General
This method statement outlines the Road Earthworks process, focusing on Soft Ground Treatment techniques such as Geo-textile installation and Prefabricated Vertical Drain systems It also includes procedures for Sand filling and the use of Borrow Material for Embankment construction, all of which will be executed in compliance with the General Specifications outlined in Division 3: "EARTHWORK."
List of document that will be submitted separately is as below:
(4) Detailed information of equipment and labor to be mobilized
Quantity
The estimated bidding quantity is provided for reference purposes only; the final design quantity will be determined based on the approved working drawings, while the actual construction quantity will be documented in the As-built Drawing.
Construction Schedule
Construction Schedule shall be referred to latest approved Overall Schedule.
Site Organization Chart
Organization Chart is as follow.
Site Engineer QC Engineer Surveyor
Sub-contractor (if any) – Road Earthwork
Equipment and Workforce
Road Earthworks of this project will be divide into five (05) section along alignment plan. Scheduled Machinery to be mobilized for Road Earthwork for each section is as below.
Item Description Quantity Use for (01 section)
1 Bulldozer 110 ~140HP Class 6 nos Earthwork
4 Vibration Roller 7 ~ 15tons Class 9 nos Earthwork
5 Tamping Rammer 54~80KG 4 nos Earthwork
6 Dump Truck 15~23tons Class as required Earthwork
7 Dump Truck 8~10tons Class as required Earthwork
8 Water Pump 2~4 inches 4 nos Dewatering
9 Diesel Generator 125 KVA 2 nos Source of power
187HP ~ 295HP 1 nos PVD installation
11 Lighting System as required Night work
12 Survey Instruments Auto level, Total station 2 set Survey work
Above stated quantity of equipments could be changed if any required and necessary.
(*) PVD machine shall be used for only PVD installation works.
Scheduled workforce to be mobilized for Road Earthworks and detailed information to be describe in “Checking record of Equipment and Labor at Site” will be submitted separately after.
Description of Materials
Materials for Embankment
The materials will be submitted to the Engineer for approval and material tests in laboratory will be implemented before commencement of embankment work under the inspection of the Engineer
The general description of Embankment materials is as follows The detailed information for materials will be submitted separately as proposal of materials.
Description Material Source of Material Borrow material Black sand or Soil River Sand or Hill Soil
Sand fill material Yellow Sand River Sand
< Tests in laboratory for Borrow material>
- Test for moisture-density relation of soil AASHTO T180-D
(maximum dry density & optimum moisture content)
- Elastic Modulus or CBR AASHTO T193
According to Clause 3.7(f) of Section 03400 "Embankment Construction" in the General Specifications, the testing frequency during construction mandates that for each borrow pit, one sample lot consisting of three samples is required for every 1500m³ of filling soil on site.
The testing result of Borrow Material should be used for the classification of soil to be approved by the Engineer
6.1.2 Sand Fill Material for Coarse Sand Blanket (CBS)
< Tests in laboratory for Sand Fill Material>
- Test for moisture-density relation of soil: AASHTO T180-D
The frequency of material test during construction is in accordance with Clause 2.4.1 “ Coarse Sand Blanket (CBS)” under Section 03500 “Soft Soil Improvement Measure” in General Specifications, as showed below.
- Sampling and test shall be carried out for each material source asked for approval.
- Materials gathered on site: Every 500m3, all testing criteria shall be checked, except for Compaction Test AASHTO T180-D which is applied with frequency of 1000m3.
The testing results for sand filling material must meet the criteria outlined in Clause 2.4.1(b) of Section 03500, titled "Soft Soil Improvement Measure," within the General Specifications.
The sand ratio of grain-size more than 0.25 mm should be more than 50%.
The sand ratio of grain-size less than 0.08 mm should be less than 5%.
Permeable coefficient of sand must be more than 1.0x10 -4 m/s.
The organic content shall be less than 5%.
D60, D30 and D10 are the grain diameter or sieve size (in mm) having a 60%, 30% or 10% respectively of the material passing through (i.e. grains with smaller diameter).
6.1.3 Cohesive Soil for Slope Protection
Slope protection using cohesive soil is essential only when the embankment material consists of loose substances like sand In contrast, if the embankment is made of adhesive materials, slope protection with cohesive soil is unnecessary.
Soil that contains more than 25% clay-sized particles (less than 0.002mm) exhibits a size gradation that can be classified as gravelly or sandy clay This type of soil must meet specific physico-mechanical properties to ensure its suitability for various applications.
- Plasticity Index: 17% ≤ PI ≤ 27% according to TCVN4197-95 (or AASHTO T90)
< Tests in laboratory for Cohesive Soil >
- Limit Liquid: LL ≤ 55% according to TCVN4197-95 (or AASHTO T89);
- Maximum dry density: γc max ≥ 1.7 g/cm3;
To ensure optimal performance, maintain a uniform density with moisture content of at least 95% as per 22TCN333-06 or AASHTO T180, and achieve a CBR value of 6% or higher according to 22TCN332-06 or AASHTO T193:90 It is essential that cohesive slope material and slope embankment are constructed simultaneously and with equal thickness.
The Testing Frequency shall be as follows:
All tests in laboratory as mentioned above shall be carried out
One test is for 1 set including 3 samples.
Test for approval shall be carried out at least one time.
Sampling for test shall be carried out at a borrow pit.
All tests in laboratory as mentioned above shall be carried out for each 1,000 m 3 Embankment.
One test is for 1 set including 3 samples
Geo-textile
Geotextile filter fabric shall be non-woven and satisfied with the 22TCN248-98 and the General Specifications Clause 2.4.3 “Separation-Geotextile Filter Fabric” under Section
The proposal of material will be submitted separately with sample.
Material tests in laboratory described as below will be implemented before commencement of work under the inspection of the Engineer for approval.
< Tests in laboratory for material approval >
Test Item Test Method Specification
Strip Tensile Strength ASTM-D4595 ≥12kN/m
Apparent Opening size O95 ASTM-D4751 ≤0.15mm
During construction, material tests will be conducted in the laboratory under the supervision of the Engineer, adhering to the standard 22TCN248-98 Testing will occur at a frequency of one test per 10,000 square meters, with each test involving three specimens.
< Tests in laboratory during construction>
Test Item Test Method Specification
Strip Tensile Strength ASTM-D4595 ≥12kN/m
Apparent Opening size O95 ASTM-D4751 ≤0.15mm
When storing at site, material shall be kept off the ground and covered to protect from rain, sun and dirty.
Prefabricated Vertical Drain (PVD) material
PVD material shall be satisfied with the General Specifications (Clause 2.4.2
“Prefabricated Vertical Drain (PVD)”) and the standard 22TCN262-2000 The proposal of material will be submitted separately with sample.
Material tests in laboratory described as below will be implemented before commencement of work for material approval under the inspection of the Engineer.
< Tests in laboratory for material approval>
Test Item Test Method Specification
Apparent opening size (O95) ASTM D4751-87 less than 75 micrometer Grab Tensile Strength ASTM D4632-91 more than 1.6 kN Drainage Capacity at 350kN/m2 pressure ASTM D4716-87 qw≥60*10 -6 m 3 /sec
Permeable Coefficient of filter cover ASTM D4491 more than 1.0*10 -4 m/sec Stretching Strength correlatively with elongation less than 10% for break resistance during installation of PVD
Width of PVD approx 100±0.05mm
During construction, material tests outlined in the laboratory will be conducted under the supervision of the Engineer Testing will occur at a frequency of one test for every 10,000 meters of Prefabricated Vertical Drain (PVD) installed, in accordance with General Specifications (Clause 2.4.2) and standard 22TCN236-97.
One roll of PVD is approximately 300m When storing at site, material shall be kept off the ground and covered to protect from rain, sun and dirty.
Through construction stage, it shall be applied the check of condition of penetration by measuring each length and recorded as stipulated in “Inspection and Test Plan”.
Construction Method
Working Flow
The flow of work is as follow.
(Sequence of Work) (The description of checking and inspection)
Case 1: Soft soil Improvement by PVD Case 2: Soft soil Removal and Replacement
Clearing, Grubbing, Stripping, Removal of Tree (if any)
Inspection of Mobilization of Equipment and Manpower Inspection of Ground Condition
The process involves a thorough survey and inspection of the site clearing boundary, along with the verification of demolition quantities and the identification of trees that need to be removed, if applicable Additionally, it includes the removal and disposal of unsuitable materials as well as any demolished materials present on the site.
The engineer will confirm and approve the subsoil layer, ensuring it meets project specifications Additionally, the topsoil will be disposed of appropriately, and any existing trees will be removed as necessary Acceptance of construction activities will include demolition, site clearing, grubbing, and the removal of trees to prepare the site for further development.
Acceptance to move to the next construction stage
Confirmation of approved working drawing Inspection of Ground Elevation and Location, Material Test
Temporary relocation of stream channel
Confirmation and Approval of the existing condition of watercourses to relative authority and Engineer with working drawing
Inspection of delivered material Inspection of Mobilization of Equipment & Manpower Inspection of location of installation and stitching Acceptance of Construction Items
Monitoring (settlement and stability) Inspection of location, installation and initial survey
Minutes of Checking (Inspection Sheet)
2 Sand filling up to designated E.L shown on approved drawings
Inspection of delivered material Inspection of Mobilization of Equipment & Manpower Inspection of Compaction including trial (Minutes of Checking) Inspection and survey location & E.L of filling
Inspection of delivered material Inspection of Mobilization of Equipment & Manpower Inspection trial installation with mandrel (without PVD) Minutes of Checking for trial installation
Inspection of PVD Installation Acceptance of Construction Items Acceptance to move to the next construction stage
Inspection of delivered material and method
Backfilling for 1 st , 2 nd layer and succeeding layer (if any) Inspection of Area and Elevation
Inspection of Site Density test Acceptance of Construction Item
Treatment of Pond and Ditches Backfilling up to site Clearing Elev of Surrounding Area Inspection of Site Density Test
Acceptance of Construction Item (for large ponds)
(sub-grade ~ pavement, drain, curb)
Inspection of delivered material and method Inspection of Mobilization of Equipment & Manpower Inspection of Compaction including trial (Minutes of Checking) Check and control the rate of Embankment placing
Check and confirmation of residual settlement
Criteria: within 10cm of the total predicted settlement
Inspection of Soil condition after Site Clearing Confirmation and Approval of Soft Soil Removal by the Engineer Survey and Inspection of Soft Soil boundary
Checking Excavated Soil condition during removal Checking slope codition of excavation during removal Confirmation of Unsuitable Material or Suitable Material during removal Checking dewartering system (if necessary)
Confirmation and Approval of Subsoil condition by the Engineer Survey and Inspection of Location and Elevation
Backfilling by Borrow material Inspection of delivered material and method
Backfilling layer by layer up to Site Clearing Elev of Surrounding Area Inspection of Field Density Test
Inspection of Area and ElevationAcceptance of Construction ItemAcceptance to move to the next construction stage
Construction Method
Topsoil in area under the embankment shall be removed and disposed as waste in accordance with Section 02100 “Site Clearing” of General Specifications and approved working drawing.
Actually condition of topsoil to be removed shall be checked with the Engineer during working
Topsoil stripping must adhere to the guidelines outlined in Clause 2.3.(c) of Section 02100, while the final depth and area for clearing and stripping will be determined based on the actual site conditions and specific instructions from the Engineer The clearing limits will be clearly indicated on the working drawings.
The existing structures beneath the embankment will be demolished in compliance with Section 02200, which outlines the demolition and removal of existing structures and obstructions, as per the general specifications and approved working drawings.
Careful execution of clearing, stripping, and demolition activities is essential to avoid damaging the sub-soil of the embankment After these processes, any pits or voids must be filled with approved borrow material and properly compacted.
The surface water on ground shall be dewatered by pump or temporary drain.
The channels and ditches crossing the area of embankment will be treated as follows.
Check condition of existing Channels and Ditches
Working Drawing for Approval (Relevant Authority)
Diversion outside the area of embankment Clearing & Grubbing ~ Common excavation for installation of temporary drainage
4 Sand filling up to designated E.L shown on approved drawings
Dry up existing ~ clearing, stripping & demolition of existing channels and ditches Install temporary drainage on designed location to keep the watercourse
Filling existing channels and ditches with suitable material, leveling and compaction as required
Backfilling after installation of drainage with suitable material, leveling and compaction as required
The existing pond in the area of embankment will be treated as follows.
Before starting any work, it is essential to verify the existing utility with the appropriate authorities Additionally, the Engineer must approve the plan for diversion or removal in collaboration with all relevant authorities.
The ground surface shall be flat and level after clearing, stripping and demolition.
Topsoil generated from clearing activities will be collected and stored in a designated area for future use in sodding or landscaping on embankments or road medians.
7.2.2 Backfilling by Borrow Material after Clearing
Backfilling and leveling with borrow material will occur in areas following clearing and grubbing, ensuring that the sand filling layer is elevated above the surrounding ground level for effective dewatering Before the backfilling process begins, the Engineer will inspect and approve the subsoil layer post-clearing.
Check condition of existing Pond (with Engineer & relevant authority)
Temporary dyke construction outside the area of embankment (In case that the pond is located within R.O.W., the temporary dyke is not necessary.)
Dewatering pond water by pump Remove unsuitable material (mud, organic… ) with Inspection
Backfilling void by approved embankment material with inspection.
(up to the Site Clearing Elevation of surrounding area)
When treating soft soil, embankment leveling must be established at or above the surrounding ground level to account for potential settlement This requirement should be clearly indicated in the working drawings.
The first layer of the embankment should be constructed with a thickness of 20 to 30 centimeters, while the second layer and any subsequent layers must each be placed with a thickness of 20 centimeters.
Compaction for the initial and subsequent layers must be performed using a Vibration Roller or suitable equipment, with water spraying as needed The process will persist until achieving 95% of the maximum dry density The Engineer will inspect the in-situ density by taking three samples for every 500m³ of fill volume or 1500m² of fill area, whichever is less.
After leveling up to its designed elevation as shown on working drawing, Inspection and Acceptance shall be carried out prior to laying and installation of Geotextile.
For the effective installation of geo-textile, it is essential that the surface is as level and flat as possible, with any unevenness not exceeding 100mm and the ground surface inclination kept below 5%.
For Pond and Ditch areas the treatment shall be as follows prior to Backfilling by Borrow Material
For small ponds and ditches, backfilling should be executed in layers following the Clearing and Grubbing process The initial layer must be compacted to a thickness of 30cm, while subsequent layers should be compacted to 20cm until reaching the site clearing elevation of the surrounding area After the In-Situ-Density Test is confirmed, backfilling and leveling with borrow material will proceed for the first and second layers, and any additional layers, up to the elevation of the geo-textile.
Backfilling for large ponds and ditches will be executed layer by layer following the Clearing and Grubbing process The initial layer will consist of 30cm of compacted material, while subsequent layers will be 20cm thick, continuing until reaching the site clearing elevation of the surrounding area Each layer must undergo compaction with appropriate equipment, and the Engineer will perform inspections to confirm in-situ density testing for every layer Once the treatment is complete, an Inspection and Acceptance process will take place Following acceptance, backfilling and leveling with borrow material will commence for the first and second layers, and any additional layers will be brought up to the elevation of the geo-textile.
Compaction will be performed using designated vibration rollers or suitable equipment until 95% of the maximum dry density is achieved The Engineer will conduct inspections to verify in-situ density testing for each layer In-situ density tests will follow AASHTO T204 or AASHTO T191, utilizing three samples for every 500m³ of filling volume or 1500m² of filling area, whichever is less.
Geo-textile installation must occur at designated locations as per the approved working drawings, following the leveling of borrow material Before laying the Geo-textile, it is essential to clear the ground surface of any sharp objects to avoid puncturing the sheet Additionally, the setting out of the center point and boundary limits of the embankment should be conducted with stakes, under the Engineer's supervision, in compliance with the approved plans.
The installation of Geotextile consists of two stages: the first stage occurs before the filling and compaction of the initial layer of Sand Fill material, while the second stage takes place before the filling and compaction of the external and second layer of Sand Fill material at the toe of the slope.
Inspection and Test Plan
The "Inspection and Test Plan" can be found in Appendix-2, while the "Inspection and Check Sheet" is included in Appendix-3 Please note that the "Inspection and Check Sheet" may be revised as needed based on the Engineer's instructions.
Safety Control
The "Safety Control Plan" must be submitted independently and included in this method statement Essential safety measures will be enforced before and throughout the execution of the Road Earthworks to ensure efficient operations and minimize the risk of accidents or injuries.
Particular Item for safety control is as follows.
No Anticipated Accident Preventive Action
1 Traffic accident with third person Setting signalman at entrance of site
2 Collision accident (heavy equipment & Truck)
Set signalman at each working site
Keep speed limit 20km/h in site
Set wheel stopper at the location of unloading soil
3 Wedged accident between equipment Notice and instruct worker the work description
Set safety fence around heavy equipment working area
Electric under ground shall be fully protected from electric leakage and shall be buried at least 40cm from the surface when electric line is crossing access road
Electrical equipment shall have earth or ground connection
Install warning sign or notice at locations of electrical connection and lines
Staff, worker and operators shall wear the Personal Protective Equipment (PPE) at all times during working
Maintain working site condition neat and tidy at all times
Environmental Control
The Environmental Management Plan must be submitted as a separate document and included within this method statement It is essential to ensure that responsibilities for the surrounding environment are upheld during road earthwork operations, adhering to the Conditions of Contract and complying with Vietnam's National Law on Environmental Protection, as well as relevant legislation such as Government Decree No 175/CP and the guidance provided for the implementation of the Environmental Protection Law of 1994.
If any other problems occurred in the site, applicable counter measures or prevention action shall be considered immediately and executed as soon as possible.
Particular Item to be controlled is as follows.
No Particular Item Action to be taken
1 Coarse particulate and dust to purlieus
Spraying water on access road daily
Cleaning entrance of site (utility road)
All sand/ soil trucks shall be covered by canvas
2 Noise and vibration to purlieus
Keep speed limit 20km/h or less in site
Motorized equipment is not allowed to operate from 10p.m to 6a.m near by residential area.
A detailed photographic documentation of the current state of residential houses and nearby utilities adjacent to the construction site will be conducted prior to any construction activities, in line with the investigation plan that will be submitted separately.
Investigation of above houses and utilities during construction
3 Water contamination Install sedimentation pit before outlet, (if required)
Set safety fence around heavy equipment working area
Equipment shall be properly maintained to prevent the emission of large amount of smoke for air pollution
Used oil and lubricants shall be disposed properly to prevent water and air pollution
For Site Clearing and Demolition
RI-1(1/2) - Inspection Sheet for Site Clearing (1) (For Checking Surface Condition) RI-1(2/3) - Inspection Sheet for Topographic Survey after Site Clearing
RI-1(3/3) - Inspection Sheet for Site Clearing (2) (Tree Removal)
RI-3(1/1) - Inspection Sheet for Demolition
RI-5(1/1) - Inspection Sheet for Pond Treatment and Ditch
RI-6(1/2) - Inspection Sheet for Construction of Backfilling after Site Clearing (1)
(For Normal Layers) RI-6(1/2) - Inspection Sheet for Construction of Backfilling after Site Clearing (2)
(For Top Layer) RI-6(2/2) - Inspection Sheet for Construction of Backfilling after Site Clearing
For Removal of Soft Soil
RI-7(1/2) - Inspection Sheet for Removal of Soft Soil (1)
RI-7(2/2) - Inspection Sheet for Removal of Soft Soil (2)
RII-1(1/2) - Inspection Sheet for Geotextile Placement – Stage I (1)
RII-1(2/2) - Inspection Sheet for Geotextile Placement – Stage I (2)
RII-4(1/1) - Inspection Sheet for Geotextile Placement – Stage II
For Settlement and Sliding Monitoring
RII-2(1/1) - Inspection Sheet for Settlement Monitoring
RII-3(1/2) - Inspection Sheet for Sliding Monitoring (1)
RII-3(2/2) - Inspection Sheet for Sliding Monitoring (2)
General - Inspection Sheet for Trial Compaction
RII-5(1/2) - Inspection Sheet for Construction of Sand Mat (1) (For Normal Layers) RII-5(1/2) - Inspection Sheet for Construction of Sand Mat (2) (For Top Layer)
RII-5(2/2) - Inspection Sheet for Construction of Sand Mat
For Prefabricated Vertical Drain Installation (PVD)
RII-7(1/1) - Inspection Sheet for Trial Installation of PVD
RII-8(1/1) - Inspection Sheet for Installation of PVD
RIII-2(1/2) - Inspection Sheet for Construction of Embankment (1)
(For Normal Layers) RIII-2(1/2) - Inspection Sheet for Construction of Embankment (2)
(For Top Layer) RIII-2(2/2) - Inspection Sheet for Construction of Embankment