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7/27/2019 Specification for Construction of Manholes,
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Specification for Construction of manholes, Joint Box and Laying of Ducts
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SPECIFICATION FOR CONSTRUCTION OF MANHOLES,
JOINT BOXES AND LAYING OF DUCTS
1.0 GENERAL
This section of the Specification describes and specifies requirements
for the supply, delivery, installation, testing, commissioning,
handing over in approved working order and maintenance during the
Defects Liability Period of the manholes, joint boxes and ducts all in
accordance with the Specification, Supplementary Notes, Bill of
Quantities, Conditions of Contract, Drawings etc.
2.0 STANDARDS AND APPROVAL
The installation works shall comply with the latest relevant British
Standard Specification and Syarikat Telekom Malaysia Berhad (STM)
specification and requirements. All material used shall be of thetypes approved by STM and acceptance by the S.O.s Representative.
Samples of materials shall be submitted to the S.O.s Representative
for approval prior to installation. Sample of the materials which have
been approved by the S.O.s Representative for use in the Works shall
be displayed at the site office for reference.
3.0 WORK PROGRAMME
The Contractor shall submit to the S.O.s Representative detail work
programme for approval within two weeks after acceptance of tender of
such shorter period as required by the S.O.s Representative. If the
work programme submitted is not acceptance by the S.O.s
Representative, the Contractor shall amend and resubmit the programme
for final approval.
4.0 SITE DIARY
The Contractor shall keep at the work site a site diary, to which the
S.O.s Representative shall have access at all times during working
hours. The Contractor shall keep the site diary posted up to date,
entering therein all measurements on the day on which they are taken
and details of any deviations or extra work. Records of works shall be
submitted daily to the S.O.s Representative for verification. All
entries in the said shall be considered to be, and shall remain, theproperty of the S.O.s Representative.
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5.0 SAFETY
Adequate approved traffic warning signs and lamps shall be provided
and displayed by the Contractor at all time. The form, placing and
light of the warning signs must comply with all local and national
regulations and safety codes for road works. The Contractor shall take
all necessary precautions and follow the correct procedures to avoid
accidents due to presence of explosive gases, asphyxiating gases and
toxic gases in the underground network. The Contractor shall take all
necessary measures to ensure the safety of the workmen, members of the
public, plant or property, especially when carrying out any works in
manholes or joint boxes.
6.0 QUALITY OF MATERIALS
6.1 CONCRETE
Concrete shall be of quality A,B,C,F or G as provided by this
Specification and the proportions of the ingredients shall be as
follows :-
Concrete
Mixture
Parts by Measure
Cement Sand Aggregate
Usage
Quality A
Quality B
Quality C
Quality F
Quality G
Cement
Mortar
1 2 4
1 2 7
1 3 9
1 2 3
1 1 3
1 4 3
1 3 -
All Jointing
Chamber, Plinth.
Placed between
two sets of plant
if separation
clearance is
152mm or less.
For supporting
protecting or
filling in
purpose.
Concrete Troughs.
Filling in
Manholes covers
3E & 7E.
Encasement of
Ducts.
Dummy ducts in
jointing chamber,
repairing damaged
or split ducts.
The concrete used for encasing ducts shall be relatively dry and
having the consistency of wet sand. In no circumstances shall the
water content be increased appreciably as this will result in a weak
concrete. The cement used for encasing ducts shall be rapid-hardening
type.
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Concrete mixing shall be done manually or by machine. Ready mixed
shall be the first preference if available. In the process of mixing
the concrete, the ingredients shall be repeatedly turned over and
mixed in a dry state on mixing boards, after which water from the nose
of a watering can shall be added and the materials shall than again be
turned over sufficiently to ensure thorough mixing. The mixing boards
shall be sufficiently large to give ample room for turning over the
ingredients entirely from one place to another and shall be so
arranged or constructed that liquid cement shall not escape through
the joints. When mixed by machine the water shall be poured in first
and the ingredients shall be put into the machine dry without prior
mixing.
The standard of cleanliness of water for mixing is that it shall be
fit for drinking. The quantity used shall be sufficient to effect the
proper hydration of cement to obtain a plastic mixture. The S.O.s
Representative may reject concrete which is, in his opinion, so over
watered that it would be deficient in ultimate strength.
The concrete shall be deposited carefully in its intended position as
quickly as possible after being mixed and all concrete footings and
foundations shall be tamped and carefully leveled. All concrete shall
be compacted by the used of a poker type vibrator until a dense solid
mass without voids is obtained. Under no circumstances must the
vibrator be used longer than is necessary to obtain compaction nor
left unattended in the concrete, otherwise segregation of the mixture
will occur.
Concrete which has become hard, dry, dirty or not placed within 30
minutes after being mixed shall not be used, and of any earth fall on
top of any concrete after laying and before the work is completed, it
shall be carefully removed.
6.2 CEMENT
All cement used shall comply with the relevant British Standard
Specification. The cement shall be fresh, fine, smooth, loose and warm
and the S.O.s Representative reserves the right to reject the cement
which is found unsatisfactory. The Contractor may employ generally
rapid hardening Portland cement or high alumina cement in lieu of
ordinary Portland cement for his convenience and acceleration of
progress. Before high alumina cement is used, all tools and plants
shall be cleaned. High alumina cement shall not be used with P.V.C.
ducts. The Contractor shall ensure that all cement is protected
adequately against moisture while being transported and stored. Theused of cement aids where an additive is added to ordinary Portland
cement to render it rapid hardening is not recommended and permission
for its use shall first be obtained from the S.O.s Representative who
shall also determine the amount of additive to be used.
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6.3 SAND
All sand to be used shall be river sand. It shall be clean, sharp,
gritty and free from loam or other impurities. If the sand is found to
contain more than 5 percent by volume of silt, the sand shall not be
used. The sand used shall be course and the grains graded in size to 5
mm.
6.4 AGGREGATE
The aggregate for concrete shall be cleaned screened river ballast,
gravel, stone or other materials as approved by the S.O.s
Representative. The aggregate shall be of the nature of cubes, not of
flakes and graded in size and free from dirt, floury stoned duct,
loam, earth or any other impurities. Clinkers, brick sandstone or
other porous stone shall not be used.
The maximum size of aggregate for each of the qualities of mixtureincluded in Section 6.1 shall be as follows :-
A ..20mm, B40mm, C..any size suitable for work, F&G 10mm, for
encasement of ducts .6mm. Any portion which will pass a 5mm mesh
shall be used as sand.
6.5 BRICKS
The bricks used shall be best quality hard burned common bricks,
either wire cut or plastic pressed, or selected hard hand-made, stock
bricks or other hard or over-burned hand-made bricks of comparable
quality. They shall be of good shape, free from visible particles or
lime and from serious cracks, and shall not absorb more than 12
percent of their weight when immersed in water for 24 hours. Five
bricks from each batch delivered at site shall be tested and all shall
be required to pass the test. The dimensions of bricks described as
type 2 and 3 in B.S. 657 shall be regarded as standard.
6.6 CEMENT MORTAR
The cement mortar shall consist of one measure of cement and three
measure of sand. The materials after being gauged shall be thoroughly
mixed in a dry state and then thoroughly mixed with sufficient water
to form a stiff mortar. Water, cement and sand shall not be added
after mortar has one been mixed and set. If mortar has once begun toset and excess water has been used for mixing, further quantity of
sand and cement not be added but the whole mortar shall be rejected.
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6.7 STEEL, IRONWORK AND HARDCORE
All structural steel shall be in accordance with British Standard
Specification. All invoices for steel shall be inspected by the S.O.s
Representative.
If the Contractor cannot procure such reinforcing steel in the
Imperial sizes as described in the Drawings but can obtain such steel
in the Metric sizes and the dimensions approximating to those in the
following table, then the Contractor shall forthwith obtain the
approval of S.O.s Representative before such steel are ordered.
Imperial size (ins) 5/16 3/8 5/7 7/8
Metric size (mm) 6 8 10 12 16 20 22
Imperial size (ins) 1 11/8 1.25 1.5
Metric size (mm) 25 28 32 40
Bolts, nuts, rivets and other accessories shall be in accordance withthe relevant British Standard Specification. All invoices for iron
shall be inspected by the S.O.s Representative. All hardcore shall
consist of hard brick, concrete or stone graded down to a minimum of
80mm. Sufficient hardcore material under the sizes of 80mm shall be
added up to fill voids and aid consolidation.
7.0 EXCAVATION
The Contractor shall carefully segregate the surface and foundation
material from the lower sub-soil. Sub-soil shall be protected whilst
above ground from weathering action which could cause a damaging
increase in the natural moisture content of soil leading to the
formation of voids and/or settlement after back-filling. Sub-soil
which is damages shall be removed and replaced by undamaged sub-soil.
Except where otherwise provided, the excavation shall include all
necessary/timbering and shoring.
Mechanical excavator shall be used in a manner as to fulfill the
requirements of excavation work. A timber base support or platform
shall be placed under the fees of the excavation machine as a
protection to prevent the carriageway surface being marked when the
machine is in operation.
Pneumatic drills or other power driver appliance shall be fitted with
efficient silencing devices and the compressor machine shall be
maintenance in an efficient condition so as to avoid undue noise.
The Contractor shall obtain prior approval of the S.O.s
Representative to dig pilot holes and excavation of trenches. Pilot
holes shall be dug at positions selected by the S.O.s Representative,
normally one per sectional length to ascertain the most suitable
position for the work.
Timber support for excavation shall be so designed and placed as to
permit wherever possible withdrawal of such timber and consolidation
of the space it occupied.
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____________________________________________________________________________________________The routes of the trench shall be marked out and approved by the
S.O.s Representative before excavation. The width of trench excavated
shall not be greater than is necessary for satisfactory execution of
the work. The routes of the excavated trench shall be as straight as
possible and any bends or curves shall be of the maximum radius
possible. Where ducts are to be encased in concrete the width of
trench shall be dependent upon the number of ducts to be laid in a
horizontal direction. In unstable ground, timbering shall be used to
support the trench and to act as a former for the concrete.
The depth of trenches shall comply with the specification and as
directed by the S.O.s Representative. The floor of the trench shall
be leveled and shall not follow surface irregularities. The bottom of
the trench shall be normally leveled with 50mm of sand and rammed.
In passing from footway to carriageway and vice versa or where ducts
enter jointing chambers below standard depth or in any other
circumstances where it is necessary to change level, the bottom of the
trench shall rise or fall gradually as directed by the S.O.s
Representative.
The Contractor shall dispose of the water in the trench so as to
prevent any risk of the ducts, cables and other materials to be laid
in it being detrimentally affected. He shall provide all pumps and
appliances required and shall carry out the necessary pumping and
bailing.
8.0 DUCTS LAYING
8.1 GENERAL PROCEDURES
The routes of ducts shall be kept as possible. In the case of 4-ways
ducts or more, the lines shall break joint by approximately half the
duct length in alternative lines, horizontally and vertically.
Unless otherwise permitted by the S.O.s Representative, no ducts
shall be laid and covered up in the absence of the S.O.s
Representative.
All ducts laid direct in the ground shall be kept well clear of water
mains, service pipes, sewers, subways, manholes, joint boxes etc.
belonging to others. In order to permit the use of tapping machine
on water mains, a minimum clearance of 152mm shall be given wherever
possible. This clearance shall also be given, if practicable, to the
other service mentioned above. In no case shall the clearance be less
than 25mm, where the two services cross each other, the minimum
vertical clearance shall be 50mm.
The following minimum separating distance between the electrical
supply cables and lines of ducts shall be provided :-
(a) High-voltage single-core cables (exceeding 650 volts)Standard minimum clearance .460mm
No exception to this requirement will be permitted.
(b) High-voltage multi-core cables (exceeding 650 volts)
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____________________________________________________________________________________________Standard minimum clearance . 300mm
If difficult cases a reduced clearance shall be permitted. Where
it is impossible to provide a greater clearance than 150mm, a
layer of quality B concrete, not less than 50mm thick and of a
width to overlap the electrical services by 50mm on each side,
shall be placed between the two services. Where the two service
cross each other, the length of the layer of concrete shall not
be less than the width of the telephone services.
(c) Low and medium-voltage cables (not exceeding 650 volts)
Standard minimum clearance .50mm
Where the two services cross each other no exception to this
requirement shall be permitted. At other points a clearance down
to 25mm shall be allowed in difficult cases. Wherever the
clearance is 50mm or less, the spare between the two services
shall be filled with a layer of quality B concrete.
In all cases the concrete shall overlap the electrical services by
50mm on each side, and at crossing, the length of the layer of
concrete shall nor be less than the width of the telephone services.
The Contractor shall cut and bend the ducts according in the
requirements of the work. Inside edges of cut ducts shall be
thoroughly rounded off to prevent damages to cables from the edges.
The trench bottom shall be filled with a layer of sand 50mm thick and
holes shall be taken out of the bottom of the trench at all points
where sockets occur so that the barrels of the ducts rest on solid
ground. In rocky soils, the trench shall be bedded with 80mm thick
sand on which the ducts are laid.
On completion of the ducts line between any two jointing chambers of
sites, a cylindrical brush connected to the following end of a mandrel
shall be passed twice through each way to clean the duct and to remove
any foreign matter which may have entered.
All test shall be carried out in the presence of the S.O.s
Representative. If any obstruction or other defect be discovered, it
shall be rectified to the satisfaction of the S.O.s Representative.
A hardwood plug shall be inserted at the ends of each way in a line of
ducts until the length has been tested and passed.
When jointing chambers are provided on an existing duct routes or when
any disturbance takes place which may affect the alignment of the
ducts, a test mandrel of appropriate dimensions shall be drawn through
each of the spare ways. The Contractor shall take all reasonable stepsto prevent damage to the paving by his plants.
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____________________________________________________________________________________________8.2 GALVANISED IRON PIPES
All galvanized iron pipes shall comply with STM Specification Lines D
0010. Galvanized iron pipes shall be provided in nominal lengths of 6m
and provided with screwed socket at one end.
The procedures of laying galvanized iron pipes shall be as specified
in Section 8.0. Where one line of ducts is laid over the lower line of
ducts and carefully rammed to form a bedding of 50mm in thickness for
the top ducts. Sand shall also be rammed between the ducts laid said
by side in the same trench. The ducts shall break joint by
approximately half the length in alternative lines, horizontally and
vertically.
Joints shall be made by positioning the threaded end of the pipes to
the screwed socket of the other pipe end. One of the pipes shall be
turned until it cannot be turned any more and the thread of the
threaded end cannot be seen.
Pipes shall be cut where necessary at right angle to the bore only.The inside edges shall be filed so that there can be no possibility of
damages to cables from the edges.
To ensure the alignment of the ducts, a working mandrel of 457mm in
length and 83mm in diameter shall be drawn through as the ducts are
laid.
The test mandrel used for testing and cleaning shall be 457mm in
length and 83mm in diameter, the cylindrical brush shall be 108mm in
diameter.
8.3 P.V.C. DUCTS
P.V.C ducts shall be supplied in 6m lengths. The ducts shall be stored
away from the direct rays of the sun. A solvent cement shall be used
for the process of jointing. The ducts shall comply with STM
Specification Lines D 0011. The trench shall be scooped out at all
points where the spigot rest, so that the duct lies upon rammed sand.
The condition for duct laying as detailed in Section 8.1 shall be
applied. Where one line of ducts is laid over another in the same
trench, sand shall be filled in and over the lower lone of ducts and
carefully rammed to form a bedding of 50mm in thickness for the top
ducts. Sand shall also be rammed between the ducts laid side by side
in the same trench. The ducts shall break joint by approximately half
the duct length in alternative lines, horizontally and vertically.
If it is necessary to deflect from a straight line or to vary the
depth, sets shall be given to the joints but deflections shall not be
greater than 12mm per 610mm run of the single ducts. Short ducts not
less than 610mm in length, shall be built into the track in order to
ensure the required deviation.
Ducts shall be cut when necessary, at right angles to the bore only,
preferably with a saw in a simple cutting guide. The inside edges of
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____________________________________________________________________________________________the ducts shall be trimmed so that there shall be no possibility of
damages to cables from the edges.
The spigot of the ducts shall be wiped clean. The solvent cement shall
be applied to the spigot as well as the end of another duct. The end
of the ducts where the solvent cement ware applied shall be positioned
and pressure applied for the two ducts to be jointed. In no
circumstances shall dirt or grit be allowed to enter the joint.
To ensure the alignment of the ducts, a working mandrel of 457mm in
length and 83mm in diameter shall be drawn through as the ducts are
laid.
When the construction of the jointing chamber is deferred, the last
joint of each duct shall be tested on completion of the jointing
chamber by means of the working mandrel mentioned above.
The test mandrel used for testing shall be 457mm in length and 83mm in
diameter, the cylindrical brush shall be 108mm in diameter.
8.4 ENCASING IN CONCRETE
The method of encasing ducts in concrete in the layer by layer method
where each duct is completely surrounded by concrete.
To install P.V.C ducts around curves, the rigid ducts shall be bent to
avoid obstacles or to negotiate curves.
The ducts shall be cold bent around stakes for radii above 10.6m. To
provide favourable cable hauling conditions, the radii should be as
large as possible. Cold bending in situ to the curve required is
achieved by provision of stakes to form the ducts to the required
shape. The stakes must be spaced at intervals not greater in length
than 1/20th of the radius of curvature or alternatively as indicated in
the Table below.
Bend
Radius
11.6m
-
11.2m
12.2m-
15.2m
15.2m-
18.2m
18.2m-
21.3m
21.3m-
24.3m
24.3m
-
27.4m
27.4m
-
304m
Support
Spacing
53.3
cm
61.0
cm
76.2
cm
91.5
cm
106.7
cm
122.0
cm
137.2
cm
Concrete cover above the top duct of a complete tier is to be a
minimum of 51mm.
After the initial set of concrete has occurred and before it sets
hard, all stakes shall be withdrawn by applying a lifting and turning
action to the stakes. Where additional ducts are to be installed abovethe first nest, the stakes shall be withdrawn until approximately
305mm remain embedded.
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8.5 FIXING DUCTS TO BRIDGES
The following two methods shall be used for fixing ducts to bridges :-
(i) fixing to steel R.S.Js or fabricated beams.(ii) Fixing to reinforced concrete bridge beams and masonry walls.It should be noted that extra care shall be taken when it is necessary
to make holes for fixing bolts in existing bridge beams. All bridge
fittings shall be thoroughly cleaned and painted with one coat of
bituminous paint.
Where it is necessary for duct to pass through abutment walls, the
masonry or brickwork shall be arched over the pipe, the diameter of
the hole thus formed shall be at least 13mm more than the external
diameter of the duct. The space between with masonry or brickwork and
the pipe shall then be filled with bitumen to provide a cushion of
bitumen to the perimeter of the pipe at least 13mm thick.
8.6 DUMMY DUCTS
One length of P.V.C ducts shall be positioned, in a wall of the
chamber or above the row of ducts terminated at a jointing chamber.
When it is necessary to increase the number of ways, the new ducts
shall be jointed to the dummy ducts and the ducts shall be made
available by breaking the mortar seal that was set previously in
position when the ducts and chamber were constructed.
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9.0 JOINTING CHAMBERS
9.1 TYPE OF MANHOLES
The standard types and sizes of manholes with code reference are shown
in the following tables :-
Reinforced Concrete Construction
Throughout
Internal Dimensions
Code STM
Standard
Drg. No.
Figures Length
(cm)
Breadth
(cm)
Height
(cm)
RO
RIA
RIB
R2Bmod
fr
RI3
RI3
mod.
R2A
R2B
R2A-
E
R2A
Mod.
R4
R6
R7
SM.
No.1
SM.No.2
SM.
No.3
13359/1
SHTI&4
}13359/1
}SHT&4
}19488/0}
}
19658/0
}
}13359/1
}SHT3&4
19636/0
19632/0
19634/0
19614/1
19615/1
}
}
}10750/2
}
}
}
}
}}
}
Rectangular
152
152
152
152
305
132
305
305
305
366
410
140
144
305
305
106
122
122
122
122
122
122
122
152
182
305
213
122
244
244
152
168
198
198
182
182
192
182-244
182
182
182
305
182
213
213
TABLE 1 (Contd.)
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R3
R5
R9
R9 MOD.
R10
R10 MOD.
R11
R12
R13
R14
R15
R16
19633/0
19609/1
19578/2
19649/0
19579/2
19652/0
19580/0
19588/0
19594/0
19638/0
19637/0
19635/0
A
S
S
O
R
T
E
D
S
H
A
P
E
S
&
S
I
Z
E
See STM Drawing
19650/0 for size and
shape
Table 1 (Contd.)
Reinforced Concrete Internal Dimensions
Code STM Standard
Drg No.
Figure Length Breadth Height
RT88 19485/0
19482/0
SHT.1&2
19484/1
19486/0
D A D
B B
F
A B C
117cm 107cm 244cm
F
274cm 182cm
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9.2 TYPE OF JOINT BOXES
The standard types and sizes of joint boxes are shown in the following
table :-
TABLE 2
Item Code STM
Standard
Drawing
Number
Length Breadth Internal
Depth
Carriag
eway
Joint
Box
Carriag
ewayJoint
Box
Carriag
eway
Joint
Box
to
accommo
date
L.P.
200 pr
JC9
Mod.
JC9C
Mod.
19647/1
19646/1
19540/0
157cm
182cm
244cm
66cm
97cm
97cm
107cm
144cm
108cm +
61cms.H
Note: Normal depths are indicated and shall be measured from the carriageway
of footway surface to the top of the floor in each case. They may
however be varied to suit the depths of the ducts.
All jointing chambers whether built of brick or reinforced concrete
shall be of waterproof construction. Ducts shall enter manholes at
such a depth to ensure a clearance of at least 460mm between the top
of the barrel of the uppermost ducts and the underside of the roof of
the manhole. Except where a duct seal is provided, when a clearance of
203mm is required clearance of 152mm depending on type of manhole,
shall be given between the outside of the barrel of the ducts and the
adjacent wall, and a minimum clearance of 460mm between the undersideof the lowest duct duct and the floor.
Where the duct capacity of any proposed manhole is not fully utilized,
the space shall be fitted with dummy ducts for future duct growth by
laying initially at standard depth. The dummy ducts shall be sealed
with cement mortar inside the chamber wall. To ensure that cables can
easily be housed in manholes with a minimum bending, the ducts shall
be splayed over the last length to enter the manhole equally on either
side.
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9.3 MANHOLE CONSTRUCTION
The ground shall be excavated to the required dimension, the sides of
the excavation shall be supported by poling boards or by other means
if there is any likelihood of the earth falling in. The foundation
shall taken leveled and rammed. Soft ground shall be dug out, filled
in with hardcore and consolidated.
Two light wooden template, slotted (not drilled) to receive the
reinforced bare shall be set up. The lower template shall be fitted
about 305mm above the foundation and shall be supported on four small
pegs at its corners. The upper template shall be fixed to correspond
with the lower template, but about 305mm below the position of the
roof of the manhole.
In the process of erecting the floor of manhole, shuttering for the
sump hole shall be set up and concrete laid over the foundation to a
thickness of 38mm.
The ends of side-wall-to-floor corner reinforcement shall be placed so
that horizontal portions are just covered by the concrete. The
vertical portions shall pass through the slots in this template and be
set so as to obtained 19mm cover from the outside face of the walls
when these are erected. Additional concrete shall next be laid until
the level is 19mm less than the concrete level for the floor. This
shall be done as soon as possible after placing the first layer of
concrete, so that the two layers units thoroughly. Anchor irons shall
be set in the floor in accordance with the relevant STM Standard
Drawings. The interior wall reinforcement shall be placed with the
horizontal portions flush with the surface of the concrete in the
floor and the vertical portions passing through the slots of both
template as to obtain 19mm cover from the interior face of the walls
when these are erected. To remaining 19mm layer of concrete shall than
be laid to reach the specified floor level.
The erection of the walls shall be commenced when the floor has been
left for at least 12 hours. The portion of the floor on which the
walls will be erected shall be cleaned and rendered with a 7mm
thickness of neat cement., well trowelled and placed in position, just
before wall concreting is commend. The wall shall as far as possible
be erected continuously to their full height, but if during erection a
break of 2 hours or more is unavoidable, the existing work shall be
cleaned and rendered as previously described.
The horizontal bars and side-to-end-wall corner reinforcement shall be
placed as walls are built up. Steps, manholes, bolts and cable bearersshall than be set in the walls. The template shall be removed when
work reaches such a stages that they impede the placing of the
concrete.
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____________________________________________________________________________________________
When the walls have been built to the requisite height, shuttering for
the roof shall be set up and the boards being arranged to form a
recess at the position of the roof beams. A 26mm thickness of concrete
shall then be laid throughout the roof area, including the recess of
the beams. The beam reinforcement which have been previously assembled
by threading and wiring of stirrups to the bars may now be laid and
the main reinforcing bars shall be set to obtain 26mm cover. The
remainder of the roof reinforcement shall be laid and to give the
correct cover of 19mm and the rods shall be just visible above the
surface of the concrete. The alternate bent bars shall be conveniently
supported by a single wire fixing at the point where they enter the
beam reinforcement. The concrete in the roof shall than be made up to
the necessary thickness and finally the roof-to-wall corner
reinforcement shall be embedded.
The correct cover of 19mm to the roof shall be checked by a wood
spike. Correction at each end of the horizontal part of the rod shall
ensure that the vertical portion has the correct cover throughout its
length. The upper face of the beams shall be spade-finished and theroof given a slight slope to the sides to avoid accumulation of water
on the roof.
The shuttering shall be struck and the floor shall be rendered with a
19mm cement mortar, with a fall to the sump hole on all sides and the
manhole frame shall then be fitted.
The arrangement of reinforcement for each type of manhole are as shown
pictorially in the relevant STM Standard Drawings as listed in Table
1.
The minimum concrete curing time for jointing chamber after completion
of concreting shall be as shown in the following table :-
TABLE 3 : Manholes Built In The Carriageway/Foot Way
Type of
Cement
Used
Minimum Period from Completion of Concreting
(a) to removal (b) before commencing c)before
of shuttering commencing allowing
reinstatement passenger
of traffic
Portland
Cement orits
equivalent
Rapid-
Hardening
Cement
High
Alumina
Carriage-
way
5days
2days
10hrs
Foot-
way
5days
2days
10hrs
Carriage
-way
7days
3days
24hrs
Foot-
Way
5days
2days
24hrs
Carriage-
way
7days
3days
24hrs
Foot-
way
7days
3days
24hrs
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____________________________________________________________________________________________Cement
The striking of the shuttering shall be commenced before the
expiration of 12 hours and the concrete shall be prevented from
becoming dry at any time by watering it within 24 hours of mixing.
9.4 JOINTING CHAMBER FITTINGS
The following fittings in the jointing chamber shall be hot-dip
galvanized and the following requirements shall be followed :-
(a) Grating for sump holes shall be fitted to the sump holes of allmanholes.
(b) Anchor iron shall be fitted in accordance with the relevantdrawing.
(c) Steps shall be installed in the position shown in the relevantdrawings for the manholes. The steps shall also be used in
entrance shafts for all manholes.
(d) Steel ladders shall be used in all type of manholes. The laddersshall be fixed in accordance with the relevant drawings to suitthe different heights of the manholes.
(e) Bolts shall be fitted for the attachment of cable bearers. Inall types of manholes, the bolts required for the walls shall be
fixed temporarily in the shuttering during the construction of
the manhole to ensure that they shall remain in their correct
position while the concrete is setting. The positions for holes
in the shuttering shall be obtained by using the cable bearer as
a template.
(f) The cable bearers shall be fixed to the walls as described in(e).
(g) The brackets for cable bearers shall be in accordance withrelevant drawing and the initial provision shall be 2 per Cable
bearer, e.g. in a R2A type manholes, where the cable bearers are
fitted 3 to a wall making a total of 6 cable bearers, the number
of brackets provided shall be 12.
(h) The pins locking and cable bearer shall be designed tofacilitate the removal of brackets.
9.5 FITTING OF MANHOLE COVERS
Manholes Cover No.3E shall be fitted in all classes of manholes inaccordance with the relevant drawings. Manholes Covers No. 7E shall be
fitted in all classes of joint boxes in accordance with the relevant
drawing.
(a) Where the manhole is to be set at the minimum depth (as shown onthe standard manhole drawings), one course of brickwork shall be
laid between the manhole roof and frame.
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____________________________________________________________________________________________(b) Where, due to anticipated alternations in level, the manhole is
to be set at an increased depth, one or more additional course
of brickwork shall be laid. This is particularly important in
the case of manholes built in the footway where there is
possibility of the frames and covers being installed to
carriageway level at a later date. Cement mortar shall be used
both for setting the brickwork and for bedding the manholes
frame.
(c) 24 hours must elapse after the building of a jointing chamberbefore the frame and cover are installed. The water used in the
concrete shall not exceed 643 litres per cubic metres.
The frame shall be positioned accurately in relation to the cover
before being filled so that the cover is flush and level with the
surrounding carriageway. Two methods of filling and setting may be
employed :-
(i) In-situ filling The frame shall be embedded on a layer ofstiff cement mortar, care being taken to ensure that the frameis fully supported along all the four side.
The level of the frame shall be adjusted to the level of the
surrounding road surface by pieces of mild steel packing
approximately 152mm x 51mm and of appropriate thickness. The
cover shall than be placed in the frame. When the cover is
correct suited, the edges of the frame and the cover shall be at
the same level. If any irregularly can be felt by running the
finger along the joint, or if the cover rocks, the frame shall
be packed up until the edges are at the same level and the cover
is free from rocking. The cover and the frame shall then be
filled with concrete of Quality G, or an asphalt and granite
mixture. Great care shall be taken when filling the frame to
ensure that no voids are left, the concrete in each pocket shall
be thoroughly tamped with to reinforcing rod. Finishing shall be
done with a trower the concrete in the cover compartments being
left slightly proud but not more than 3.2mm at the edge to 6.4mm
crown in the center of the cover to allow for shrinkage, wear
and to protect the metal webs. The lettering on the plate
bearing the STM marking shall be left clear.
(ii) Where in-situ filling is not possible, the frame shall be placed
on a level surface with a piece of building paper beneath it to
prevent concrete adhering to the floor. The leveling of the
frame and cover, and the concrete filling shall then be done as
described in method (i). The frames and covers must be left
undisturbed for a minimum of 3 days. When the frame isinstalled, it shall be bedded on stiff 1:3 cement mortar.
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____________________________________________________________________________________________Shuttering shall be struck as follows :-
(i) For carriageway joint boxes, after the lapse of time given in
Table 3 of section 9.3 of this specification.
(ii) For footway joint boxes, after 24 hours, irrespective of the
type of cement used. A 20mm cement mortar rendering shall be
applied to level the floors or they shall be built up to give
25mm drainage fall where required.
Manhole cover No.7E shall be fitted to all joint boxes and the method
as described in Section 9.5 of this specification shall apply.
9.7 PROTECTION OF CABLES AND ASSOCIATED EQUIPMENT
The Contractor shall take such measures, to protect cables and
associated equipment during the cutting of duct entries into existing
structures or the demolition and rebuilding of jointing chambers. Such
measures may include any or all of the following :-
(a) A ladder must be provided by the Contractor for the access ofmanhole excavation. Under no circumstances shall cable, joints
and associated equipment be used for climbing, standing or
sitting on.
(b) Sufficient pumping capacity shall be made available to ensurethat when cables are removed from their bearers they shall not
be immersed in water at any time.
(c) All cables shall be protected at duct entries by packing withfoam rubber to act as cushion when any movement occurs.
(d) During demolition of the roof of a manhole the Contractor shallerect a deck of timber between the cables and the roof of the
manhole to protect the cables etc. from falling debris in the
following manner :-
(i) A minimum of three 229mm x 76mm timber upright shall be
evenly spaced against each long wall of the manhole with
the 229mm side against the wall. The length of the upright
shall be such that the terminate approximately midway
between the uppermost cables and the roof. Further length
of horizontally on top of the uprights and between the
uprights at the bottom, all positions shall be wedged and
blocked to the satisfaction of the S.O.s Representative.
Lengths of poling boards or other similar timber shallthen be placed on top of the horizontal supports.
(ii) When the manhole roof and walls have been demolished down
to the level of the timber decking and all debris and
decking removed, the cables and other associated equipment
shall be suspended from beams on the surface of the ground
to the satisfaction of the S.O.s Representative.
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____________________________________________________________________________________________(iii) Cables and joints and other equipment shall be protected
by wrapping (not tying) with several layers of sacking
while timber decking is being erected or dismantled.
(e) During rebuilding operations, cables shall be supported on
wooden benches with cushions of sacking or similar
material once the floor has been laid and the concrete
allowed to set.
9.8 BONDING AT JOINTING CHAMBERS FOR EARTHING FACILITIES
Where metal pipes are laid and terminated at jointing chambers, the
break in continuity shall be made good by embedding 51mm x 3.2mm G.I.
strips of required lengths in the walls of the jointing chambers
during construction. The ends of the G.I. strips shall be welded to
the pipes.
10.0 INTERIM RESTORATION, BACKFILLING AND PERMANENT REINSTATEMENT OF ROADSAND OTHERS
10.1 INTERIM RESTORATION
The Contractor shall execute interim restoration of all trenches and
ducts in accordance with the provisions and specification laid down by
JKR and other relevant authorities. A layer of sand shall first be
laid on the bed of the trench and hand punned to a thickness of not
less than 50mm before ducts are laid. All ducts shall be covered by a
layer of sand and hand punned to a thickness of not less than 50mm.
10.2 BACKFILLING
The spaces outside the walls of jointing chambers and surrounding area
shall be completely filled with sand free from stones in 230mm layers
and rammed. Care shall be taken such that the ramming shall not
disturb any recently completed work.
All materials shall be replaced in 150mm layers in the reverse order
to which they were excavated. The remaining 300mm top of the trench
shall be backfilled with good quality red earth and the materials
previously excavated shall be placed on top and the gaps filled with
quarry dust. All backfilling shall be thoroughly compacted at each
layer using a mechanical rammer. If mechanical rammer is impracticable
and hand ramming is employed, there shall be at least three persons
ramming to one filling. Where S.O.s Representative required
backfilling of trenches completely with sand or quarry duct, allexcavated materials shall be removed from site, and backfilling shall
be carried out as described in the following paragraph.
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____________________________________________________________________________________________For all road crossing in carriageway, after the bedding of a layer of
sand in the trench has been satisfactorily carried out, the
backfilling shall be done with nothing else except sand or quarry duct
in layers. Each layer shall not be more than 230mm in thickness and
well rammed with mechanical rammer or watered down before the next
layer is laid. The top 300mm shall be backfilled with quarry dust
only. This shall be done in tow layers, one layer to be rammed with
mechanical rammers before the next layer is laid. The top layer shall
be rammed with mechanical rammer until it is flushed with the road
surface.
Backfilled excavation shall be tested by applying a power frog rammer
repeatedly over on half a square meter area for a period 3 minutes and
shall performed by the Contractor as instructed by the S.O.s
Representative at intervals he considers necessary.
The compactness shall be considered satisfactory of the test shows no
measurable change in level, a measurable change in level being a
depression which cannot be rectified by reshaping the tested area and
consequently requires additional imported material to restore thesurface of the test to the original level. Should any measurable
change in level occurred, then the area of faulty compaction, defined
by the results of this and further tests, shall be rectified by the
Contractor.
The reinstatement portions of unpaved footways or other excavations
shall be maintained by the Contractor and he shall ensure that they
shall be leveled and turfing shall be replaced to the satisfaction of
the S.O.s Representative. Any subsidence of other defects arising
during the Defects Liability Period shall be made good by the
Contractor.
10.3 PERMANENT REINSTATEMENT OF ROADS
Permanent reinstatement shall commence only after the back filling and
interim restoration has been allowed to settle well and that there is
no measurable change in level.
The reinstatement shall be carried out by removing the back filled
material from the trench to a depth of 300mm which shall then be
filled with a 250mm crusher-run stone (limestone or granite) not
exceeding 62mm in size and the voids between the metal filled with
quarry dust to serve as a bind. Where possible, consolidation by
rolling shall be carried out with an 8 tonne roller utilizing a
special hydraulic rolling wheel attachment. Elsewhere consolidation
shall be effected by means of power driven rammer. The 300mm crusher-run stone base for trenches within carriageway shall be consolidated
in 2 layers of 150mm each. The foundation of the footway shall be
consist of a layer of not less than 125mm of quarry dust. The layer of
quarry dust shall be rolled with a 2 tonne roller or by means of a
power driven rammer.
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____________________________________________________________________________________________A tack coat cationic bituminous emulsion (40%) must be applied to the
rolled crusher-run stone base/quarry dust base at the rate of 4.5
square metre per litre before the premixed asphalt macadam surface is
laid.
When the consolidation of the stone foundation is completed, premixed
asphalt shall be spread evenly over the treated stone surface/quarry
dust surface and rolled until complete consolidation has been obtained
and the resultant surface left slightly proud of the existing adjacent
surface. For carriageway consolidation, an 8 tonne roller shall be
used and for footpath consolidation, a roller not exceeding 2 tonne
shall be used. All surplus material shall be removed from site by the
Contractor on the same day the trench has been backfilled. The
Contractor shall be responsible for maintaining the backfilled trench
until the surface reinstatement is complete.
11.0 WORKING DRAWINGS
Within three weeks after award of the tender or such shorter period as
may be required by the S.O.s Representative, the Contractor shallsubmit to the S.O.s Representative for his approval, four sets of
detailed drawings the positions of manholes/joint boxes and cable
ducts routes. The drawings submitted shall be modified if necessary as
required by the S.O.s Representative and submitted for final
approval. It is to be understood, however, that approval of the
drawings will not exonerate the Contractor from any responsibility in
connection with the works.
12.0 SERVICE AND MAINTENANCE
During the Defects Liability Period, the Contractor shall perform
service and maintenance work for the complete installation by skilled
persons. All works, materials, tools and parts necessary to rectify
the defects due to manufacturing/installation/construction faults
shall be supplied/executed by the Contractor at no extra cost to the
Government.
The works to be performed shall include but not be limited to the
following :-
(a) Replacing and making good all manholes, joint boxes, ducts etc.(b) Making good any damage to roads, buildings, drains, cables,
pipes, concrete areas, paved areas etc. which had not been
properly made good.
(c) All other works as deemed necessary by the S.O.sRepresentative.
The maintenance work shall be carried out as soon as the
Contractor has been informed by the S.O.s Representative. If
the work has not been carried out and completed within a
reasonable period, the S.O.s Representative reserve the right
to engage another party to carry out the work in which case, the
Contractor shall be responsible for all the expenses incurred.
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____________________________________________________________________________________________13.0 AS INSTALLED DRAWINGS
Within three calendar months after the practical completion of the
project, one set of true to scale negative (110/115gm sq.m) and four
sets of prints of the layout of cable duct routes, manholes and joint
boxes with reference to easily recognizable buildings and structures
shall be submitted.
These drawings shall be provided whether or not they are separately
itemzed in the Bills of Quantities of the Tender Document. The cost of
all these drawings is deemed to be included in the Tender Price.
These drawings shall be properly stenciled and shall have at the lower
right hand corner the Contractors name and address date of
commissioning, scale, drawings number.
If the drawings submitted are not acceptable by the S.O.s
Representative, the Contractor shall amend and resubmit the drawing
within two weeks from the date of return of the drawings.