Biện pháp được viết bằng tiếng anh, mô tả quy trình thi công hạng mục sub-base and base course. Được viết dựa trên chỉ dẫn kỹ thuật dự án và AASHTO
GENERAL DESCRIPTION
Project Information
The Cambodia Road Connectivity Improvement Project (CRCIP) is being implemented by the Ministry of Rural Development (MRD) in Cambodia with funding from the World Bank (WB) The project aims to support the improvement of climate resilient road accessibility in three (3) provinces, namely: (i) Kampong Cham, (ii) Tboung Khmum, and (iii) Kratie.
The RCIP which includes a total of 27 roads with a total length of 277.3 km is located in three provinces of Cambodia, namely: (i) Kampong Cham, (ii) Tboung Khmum, and (iii) Kratie Of which,
7 roads with a total length of 75.3 km are located in Kampong Cham province, 6 roads with a total length is 67.6 km is located in Tboung Khmum province, and 14 roads with a total length of 134.4 km are situated in Kratie province.
RCIP is divided into 3 civil work package by provinces and CW1 covering Kratie province subdivided into 2 lots: CW1-Lot 1 (72.9Km) and CW1-Lot 2 (61.5 Km)
In there, CW1-Lot 2 include 6 roads: KRT-1 (11.1 Km), KRT-2 (8.2 Km), KRT-3 (11.9 Km), KRT-6 (14.2 Km), KRT-20 (8.1 Km) and KRT-29 (8.0 Km) CW1-Lot 2 location is shown as Figure 1.1-1
Figure 1.1-1 Location of Contract Package on CW1-Lot 2
Project Objective
The Cambodia Road Connectivity Improvement Project (RCIP) will support the improvement of climate resilient road accessibility in targeted provinces The Royal Government of Cambodia(RGC) has requested the World Bank (WB) provide an Investment Project Financing (IPF).Targeted provinces under the proposed investment include Kampong Cham, Kratie, and TboungKhmum with a total population of over 2.3 million people The design of the proposed project builds on a network connectivity approach to improve road accessibility in rural areas, between rural areas and urban centers, and to the main network The project provinces were selected considering several criteria including density of rural population, agricultural potential, vulnerability to floods, condition of roads, and connectivity of provincial road networks to cover larger geographic area.
Road works will help to improve climate resilience and safety of road infrastructure The scope of works will include paving/sealing of the roads with climate adaptation and resilience measures and improving bridges and other road structure to climate-resilient standards The technical design will ensure that the identified climate-resilient measures reduce transportation costs and flooding risks and achieve the target of creating durable access to the main road network, markets, and services for the rural population.
INTRODUCTION
Reference Construction Specification
Other Standard Related
AASHTO M147 Standard Specification for Materials for Aggregate and Soil-Aggregate
Subbase, Base, and Surface Courses AASHTO M145 Classification of Soils and Soil-Aggregate Mixtures for Highway
Construction Purposes AASHTO M147 Standard Specification for Materials for Aggregate and Soil-Aggregate
Subbase, Base, and Surface Courses AASHTO M 43 Sizes of Aggregate for Road and Bridge Construction
AASHTO T27 Sieve Analysis of Fine and Coarse Aggregates
AASHTO T89 Determining the Liquid Limit of Soils
AASHTO T90 Determining the Plastic Limit and Plasticity Index of Soils
AASHTO T96 Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion AASHTO T104 Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate
AASHTO T180 Moisture-Density Relations of Soil Using a 4.54kg Rammer 457mm Drop
AASHTO T191 Testing procedure on definition of compaction of road foundation and embankment by sand cone method AASHTO T193 The California Bearing Ratio
Description
Sub-Base Work shall consist of furnishing, placing and compacting sub-base material on a prepared and accepted sub-grade in accordance with these Specifications, to the lines, levels, grades, dimensions and cross sections shown on the Drawings and as required by Engineer.
Base Course Work shall consist of providing a base course layer composed of crushed aggregate material or other approved base course material placed and compacted on a prepared and approved sub-base in accordance with these Specifications and to the lines, levels, grades, dimensions and cross sections shown on the Drawings and as required by Engineer.
SCOPE OF WORK
Description
The scope of work covers the following activities such as:
1 Preparation Works (Manpower, Equipment, Materials etc.);
2 Setting of Traffic Safety Devices;
3 Survey works and Staking Out;
4 Construction, Inspection and Acceptance Sub-Base Layer
Spreading Material Work of Sub-Base Layer
Spreading Material Work of Sub-Base Layer
Compaction Work of Sub-Base Layer
Spreading Material Work of Sub-Base Layer
Inspection and Acceptance of Sub-Base Layer
Spreading Material Work of Sub-Base Layer
5 Construction, Inspection and Acceptance Base Course Layer
Spreading Material Work of Base Course Layer
Spreading Material Work of Sub-Base Layer
Compaction Work of Base Course Layer
Spreading Material Work of Sub-Base Layer
Inspection and Acceptance of Base Course Layer
Spreading Material Work of Sub-Base Layer
Table List of Rural Roads under Project Scope
KRT-1 Thmor Krae – Chong Krang 11.1 Chetborei Dar
KRT-2 Sambok – Korsang 8.2 Chetborei Thmor Krae
KRT-3 Kbal Chour – Dei Sampateankakot 11.9 Chetborei Kou Loab
KRT-6 Prek Brosob Ler - Sraengeat 14.2 Chetborei Sambok
KRT-20 Banteay - Koh dach 8.1 Chetborei Dar
KRT-29 Thmorreab - Sre ngiet 8.0 Chetborei Thmey
Table 3.2-1: Table List of Rural Road under Project Scope
Work Quantities
The following tables are the estimated quantities of Sub-Base and Aggregate Base Course from the Bill Quantities of the main Contract intended for references only and not for measurement purposes.
Description Items No Unit Quantities
ORGANIZATION CHART
Organization Chart is as follow:
MANPOWER AND EQUIPMENT
Equipment
Table of Equipment serving for the construction:
No Equipment Capacity Unit Qty Remarks
If necessary, used for spreading Sub-Base material at location where work area is limited
2 Motor Grader 108CV each 1 For Spreading the Sub-Base materials along road route
3 Spreading Machine each 01 For Spreading the Base Course materials along road route
4 Excavator 0.8m 3 each 1 For isolated special spreading works & scarifying
5 Backhoe Loader 0.5 m 3 each 1 For isolated special spreading works & scarifying
6 Tandem Roller 12 tons each 2 For compaction works
7 Vibrator Roller 25 tons each 2 For compaction works
8 Mini Compaction each 02 Used for special working area, Limited
9 Dump Truck 15 tons each 5 For hauling and Dumping of material
10 Water Supply Truck 10m3 each 2 For watering the SB or BC, Control dust
11 Survey Instruments set 1 Serving survey works/ Control elevation
* Note: This equipment will be increased according to the site requirements
Manpower
Manpower to be mobilized for construction work as below:
8 Safety Worker Person 2 Depend on site condition
* Notes: This manpower will be increased according to the site requirements
MATERIALS REQUIREMENT
Sub-Base Material
Refer Sub-Clause 3.1.2.2 of General Specification
- The grading shall conform to grading envelopes A, B, C, D or E as determined by AASHTO test method T 27 and given in Table 6.1-1 below
Table 6.1-1: Grading Requirements for Soil Aggregate Material
- The fraction of material passing the 0.425 mm sieve, a liquid limit, as determined by AASHTO T
89, of not greater than 35 percent and a plasticity index, as determined by AASHTO T 90, of not less than 3 and not greater than 15.
- The fraction passing the 0.075 mm sieve shall be not greater than two thirds of the fraction passing the 0.425 mm sieve.
- Abrasion of the coarse part of the material shall be tested in accordance with AASHTO T 96 and shall show a percentage of wear no greater than 50 percent Shale material shall NOT be used for sub-base.
- The minimum required CBR shall be 30 percent, after 4 days soaking in accordance withAASHTO T 193, on samples compacted to 95% of the dry density determined by AASTHO T180.
Aggregate Base Course Material
Refer Sub-Clause 3.3.2.1 of General Specification
- Base course aggregate shall consist of a mixture of hard durable crushed rock particles and mineral filler which satisfies the grading limits A, B or C in Table 6.1-1 of this method statement.
- The portion that passes the 0.075 mm sieve shall not be more than 2/3 of that portion passing the 0.425 mm.
- The coarse aggregate, defined as that material retained on the 4.75mm sieve, shall have a percentage of wear not greater than 40 percent for 500 revolutions, when tested according to AASHTO T 96.
- Where the coarse aggregate is produced from crushing a river source gravel, at least 90 percent of the particles shall have at least 2 crushed faces.
- The portion passing the 0.425 mm sieve of the total mixture shall have a liquid limit of not more than 25 and a plasticity index of not less than 2 and not more than 6 percent, as determined in AASHTO T 90.
- The CBR strength of the whole mixture, as determined in AASHTO T 193, shall be no less than
80 percent after 4 days soaking, on samples compacted to 95 percent of the maximum dry density as determined in AASHTO T 180 and over a moisture range of 4 percent Shale material shall NOT be used as base course
- If the stone used to prepare the fine material has unsatisfactory cementing qualities, it may be used provided limestone fines in an amount of 20% by mass of that proportion passing the 4.75mm sieve, are blended therewith at no additional cost to the Employer.
TESTING AND SAMPLING
Lab
The contractor will submit to the consultant a qualified testing unit The profile will be submitted separately by the contractor The experimental unit will serve the project with the approval of the consultant.
Testing Standards
Unless otherwise specified, all tests shall be performed in accordance with the methods used by AASHTO/ASTM and shall be made by the Engineer or his designated representative Refer
“Table 2.2-1: Standard Related” of Sub-Clause 2.2 of This Method Statement.
Sampling and Testing Frequency
No Stage/ Activity Inspection required Reference
1.1 Approval of Materials Sampling & testing AASHTO Method
Gradation AASHTO T-27 3 per Source plus 1 per 1000 cu-m
T-90 3 per Source plus as required based on visual observation.
CBR AASHTO T-193 3 per Source plus as required based on variation in gradation. Abrasion AASHTO T-96 3 per Source plus 1 per 500 cu.m Moisture Density AASHTO T-180 1 per 1,000m
2.1 Length, width & height of work Line & level As per the drawings Per area
2.2 Formation level Finish level As per the drawings Per area
3.1 Placing of Sub Base Evenness 150mm thickness Visual inspection Per area 3.2 Compaction Density 95% of MDD AASHTO T-191 5 tests per 2000 Sq.m or 3 tests if it’s less than 2000 Sq.m
No Stage/ Activity Inspection required Reference Method Frequency
1.1 Approval of Materials Sampling & testing AASHTO Method
Gradation AASHTO T-27 3 per Source plus 1 per 1,000 cu.m
Plasticity Index AASHTO T-90 3 per Source plus as required based on visual observation
T-193 3 per Source plus as required based on variation in gradation. Abrasion AASHTO T-96 3 per Source plus 1 per 500 cu.m
Sodium Sulphate Soundness AASHTO T-104 3 per Source plus 1 per 500 cu.m Fractured faces Visual 3 per Source plus as required based on visual observation
2.1 Length, width & height of work Line & level As per the drawings Per area
2.2 Formation level Finish level As per the drawings Per area
Base Course Evenness 150mm thickness Visual inspection Per area
MDD AASHTO T-191 5 tests per 2000 Sq.m or 3 tests if it’s less than 2000 Sq.m
Experimental Work
- Contractor will provide full test certificates, origin of all supplier's materials Suitable samples of the sources of sub-base, Base course materials shall be submitted to the Engineer.
- The material criteria shall conform to the requirements in Sub-Clause 6 “Materials Requirement” of this Method Statement and the requirements of Project General Specification.
- All samples material tests shall be conducted in a manner approved by the engineer and shall be conducted in the contractor's laboratory.
- During compaction of Sub-Base or Base Course material, the Field Density Test shall be used to determine the in-place density of materials, ensuring they meet the required specifications The test involves measuring the dry density and moisture content of the material, which are then compared to the maximum dry density and optimum moisture content values obtained from laboratory tests.
- Where shown on the plans or indicated by the Engineer, a proof-roll test by contractor on the compacted sub-base surface to evaluate the strength and stability of sub-bases and base courses.The testing work shall comply with the requirements of sections 3.1.3.5 and 3.3.3.7 of GeneralSpecification.
CONSTRUCTION PROCEDURE
Work Flow Chart
The Work Flow Chart is shown in Figure 8.1-1 below.
General Preparation Before Working
- Submitting construction method documents to consultants;
- Mobilizing necessary machinery and equipment for construction;
- Material source selection, Testing and Inspection of materials supplied for Sub-Base, Base Course works;
- Aggregate Base/ Sub-Base materials from the supply resource will be gathered in Contractor’s material stockpile at the construction area.
- Inspection and Acceptance below layer before construction of above layers (construction implementation of Sub-Base after acceptance of Subgrade layer; construction implementation of Base Course after acceptance of Sub-Base layer);
- Contractor shall proceed to restore and check the pile positioning system at the center line and road foundation edge Setting out alignment with Bamboo and Level;
- Arrangement of traffic safety control devices at the working area.
Figure 8.2-1: Plan Traffic Control for Sub-Base or Base Course Construction
Construction of Sub-Base
- Surveying and Staking: Firstly, define the center line, each stake separated by 20 m in distance, then specify the path to examine stakes at positions on the two sides of road base, followed by determining the boundary of each layer of Sub-Base according to elevation of top surface of each layer Border will be controlled and marked with bamboo stakes, each stakes 20m apart.
- The contractor will divide the construction phase accordingly Deploy construction on 1/2 of the roadbed width with a construction section of 200-300m long Arrange construction sections staggered to separate traffic flow, ensuring safety during construction Traffic control for construction of Sub-Base, please refer to Annex 3-Traffic Management Plan (TMP) of Project Quality Assurance Plan Document.
- After accept from Engineer for Subgrade layer, we must spread water before filling Sub-Base.
- Transport material Sub-Base to construction site by dump truck Check moisture content of Sub- Base material before transportation If material too wet is not allowed to use.
Figure 8.3.1-2: Construction of Sub-Base and Traffic Control
- Material will spread by Motor grader combine with Bulldozer
- If the material is too dry at the compaction time, water shall be sprinkled by water truck to adjust the water content to Optimum Moisture Content (OMC) before compaction Maximum compacted thickness of each layer shall be 150mm.
- According to the design, the sub-base thickness is 200mm after compaction of 95% of MDD TheContractor will divide it into two spreading stages with each layer thickness of 100mm after compaction.
- To control the thickness of each layer, marked stakes (loose material thickness approximately 125mm to 135mm) shall be installed The thickness of loose material will be determined based on the test results.
Figure 8.3.2-1: Sub-Base Thickness of 200mm
- Compute the volume of materials for each segment by un-compacted thickness, average width and length of each layer, then calculate the volume of one trucks transporting materials to the site by transport capacity of each vehicle, and determine the distance of material unloading between the two consecutive trucks.
- Un-compacted thickness of each layer = Design thickness x Compacting Factor
- The compaction coefficient of Sub-base layer is determined by the ratio between the maximum dry volume value, γkmax, of the mixture determined according to the compaction test with Dry mass and volume value of the mixture when leaving the mixer This coefficient is accurate through conducting trial construction.
- Ensure Sub-base course materials are always within 2% of the optimum moisture content during transportation, gathering, spreading and compacting Before and during construction, need to duly check and adjust the material moisture.
- If the material has a lower moisture than the optimal range of moisture, supplement watering with shower sprinklers and avoid runoff of fine particles Contractor will also supplement the moisture in the process of spreading, compacting by the attached mist sprayer If the moisture is greater than the optimal range of moisture, it will be laid out to dry before compacting.
Spreading of Sub-Base Materials
- The contractor will use a Motor Grader combine with Bulldozer to laying sub-base materials. Decision of spreading thickness (in particular through the compacting factor) will be based on results of trial construction.
- Materials will be laid and shaped by approved measures, no segregation between coarse aggregate and fine particles The stratified materials will be repaired and replaced with qualified materials.
Figure 8.3.2-2: Motor Grader and Dump Truck
- To ensure the compactness on the entire width, when there is no line mold or curb, material will be spread wide on each side 25cm more than the width of the design (In any case, it shall be ensured minimum 7cm width each side) At the position adjacent to the previous spreading trace, remove loose sub-base course materials at the edge of spreading traces before spreading the next traces.
- Immediately after spreading and leveling, The contractor conduct compaction of each layer across the entire width Begin compacting from the side of road to the center line in vertical line In the ultra-high, compact from the low side to the high side Continuously compact until there is no deflection trace of rollers and each layer of materials are compacted and the aggregates are closely matched If subsidence or surface heterogeneity, it need to repairing by tilling the material at that location, then the addition or removal until the materials reach homogenous and smooth surface. Repair of sub-base must comply with Technical Specifications Along curb, top edge, wall and at position where the roller cannot access, the materials must be properly compacted by appropriate compactors that were approved by the Engineer to ensure the technical requirements and quality.
8.3.3 Compaction of Sub-Base Material
Numbers of compaction pass will be complied with the approved result of construction process after trial construction of Sub-Base Below is an example of the compaction order: o Preliminary compaction: Use static roller (Steel roller, 8T), rolling 3-4 passes at a speed of 2-3 km/h. o Density compaction: Use vibratory roller (13T or 18T), with centrifugal force drum max 22T or
26T, rolling 12-18 passes at a speed of 2-4 km/h. o Completed compaction: Use static roller, rolling 2-3 passes at a speed of 3-4 km/h
- While spreading and rolling, if layering is detected, Contractor shall carry out re-mixing or removing and replace them with new materials.
- While rolling, sub-base surface must still be slightly watered to make up the water lost while spreading and rolling.
- The order of compaction is from the outside into the center line The compacting trace afterward will overlap the previous compacting trace with 25cm (For horizontal joints positions the compacting trace afterward will overlap the previous compacting trace with 1m).
- Compaction process must ensure the flatness to surface of layer construction and horizontal drainage slope If detecting any unusual matters such as cracks, corrugation, dash or un- connection, stop compaction to find the cause and absolute solution then continue compaction All these works must be completed before reaching to 80% of compacting passes.
Construction of Base Course
- Surveying and Staking: Firstly, define the center line, each stake separated by 20 m in distance, then specify the path to examine stakes at positions on the two sides of road base, followed by determining the boundary of each layer of Base Course according to elevation of top surface of each layer Border will be controlled and marked with bamboo stakes, each stakes 20m apart.
- The contractor will divide the construction phase accordingly Deploy construction on 1/2 of the roadbed width with a construction section of 200-300m long Arrange construction sections staggered to separate traffic flow, ensuring safety during construction Traffic control for construction of Base Course, please refer to Annex 3-Traffic Management Plan (TMP) of Project Quality Assurance Plan Document.
- After accept from Engineer for Sub-Base layer, we must spread water before filling Base Course.
- Transport material Base Course to construction site by dump truck Check moisture content of Base Course material before transportation If material too wet is not allowed to use.
Figure 8.4.1-2: Construction of Base Course and Traffic Control
- Base Course material will be spread by a self-propelled spreading machine.
- If the material is too dry at the compaction time, water shall be sprinkled by water truck to adjust the water content to Optimum Moisture Content (OMC) before compaction Maximum compacted thickness of each layer shall be 150mm.
- According to the design, the base course thickness is 200mm (used for DBST pavement) and 150mm (used for Reinforced Concrete Pavement) after compaction of 98% of MDD
- In case, designed thickness of Base course is 200mm, the Contractor will divide it into two spreading stages with each layer thickness of 100mm after compaction To control the thickness of each layer, marked stakes (loose material thickness approximately 135mm to 140mm) shall be installed The thickness of loose material will be determined based on the test results.
Figure 8.4.2-1: Base Course Thickness of 200mm
- In case, designed thickness of Base course is 150mm, the Contractor will divide it into one spreading stages with layer thickness of 150mm after compaction To control the thickness of each layer, marked stakes (loose material thickness approximately 200mm to 210mm) shall be installed The thickness of loose material will be determined based on the test results.
Figure 8.4.2-2: Base Course Thickness of 150mm
- Compute the volume of materials for each segment by un-compacted thickness, average width and length of each layer, then calculate the volume of one trucks transporting materials to the site by transport capacity of each vehicle, and determine the distance of material unloading between the two consecutive trucks.
- Un-compacted thickness of each layer = Design thickness x Compacting Factor
- The compaction coefficient of aggregate base course layer is determined by the ratio between the maximum dry volume value, γ , of the mixture determined according to the compaction test with
Dry mass and volume value of the mixture when leaving the mixer This coefficient is accurate through conducting trial construction.
- Ensure aggregate base materials are always within ±2% of the optimum moisture content during transportation, gathering, spreading and compacting Before and during construction, need to duly check and adjust the material moisture.
- If the material has a lower moisture than the optimal range of moisture, supplement watering with shower sprinklers and avoid runoff of fine particles Contractor will also supplement the moisture in the process of spreading, compacting by the attached mist sprayer If the moisture is greater than the optimal range of moisture, it will be laid out to dry before compacting.
Spreading of Aggregate Base Materials
- The contractor will use a Self-Propelled Spreader to laying base course materials Decision of spreading thickness (in particular through the compacting factor) will be based on results of trial construction.
Figure 8.4.2-3: Self-Propelled Spreader Combine with Dump Truck
- Materials will be laid and shaped by approved measures, no segregation between coarse aggregate and fine particles The stratified materials will be repaired and replaced with qualified materials.
- To ensure the compactness on the entire width, when there is no line mold or curb, material will be spread wide on each side 25cm more than the width of the design (In any case, it shall be ensured minimum 7cm width each side) At the position adjacent to the previous spreading trace, remove loose base course materials at the edge of spreading traces before spreading the next traces.
- Immediately after spreading and leveling, The contractor conduct compaction of each layer across the entire width Begin compacting from the side of road to the center line in vertical line In the ultra-high, compact from the low side to the high side Continuously compact until there is no deflection trace of rollers and each layer of materials are compacted and the aggregates are closely matched If subsidence or surface heterogeneity, it need to repairing by tilling the material at that location, then the addition or removal until the materials reach homogenous and smooth surface. Repair of base course must comply with Technical Specifications Along curb, top edge, wall and at position where the roller cannot access, the base course materials must be properly compacted by appropriate compactors that were approved by the Engineer to ensure the technical requirements and quality.
8.4.3 Compaction of Base Course Material
Numbers of compaction pass will be complied with the approved result of construction process after trial construction of Base Course Below is an example of the compaction order: o Preliminary compaction: Use static roller (Steel roller, 8T), rolling 3-4 passes at a speed of 2-3 km/h. o Density compaction: Use vibratory roller (13T or 18T), with centrifugal force drum max 22T or
26T, rolling 12-20 passes at a speed of 2-4 km/h. o Completed compaction: Use static roller, rolling 2-3 passes at a speed of 3-4 km/h
- While spreading and rolling, if layering is detected, Contractor shall carry out re-mixing or removing and replace them with new materials.
- While rolling, sub-base surface must still be slightly watered to make up the water lost while spreading and rolling.
- The order of compaction is from the outside into the center line The compacting trace afterward will overlap the previous compacting trace with 25cm (For horizontal joints positions the compacting trace afterward will overlap the previous compacting trace with 1m).
- Compaction process must ensure the flatness to surface of layer construction and horizontal drainage slope If detecting any unusual matters such as cracks, corrugation, dash or un- connection, stop compaction to find the cause and absolute solution then continue compaction All these works must be completed before reaching to 80% of compacting passes.
- Compaction will be executed when the material moisture ranges suitable with optimum moisture content The optimum moisture content that is determined by the adjusted maximum density under provisions in the AASHTO Standard T180, method D.
- Compaction shall continue until a field density of at least 98% of the maximum density determined in accordance with AASHTO T180.
Stage 1: Transportation Base Course material to site construction and the work of loading materials onto the self-propelled spreader.
Figure 8.4.3-2: Transportation and The work of loading materials onto the self-propelled spreader
Stage 2: Spreading Base Course Material
Spreading Base Course material with non-compaction thickness by the self-propelled spreader.
Figure 8.4.3-3: Spreading Base Course Material by Self-propelled spreader
Stage 3: Watering, Rolling and Compacting
During compaction the moisture content shall be so controlled by using water truck Compacting base course layer by vibration roller.
Figure 8.4.3-4: Watering, Rolling and Compacting
Maintenance Sub-Base/ Base Course
- Maintenance should be done throughout the completed sub-base layer except for some stretches where succeeding course layer are under construction.
- This activity includes drainage, rolling, shaping, and watering as necessary as possible to maintain the proper condition of the finished sub-base layer.
- Deficiencies in the condition of the completed layer during the maintenance must be corrected to up keep the conformance to the requirements in the specification.
- Continued moisture sufficiency on the surface of the completed sub-base layer must be maintained to prevent the development of a dusty condition by applying a light spray of water at an appropriate time interval.
TRIAL COMPACTION OF SUB-BASE/ BASE COURSE WORKS
Outline of Trial Compaction of Sub-Base/ Base Course Work
Item Sub-Base Base Course
Thickness = 150mm (RC Pavement) (after compaction)
Thickness = 200mm (DBST Pavement) (after compaction)
Test Layer 1 Layer (depend on result of first trial compaction)
Compaction When material or equipment is changed
Foundation of the Trial Compaction of Sub-Base/ Base Course Work
- Each trial area shall be prepared as per specification or instruction by the Engineer.
After inspection and acceptance Sub-Grade layer by Engineer
Contractor or instruction by the Engineer
After inspection and acceptance Sub-Base layer by Engineer
Contractor or instruction by theEngineer
Work flow chart for Trial Section for Sub-Base/ Base Course
Figure 9.3-1: Work Flow Chart of Trial Section for Sub-Base and Base Course Work
Sub-Base and Base Course Working Plan according to thickness of layer
9.7.1 Sub-Base thickness of 200mm
Figure 9.4.1-1: Sub-Base Thickness of 200mm 9.7.2 Base Course thickness of 150mm (Apply to Reinforced Concrete Pavement Section)
Figure 9.4.2-1: Base Course Thickness of 150mm
9.7.3 Base Course thickness of 200mm (Apply to DBST Pavement Section)
Figure 9.4.3-1: Base Course Thickness of 200mm
Station number to use for Trial Section of Sub-Base and Base Course
- Thickness of Trial Section for Sub-Base or Base Course is t = actual thickness is compacted as instructed by Engineer.
- Trial Section for Sub-Base Station or Base Course Station as shown figure below:
Figure 9.5-1: Top View Trial Section Sub-Base or Base Course Stations
Figure 9.5-2: Cross Section for Trial Section Sub-Base Station
Figure 9.5-3: Cross Section for Trial Section Base Course Station
Material Selection
- All materials shall be selected from the quarry locations (the contractor will submit to the consultant) and each plant need each trial compaction as instructed by the Engineer.
- Suitable samples of sub-base and aggregate shoulder materials shall be submitted to the Engineer of not less than 30 days before sub-base construction will commence.
- Additional samples shall be furnished during construction as required upon Engineer's request.
- The materials shall comply with sub-clause 6.1 and 6.2 of this Method Statement and ProjectGeneral Specification.
Work Implementation Steps
- For the sequence of construction steps, please refer to sub-clauses 8.3 “Construction of Sub-Base” and 8.4 “Construction of Base Course” of this Method Statement.
Figure 9.7.1-1: Sub-Base Material Spreading
Figure 9.7.1-2: Base Course Material Spreading
Figure 9.7.2-1: Sub-Base/ Base Course Material Watering and Compaction
Figure 9.7.2-2: Rolling Diagram During Compaction 9.7.3 Field Density Test
Figure 9.7.3-1: Field Density Test at Site Construction 9.7.4 Proof Rolling Test
- To confirm actual compaction at site, Engineer may indicate a location in the plan of a completely compacted layer to conduct a proof rolling test Refer to sub-clause 3.1.3.5 and 3.3.3.7 of General Specification for Proof-Rolling.
- Any compacted portions that shows visible movements shall be considered fail.
- Inspection sheet of Elevation, Thickness, Completed width
- Inspection sheet of Surface Regularity
Summary of the Trial Compaction
Results of the Trial Compaction will be summarized and submitted to the Engineer for his review.
Figure 9.8-1: Example Chart of Number of Passes and Degree of Compaction
Figure 9.8-2: Example Chart of Number of Passes and Consolidation Measurement
QUALITY CONTROL
- QC Engineer shall inspect all work to ensure compliance to the requirement of Specification and Drawings.
- Strictly control of materials according to specifications and construction equipment All materials to be used for this work shall be subject to Engineer’s approval.
- Method statement: “Quality Assurance Plan” shall be submitted separately and shall be a part of this Method Statement.
Description: The completed construction items will be inspected by the contractor's field engineer The qualified items will be reported to the contractor's office by the field engineer The contractor's quality control department will plan to inspect the construction quality After the item meets the quality requirements and is approved by the contractor's quality director, the contractor will plan and notify the consultant about the joint site inspection between the contractor and the consultant After the consultant inspects and approves the work, the contractor will carry out the construction of the next work items in accordance with the construction phase All unapproved work items will be resolved and handled by the contractor so that the work items meet the project requirements The next work will not be constructed without the consent of the consultant.
TRAFFIC SAFETY CONTROL
Maintenance of Existing Road and Bridges
When public traffic is to be passed though the Works in an incomplete state the Contractor shall take all steps necessary to provide a smooth free-draining running surface and to maintain it in that condition.
The contractor shall ensure that the surface is neither excessively dusty nor dangerously slippery and shall, if directed by the Engineer, water the surface to lay dust or provide a thin gravel topping to the trafficked surface.
The Contractor shall ensure that safe access is maintained at all times across bridges and culverts within the limits of the site This may include the repair or replacement of bridge deck materials or the construction of a by-pass where more appropriate, but at all times the Contractor should not delay the passage of vehicles for excessive periods.
The Contractor shall render such assistance to the public as shall be necessary to allow safe and convenient passage of traffic at all times
Traffic Closing Basis
- Part of lanes shall be closed to execute without changing the directions of the traffic flow in the existing road A section shall be rationally divided based on the principles of facilitating the construction vehicles to enter or leave the site and the passing vehicles to pass smoothly.
- All traffic control measures shall be in operation 24 hours per day and shall be supplemented by lights at night when the Engineer considers this necessary.
- At least two weeks before he intends to alter trafficking patterns in any way the Contractor shall present plans to the Engineer for traffic signing and control If the Engineer does not approve these plans the Contractor shall make such amendments to them as are necessary in order to make them, in the Engineer’s opinion, satisfactory Prior to implementation of the new trafficking arrangements, the Engineer shall inspect the Contractor’s signs, barriers and signals and only when the Engineer agrees shall they be put into operation.
- Some typical arrangements for traffic safety control:
Site Layout
Part of lanes shall be closed to execute without changing the directions of the traffic flow, which is to say one or two lanes be closed, the rest is used to pass through.
The control area is divided into the parts: warning zone, buffer zone, operation zone and termination zone.
Warning zone: 200m-long warning zone shall be set, in which the signs of "Speed Limit",
"Operation Ahead", "No Overtaking", "Narrow Lane Ahead", "No Passing" shall be marked The space between adjacent signs shall be less than 30m, usually 10m to 30m The last sign is at a distance of not less than 15m from the first device (tapered sign) of the upper transition zone.
Buffer zone : The length of buffer zone is 8m The reflective cone is transited gradually to the traffic lane.
Operation zone: 0.l-0.5km-long operation zone shall be set as a construction unit, one half widths of which is closed for construction The tapered signs with interval of 2- 4m are placed on the sides of construction area.
Termination zone: The length of the termination zone shall not be less than10m The sign of
"Restored Traffic" shall be placed at the end of the termination zone.
The special person shall be appointed at the beginning and finishing end of the closed sections to direct traffic with a red flag.
Traffic Control of Blocked Sections
The construction of bridges or culvert or road section will affect the circulation of the vehicles on the Road, the contractor tends to occupy the entire road or a part of road Therefore, at each construction site and based on the actual conditions on the construction site, the contractor will propose a solution to block the entire road or a part of the road to serve the construction process of the items In case of blocking the entire road section, we will construct a detour or a plan to direct traffic on another suitable route to ensure two-way traffic according to technical requirements and limit congestion.
At locations where traffic needs to be blocked, the contractor will have a specific plan and discuss with the consultant before implementing the work. b) Some regulations of safety
- For construction personnel in accordance with the safety regulations for construction The Personal Protective Equipment shall be worn
- No drinking, slippers, and sandals are allowed on site.
- The insurance fee shall be paid on time and warning flashlights be installed for the construction vehicles.
- The traffic rules shall be com plied with and no parking on the lane or turning around randomly be permitted for construction vehicles.
- A full-time safetyman shall be arrangement to supervise the execution of the project.
- The finished sections shall be protected carefully, and roadblocks or warning signs shall be placed if necessary.
- The damaged safety signs which affect the expression of the safety information shall be replaced in time.
- Safety signs shall be placed in bright environment and at a proper distance from the danger location so that the relevant people have enough time to note the information that it represents.
- The safety signs with dirt, grease shall be cleaned timely to ensure the safety information without the mistakable messages.
- The safety signs with displacement shall be adjusted in place to avoid accidents, which result from the relevant people's not quickly noticing and understanding the safety information.
ENVIROMENT AND SAFETY CONTROL
Safety Control
Prior to starting of construction works, warning signs and instruction boards shall be fully installed either inside or surrounding the construction site and the following particular matters are to be through to all members working in the construction site in order to complete the work efficiently without any accident or casualty. a) Joint Meeting
- Prior to start any activity, a joint meeting with relevant staffs shall be held for the purpose of general explanation on the whole contents of works as well as the method for the implementation of efficient work. b) Basic Instruction
- All workers shall always wear Personal Protective Equipment (PPE), such as hardhat (helmet),safety shoes, hand gloves and working uniform. c) Prevention of Accident by Heavy Machine
- Only skilled operator shall be allowed to operate equipment on site In case of new operators, a test of skill shall be conducted first prior to his acceptance to the job Preventive maintenance check shall be done regularly at equipment working at site prior to full operation Stability of working area and foundation of equipment shall be checked particularly at locations of outrigger and track pad of cranes. d) Prevention of Accident of Electrocution
- Electric generating equipment shall be properly protected and properly installed with earth connection Electric wires shall relate to electrical tapes to prevent electric leakage Only skilled operator shall be allowed to operate equipment on site. e) Prevention of Accident in Night Shift Works
- Enough lighting system shall be provided for night shift works especially installed at working platforms If necessary, all the surrounding working area shall be lighted up The people who work on the site must wear reflective jacket, if worked at night. f) Existing Facilities
- Existing facilities especially existing overhead electric line, water line, telecommunication line and other important facilities at surrounding area shall be taken with care not to damage.
Environmental Control
Responsibility for surrounding environment during construction and shall comply with the Condition of Contract on Protection of Environment.
If any other problems occurred in the site, applicable counter measures or prevention action shall be considered immediately and executed as soon as possible.
The Contractor shall be responsible for implementing and managing mitigation measures during the construction of the Works The recommended mitigation measures are presented below. a) Ambient air quality
- Exhaust emissions from construction equipment shall be strictly controlled in accordance The Contractors are requested to use standard equipment.
- Where possible the Contractor ’s chosen access routes to and from the site should avoid residential areas Vehicles carrying sand, aggregates or other loose materials shall be fully covered Brushing and watering shall be used where required to control dust and the spraying of mud.
- Stockpiles should be covered or kept damp to avoid windblown dust.
- The Contractor shall be co-ordinate his activities with local environmental management authorities to control and supervise the ambient air quality within the program of regional pollution control.
- Spraying Water for Dust Control: To protect the passenger and the residents from dust during construction period, the Contractor shall spray water along the road at least two times per day except rainy season or directed by the Engineer b) Noise and vibration level
- The Contractor shall use equipment and facilities conforming to Standards for traffic noise level
- In order to protect residents’ houses, public buildings and other structures, the maximum vibration at these locations should ensure the allowable range. c) Water environment
- To ensure the water quality of local watercourses, ponds, and lakes the Contractors shall comply with the following environmental protection measures Care shall be taken with fuels and oils.
- No waste material of any kind shall be disposed of into local watercourses, ponds, or lakes.
- Stationary construction equipment, offices and accommodation, workshops and storage areas and other temporary facilities shall not be located near to local watercourses, ponds, and lakes.
- Oil waste shall be collected, treated, and disposed of in approved disposal areas.
- Fuels and oils shall not be stored nearly local watercourses, ponds or lakes and shall be stored in areas located at least 200m away from such water features.
- Oil and fuel storage tanks shall be at an elevation higher than the flood level Warning signs shall be installed at all fuel storage areas to avoid collision with construction equipment.
- Suitable temporary drainage should be provided to prevent localized flooding or contaminated run-off from the site and to ensure construction work is not damaged or delayed by standing water.
APPENDIX
Some Photos of Main Construction Equipment:
Double drum steel roller (13T) 20-ton single drum steel roller
20-ton single drum steel roller Sprinkler truck