Borrow
Material
Borrow material shall meet the requirement specified for
satisfactory fill materials per ASTM D2487 or ASTM D2488 and shall be free from
refuse, or other material that might prevent proper compaction or caused the
completed backfill to have insufficient bearing capacity for the expected
superimposed load.
Granular
Bedding Material
Well graded sand, gravel, or manufactured aggregate
containing no particles larger than 1/2 –inch (12.7 mm), and free from roots,
debris, or any other substance that would harm the pipe or might impair the
performance of the material as bedding for the pipe.
Sand
Sand shall be fine aggregate per ASTM C33.
Select
Granular Backfill
Any soil classified per ASTM D2487 or ASTM D2488
EXECUTION
No grading and earth-moving shall start in any area until
clearing, grubbing and stripping have been completed for that area. This works consists of clearing, grubbing and stripping of
areas where excavation, filling to be done, including removal and proper
disposal of unsuitable and waste materials removed during the operation. Before
starting, erect protective barriers and after the work is complete, remove and
dispose of them.
Clearing
Clearing includes removal and proper disposal of trees and
downed timber, brush, hedges, bushes and other vegetation or organic materials
and rubbish , debris , or other foreign or objectionable materials on or
protruding through the surface areas to be cleared.
Grubbing
Grubbing including removal and disposal of stumps, large
roots, buries logs other objectionable materials to 300 mm below ground
surface.
Stripping
Stripping consists of removing of all rubbish, humus,
vegetable matter and all or part of the organic topsoil in the respective areas
which can be removed by simply excavation methods and to a depth as directed by
Company. All borrow pit shall be stripped to a depth which allows for suitable
material to be produced.
Topsoil
Removal and Stockpiling
a. Topsoil
is generally representative of agriculturally productive soil. Topsoil shall be
free from subsoil and objectionable material that would hinder plant growth or
maintenance and shall not contain more than 5% by volume of stones large than
25 mm.
b. Remove
materials only to such depth that it meets the definition of topsoil. Strip and
stockpile removed topsoil in areas to be excavated separately from other
excavated materials. Protect topsoil stockpile from contamination during
progress of the work until these materials have been used in finishing
operation. Conserve acceptable topsoil from the site sufficiently to cover area
requiring planting.
Disposal
Disposal areas shall be left with neat and acceptable
appearance, graded surfaces and slopes assuring proper drainage. Areas from which the materials will be used again shall be
cleared of trees, stumps, roots down timber and other regression. The disposal shall be located where they will not interfere
with the natural flow of construction operations.
In the borrow pit area the accessibility to the site shall
be granted for the construction works. Excavated material designated to be reused to receive
vegetation shall be separately disposed. The height of its heaps or stock piles shall not exceed 2 m,
and not be driven over by excavating or transport equipment.
Fills and
Embankments
Where the structure or pipeline is to be installed in an
area of fill or embankment, verify that such work has been completed.
Erosion,
Sedimentation and Dust Control
Before starting earthwork operation on any particular area
of the project site, install measures for the control, prevention, and
abatement of erosion and sedimentation for that area is required. Schedule and
conduct construction operation in such a manner and sequence that erosion,
sedimentation, and dust on the project site is minimized. Coordinate the
installation of temporary erosion control features with the construction of the
permanent erosion control features to the extent necessary to ensure effective
and continuous control of erosion throughout the period of work. Measure to
control dusting including routine watering and seeding of stockpile soils. All
erosion, sedimentation, and dust control facilities shall be installed as
indicated on the drawing when required, checked after each rainfall and
maintained in order to continue to perform efficiently.
Excavation
Safety
Plan and assemble for materials and equipment required to
stabilize excavation sidewalls as necessary to ensure the safety of personnel
working in the excavation, and the protect existing facilities and structures
in the vicinity of the work from damage. The systems, methods, and techniques
used shall meet or exceed all applicable requirements of the OSHA Construction
Industry Standards, and all other local codes and regulations. Barriers and
warning devices shall be placed around the excavations, especially where
excavations are unattended, to indicate a hazard exists, in the immediate
vicinity.
Slope Stabilization
Stabilize the
sides of excavations as necessary to prevent slope failure or any other earth
movement that might injure personnel, or damage existing buildings, structures,
or other facilities in the vicinity of the work. Earth retainers, such as
shoring and sheet piling, shall be installed where required. The stabilization
method employed shall comply with pertinent requirements of the OSHA
Construction Industry Standards and other applicable local codes and
regulations.
Removed sheeting,
bracing, and shoring systems employed for slope stabilization as the progress
of the work eliminates their need, unless they are permitted or required to
remain by other provisions of these specifications or the other contract
documents. Carefully remove such system in other to prevent subsidence or other
soil movement that might damage existing or newly constructed structures or
other facilities.
Existing or
Complete Utilities
Carefully move machinery and equipment over existing or
newly installed pipes and utilities during construction so as not to damage
completed work. For work immediately adjacent to, or excavation exposing an
existing utility or other structure, use manual or light equipment excavating
techniques. Do not use power driven equipment to excavate closer than 2-feet
(600 mm) from any existing utilities or structures. Support uncovered pipes and
other existing work effected by the excavation until they properly supported by
backfill. Report immediately any damage to utility lines other subsurface
facilities.
Structures
and Surfaces Condition
Protect newly backfilled areas and adjacent structures,
slopes, or grades from damage. Repair and re-establish damaged grades and
slopes. Protect existing streams, ditches, and other stormwater facilities from
silt accumulation and erosion.
Control of
Water
Prevent of control water flow into excavations, or water
accumulation in excavations, to ensure that the bottom and sides of excavations
remain firm and stable throughout construction operations.
Surface
Water
Plan and conduct excavation operation so as to minimize the
disruption of stormwater drainage in the vicinity of the work. Provide
diversion ditches, dikes, and other suitable measure to control and direct runoff
around and away from the excavation. Protect the sides of excavations from
erosion and sloughing caused by stormwater runoff. Promptly remove stormwater
accumulations in excavations. The system and equipment for controlling surface
water shall be of sufficient capacity to accommodate the runoff rate expected
from the 2-years (50 percent annual chance) rainfall event, with no significant
disruption of the construction schedule, or damage to existing features or
facilities in the vicinity of the work.
Ground Water
When the bottom of the excavation must be carried to an
elevation below the groundwater piezometric surface, or to such proximity to
the piezometric surface that the excavation bottom will become soft due to its
being saturated by groundwater, take measures to lower the piezometric surface
sufficiently to maintain the stability of the excavation bottom. Design the
groundwater control system using accepted professional methods of design and
engineering consistent with the best modern practice. The system shall includes
trenches and sumps with pumps, well points, and such other equipment,
appurtenances, and related earthwork necessary to achieve the groundwater
control need the work. Carefully design and operate the system to avoid damage
to existing structures and other facilities in the vicinity of the work.
Disposal of
Removed Water
Convey water removed by the water control system to an
existing stormwater drainage facility that has sufficient capacity to
accommodate the flow rates involved without damage. Secure permits or other
approvals required from authorities having jurisdiction for such stormwater
discharge. After completing construction operations needing water
control, remove materials, equipment, and other facilities used for that purpose, and clean up and
restore affected areas as required.
Excavation,
Backfill and Compaction
Remove soil, rock, and other materials as necessary to
achieve the finish grades, sub-grades, or other limits of excavation indicated.
Use satisfactory materials resulting from excavation work in the construction
of fills and embankments, and for the replacement of removed unsuitable
materials. After the excavation to the required finish grade is completed, re-compact
materials that are to remain but have been loosened or otherwise disturbed by
the excavation operations, to a firm, stable condition, and to a density equal
to or greater than the surrounding undisturbed material.
Stockpiling
and Disposal of Materials
Stockpile excavated satisfactory materials that are surplus
to the quantity needed for construction of required fills and embankments, or
for replacement of unsuitable. Stockpiles shall be neatly shaped and free
draining, with sides sloped at 4 horizontal to 1 vertical or flatter. Dispose
of excavated materials that are unsatisfactory for use as fill or are surplus
to that needed for backfilling, in a safe and proper manner off the project
site or in areas of the project site designated for that purpose.
Rock
Excavation
Remove rock encountered in areas requiring excavation using
mechanical methods (such as ripping, wedging, or impacting) to reduce the rock
to manageable sized fragments. Except as otherwise shown, required, or
specified, excavate rock to a depth of no less than 300 mm below the indicated
finished grade. Backfill undercut areas with satisfactory materials placed and
compacted in accordance with requirements for fills and embankments. In areas
to be paved, remove rock to a depth of no less than 75 mm below the pavement
sub-grade surface. The remaining rock surface shall be free of projecting ribs
or points, and shaped so that positive drainage of the surface is provided and
no water will be pocketed at any point. Grout crevices in the surface with lean
concrete. Backfill undercut areas with cohesion less, satisfactory material,
placed and compacted in accordance with the requirements for fills and
embankments.
Excavation,
Backfill, and Compaction for Structure
Excavation pits for constructing cast-in-place concrete
foundations, footings, and other structures to permit the placement of each
monolithic element of the structure to the full width and length required with
a full horizontal bed. If the excavation sidewalls are to be used to form the
sides of the structure, take special care during excavation to secure a true
surface conforming to the lines and dimensions indicated on the plans for the
structure. Corners and edges of the excavation shall be true and square, not
rounded or undercut.
Foundation
Material Other than Rock
When the bottom of the foundation is to rest on an excavated
surface other than rock, take special care to avoid disturbing the virgin soil
at the bottom of the excavation, and to protect the soil from the changes in
moisture content. To accomplish this, do not excavate the final 150 mm of
material until just before the structure is to be placed. When the bottom of
the excavation must be exposed for extended period of time, during which time
inclement weather may damage It, lower the bottom of the excavation
approximately 50 mm below the indicated bottom of the structure, and backfill
the over excavated area with lean concrete.
Rock
Foundation Material
When the bottom of the structure is to rest on rock or other
unyielding material, clean the bearing surface of loose material, and cut to a
firm, level bed that is stepped, keyed, or serrated.
Backfill and
Compacted
a. As soon
as practical after completing construction of the related structure, including
expiration of the specified minimum curing period for cast-in-place concrete,
backfill the excavation to restore the required finished grade. Backfill by
placing and compacting satisfactory backfill material or select granular
backfill material, when required, in uniform horizontal layers of no greater
than 150 mm loose thickness.
b. Insofar
as possible, place and compact backfill symmetrically about the structure to
avoid the development of unbalanced earth pressure loads on the structure.
c. Do not place
backfill around new cast-in-place concrete structures until the concrete has
cured at least 3 days, or, when the backfill result in the development of
unbalanced earth pressure loads on the structure, do not start backfill until
the concrete has cured for at least 7 days or compressive strength test
indicated the concrete has achieved more than 80 percent of its specified
compressive strength.
d. Step
excavation side slope with each layer of backfill to avoid the development of
unnecessary loads against the structure caused by backfill wedging between the
structure and the excavation sidewalls.
Excavation,
Backfill, and Compaction for Underground piping.
Carefully excavate trenches to the minimum depths and widths
necessary for installing the pipe line and associated appurtenances in
accordance with the requirements of this specification, and the lines and
grades indicated on the plans or elsewhere in the contract documents. In the
pipe embedment zone, the trench sidewalls shall be either sloped sufficiently
to prevent sloughing or cave-in, or shall be properly supported. Stockpile
excavated materials in an orderly manner a sufficient distance from the trench
sidewalls to avoid endangering the stability of the bank.
Unstable
Grade
When soft, yielding, or otherwise unstable soil conditions
are encountered at the required trench bottom elevation, over excavate the
trench to a depth of no less than 300 mm below the required pipe bottom
elevation, and backfill with granular bedding material. If conditions are so
severe that over excavating and backfilling will not achieve a stable
condition, notify engineer immediately so that appropriate corrective measure
may be identified.
Unyielding
Grade
Whenever rock, stone, masonry, or other hard, unyielding
materials is encountered at or above the required trench bottom elevation,
remove it to provide a clearance of no less than 150 mm below and on each side
of pipes and associated fittings, valves, and other appurtenances. Backfill the
over excavated area with granular bedding material.
Previous
Excavation
In the event that the trench passes over a sewer or through
any other previous excavation, carefully compact the bottom of the trench to a
density equal to or greater than that of the native soil adjacent to the
previous excavation. Perform this compaction carefully to avoid damaging the
previously installed facility.
Excavation
for Appurtenances
a. Excavation
for pre cast manholes, catch basins, drainage inlets, and other similar
structures shall be of sufficient size to permit proper placement of the
structure in their intended positions, and to permit proper placement and
compaction of backfilling around the structure after their placement. For
cast-in-place appurtenances, excavation shall be of sufficient size to permit
placement and removal of necessary formwork.
b. When
concrete is to be placed against the bottom or sides of an excavation, take
care not to disturb the native soils that the concrete bears against. Excavate
to final line and grade before the concrete or masonry is to be placed. Remove
loose or unstable materials. Clean rock of loose material and other debris, and
cut to a firm and stable surface, remove loose or deteriorated rock and thin
strata.
Bedding
After excavation reaches the required trench bottom
elevation and any unsatisfactory subgrade conditions are corrected as
specified, prepare the bottom of trench for placement of the pipe by spreading
in the trench a layer of loose granular bedding material to attain a level just
above the required grade of the outside bottom of the pipe.
Initial
Backfill
Place and compact select backfill from the spring line of
the pipe to the top of the pipe embedment zone in uniform horizontal lift of
not over 150 mm loose thickness. Bring up the level of backfill uniform on
opposite sides of the pipe along the full length of each pipe section. Take
care not to damage the pipe or any protective coating it may have.
Final
Backfill
Place and compact satisfactory backfill material in 200 mm
maximum loose thickness lifts to restore the required finished surface grade.
During final backfill for plastic or other non-ferrous pipelines (if any
indication on the section drawing), install plastic marking tape above the
pipeline at a depth 300 mm to 600 mm below the required finish grade.
Compaction
Except in areas of load bearing subgrade, compact final
backfill composed of satisfactory materials from the original trenching to a
density equal to or greater than that of the existing undisturbed material
immediately adjacent to the trench. Where the excavated material is
unsatisfactory for use as backfill and, therefore, imported material are used,
compacted the backfill to no less than 92 percent of maximum density at optimum moisture content
(Standard Proctor density) unless
otherwise stipulated elsewhere in specification herein.
Ditches
and Channels
Construct new and modified ditches, and channels to conform
to the lines, grades, and cross sections indicated on the plans or otherwise
required by the contract documents. Trim and dress roots, slumps, rock, and
other foreign material exposed by the work to conform to the required surface.
Do not over excavate.
Soil
Improvement
Geosynthetic material to be used as soil improvement in
existing soft ground or swampy areas.
The existing soil condition does not have enough bearing
strength then if load applied to the soil it can result in settlement of the
soil. Therefore the soil is not stable to support the structure to put above it
The purpose of soil improvement is to :
• Reduce
the settlement of structures
• Improve
the shear strength of soil and thus increase the bearing capacity of shallow
foundation
• Increase
the factor of safety against possible slope failure of embankments
• Reduce
the shrinkage and swelling characteristics of soils.
Method and materials selected for the soil improvement shall
be designed by the specialist engineer.
The selection of the right materials to be used and suitable
selection of the implementation procedure are essential to the success of the
method.
Geosynthetic materials shall meet the requirement specified
for satisfactory soil improvement material per ASTM in tensile strength, grab
strength, puncture resistance, elongation, thermal stabilization and
ultraviolet ray resistance.
Combination of some methods (overlapping method between
different type of geosynthetic materials) should be evaluated as an alternative
as well.
The soil improvement shall be design for different soil
condition such as soft soil (clay or silt) that have N value of the Standard
Penetration Test (SPT) less than 4 or cohesionless granular (N <10) and
swampy area
Design shall be conducted with taking into consideration at
what type and the quantity of load above the soil. The load may be the rig,
camp, facility, vehicle, depth of embankment,
etc.
Soil investigation is then carried out, consisting of
Standard Penetration Test (SPT/ borehole) and Dutch Penetration Test (DPT). The
purpose of soil investigation is to know the actual soil stratification at a
given site, the laboratory test results of the soil samples obtained from
various depths and the observations made during the construction of other
structures built under similar condition
Fills and
Embankments
a. Construct
fills and embankments by placing and compacting satisfactory materials in
successive. Uniform horizontal lifts of no greater than 200 mm (8-inches) loose
thickness. Compact each lift to the specified density before placing materials.
b. Where the
required finish grade has slope steeper than 1 vertical to 8 horizontal,
overbuild the slope by no less than 600 mm (measured horizontally) and trim
back to finish grade after compaction.
Fill
Material
Material will also be selected preferentially to exclude the
use of highly plastic clay soils classified as CH, by ASTM Specification D2487. Highly expansive (cracking) soil having an Activity value
greater than 1.25, or a degree of expansion classified by ASHTO T258 as “Very
High“ or “Extra High” , shall not be used as Fill Material. The activity value shall be measured as the ration Plasticity
Index (ASTM D424) / Percent Clay Sizes (ASTM D422)
Large Rocks
Rocks exceeding the maximum size allowed in satisfactory
fill material shall be incorporated into deep fills and embankments subject to
the following size and depth limitations:
Depth below Finish Grade
(m) Maximum size allowable (mm)
0.90 – 1.50 150
Over 1.50 300
Fill
Material Test
Prior to the commencement of will work fill material samples
have to be taken from each source to be
tested in respect to :
Relative Density
- ASTM D2049
Moisture Content
- ASTM D2216
Grain size distribution
- ASTM D422
A set of three samples shall be taken for every 5000 m³ of
homogeneous in situ material. Permeability test per ASTM D2434 have to be performed for
previous fill material on the basis of one test for 2500 m³.
Compaction
requirements and Moisture Control
a. Compact
satisfactory fill material to a uniform dry density of no less than 92 percent
(92%) of maximum density at optimum moisture content (Standard Proctor
density) unless otherwise stipulated
elsewhere in specification herein.
b. The depth
1st layer, 2nd layer etc, is 30 cm of sub grade beneath structurally loaded
areas such as road, slab and foundation shall be compacted not less than 95
percent of maximum density at optimum moisture content (Standard Proctor
density).
c. Compact
each layer to a firm, stable condition using vibratory or impact type
compaction equipment suitable for the material and lift thickness and operated
in accordance with manufacture’s instruction.
d. Adjust
the moisture content as necessary to achieve a condition suitable for
compaction. For cohesive materials. The moisture content at the time of
compaction shall be within 2 percentage points of optimum.
e. When
water must be added, distribute it uniformly over the surface of the layer, and
thoroughly incorporate it into the soil to achieve a uniform distribution of
moisture throughout the material. When the moisture content is excessive, defer
compaction until the material has dried to suitable moisture content.
f. The type
of compaction equipment and number of passes to be achieved the required
compaction degree have to be specified.
Compaction
Test
The most suitable equipment for compaction shall be
evaluated from a trial fill of about 50 m length of each type road. Variable to
be considered in the fill are lift thickness and number of passes of the
compaction device. The purpose of the trial fill is to determine the most
suitable combination of lift thickness and number of passes to achieve the
required degree of compaction.
The lift thickness shall not exceed 0.30 m if not otherwise
approved.
The following test program shall therefore be carried out :
Lift thickness Number
of passes
0.20 m 2, 4, 6,
8, or more
0.30 m 2, 4, 6,
8, or more
The settlement shall be measured after each group of passes
and plotted versus the number of passes and the lift thickness
Compaction
Control
The required degree of compaction has to be controlled by
field and laboratory test as follows :
Plate bearing test per ASTM D 1194 on top or previously fill
and to layer. One test for every 5000 m² on each sub layer. Field density test using sand cone method per ASTM D1556.
One test for every 5000 m² on each sub layer. Permeability test (drainage material) per ASTM D2434. One
test for every 5000 m ² on each sub
layer (25 cm).
Backfill
of Culvert trenches
Backfill around culvert shall not be performed until culvert
run have been bedded inspected and tested. Care shall be exercised in placing and compaction material
around culvert to maintain the material approximately at the same level, not in
excess of a 300 mm different, on both sides of the pipe, throughout and placing
and comp-acting of the material.
Placing and compaction of material shall be performed
simultaneously on both side of culvert in such manner as will prevent injurious
side pressures on culvert Material shall be thoroughly compacted using hand operated
power tampers until compacted is at least 600 mm above culvert. Self-propelled compaction equipment shall not be used above
culvert until the compacted material has reached the 600 mm minimum. A flat bed is required for the bottom of a trench for culvert,
granular material shall be provided for bedding to depth indicates on the
approved drawings
Testing of
Earthfilling
The frequency of test shall be adapted to the nature and the
extend of the earth filling works.
the standard specification the moisture-density relationship
determination for each type of soil encountered in the works. A sample of each
soil type shall be maintained in glass containers for subsequent reference.
Each container shall be labeled with sample number, maximum dry density, and
optimum moisture content. A record shall be maintained which will provide
information regarding the areas of the project in which each soil type is
encountered. Maximum density and optimum moisture content for each soil shall
be determined by the procedures stated by ASTM.
The testing shall conduct a minimum of one in place density
determination per 1250 m² of fill placed
The density determination shall be made at locations
selected randomly. The density determination shall be made in accordance with
ASTM designation D1556.
Other methods of determination of in-place density may be
used, but in the event of dispute, the designated method shall be used as the
compacted soil is less than the specified dry density, additional tests as
required shall be taken to delineate the area having un-sufficient compaction.
This area shall then be worked and/or re-compacted until the required specified
density is obtained. Dry density test shall be determined in accordance with the
procedures of approved standards.
Tolerance
The finished surface level shall be free of irregularities
and depressions and shall have tolerance of ± 5 cm. In areas where roads are to be placed, the tolerance is
limited to + 5 cm in case of excavation and - 5 cm in case of earth fill and
the top of the sub grade shall be of such smoothness that when test with a 4
meter straightedge it shall not show any deviation in excess of 2.5 cm or shall
not be more than 2.5 cm from grade as established by grid hubs or pins. Any deviation is access of this amount shall be corrected by
loosening, adding or removing materials, reshaping and re-compacting by
moistening and rolling.
Site
Restoration
After completing backfill placement and compaction, restore
or replace shrubbery, turf, fences, and other features, surfaces, and
structures disturbed during the work except as otherwise indicated. Return
restored features and facilities to a condition equal or superior to that which
existed before the work.
Finish
Grading
At the completion of all construction work, the site shall
be graded to provide for the runoff of surface drainage without trapping and
pounding water. Trim and finish grade the surface of areas involved in work
covered by this specification. The resulting surface shall be reasonable smooth
and free of ruts, ridges, depressions, and other significant irregularities.
Leave areas designated to be grassed in
a condition suitable for subsequent top soiling, and seeding or sodding
operations.
Clean Up
Remove off the jobsite and properly dispose of surplus
piping materials, soils, temporary structures, and other debris resulting from
the work. Leave the site in a neat and clean condition, ready to receive
topsoil, seeding, or whatever final surface treatment is indicated.
