Abu Dhabi, United Arab Emirates. STANDARD CONSTRUCTION SPECIFICATIONS (PART 2 - ROAD STRUCTURES, 2020)

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-7

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Backfill that is not subject to piping action is classified as non-erodible. Such backfill typically
includes granular soil (with grain sizes equivalent to coarses and, small gravel, or larger) and
cohesive soils. Backfill that is subject to piping action and that tends to either infiltrate the
pipe or be easily washed by water exfiltration is classified as erodible. Such backfill typically
includes fine sands and silts.

For non-erodible or erodible soils, the ratio of D

soil size to the size of the opening must be

greater than 0.3 for medium to fine sand or 0.2 for uniform sand. These ratios need not be
met for cohesive backfills where the plasticity index exceeds 12 percent. Alternatively, a joint
that withstands 14 kPa hydrostatic tests without leakage shall be considered soil tight. Joints
that do not meet these requirements may be made soil tight by wrapping them with a suitable
geotextile.

c. Water Tightness: The adjoining pipe ends in any joint shall not vary more than 13 mm in

diameter or more than 38 mm in circumference for watertight joints.

Water tightness may be specified for joints of any category, where needed, to satisfy other
criteria. Leakage rates shall be measured with the pipe in place or at an approved test facility.
Tolerances indicated may be attained by proper production controls or by match-marking
pipe ends.

Table 31-3: Categories of Pipe Joint

Soil Condition

Non-erodible

Erodible

Joint Type

Joint Property

Standard

Special

Standard

Special

Down Drain

Shear Resistance

Moment Resistance

15%

Tensile Resistance up
to 1,060 mm Diameter

22.2 kN

Tensile Resistance
1,200 mm

– 2130 mm

Diameters

44.5 kN

Joint Overlap,
Minimum

265 mm

Soil Tightness

0.3 or 0.2

31.5.3

Assembly of Long-span Structures

Unless held in shape by cables, struts, or backfill, longitudinal seams shall be tightened when the
plates are hung. Prior to bolt tightening, the Contractor shall take care to align plates to ensure
properly fitted seams. Variations in structure dimensions before backfill shall comply with the
following provisions:

a. For horizontal elliptic shapes having a ratio of top to side radii of three or less, the span and

rise shall not deviate from the specified dimensions by more than 2 percent.

b. For arch shapes having a ratio of top to side radii of three or more, the rise shall not deviate

from the specified dimensions by more than 1 percent of the span.

c. For all other long-span structures, the span and rise shall not deviate from the specified

dimensions by more than 2 percent, or more than 125 mm, whichever is less.

When required by structural design, the Contractor shall attach reinforcing ribs to the structural plate
corrugation crown prior to backfilling, using a bolt spacing of not more than 300 mm. To designate

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-8

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

its proper position in the finished structure, the Contractor shall place legible, identifying letters or
numbers on each rib.

When required for control of structure shape during installation, the Contractor shall space
reinforcing ribs and attach them to the corrugated plates at the discretion of the Manufacturer with
the approval of the Engineer.

Erection processes specified herein may require temporary shoring.

31.6

Installation

31.6.1

General

All culvert pipes shall be laid by the Contractor true to the lines and grades given in the Contract
documents, or as approved in the working drawings. Departure from and return to plan alignment
and grade that exceeds 5 mm per metre of nominal pipe length, with a total of not more than 25 mm
departure from the theoretical line and grade shall not be permitted by the Contractor. Any culvert
pipe that is not in true alignment or which shows any settlement after laying shall be taken up and
relayed by the Contractor at no additional expense to the Owner.

For  trench conditions, the  trench  shall  be  excavated to  the  width,  depth, and grade shown  in  the
Contract  documents.  Trenches  shall  be  wide  enough  to  allow  the  Contractor  to  prepare  the
foundation,  lay  the  culvert  pipe,  and  place  and  compacting  backfill  as  specified;  except  that  the
trench width shall not exceed the culvert pipe's outside diameter by more than 915 mm.

All temporary drainage facilities necessary shall be provided by the Contractor to protect the work
and adjacent property. Temporary drainage shall be maintained in effective operating condition by
the  Contractor,  as  the  Engineer  approves,  until  the  permanent  culvert  pipe  installations  are
operational.  Temporary  culverts  shall  be  removed  and  disposed  by  the  Contractor  after  the
permanent culvert pipe installations are operational.

Proper preparation of foundations; placement of foundation materials, where required; and
placement of bedding materials shall precede the installation of all culvert pipe. This work shall
include necessary levelling of the native trench bottom or the top of the foundation material

— as

well as placement and compaction of required bedding material to a uniform grade so that a uniform
base can support the entire length of pipe. Backfill materials shall be placed and compacted around
the pipe in a manner to meet the requirements specified.

Materials used for foundation improvements, bedding, and structure backfill must have gradations
compatible with adjacent soils to avoid migration. Where material gradations cannot be properly
controlled, adjacent materials must be separated with a suitable geotextile.

All pipes shall be protected by sufficient cover before permitting heavy construction equipment to
pass over them during construction.

31.6.2

Foundation

Foundations under the pipe and structure backfill shall be investigated for their adequacy to support
the loads. Foundations shall be provided, such that the structure backfill does not settle more than
the pipe to avoid down drag loads on the pipe.

Foundations must provide uniform support for the pipe invert. Boulders, rock, or soft spots in the
foundations shall be excavated to a suitable depth and backfilled with material compacted sufficiently
to provide uniform bearing, as shown in Figure 31-1.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-9

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Figure 31-1: Pipe Installation Nomenclature.

Where the natural foundation is judged inadequate to support the pipe or structure backfill by the
Engineer, the Contractor shall excavate it to a suitable depth and backfill it with material compacted
sufficiently to control settlements

— as shown in Figure 31-2 and Figure 31-3.

Foundation on Localised Soft Zone

Foundation on Rock

Note: d = 40 mm per metre of fill over pipe, with 0.63 m maximum

Figure 31-2: Foundation Treatment for Localised Soft Spots or Rock

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-10

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Figure 31-3: Foundation Treatment for Settlement Control

Where relatively large-radius inverts adjoin small-radius corners or sides for sections such as pipe
arches, elliptic pipe or underpasses, the foundation shall be designed to support the radial pressures
exerted by the smaller radius portions of the pipe. Principal foundation support shall be provided in
the area extending radially outward from the smaller radius areas. These pressures may be two to
five times the loading pressures on top of the pipe, depending on the pipe shape. When corrective
measures are necessary, providing less support under the invert allows the pipe to maintain its shape
as minor settlements occur.

Where settlement of the pipe is expected to be so large that the required grade under high fills will
not be maintained, pipe may be cambered to prevent excessive sag. Camber amounts shall be
determined based on consideration of the flow line, gradient, fill height, the compressive
characteristics of the foundation material, and the depth to incompressible strata.

31.6.3

Bedding

Pipe bedding is a relatively thin layer of loosely placed material that cushions the pipe invert and
allows the corrugation to nest or seat into it, thus supporting the corrugation.

When, in the opinion of the Engineer, the natural soil does not provide a suitable bed, the Contractor
shall provide a bedding blanket with a minimum thickness of twice the corrugation depth.

Pipe arches and horizontal elliptic and underpass shapes with spans exceeding 3.6 m shall be
placed on a shaped bed. Shaped areas shall be centered beneath the pipe and shall have a minimum
width of one-half the span for pipe arch and underpass shapes, and one-third the span for horizontal
elliptic shapes. Preshaping may consist of a simple V-shape graded into the soil as shown in Figure
31-4.

Figure 31-4: Shaped Bedding for Large Pipe-Arch, Horizontal Elliptic, and Underpass

Structures

31.6.4

Structure Backfill

31.6.4.1

General

To ensure that the quality of the soil and the compactive effort obtained is as specified, the Contractor
shall undertake sufficient inspection and testing.

Backfill material shall meet the requirements of Section 31.4.8, Bedding and Backfill Materials, and
shall be placed in layers not exceeding 200-mm, loose lift thickness to a minimum 90 percent
standard density per AASHTO T 99-10. Equipment used to compact backfill within 900 mm from the
pipe sides

— or from the edges of footings of arches and box culverts — shall be approved by the

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-11

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Engineer prior to use. Except as provided below for long-span structures, the equipment used for
compacting backfill beyond these limits may be the same as used for compacting embankment.

Backfill materials shall be placed and compacted with care under the haunches of the pipe and shall
be raised evenly on both sides of the pipe by working backfill operations from side to side. This
backfill differential shall not exceed 600 mm, or one-third, of the rise of the structure, whichever is
less. Backfill shall continue to not less than 300 mm above the top for the full length of the pipe. Fill
above this level shall become embankment fill or other materials, as specified to support the
pavement. Trenched shall be kept to the minimum width required for placing pipe, placing adequate
bedding and side fill, and creating safe working conditions. Ponding or jetting of backfill shall not be
permitted except upon written permission by the Engineer.

Structural integrity of the corrugated metal structure is vitally affected by the quality of construction
in the field; therefore, quality control is of extreme importance.

Where single or multiple structures are installed at a skew to the embankment, the Contractor shall
provide proper support for the pipe. This support may be achieved with a rigid, reinforced concrete
headwall or by warping the embankment till to provide the necessary balanced side support. Figure
31-5 provides guidelines for warping the embankment.

Figure 31-5: End Treatment of Skewed Flexible Culvert

31.6.4.2

Arches

Arches may require special shape control during the placement and compaction of structure backfill.

Prior to construction, the Manufacturer shall attend a preconstruction conference to advise the
Contractor and the Engineer of the critical functions to be performed during backfilling and to present
the intended quality control steps to be used to control loads, shapes, and movements.

Pin connections at the footing restrict uniform shape change. Arches may peak excessively or
experience curvature flattening in their upper quadrants during backfilling. Using lighter compaction
equipment, easily compacted structure backfill, or top loading by placing a small load of structure
backfill on the crown will aid installation.

31.6.4.3

Long-span Structural Plate Structures

Backfill requirements for long-span, structural-plate structures are similar to those for smaller
structures. Their size and flexibility require special control of backfill and continuous monitoring of
structure shape.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-12

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Equipment and construction procedures used to backfill long-span, structural-plate structures shall
be such that excessive structure distortion will not occur. Structure shape shall be checked regularly
while backfilling to verify acceptability of the construction methods used. Allowable shape changes
and  their  magnitudes  will  be  specified  by  the  Manufacturer,  or  the  Fabricator,  of  the  long-span
structures.  A  qualified  shape-control  inspector  shall  be  provided  by  the  Manufacturer  to  aid  the
Engineer during the placement of all structure backfill to the minimum cover level over the structure.
This inspector shall advise the Engineer on the acceptability of all backfill material and methods and
the proper monitoring of the shape.

Structure  backfill  material  shall  be  placed  in  horizontal,  uniform  layers  not  exceeding  a  200-mm,
loose lift thickness and shall be brought up uniformly on both sides of the structure. Each layer shall
be  compacted  to  a  density  not  less  than  90  percent  modified  density  per  AASHTO  T  180-10.
Structure  backfills  shall  be  constructed  to  the  minimum  lines  and  grades  shown  in  the  Contract
documents, keeping them at or below the level of adjacent soil or embankment. Exceptions to the
required structure backfill density shall be as follows:

a. Areas under the invert;

b. 300-mm to 450-mm widths of soil immediately adjacent to the large radius side plates of high-

profile arches and inverted-pear shapes; and,

c. Lower portions of the first horizontal lift of overfill carried ahead of and under the small,

tracked vehicle initially crossing the structure.

31.6.4.4

Box Culverts

When specified in the Contract document, or required by the Engineer, a preconstruction conference
on backfilling shall be required. Shape control considerations shall be similar to those needed for a
metal culvert. Metal box culverts are not long-span structures because they are relatively stiff, semi-
rigid frames.

Structure  backfill  materials  shall  be  placed  in  uniform,  horizontal  layers  not  exceeding  a  200-mm
maximum, loose lift thickness and compacted to a density not less than 90 percent modified density
per  AASHTO T  180-10. Structure  backfills shall be  constructed  to  the minimum  lines  and grades
shown  in  the  Contract  documents,  keeping  them  at  or  below  the  level  of  the  adjacent  soil  or
embankment.

31.6.4.5

Concrete Backfill

Concrete backfill shall be placed in the trench against undisturbed material at the sides and bottom
of the trench and in a manner that will prevent floating or shifting of the pipe, and voids in, or
segregation of, the concrete. Foreign material that falls into the trench, prior to or during placing of
the concrete, shall be immediately removed. Where necessary, earth plugs shall be constructed and
compacted at the ends of the planned concrete backfill to contain the concrete within the trench.

Concrete backfill surfaces shall be broomed with a heavy broom to produce a uniform rough surface,
if asphalt concrete is to be placed directly thereon. No material shall be placed on top of the concrete
backfill until eight hours after placing the concrete backfill.

Lean concrete backfill levels around culverts shall be determined by the Engineer, according to the
nature of soil surrounding the culvert.

31.6.5

Bracing

When required, temporary bracing shall be installed and shall remain in place as long as necessary
to protect workers and to maintain structure shape during erection.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-13

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

For long-span structures that require temporary bracing or cabling to maintain their shapes, the
Contractor shall not remove supports until backfill reaches an elevation that provides the necessary
support. In no case shall internal braces be left in place when backfilling reaches the top quadrant
of the pipe or the top radius arch portion of a long-span structure.

31.6.6

Arch Substructures and Headwalls

If not detailed in the Contract plans, the Contractor shall design the substructures and headwalls in
accordance with the applicable requirements of AASHTO LRFD

Bridge Design Specifications,

and

Road Structures Design Manual

ADQCC (TR-516)

Corrugated metal arch ends shall rest in a keyway formed into continuous concrete footings, or shall
rest on a metal bearing surface

— usually an angle or channel shape — that is securely anchored

to or embedded in the concrete footing.

When  specified,  the  metal  bearing  may  be  a  hot-rolled  or  cold-formed  galvanised  steel  angle  or
channel.  These  shapes  shall  not  measure  less  than  5  mm  in  thickness  and  shall  be  securely
anchored to  the footing at  a maximum  spacing of  0.6  m. When  the metal  bearing member  is  not
completely embedded in a keyway in the footing, the Contractor shall punch one vertical leg to allow
the bolting of the end of the corrugated plates to this leg of the bearing member.

Where an invert slab is provided that is not integral with the arch footing, the invert slab shall be
continuously reinforced.

31.6.7

Inspection Requirements for CMP

31.6.7.1

Visual Inspection

Inspections at the appropriate times during installation allow corrections to be made in assembly and
backfill practices. Construction inspection during early Project stages will allow the Contractor to
evaluate and, if necessary, modify construction and quality control practices.

CMP shall be inspected after placement in the trench, as required during backfilling, and after
completion of installation to ensure that final installation conditions allow the pipe to perform as
designed. Bedding and backfill material installations

— as well as their placement and compaction

— shall be determined to meet the requirements of this article.

During the initial phase of the installation process, inspections shall concentrate on detecting
improper practice and poor workmanship. Errors in line and grade

— as well as any improper

assembly or backfill techniques

— shall be corrected prior to placing significant backfill or trench fill.

Coupling bands shall be properly indexed with the corrugation and tightened, and bell and spigot
joints shall be properly seated to prevent the infiltration of soil fines. When used, gaskets shall not
bulge or hang into the pipe. If they are visible, gaskets shall appear uniformly oriented around the
pipe.

Racking or denting of the pipe shall be taken to indicate improper backfill placement and shall be
corrected by the Contractor. Wall sections damaged during installation shall be evaluated and then
repaired or the section of the pipe shall be replaced.

Coated pipes shall be inspected to ensure the coating has no cracks or scratches or locations of
peeling. Coatings shall be repaired in accordance with material specification requirements.

Final internal inspections shall be conducted on all buried CMP installations to evaluate issues that
may affect long-term performance. Final inspections shall be conducted no sooner than 30 days
after completion of installation and final fill. To ensure the minimum cover level is provided, the
Contractor shall check shallow cover installations.

These inspections will verify that bedding, backfill, and compaction requirements are followed during
installation. Pipes shall be checked for alignment, joint separation, cracking at bolt holes, localised

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-14

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

distortions, bulging, flattening, or racking. Minimum or near-minimum cover installations shall be
inspected prior to and immediately after vehicular load is applied.

31.6.7.2

Installation Deflection

Pipes shall be evaluated to determine whether the internal diameter of the barrel has been reduced
more than the limits set forth in this specification when measured not less than 30 days following
completion of installation.

Because of their broad diameter tolerances, metal pipes measuring 600 mm in diameter and smaller
typically are not deflection tested. A visual inspection shall be performed to check for denting or other
damage using a video camera conforming to Article 31.6.7.3, Internal Inspection of Culverts. If
deflection testing is required by the Owner or the Engineer

— or the visual inspection indicates

excessive deflection

— the Contractor shall use a device conforming to Article 31.6.7.3, Internal

Inspection of Culverts, and approved by the Engineer, that can physically verify the dimensions of
the pipe and is not limited by poor lighting, water flow, pipe length, or other limiting conditions of the
installed environment. If deflection testing is performed, deflection for metal pipes measuring 600
mm in diameter and smaller shall not exceed 7.5 percent of the pipe’s nominal diameter plus a
manufacturing tolerance

— as determined to be appropriate by the Owner or the Engineer.

Pipes measuring larger than 600 mm may be entered and deflection levels measured directly. In lieu
of direct measurements, the Contractor may use a calibrated video camera

— or any other device

approved by the Engineer

— that can physically verify the dimensions of the pipe and is not limited

by poor lighting, water flow, pipe length, or other limiting conditions of the installed environment.

In all installations of pipes measuring larger than 600 mm in diameter, at least 10 percent of the total
number of pipe runs representing at least 10 percent of the total pipe footage on the Project shall be
randomly selected by the Engineer and inspected for deflection. Also, as determined by the 100
percent visual inspection in Article 31.6.7.1, Visual Inspection, all areas in which deflection can be
visually detected shall be inspected for deflection.

Ten percent of each pipe installation shall be defined as 10 percent of the number of pipe runs, and
not less than 10 percent of the total length of installed pipe on the Project. Deflection testing
requirements are intended to serve as a minimum and do not limit the Owner from more stringent
requirements.

Where direct measurements are made, a measurement shall be taken once every 3 m for the length
of the pipe, and a minimum of four measurements per pipe installation is required.

Pipes  measuring  larger  than  600  mm  in  diameter  shall  be  evaluated  by  direct  measurement.
Deflection  shall  be  determined  by  comparing  span  and  rise  measurements  with  the  nominal pipe
diameter. Vertical deflection, such as a percentage, shall be expressed as the following:

100 x {

rise

diameter

− 1.0 }

Equation 31-1: Vertical deflection

Similarly, horizontal deflection shall be expressed as the following:

100 x {

span

diameter

− 1.0 }

Equation 31-2: Horizontal deflection

For  all round pipes measuring larger than 600 mm in diameter, including round and single radius
arch structural plates, deflections exceeding 7.5 percent the nominal diameter of the pipe plus the
manufacturing  tolerance  of  either  1  percent  of  the  nominal  diameter  or  12.5  mm,  whichever  is
greater,  shall  be  considered  as  indicative  of  poor  backfill  materials,  poor  workmanship,  or  both.
These pipes shall require remediation or replacement. Passing deflection criterion shall not eliminate
the Contract

or’s need to evaluate associated denting, racking, or other shape damage.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-15

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

For pipe arches, deflections resulting in a decrease in rise or increase in span exceeding 7.5 percent
shall be considered indicative of poor backfill materials, poor workmanship, or both. These pipes
shall require remediation or replacement. Passing deflection criterion shall not eliminate the
Contract

or’s need to evaluate associated denting, racking, or other shape damage.

Structural plate structures shall be inspected by direct measurement. They shall be assembled in
accordance  with  the  shape  tolerances  of  Section  31.5.3,  Assembly  of  long-span  structures.
Immediately  after  backfilling,  these  structures  shall  be  measured  to  check  for  any  immediate
deflections  that  occurred  during  the  backfilling operation.  After  30  days,  these  structures shall  be
measured again to check for any additional deflection. All deflection measurements shall be based
on design dimensions. For multiple radius structures, such as ellipses, pipe-arches, and low- and
high-profile arches, the crown (top) radius shall not increase by more than 10 percent of the design
radius

— as calculated from the measured middle ordinate off a suitable length straight edge. If the

top  radius  exceeds  the  design  value  by  more  than  10  percent,  or  if  the  structure  is  racked  or
unsymmetrical  by  more  than  2  percent,  it  shall  require  remediation.  Racking  degrees  or  loss  of
symmetry shall be determined by dropping a plumb line from the actual top centreline of the installed
structure and measuring the half spans that exist on  each side of the plumb line to the maximum
span line. For a symmetrical structure, these measurements at each individual cross section shall
be equal. Racking degrees or loss of symmetry shall be expressed as a percentage, as follows:

100 x {

half span A – half span B

span

} < 2

Equation 31-3: Racking degrees or loss of symmetry

31.6.7.3

Internal Inspection of Culverts

It is recommended that inspection personnel not enter culverts measuring less than 600 mm in
diameter. Internal inspection of culverts in this size range is best conducted using video cameras.
Culverts should only be entered by inspection personnel trained in working within confined spaces
and using procedures in full compliance with applicable

Owner’s EHS regulations and

Occupational

Safety and Health Administration

(OSHA)

Regulations

(Standards - 29 CFR).

For culvert pipes measuring 600 mm or less in diameter, or if requested by the Engineer for pipes
measuring up to 1,200 mm in diameter, the Contractor shall provide the Engineer a video DVD and
report using low-barrel distortion video equipment with laser profile technology, non-contact video
micrometer, and associated software that provides the following:

•

Actual recorded length and width measurements of all cracks within the pipe;

•

Actual recorded separation measurement of all pipe joints;

•

Pipe ovality report;

•

Deflection measurements and graphical diameter analysis report in terms of x and y axis;

•

Flat analysis report;

•

Representative diameter of pipe;

•

Pipe deformation measurements, leaks, debris, or other damage or defects; and,

•

Deviation in pipe line and grade, joint gaps, and joint misalignment.

Laser profiling and measurement technology must be certified by the company performing the work
and must be in compliance with the calibration criteria approved by the Engineer. Reports may be
submitted in electronic media, if approved by the Engineer.

For video recorded, laser-profiled pipes that indicate deflection and appears to be in excess of that
allowed by specification, the Engineer may require further testing. If directed by the Engineer, the
Contractor shall test pipes using a mandrel, which shall be pulled by hand and be approved by the
Engineer pri

or to use. If use of a mandrel is selected as the means of further testing, the mandrel’s

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-16

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

diameter, length, and other requirements shall conform to Sub-article b of Article 31.6.7.3. The
Contractor shall remove, replace, and retest pipe failing to meet the specific deflection requirements
for the type of pipe installed, at no cost to the Owner.

a. Video Report

The Contractor shall provide a high quality DVD in a MPEG2 format with a standard resolution of
720 by 480. The Contractor shall use a camera with lighting suitable to allow a clear picture of the
entire periphery of the pipe. Cameras shall be centred in the pipe both vertically and horizontally and
be able to pan and tilt to a 90-degree angle with the axis of the pipe and rotating 360 degrees. The
Contractor shall use equipment to move the camera through the pipe that will not obstruct the
camera’s view or interfere with proper documentation of the pipe’s condition.

Video images shall be clear, focused, and relatively free from roll, static, or other image distortion
qualities  that  prevent  the  reviewer  from  evaluating  the  condition  of  the  pipe.  Videos  will  include
identification before each section of pipe filmed, which will include the Project number, the structure
number corresponding to the structure number on the set of the Contract plans for the Project, size
of pipe, the date and time, and indicate which pipe is being filmed if multiple pipes are connected to
the  structure.  Notes  shall  be  taken  during  the  video  recording  process.  Copies  of  the  video  and
corresponding notes shall be provided by the Contractor to the Engineer.

Cameras shall move through the pipe at a speed not greater than 9 m per minute. Videos shall be
marked with the distance down the pipe. These distances shall have an accuracy of 300 mm per 30
m. The Contractor shall film the entire circumference at each joint and shall stop the camera and
pan when necessary to document defects.

b. Mandrels

The Contractor shall use mandrels that are rigid; nonadjustable; have an odd number of legs with a
minimum nine legs; and have a length not less than its nominal diameter. Diameters at any point
shall not be less than the allowed percent deflection of the certified actual mean diameter of the pipe
being tested. Mandrels shall be fabricated of metal, fitted with pulling rings at each end, and stamped
or engraved on some segment other than a runner with the nominal pipe size and mandrel outside
diameter.

31.7

Construction Precautions

Structures covered by this section shall be investigated for all critical stages in their installation and
in the final intended purpose. For construction loads, additional cover may be required beyond that
required in the final condition to which the design loads apply. In the absence of more specific
information, the cover depths in Table 31-4 may be considered for the smaller structures indicated.
Minimum covers indicated shall be increased when site conditions so indicate. Guidance for structure
spans or axle loads not listed shall be provided by the Manufacturer and approved by the Engineer.

Table 31-4: Minimum Cover for Construction Loads on Circular, Pipe-Arch, Elliptic, and

Underpass Shapes

Minimum Cover, m, for Indicated Axle Loads

Pipe Span

(80

– 222) kN

(222

– 333) kN

(333

– 490) kN

(490

– 667) kN

(0.3

– 1.0) m

0.6

0.75

0.9

(1.2

– 1.8) m

0.9

1.2

(2.0

– 3.0) m

0.9

1.2

(3.2

– 3.65) m

1.2

1.4

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-17

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

Any additional cover required to avoid damage to the pipe shall be provided by the Contractor.
Minimum cover shall be measured from the top of the pipe to the top of the maintained construction
roadway surface.

Surfaces shall be maintained to provide adequate cover until paving is completed, or until the Project
is accepted by the Owner, if paving is not required.

31.8

Salvaged Metal Culverts

31.8.1

Description

This section describes excavating and removing existing metal culverts and transporting, cleaning,
and reinstalling at new locations as per the Contract plans or the Engineer directions.

31.8.2

Construction

If existing culvert pipes are designated for salvage and use in the new work, the Contractor shall
remove them from the existing location and then clean, handle, transport, and install them at the new
location without damaging the culvert pipes. Any material damaged by this process shall be replaced
by the Contractor at no expense to the Owner.

Culvert pipes shall be constructed by the Contractor at the new location as specified in this chapter.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 31-18

HAPTER

31:

ETAL

ULVERTS

First Edition -January 2018

NDEX

additional cover, 16, 17
aluminium, 5, 6, 7
apron end walls, 4, 5
arches, 3, 5, 6, 11, 13, 15
Backfill material, 11
backfill materials, 6, 11, 13, 15
Bedding, 6, 11, 14
bituminous coating, 6
box structures, 3, 5
camera, 14, 16
circular, 3
compaction, 6, 9, 12, 14
Concrete backfill, 13
conduits, 3
corners, 11
corrections, 14

Corrugated

, 4, 5, 6, 7, 13

corrugation depth, 6, 11
culvert, 3, 4, 9, 13, 15, 17
deep corrugated structures, 3, 6, 7
Department of Transport, 31-2
downstream end, 7
existing metal culverts, 17
footings, 3, 11, 13
foundations, 9
galvanised, 5, 6, 13
geotextile, 8, 9
granular material, 6
headwalls, 3, 13
horizontal deflection, 15
horizontal elliptic, 3, 8, 11
inspection personnel, 15

installation, 5, 6, 9, 12, 14, 16
internal diameter, 14
invert slab, 3, 13
inverted pear, 3
Joint Overlap, 8
Joints, 7, 8
large-radius, 11
long-span structures, 3, 9, 11, 12, 13, 15
mandrels, 16
metal pipes, 3, 6, 7, 14
multiple radius arch, 3
paving, 17
pipe arches, 3, 5, 6
prestressing, 4
rational analysis, 8
salvage, 17
settlement, 9, 11
soil conditions, 8
Soil Tightness, 8
steel sheets, 5
structural plate metal pipes, 3
substructures, 3, 13
temporary bracing, 13
temporary drainage facilities, 9
trench conditions, 9
underpass, 3, 11
Vertical deflection, 15
Video images, 16
Water Tightness, 8
welding, 6
workmanship, 14, 15
Zinc-coated, 5

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page i

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Chapter 32: Precast Concrete Culverts

ABLE OF

ONTENTS

Table of Contents............................................................................................................................. i

List of Figures ................................................................................................................................. ii

List of Tables .................................................................................................................................. ii

Precast Concrete Culverts ............................................................................................... 32-1

32.1

General ........................................................................................................................ 32-1

32.2

Reference Standards and Codes ................................................................................. 32-1

32.3

Working Drawings ........................................................................................................ 32-2

32.4

Materials ...................................................................................................................... 32-2

32.4.1

Reinforced Concrete Culverts ............................................................................... 32-2

32.4.2

Joint Sealants ....................................................................................................... 32-3

32.4.2.1

General .......................................................................................................... 32-3

32.4.2.2

Cement Mortar ............................................................................................... 32-3

32.4.2.3

Bituminous Plastic Cement ............................................................................ 32-4

32.4.2.4

Flexible Watertight Gaskets ........................................................................... 32-4

32.4.2.5

Other Joint Sealant Materials ......................................................................... 32-4

32.4.3

Bedding and Backfill Materials .............................................................................. 32-5

32.5

Fabrication and Assembly ............................................................................................ 32-5

32.5.1

General ................................................................................................................. 32-5

32.5.2

Testing .................................................................................................................. 32-5

32.5.3

Lifting Holes .......................................................................................................... 32-5

32.5.4

Marking ................................................................................................................. 32-5

32.5.5

Tolerances ............................................................................................................ 32-5

32.5.6

Defects and Repair ............................................................................................... 32-6

32.5.7

Storage and Shipment .......................................................................................... 32-6

32.6

Installation ................................................................................................................... 32-6

32.6.1

General ................................................................................................................. 32-6

32.6.2

Joints .................................................................................................................... 32-6

32.6.3

Foundation Bedding and Backfill ........................................................................... 32-7

32.6.3.1

General .......................................................................................................... 32-7

32.6.3.2

Precast Reinforced Concrete Circular, Arch, and Elliptical Pipe ..................... 32-7

32.6.3.3

Precast Reinforced Concrete Box Sections ................................................. 32-13

32.6.4

Placing Culvert Sections ..................................................................................... 32-14

32.6.5

Haunch, Lower Side, and Backfill or Overfill ....................................................... 32-15

32.6.5.1

Precast Reinforced Concrete Circular Arch and Elliptical Pipe ..................... 32-15

32.6.5.2

Precast Reinforced Concrete Box Sections ................................................. 32-15

32.6.5.3

Placing of Haunch, Lower Side, and Backfill or Overfill ................................ 32-15

32.6.5.4

Cover Over Culvert During Construction ...................................................... 32-16

32.7

Field Inspection .......................................................................................................... 32-16

32.7.1

General ............................................................................................................... 32-16

32.7.2

Misalignment ...................................................................................................... 32-16

32.7.3

Joint Defects ....................................................................................................... 32-17

32.7.4

Longitudinal Cracks ............................................................................................ 32-17

32.7.5

Transverse Cracks .............................................................................................. 32-17

32.7.6

Spalls .................................................................................................................. 32-17

32.7.7

Slabbing ............................................................................................................. 32-18

32.7.8

End Section Drop-off .......................................................................................... 32-18

32.7.9

Follow-up ............................................................................................................ 32-18

32.8

Surface Finish ............................................................................................................ 32-18

32.9

Waterproofing ............................................................................................................ 32-18

32.10

Removing and Replacing Culverts ............................................................................. 32-18

Index 32-19

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-1

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

PRECAST CONCRETE CULVERTS

32.1

General

This work shall consist of fabricating, furnishing, installing, and inspecting buried precast concrete
culverts conforming to these specifications,

Road Structures Design Manual

(ADQCC TR-516),

Section 12 of the

American Association of State Highway and Transportation Officials

(AASHTO)

Load and Resistance Factor Design

(LRFD)

Bridge Design Specifications

, and the details shown in

the Contract documents. Precast, reinforced concrete pipe shall be circular, arch, or elliptical, as
specified in the Contract documents. Precast, reinforced concrete box sections shall be of the
dimensions specified in the Contract documents.

32.2

Reference Standards and Codes

Standards and codes for precast concrete culverts shall be as specified in these specifications, in
the Contract documents, if any, and the following, in their latest edition:

AASHTO LRFD American Association of State Highway and Transportation Officials - Load and

Resistance Factor Design, Bridge Construction Specifications;

AASHTO LRFD American Association of State Highway and Transportation Officials - Load and

Resistance Factor Design, Bridge Design Specifications;

AASHTO

Standard Specifications for Transportation Materials and Methods of Sampling
and Testing;

AASHTO

Soil Classification System;

ADQCC (TR-516) Road Structures Design Manual;

ASTM

American Society for Testing and Materials;

OSHA

Occupational Safety and Health Administration;

Standards - 29 CFR

OSHA Regulations;

USCS

Unified Soil Classification System.

Table 32-1 presents American Association of State Highway and Transportation Officials (AASHTO)
and American Society for Testing and Materials (ASTM) standards that are related to materials for
precast concrete culverts. It also includes designations and titles.

Table 32-1: Designations and titles for AASHTO and ASTM standards that apply to precast

concrete culverts construction works

AASHTO

Designation

ASTM

Designation

Title

AASHTO M

170-12

ASTM C76 - 12

Standard Specification for Reinforced Concrete Culvert,
Storm Drain, and Sewer Pipe

AASHTO M

242M/M 242-12

ASTM C655 - 12

Standard Specification for Reinforced Concrete D-Load
Culvert, Storm Drain, and Sewer Pipe

AASHTO M

206M/M 206-12

ASTM C506 - 12

Standard Specification for Reinforced Concrete Arch
Culvert, Storm Drain, and Sewer Pipe

AASHTO M

207M/M 207-10

ASTM C507 - 12

Standard Specification for Reinforced Concrete Elliptical
Culvert, Storm Drain, and Sewer Pipe

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-2

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

AASHTO

Designation

ASTM

Designation

Title

AASHTO M

198-10

ASTM C990 - 09

Standard Specification for Joints for Concrete Pipe,
Manholes, and Precast Box Sections Using Preformed
Flexible Joint Sealants

AASHTO M

315-06

ASTM C443 - 12

Standard Specification for Joints for Concrete Pipe and
Manholes, Using Rubber Gaskets

AASHTO M

273-11

ASTM C1433 -

Standard Specification for Precast Reinforced Concrete
Monolithic Box Sections for Culverts, Storm Drains, and
Sewers

ASTM D2939-03

Standard Test Methods for Emulsified Bitumens Used as
Protective Coatings (Withdrawn 2012)

ASTM D128 -

98(2008)

Standard Test Methods for Analysis of Lubricating
Grease

ASTM D2487 -

Standard Practice for Classification of Soils for
Engineering Purposes (Unified Soil Classification
System)

AASHTO M

259-11

ASTM C1433 -

Standard Specification for Precast Reinforced Concrete
Monolithic Box Sections for Culverts, Storm Drains, and
Sewers

AASHTO T187-

1992

Standard Method of Test For Concrete Joint Sealers

AASHTO M

145-91 (2008)

ASTM D3282 -

Standard Practice for Classification of Soils and Soil-
Aggregate Mixtures for Highway Construction Purposes

32.3

Working Drawings

When complete details are not provided in the Contract plans or Contract documents, the Contractor
shall  submit  working  drawings  and  substantiating  calculations  of  the  proposed  structure  or
installation system. Fabrication or installation of the structure shall not begin until the Engineer has
approved  the  drawings.  Working  drawings  shall  show  complete  details  and  substantiating
calculations of the structure, the materials, equipment, and installation methods proposed.

Working drawings shall be submitted in advance of the start of the work to allow for their review,
revision, and approval without delay to the work. Approval by the Engineer shall not relieve the
Contractor of any contractual responsibility.

32.4

Materials

Materials for precast concrete culverts shall comply with the requirements outlined in this section.

32.4.1

Reinforced Concrete Culverts

Reinforced concrete culvert materials shall meet the requirements of the classes and sizes specified
in Table 32-2.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-3

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Table 32-2: Reinforced Concrete Culvert Specification Requirements

Type

Specification

Circular pipe

AASHTO M 170-12 (ASTM C76 - 12) or
AASHTO M 242M/M 242-12 (ASTM C655 - 12)

Arch pipe

AASHTO M 206M/M 206-12 (ASTM C506 - 12)

Elliptical pipe

AASHTO M 207M/M 207-10 (ASTM C507 - 12)

Box sections

AASHTO M 259-11 and AASHTO M 273-11 or
ASTM C1433 - 10

32.4.2

Joint Sealants

32.4.2.1

General

A certificate of compliance shall be submitted by the Contractor to the Engineer stating that the
furnished material conforms to the joint property requirements.

Design and production tolerances for the annular space within the manufactured joint will determine
the type of joint required when sealing the joints, per the manufacturer.

When the annular space within the pipe joints, also known as the algebraic difference in diameters
measured between the exterior edges of the pipe at the spigot end and the interior faces of the hub
at the shoulder of the joint, falls within the following ranges shown in Table 32-3, the type sealer
noted thereafter will be used.

Table 32-3: The Annular Space Range and the Type Sealer

Total Annular Space

Type Sealer

6 mm or less

Bituminous plastic cement

6 mm to 13 mm

Mortar or bituminous plastic cement as elected by

the Contractor

13 mm or more

Mortar

32.4.2.2

Cement Mortar

Mortar shall be composed of one part cementitious material as defined in Section 4.3.1 of Chapter
4, Concrete Works, of these standard specifications, and two parts sand by volume. Sand shall be
well  graded  and  of  such  size  that  all  will  pass  sieve  No.  8,  which  shall  measure  2.4  mm.  These
materials  shall  be  mixed  to  a  consistency  suitable  for  the  purpose  intended  and  used  within  30
minutes  after  the  water  mixture  has  been  added.  Admixtures,  if  any,  shall  be  approved  by  the
Engineer prior to use.

a. Placing Cement Mortar

When placing cement mortar, the Contractor shall clean the lower portion of the receiving end of the
pipe and shall plaster the inside with sufficient joint mortar to bring the inner surfaces of the abutting
pipe sections flush and even. These sections shall be fitted by the Contractor as close as the
construction of the culvert permits. Joints shall be filled and sealed with mortar inside and out. Excess
mortar shall be cleaned from the inside of the joint by the Contractor.

Mortar shall be cured outside of joints by covering with polyethylene sheeting or spraying with a
curing compound. The Contractor shall backfill while mortar is plastic. If mortar sets before backfilling
operations occur, the Contractor shall wait at least 24 hours before backfilling.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-4

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

32.4.2.3

Bituminous Plastic Cement

Bituminous plastic cement meeting the specifications noted in this article, or other kinds of mastic
joint sealer that the Engineer has approved, shall be used on joints whose design or manufacturing
process produces an annular space within the limits noted in Table 32-3.

Bituminous joint sealing compounds may be applied cold for sealing the joints of bell and spigot or
tongue and groove culvert pipe. Material furnished shall be composed of a steam-refined petroleum
asphalt dissolved in a suitable solvent and stiffened with a mineral filler.

a. Properties of Bituminous Plastic Cement

Bituminous plastic cement shall consist of a smooth uniform mixture, not thickened or livered, and it
shall show no separation that cannot be easily overcome by stirring. Consistencies and properties
of these materials shall permit their application by the Contractor with a trowel, putty knife, or caulking
compound gun without pulling or drawing. When applied to the joint surfaces, these materials shall
exhibit good adhesive and cohesive properties. The material shall meet the requirements specified
in Table 32-4.

Bituminous plastic cement shall set to a rough, plastic coating, free from blisters, when applied in a
layer 1.5 mm to 3 mm thick on a tinned metal panel and cured at room temperature for 24 hours.

Table 32-4: Bituminous Plastic Cement Material Requirements

Minimum

Maximum

Grease cone penetration

175

250

Unit weight in kilograms per litre

1.17

Non-volatile

Ash, by ignition, by weights or masses

Methods of tests shall be in accordance with the following:

Grease cone penetration

AASHTO T187-1992

Non-volatile

ASTM D2939-03

Ash

ASTM D128 - 98(2008)

32.4.2.4

Flexible Watertight Gaskets

Flexible watertight, gasketed joints shall conform to the requirements of AASHTO M 198-10 (ASTM
C990 - 09) or AASHTO M 315-06 (ASTM C443-12) and shall be flexible and capable of withstanding
expansion, contraction, and settlement of the pipeline.

All rubber gaskets shall be stored in as cool a place as practicable, preferably at 21 degrees Celsius
or less.

Rubber gaskets that require lubrication shall be lubricated with the lubricant recommended and
supplied by the pipe manufacturer.

32.4.2.5

Other Joint Sealant Materials

Other joint sealant materials shall be submitted for testing in advance of their use and shall not be
used prior to receiving approval from the Engineer.

Other materials for joint sealant may include the following:

a. Oakum and mortar;

b. Oakum and joint compound;

c. Coupling bands; and,

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-5

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

d. Preformed plastic sealing compound.

32.4.3

Bedding and Backfill Materials

Bedding and backfill materials shall conform to the provisions of Section 32.6, "Installation."

32.5

Fabrication and Assembly

32.5.1

General

Precast concrete units or elements shall be fabricated in accordance with the applicable
requirements of Section 21.17 of Chapter 21, Concrete Structures, of these standard specifications,
and assembled in accordance with the manufacturer's instructions. All units or elements shall be
handled with reasonable care and shall not be rolled or dragged over gravel or rock. Care shall be
taken to prevent the units from striking rock or other hard objects during placement.

32.5.2

Testing

Test specimens shall be produced by the Contractor in accordance with Sections 21.3.3 and 21.5.2
of Chapter 21, Concrete Structures, of these standard specifications. All equipment required for
testing concrete for boxes produced in a precasting plant shall be furnished by the producer.

32.5.3

Lifting Holes

For precast boxes, the Contractor shall provide no more than four lifting holes in each section. Lifting
holes may be cast, cut into fresh concrete after form removal, or drilled and shall be of a sufficient
size for adequate lifting devices based on the size and weight of the box selection. Lifting holes
measuring larger than 75 mm in diameter shall not be used. When locating lift holes, the Contractor
shall not cut more than one longitudinal wire or two circumferential wires per layer of reinforcing
steel. Spalled areas around lifting holes shall be repaired by the Contractor.

32.5.4

Marking

Precast boxes shall be marked by the Contractor with the following:

•

Name or trademark of the producer;

•

Date of manufacture;

•

Box size;

•

Minimum and maximum fill heights; and,

•

Match marks for proper installation, when required, under Section 32.5.5, Tolerances.

For boxes without lifting holes, the Contractor shall mark one end of each box section on the inside
and outside walls to indicate the top or bottom

— as it will be installed. Markings shall also be

indented into the box section, or the Contractor shall paint them on each box with waterproof paint.

32.5.5

Tolerances

Precast sections, of either type, shall meet the following requirements:

a. The inside vertical and horizontal dimensions shall not vary from the Contract plan

requirements by more than 12.5 mm, or 1 percent, whichever is greater.

b. The horizontal or vertical plane at each end of the box section shall not vary from the

perpendicular by more than 12.5 mm, or 1 percent, whichever is greater, when measured on
the inside faces of the section.

c. The sides of a section at each end shall not vary from being perpendicular to the top and

bottom by more than 12.5 mm, or 1 percent, whichever is greater, when measured diagonally
between opposite interior corners.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-6

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Wall and slab thicknesses shall not measure less than what is shown in the Contract plans and in
the approved working drawings

— except for occasional deficiencies not greater than 6 mm, or 5

percent, whichever is greater. If proper jointing is not affected, the Contractor may use thicknesses
in excess of plan requirements.

Deviations from the above tolerances will be acceptable if the sections can be fitted at the plant, or
jobsite, and the joint opening at any point does not exceed 25 mm. Match marks shall be used by
the Contractor for proper installation on sections that have been accepted in this manner.

32.5.6

Defects and Repair

Fine cracks along surfaces that do not extend to the plane of the nearest reinforcement are
acceptable

— unless the cracks are numerous and extensive. Cracks that extend into the plane of

the reinforcing steel shall be repaired by the Contractor in an approved manner. Excessive damage,
honeycombs, or cracking will be subject to structural review. Repaired boxes that are sound, properly
finished, and cured in conformance with pertinent specifications may be accepted by the Engineer.
When fine cracks on the surface indicate poor curing practices, the Contractor shall discontinue
further production of precast sections until corrections are made and proper curing is provided.

32.5.7

Storage and Shipment

Precast sections shall be stored on a level surface by the Contractor. These sections shall not hold
any load until design strength is reached and curing is complete. Shipment of sections shall occur
when the design strength and curing requirements have been met.

32.6

Installation

32.6.1

General

Cracks in an installed precast concrete culvert that exceed 0.25 mm in width shall be appraised by
the Engineer and assessed for structural integrity, environmental conditions, and the design service
life of the culvert. Cracks having greater widths, or otherwise determined to be detrimental, shall be
sealed by a method approved by the Engineer.

For trench conditions, the trench shall be excavated to the dimensions and grade specified in the
Contract documents

— or as directed by the Engineer. Provisions shall be made by the Contractor

as required to insure adequate drainage of the trench to protect the bedding during construction
operations.

Proper preparation of foundations; placement of foundation materials, where required; and
placement of bedding materials shall precede the installation of the culvert. This work shall include
necessary levelling of the native trench bottom, or the top of foundation materials; as well as the
placement and compaction of required bedding material to a uniform grade so that the entire length
of pipe shall be supported on a uniformly, slightly yield of bedding. Backfill materials shall be placed
and compacted around the culvert in a manner to meet the requirements specified.

Materials used for foundation improvements, bedding, and structure backfill shall have gradations
compatible with adjacent soils to avoid migration. Where material gradations cannot be properly
controlled, adjacent materials shall be separated with a suitable geotextile.

32.6.2

Joints

Joints for reinforced concrete pipe and precast reinforced concrete box sections shall comply with
the details shown in the Contract documents and in the approved working drawings. Each joint shall
be sealed to prevent infiltration of soil fines or water, as required by the Contract documents. Field
tests may be required by the Engineer whenever there is a question regarding compliance with the
Contract requirements.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-7

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

32.6.3

Foundation Bedding and Backfill

32.6.3.1

General

If rock strata or boulders are encountered under the culvert within the limits of the required bedding,
the rock or boulders shall be removed and replaced with bedding material. Foundations shall be
comprised of stiff to hard in situ soil, stabilized soil, or compacted fill material. If the foundation is
rock or other unyielding soil, then a minimum bedding thickness of 150 mm, or 2 percent of the fill
height

— whichever is greater — shall be considered. Where, in the opinion of the Engineer, the

natural foundation soil is such as to require stabilization, such material shall be replaced by a layer
of bedding material. Where unstable or unsuitable material, such as peat or muck, is encountered at
or below invert elevation during excavation, the necessary subsurface exploration and analysis shall
be made and corrective treatment shall be as directed by the Engineer.

Where rock or other unyielding foundations exist and blasting is anticipated, the Engineer may
require that suitable steps be taken to protect the pipe.

32.6.3.2

Precast Reinforced Concrete Circular, Arch, and Elliptical Pipe

The bedding of the class, specified in the Contract documents or in the working drawings, shall be
provided. Installation types specified shall conform to one of the types of installation given in Table
32-5 and Table 32-6 and the details shown in Figure 32-1 through Figure 32-8, which define soil
areas and critical dimensions for circular, arch, and elliptical pipes.

Table 32-5 and Table 32-6 list general soil types, minimum compaction requirements, and minimum
bedding thicknesses for the four standard installation types for embankment and trench installations,
respectively.

Figure 32-1: Standard Embankment Installation for Round Pipe

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-11

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Figure 32-8: Trench Beddings for Vertical Elliptical Pipe

Table 32-5: Standard Embankment Installation Soils & Minimum Compaction Requirements

Installation

type

Bedding

thickness

Haunch and outer

bedding

Lower

side

Type 1

For soil foundations, B

/24

minimum, not less than 75 mm.
For rock foundations, use B

/12

minimum, not less than 150
mm.

95% (A1, A3 or
SW)

90% (A1, A3 or SW),
95% (A2, A4 or ML),
or 100% (A5, A6 or
CL)

Type 2 – installations
are available for
horizontal elliptical,
vertical elliptical, and
arch pipe

For soil foundations, B

/24

minimum, not less than 75 mm.
For rock foundations, use B

/12 minimum, not less than 150
mm.

90% (A1, A3 or
SW), or 95% (A2,
A4 or ML)

85% (A1, A3 or SW),
90% (A2, A4 or ML),
or 95% (A5, A6 or
CL)

Type 3 – installations
are available for
horizontal elliptical,
vertical elliptical, and
arch pipe

For soil foundations, B

/24

minimum, not less than 75 mm.
For rock foundations, use B

/12 minimum, not less than 150
mm.

85% (A1, A3 or
SW), 90% (A2, A4
or ML), or 95%
(A5, A6 or CL)

85% (A1, A3 or SW),
90% (A2, A4 or ML),
or 95% (A5, A6 or
CL)

Type 4

For soil foundations, no
bedding required.
For rock foundations, use B

/12 minimum, not less than 150
mm.

No compaction
required, except if
(A5, A6 or CL),
use 85% (A5, A6
or CL)

No compaction
required, except if
(A5, A6 or CL), use
85% (A5, A6 or CL)

The following interpretations apply to Table 32-5:

a. Compaction and soil symbols, such as 95 percent (A1, A3, or SW), shall be taken to refer to

(A1, A3, or SW) soil material with minimum standard proctor compaction of 95 percent.
Equivalent modified proctor values shall be as given in Table 32-7.

b. Soil in the outer bedding, haunch, and lower side zones, except within B

/3 from the pipe

spring line, shall be compacted to at least the same compaction as the majority of soil in the
overfill zones.

c. The minimum width of a subtrench for Type 1 through Type 3 installation shall be B

+0.6 m

or 1.33 B

, whichever is greater or wider

— if required for adequate space to attain the

specified compaction in the haunch and bedding zones.

d. A subtrench is defined as a trench in the natural material under an embankment used to

retain bedding material with its top below finished grade by more than 10 percent of the depth
of soil cover on the top of the culvert or pipe, or, for roadways, its top is at an elevation lower
than 300 mm below the bottom of the pavement base material.

e. For subtrenches with walls of natural soil, any portion of the lower side zone in the subtrench

wall shall be at least as firm as an equivalent soil placed to the compaction requirements
specified for the lower side zone and as firm as the majority of soil in the overfill zone, or shall
be removed and replaced with soil compacted to the specified level.

f. Only Type 2 and 3 installations are available for horizontal elliptical, vertical elliptical, and

arch pipe.

g. The required bedding thickness is the thickness of the bedding after placement of the pipe

on the bedding and is prior to placement of the backfill.

Table 32-6: Standard Trench Installation Soils and Minimum Compaction Requirements

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-12

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Installation

type

Bedding

thickness

Haunch and

outer bedding

Lower

side

Type 1

For soil foundations, B

/24

minimum, not less than 75
mm.
For rock foundations, use
B

/12 minimum, not less

than 150 mm.

95% (A1, A3 or
SW)

90% (A1, A3 or
SW),
95% (A2, A4 or ML),
100% (A5, A6 or
CL), or natural soils
of equal firmness

Type 2

–

installations are
available for
horizontal elliptical,
vertical elliptical,
and arch pipe

For soil foundations, B

/24

minimum, not less than 75
mm.
For rock foundations, use B

/12 minimum, not less than
150 mm.

90% (A1, A3 or
SW),
or 95% (A2, A4
or ML)

85% (A1, A3 or
SW),
90% (A2, A4 or ML),
95% (A5, A6 or CL),
or natural soils of
equal firmness

Type 3

–

installations are
available for
horizontal elliptical,
vertical elliptical,
and arch pipe

For soil foundations, B

/24

minimum, not less than 75
mm.
For rock foundations, use B

/12 minimum, not less than
150 mm.

85% (A1, A3 or
SW),
90% (A2, A4 or
ML), or
95% (A5, A6 or
CL)

85% (A1, A3 or
SW),
90% (A2, A4 or ML),
95% (A5, A6 or CL),
or natural soils of
equal firmness

Type 4

For soil foundations, no
bedding required.
For rock foundations, use B

/12 minimum, not less than
150 mm.

No compaction
required, except if
(A5, A6 or CL),
use 85% (A5, A6
or CL)

85% (A1, A3 or
SW),
90% (A2, A4 or ML),
95% (A5, A6 or CL),
or natural soils of
equal firmness

The following interpretations apply to Table 32-6:

a. Compaction and soil symbols, such as 95 percent (A1, A3, or SW), shall be taken to refer to

(A1, A3, or SW) soil material with minimum standard proctor compaction of 95 percent.
Equivalent modified proctor values shall be as given in Table 32-7.

b. Trench top elevation shall be no lower than 0.1

below finish grade, or for roadways, its top

shall be no lower than an elevation of 300 mm below bottom of pavement base material.

c. Soil in bedding and haunch zones shall be compacted to at least the same compaction as

specified for the majority of soil in the backfill zone.

d. The minimum trench width for Type1 through Type 3 installation shall be B

+0.6 m or 1.33

, whichever is greater, or wider, if required for adequate space to attain the specified

compaction in the haunch and bedding zones.

e. For trench walls that are within 10 degrees of vertical, the compaction or firmness of the soil

in the trench walls and lower side zone need not be considered.

f. For trench walls with greater than 10-degree slopes that consist of embankment, the lower

side shall be compacted to at least the same compaction as specified for the soil in the backfill
zone.

g. Only Type 2 and 3 installations are available for horizontal elliptical, vertical elliptical, and

arch pipe.

h. The required bedding thickness is the thickness of the bedding after placement of the pipe

on the bedding and is prior to placement of the backfill.

AASHTO M 145-91 (2008) (ASTM D3282

– 09), ASTM D2487 - 11, and Unified Soil Classification

System (USCS) soil classifications equivalent to the generic soil types in the standard installations
may be taken from Table 32-7.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-13

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Table 32-7: Equivalent USCS and AASHTO Soil Classifications for SIDD Soil Designations

*SIDD Soil

Representative Soil Types

Percent Compaction

USCS

AASHTO

Modified Proctor

Gravelly Sand

SW, SP, GW, GP

A1, A3

Sandy Silt

GM, SM, ML

Also GC, SC with than 20
percent passing a No. 200
sieve

A2, A4

Silty Clay

GL, MH, GC, SC

A5, A6

Not allowed for haunch or
bedding

*Standard Installation Direct Design Soil

32.6.3.3

Precast Reinforced Concrete Box Sections

Unless otherwise permitted herein, a bedding shall be provided for the type of installation specified
conforming to Figure 32-9, unless in the opinion of the Engineer, the natural soil provides a suitable
bedding.

Bedding material may be granular material, all of which passes a 9.5-mm sieve and not more than
10 percent of which passes sieve No. 200, measuring

75 μm. Backfill shall be selected material and

shall be free of organic material, rock fragments larger than 75 mm in the greatest dimension, and
shall have moisture content within the units required for compaction.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-14

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

Figure 32-9: Bedding and Backfill Requirements

32.6.4

Placing Culvert Sections

Unless otherwise authorized by the Engineer, the laying of culvert sections on the prepared bedding
shall be started at the outlet and with the bell end pointing upstream and the spigot or tongue end
pointing downstream and shall proceed toward the inlet end with the abutting sections properly
matched, true to the established lines and grades. Where pipe with bells is installed, bell holes shall
be excavated in the bedding to such dimensions that the entire length of the barrel of the pipe will
be supported when properly installed

— as shown in Figure 32-10. Proper facilities shall be provided

for hoisting and lowering the sections of culvert into the trench without disturbing the prepared
bedding and the sides of the trench. Section ends shall be carefully cleaned before the section is
jointed. Sections shall be fitted and matched so that when laid in the bed they shall form a smooth,
uniform conduit. When elliptical pipe with circular reinforcing or circular pipe with elliptical reinforcing
is used, the pipe shall be laid in the trench in such position that the markings "Top" or "Bottom," shall
not be more than five degrees from the vertical plane through the

pipe’s longitudinal axis.

Adjustments in grade by exerting force on the culvert with excavating equipment or by lifting and
dropping the culvert shall be prohibited. If the installed culvert section is not on grade after joining,
the section shall be completely un-joined, the grade corrected, and the section rejoined.

Figure 32-10: Excavation of Bell Holes for Uniform Support

Multiple installations of reinforced concrete culverts shall be laid with the centre lines of individual
barrels parallel at the spacing shown in the Contract documents. Pipe and box sections used in
parallel installations require positive lateral bearing between the sides of adjacent pipe or box
sections. Compacted earth fill, granular backfill, or grouting between the units is considered means
of providing positive bearing.

The joint ends, when using rubber gaskets, shall be protected from mud, silt, gravel, or other
unwanted material. The pipe sections with gaskets attached shall be laid, removed, cleaned, and
relubricated. Gaskets disturbed or contaminated shall be reseated.

The joints shall be forced-home using the pipe

manufacturer‘s recommended procedure. Driving or

ramming by hand or machinery shall not be done. The last section of each day's run shall be blocked
to prevent creep.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-15

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

A dike or plug of impervious material shall be placed near the intake end of the culvert to prevent
piping. The dike shall measure 0.6 m long and adequately surround the pipe to form an impervious
barrier.

The ends of the pipe or pipe arch shall be rigidly supported to prevent movement before and during
the construction of end walls or headers.

Culverts shall not be left extending beyond the staked limits, unless approved by the Engineer.

32.6.5

Haunch, Lower Side, and Backfill or Overfill

32.6.5.1

Precast Reinforced Concrete Circular Arch and Elliptical Pipe

Haunch, low side, and overfill materials shall be installed to the limits shown in Figure 32-1 through
Figure 32-8.

32.6.5.2

Precast Reinforced Concrete Box Sections

Backfill material shall be installed to the limits shown in Figure 32-9 for the embankment or trench
condition.

32.6.5.3

Placing of Haunch, Lower Side, and Backfill or Overfill

Fill material shall be placed in layers with a maximum loose thickness of 200 mm and compacted to
obtain the required density. These materials shall be placed and compacted with care under the
haunches of the culvert and shall be raised evenly and simultaneously on both sides of the culvert.
For the lower haunch areas of Type 1, 2, and 3 standard installations, soils requiring 90 percent or
greater standard proctor densities shall be placed in layers with a maximum thickness of 200 mm
and compacted to obtain the required density. Trench widths shall be kept to the minimum required
for installation of the culvert. Ponding or jetting will be only by the permission of the Engineer.

Backfill shall be placed in horizontal layers, and shall not be placed against concrete less than seven
days old or until 80 percent of the design strength is achieved.

Backfill for the most shapes of culverts is explicated in the following:

a. Pipe Culverts

Material shall be placed and compacted in evenly balanced layers on each side of each pipe culvert.
The Contractor shall backfill according to one of the following:

1. Pipe Culverts with Compacted Backfill

Backfill material shall be placed and compacted to a height of 0.3 m above the top of the
pipe. Backfilling the trench shall be completed by the Contractor with suitable roadway
excavation or unclassified borrow.

2. Pipe Culverts with Lean Concrete Backfill

Pipe shall be placed and staked to prevent floating and movement.

Lean concrete backfill shall be mixed and placed by pug-mill, rotary drum, or other approved
mixer to obtain a uniform mix. Lean concrete backfill shall be placed in a uniform manner that
prevents voids in, or segregation of the backfill.

When backfilling around culverts and other structures, lean concrete backfill shall be placed
in a manner that does not float or shift the structure. Backfill shall be brought up evenly on all
sides of the structure.

Lean concrete backfill levels around culverts shall be determined by the Engineer, according
to the nature of the soil in which the culverts will be placed.

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-16

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

b. Arch Culverts with Headwalls

When backfilling culverts with headwalls, the Contractor shall backfill according to one of the
following:

1. Before Headwalls Placement

Material backfilled first shall be placed and compacted midway between the ends of the arch.

Backfill material shall be placed and compacted in layers on both sides of the arch to form as
narrow a ramp as possible.

Ramps shall be built evenly on both sides until reaching the top of the arch.

Backfill materials remaining shall be placed from the top of the ramp working both ways to
the ends.

Backfill materials shall be compacted evenly in layers on both sides of the arch.

2. After Headwalls Placement

Materials backfilled first shall be placed and compacted adjacent to one headwall.

Backfill materials shall be placed and compacted evenly in layers on both sides of the arch
adjacent to the headwall until reaching the top of the arch.

Backfill materials remaining shall be placed from the top of the arch working toward the other
headwall.

Backfill materials shall be compacted evenly in layers on both sides of the arch.

32.6.5.4

Cover Over Culvert During Construction

If the passage of construction equipment over an installed culvert is necessary during the Project
construction, compacted overfill in the form of a ramp shall be constructed to a minimum elevation
of 0.9 m over the top of the culvert or to a height such that the equipment loads on the culvert do not
exceed the culvert design strength. In an embankment installation, the overfill shall extend a
minimum of one culvert diameter width or 0.9 m, whichever is greater, beyond each side of the
culvert to prevent possible lateral displacement of the culvert. If a large volume of construction traffic
must cross an installed culvert, the point of crossing shall be changed occasionally to minimize the
possibility of lateral displacement.

32.7

Field Inspection

32.7.1

General

Internal inspections shall be conducted on all buried rigid pipe installations to evaluate issues that
may affect long-term performance, such as cracks, joint quality, and alignment. Inspections shall be
conducted no sooner than 30 days after completion of installation and final fill.

It is recommended that inspection personnel not enter culverts less than 600 mm in diameter.
Internal inspection of rigid culverts in this size range is best conducted using video cameras. Culverts
shall only be entered by inspection personnel trained in working within confined spaces and using
procedures in full compliance with applicable

Abu Dhabi Road Regulations

and

Occupational Safety

and Health Administration

(OSHA)

Regulations

(Standards - 29 CFR).

32.7.2

Misalignment

Misalignment may be taken to indicate the presence of problems in the supporting soil or the
Contractor grade control.

Culvert barrel’s vertical and horizontal alignments shall be checked by the

Contractor by sighting along the crown, invert, and sides of the culvert, and by checking for
differential movement or settlement at joints between pipe sections. Vertical alignments shall be
checked for sagging, faulting, and invert heaving. Pipes laid with camber or a grade change shall be

TANDARD

ONSTRUCTION

PECIFICATIONS

ART

–

OAD

TRUCTURES

Page 32-17

HAPTER

32:

RECAST

ONCRETE

ULVERTS

First Edition -January 2018

accounted for by the Contractor. Horizontal alignments shall be checked for straightness or smooth
curvature.

32.7.3

Joint Defects

Leaking joints may be detected during low flows by visual observation of the joints, by checking
around the ends of the culvert for evidence of piping, and if required in the Contract documents, by
special testing methods typically employed for sanitary sewers.

Differential movement, cracks, spalling, improper gasket placement, movement or settlement of pipe
sections, and leakage shall be noted in the inspection report. Severe joint cracks are similar in
significance to separated joints.

Joint separations greater than the pipe manufacturer's maximum limit shall be considered significant
because they can accelerate damage caused by exfiltration and infiltration, resulting in the erosion
of the backfill material. Exfiltration occurs when leaking joints allow water flowing through the pipe to
leak into the supporting material. Infiltration is the reverse of exfiltration. Open joints, staining at the
joints on the sides and top of the culvert, deposits of soil in the culvert, or depressions over the
culvert are indicative of infiltration.

Evidence of any soil migration through the joint warrants further investigation by the Contractor to
determine the source, and if repair or replacement is required.

32.7.4

Longitudinal Cracks

Hairline longitudinal cracks in the crown or invert indicate that the steel has accepted part of the load.
Cracks equal to or less than 0.25 mm in width are considered minor and only need to be noted in
the inspection report.

Other signs of distress, such as differential movement, efflorescence, spalling, or rust stains shall
also be noted. When cracks are wider than 0.25 mm, measurements shall be taken of the width,
length, and locations of the cracks and diameter of the pipe, both horizontally and vertically. An
evaluation shall be conducted by the Contractor and shall be submitted to the Engineer for review
and approval considering the structural integrity, environmental conditions, and the design service
life of the culvert.

Cracks having widths equal to or greater than 0.25 mm and determined to be detrimental shall be
sealed by a method approved by the Engineer. Pipes with cracks having widths greater than 2.5 mm
and determined by the Engineer to be beyond satisfactory structural repair shall be remediated or
replaced. Pipes having displacement across the crack shall be repaired or replaced.

Inspection records for pipes with crack widths exceeding 0.25 mm, shall be kept on file for monitoring
conditions during subsequent inspections. Crack measurements and photographs shall be taken for
monitoring conditions during subsequent inspections.

32.7.5

Transverse Cracks

Poor bedding may cause transverse or circumferential cracks and is a result of poor installation
practices, such as not providing indentations, or bell holes, in hard foundation material for the end of
the bell- and spigot-type pipe; or, not providing a sufficient depth of suitable bedding material.

Where transverse cracks are observed, the Contractor shall monitor them as described in Section
32.7.4, Longitudinal Cracks.

32.7.6

Spalls

Spalling is a fracture of the concrete parallel or inclined to the surface of the concrete. In precast
concrete pipe, spalls often occur along the edges of either longitudinal or transverse cracks when
the crack is due to overloading or poor support rather than simple tension cracking.

Spalling may be detected by visual examination of the concrete along the edges of cracks. Tapping
with a hammer shall be performed along the cracks to check for areas that have fractured but are

Abu Dhabi, United Arab Emirates. STANDARD CONSTRUCTION SPECIFICATIONS (PART 2 - ROAD STRUCTURES, 2020) - page 20