Rev Date of Issue
Prepared by Reviewed by Description
QA/QC Engineer QA/QC Manager
0 15 July 2012 Salvador D. Paguntalan Nabeel Abusadah Initial issue
1 14 August 2012 Salvador D. Paguntalan Nabeel Abusadah 1P
st
Page 2 of 7
Table of Contents
Page Number C10Tover Page 1 10T Revision Page 2 10T TABLE OF CONTENTS10T ... 2 10T 1.10T 10TSCOPE OF WORK10T ... 3 10T 2.10T 10TPURPOSE10T ... 3 10T 3.10T 10TREFERENCES10T ... 3 10T 4.10T 10TRESOURCES10T ... 3 10T5.10T 10TDEFINITION & ABBREVIATIONS:10T ... 3
10T 6.10T 10TRESPONSIBILITIES:10T... 3 10T 7.10T 10TPROCEDURE:10T ... 4 10T 7.110T 10TGENERAL10T 4 10T 7.210T 10TSURVEY LAYOUT10T 4 10T
7.310T 10TTEST METHODS AND MINIMUM SAMPLING FOR SUBBASE MATERIAL10T 5
10T
7.410T 10TSUBGRADE PREPARATION ON ROCK SOIL10T 6
10T
7.510T 10TSUBGRADE PREPARATION ON COMMON SOIL:10T 6
10T
7.610T 10TSUBGRADE PREPARATION ON EMBANKMENT10T 6
10T
7.710T 10TSUBGRADE LEVEL TOLERANCES10T 7
10T
8.10T 10TQUALITY:10T ... 7
10T
Page 3 of 7
1. SCOPE OF WORK
The Subgrade preparationinvolves preparation of subgrade in an in-situ layer of rock and common soil and on an embankment.
2. PURPOSE
To describe and outline the methodology and work procedures for asphalt road subgrade preparationon a rock, common soil, and on an embankment layer.
3. REFERENCES
3.1 Contract Document and Specifications 3.2 Shop Drawings
3.3 Approved Quality Assurance and Quality Control Plans.
4. RESOURCES
4.1 Materials 4.2 Equipment 4.3 Personnel
- Wooden Stake - Warning Tapes
- Spray Paints and Markers
- Grader - Excavator - Compactor - Dump Truck - Shovel - Wheelbarrow - Set of Minor Tools
- Project Engineer - Site Engineer - Surveyor - Safety Officer
5. DEFINITION & ABBREVIATIONS:
PE – Project Engineer SE - Site Engineer
QCE – Quality Control Engineer SU – Surveyor
SO - Safety Officer
6. RESPONSIBILITIES:
6.1 The Project Engineer shall direct when and where to start the Subgrade Preparation and establish deadlines for activity to be finished. He shall make sure that Subgrading shall be finished with-in the time frame set forth on the construction schedule.
6.2 The Site Engineer shall be responsible for the execution of the Subgrade Preparation Works.
Page 4 of 7 6.3 The Quality Control Engineer shall be responsible for monitoring the working Subgrade
elevations level as per the approved plans and specifications.
6.4 The Surveyor is responsible for establishing the boundaries, limits and extent of Subgrade elevations.
6.5 The Safety Officer shall ensure that safety of the workers is taken into consideration at all times. He shall make sure that stake/poles and barricades with warning tapes on it shall be in place whenever required as work progresses. Warning lights shall likewise be introduced if found necessary.
7. PROCEDURE:
The foregoing procedure for the Subgrade Preparation Works will serve as a guide by the Site Engineer together with the surveyor along the course of their work in order to achieve an acceptable quality of workmanship and attaining the optimum results with less time and effort:
7.1 GENERAL
The Subgrade preparation shall be done by the use of the Grader, Excavator,
Compactorand Dump Truck for soil disposal and a set of minor tools such as shovel, wheel borrow, etc.
All submerged stumps, roots, or other existing vegetation and/or perishable matter
encountered in the preparation of the subgrade shall be removed to a depth of not less than 300mm or as specified by the Engineer.
The excavated surfaces shall be kept smooth and sloped to slide ditches until the subgrade is finished. All areas of roadway excavation, during the entire period of construction operations, shall be thoroughly drained.
7.2 SURVEY LAYOUT
7.2.1 The Surveyor in coordination with the site engineer shall stake out the limits and extent of the Subgrade and constantly check the depth of excavation for finishing level and inform the grader when and where to stop grading.
7.2.2 He shall make sure also that the finishing level is constantlycheck so as to avoid over cutting.
7.2.3 The surveyor together with the QCE will ensure that excavation of cut sections containing unsuitable materials within the subgrade zone shall be staked and
measured to a minimum of thirty (30) centimeters below the bottom of the subgrade zone. It may be increased in additional increments of thirty (30) centimeters at the direction of the Engineer.
Page 5 of 7
7.3 TEST METHODS AND MINIMUM SAMPLING FOR SUBBASE MATERIAL
MOT
Specs. Material Name Characteristics Test Method Sampling Frequency Point of Sampling
2.06.3.6 Subgrade in
Earth Cuts Soil Classification AASHTO
10T
M 14510T One per source or
material change then
One per 50,000 sq. m. of completed subgrade.
50 Kg sample to be collected from material source and to be tested in lab.
In place (from road bed) and to be tested in lab, 50 Kg Sample
Moisture Density (Modified Proctor)
AASHTO10T T 18010T One per layer per
20,000 SQ. M. In place (from road bed) and to be tested in lab, 50 Kg Sample
Field Density AASHTO10TT19110T,O
R10TT23810T and
10T
T 23910T.
One per layer per 20,000 SQ. M. For cohesionless soils, use relative density ASTM 10TD 425310T
In place immediately prior to placement of next layer.
California Bearing Ratio (CBR) ASTM 10T D 188310T
One per 5,000 square meters of completed subgrade.
Use same collected sample from
Road bed.
Final approval of the material shall be based on
acceptance samples taken from each layer of subgrade. 2.06.3.7 Subgrade in
Rock Cuts Gradation AASHTO M43 OR
10T
ASTM D 44810T
One per source or material change then
One per 50,000 sq. m. of completed subgrade.
50 Kg sample to be collected from material source and to be tested in lab.
In place (from road bed) and to be tested in lab, 50 Kg Sample
Rock Quality ASTM 6032 As Per Specifications. Sample to be collected from project site and to be tested in lab. 2.06.03. 8 Subgrade on Embankmen t (including Sand Dunes Areas) Soil Classification AASHTO 10T M 14510T One per 50,000 sq. m.
of completed subgrade. In place (from road bed) and to be tested in lab
Moisture Density (Modified Proctor)
AASHTO 10TT 18010T One per layer per
20,000 SQ. M. Use same collected sample for lab test. California
Bearing Ratio (CBR)
ASTM10TD 188310T One per 5,000 square
meters of completed subgrade.
Use same collected sample from
Road bed.
Final approval of the material shall be based on
acceptance samples taken from each layer of subgrade. Field Density AASHTO
10T
T 19110T OR 10TT 23810T
and10TT 23910T
Minimum of 8 nuclear gage or 5 cone density test on each
embankment lift or portion lift up to a
In place immediately prior to placement of next layer
Page 6 of 7
maximum of 50,000 cubic meters lot. % Relative
Compaction AASHTO
10T
T 18010T 1 test per (3) lots.
Percent of compaction is based on 3 consecutive tests.
In-place after compaction. Lot size is 5,000 square meters 2.06.3.9 Preparation of Existing Subgrade As specified in Paragraph 10T2.06.3.610T
7.4 SUBGRADE PREPARATION ON ROCK SOIL
7.3.1 Design subgrade level on rock soil shall be trimmed down or excavated to a depth of 150mm or other depth as shown on the plans and to be backfilled with suitable subgrade material designated on the plans or as approved by the consultant.
7.5 SUBGRADE PREPARATION ON COMMON SOIL:
7.4.1 Soil material below subgrade other than solid rock shall be thoroughly scarified to a depth of 150mm reducing or increasing moisture content for a suitable maximum compaction. If existing soil found to be unsuitable that cannot be properly
compacted shall be removed to a depth as prescribed by the consultant and only approved materials as directed shall be used in the construction of embankments and backfills.
7.6 SUBGRADE PREPARATION ON EMBANKMENT
7.5.1. General
The work consist of preparation of the existing ground on which embankment is to be constructed. For detailed embankment preparation see Method Statement for Roadway Embankment.
7.5.2. Soil examination / testing on an area for embankment
a. The existing area or section for roadway embankment shall be examined and/or tested whether the existing ground is ready to receive an embankment.
7.5.3. Acceptable Material for Roadway Embankment
a. An acceptable backfill or embankment material shall be approved by the Engineer prior to the start of embankment.
7.5.4. Compaction
a. Roadway embankment of approved type shall be placed in horizontal layers not exceeding 200mm and shall be compacted as specified before placing the next layer.
b. A Maximum Dry Density of 95% shall be obtained by rolling and compacting sub-soil as determined by Modified Proctor Test.
Page 7 of 7
7.7 SUBGRADE LEVEL TOLERANCES
Allowable variation from Design Subgrade Level Surface: ±20mm Allowable Surface Irregularity Measured by 3m- Straight Edge: 30mm
8. QUALITY:
DESCRIPTION OF WORK IN-CHARGE
The QA/QC Manager will monitor and ensure that this Method Statement shall be strictly enforced so that smooth Work Flow will be attained and prior work compliance obtained such as the following:
8.1 Materials Submittal. All required materials approved by the consultant shall be obtained prior to the start of the work.
8.2Approved Drawings. All relevant drawings such as subgrade elevations and line cross-sections shall be approved by the consultant prior to commencing work.
8.3 Routine Work. The SE, QCE, together with the Surveyor shall
constantly monitor and check the grading preparation to conform with the above procedures. They have to ensure not to overcut beyond the subgrade elevation so as to maintain in-situ layer already capable to withstand the design load for the roadway.
QA/QC Manager
SU, SE, QCE,
9. SAFETY:
DESCRIPTION OF WORK IN-CHARGE
The Safety Officer of the contractor and the Survey Team together with the QA/QC Team shall work together in the prevention of any work related accidents in the job site.
The following safety requirements must always be observed and adhered in the site at all times:
9.1 Safe means of access when working on grading area will be provided & maintained.
9.2 Appropriate wearing of Personal Protective Equipment (PPE)
PE, SO, QCE
Page 1 of 7