto-switcher, which is able to maintain the vacuum efficiency for up to hours if the power is switched off Meanwhile, a manual switcher can also be used alternatively  Technical Requirements of Vacuum Systems - Injector vacuum pumps are equipped The power of the pumps is 7.5 kW, which is able to provide over 95kPa vacuum efficiency and 80kPa vacuum effects beneath the geo-membranes - Vacuum pumps shall be assembled in rigid sequences of engine, pump, water box, switcher, and outlet The joint shall be sealed with rubber pads or binding agents The pumps rest on compacted sand bags The outlet and 21/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 water box are connected by corrugated tubes - As the vacuum pumps are submerged, the pumps can be placed in the water pool in the worksite, if no surcharge is loaded Otherwise, the pumps shall be placed in the water boxes or pools out of the worksite During operation of vacuuming, soils and miscellaneous materials shall not be disposed into the water pools or boxes - Each vacuum pump shall be equipped with a small size vacuum meter, which is used to monitor the operation of vacuum pumps and vacuum efficiency Every treatment area of 600 m2 shall be equipped with a large meter, which is used to monitor the vacuum efficiency in the sand - To maintain the vacuum efficiency, every treatment area of 800-1000 m2 shall be equipped with a set of vacuum pump All pumps run 24 hours a day Adequate pumps of back-up shall be prepared The access points of the pumps shall be preserved At the later stage of vacuuming, at least 80% pumps shall be in operation In this project, because the shape stretches to the length, hence every treatment area of 700m2 shall be equipped with a set of vacuum pump to have the best efficiency - The pipe joints of vacuum systems shall be strictly sealed Auto and manual switchers shall be equipped in the systems to maintain the vacuum efficiency - During vacuum preloading, the vacuum pressure under the geomembranes shall be maintained equal or more than 65kPa After the preparations of vacuum systems, run vacuuming When the vacuum degree beneath the geo-membranes reaches 50 to 60kPa, check any leaking point Start to measure the time when the vacuum pressre at mid- length of PVD is bigger 60kPa  Vacuum Operation  Initial Pumping - Vacuum Operation will be started after all monitoring equipment shall be arranged at design ated location and finish their calibrations - Vacuum pressure will be controlled about 30kPa by the valve at Vacuum Pump just after start pumping and checking Vacuum Conditions - Then, valve will be fully opened after checking the vacuum pressure under airtight sheet At the Expected Vacuum Pressure at the pump is more than 65kPa - Initial pumping duration will be seven (7) days to fourteen (14) days for air leak repairing and treatment for embankment depend on the weather 22/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 condition  Air Leak Check and Airtight Sheet Repair - Air leak shall be repaired during initial pumping duration - Same material shall be patched on pin holes or some other damaged part with special glue from the same manufacture - Stones or some other non-compressive particles in platform shall be removed and repaired  Vacuum Pressure The vacuum pressure shall be reached almost 80kPa at the vacuum pump The embankment shall be started after initial vacuum period of 20 days in order to increase the strength of the ground The vacuum pressure requirement shall be at least 60kPa at mid-length of PVD during embankment work  After the repairing and Embankment works - After the repairing of the sheet, Embankment work can be executed - However, Geotextile sheet shall be arranged on the airtight sheet for its protection - Vacuum pressure shall be monitored during embankment work  Settlement Durat ion Vacuum operation shall be continued until the monitoring data will show settlement reach to designate level of settlement ratio and to get the approval of the Engineer  Additional Monitoring - During Vacuum Operation, Sub-contractor shall monitor the Vacuum 23/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 Pressure under the airtight sheet, Discharge Volume, the Vacuum Pressure at the Pump by Pressure Gauge manually - Pore Water Pressure in the treating soil shall be monitored for checking of efficiency of Vacuum Operation and to control Embankment speed during contraction work - These data shall be recorded and checked by their geotechnical engineer every day and used for stability control during embankment work  Stop vacuum pumping condition - Approved by Supervisor - According to the inspection standard - The consolidation degree reach to the requirement of Engineer Vacuum Gauge at Pump  Attention With the Vacuum consolidation method, there are several points to note as follows: - To ensure the compaction does not affect to the Geo-membrane layer, the thickness of the first 24/ 27 compaction layer should be trial at site PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 RESOURCES TO BE USED Equipment to be used for the PVDs, Vacuum operation works are listed below No Description PVD installation rig ≥ 30m Uni t Q’ty ea Excavator ea Survey machine ea VCM equipment set Remarks QUALITY CONTROL With regard to the quality control, all the works shall be carried out following the established Project Quality Control Plan 1) Sealing of each unit shall be ensured, in particular, the side of the unit, where the geo-membranes embedding shall meet the design requirements Only the qualified sealing measures are able to enhance the vacuum efficiency 2) As the vacuum preloading is long-time, ruins or damages of pumps are unavoidable Pumps of 20% design quantifies are preserved 3) There is a test period of 7-10 days following the commencement of vacuum preloading: In the period, the vacuum pressure under airtight sheet will increase and more than 65kPa, the vacuum pressure at mid-length of PVD is not less than 60kPa; Sealing shall be examined: special personal shall be appointed to examine and remediate the leaking The geo-membranes shall be placed over the backfills completely The edge of the geomembranes shall also be embedded into the cut-off sealing walls (clay mixing wall) 4) During the vacuum preloading, soil treatment data, e.g., the ground settlement, pore water pressures and soil layer compression shall be 25/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 measured, which are used to estimate the soil treatment effect The data shall also be used to back analyses, which lead to the estimation of final settlement and consolidation degree 5) Based on the back-analyses, measures are taken to ensure the construction quality and schedule OCCUPATIONAL HEALTH AND SAFETY CONTROL With regard to the occupational health and safety control, all the works shall be carried out following the established Project Occupational Health and Safety Control Plan - All equipment should be regularly maintained and checked by Constructor before work - Keep a safe distance depending on the type of work to be carried out by the workers within close vicinity of machineries Site Engineer should inform such requirements to the workers and operators of machineries - Temporary safety fence and barricade are established following site condition Constructor must confirm the situation of safety every day before starting the work ENVIRONMENTAL CONTROL With regard to the quality control, all the works shall be carried out following the established Project Environmental Control Plan 26/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE CMDRCP / CW2C PACKAGE CW2C KM 18+200 – KM 23+450 27/ 27 PHUONG THANH - QUYET TIEN - ANH GIANG – THANG LOI JOINT VENTURE ... stability of the embankment for approval by the Engineer At interfaces between VCM method and non -VCM sections, in principle the VCM treatment should be carried out first, in order that embankment construction... construction using VCM, reference is made to MOT Decision 384/QD-BGTVT of February 2013 Temporary regulations on vacuum treatment method using membrane method In principle construction using VCM should... construction time) plus the “waiting time” (consolidation time) as shown on the Drawings VCM shall be implemented by zones VCM shall be terminated when the criteria for acceptance are satisfied for the