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

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Performance Test:

Application of an incremental cyclic test load, including an alignment load, to

an anchor while recording the

anchor’s total movement at each increment.

Permanent Anchor: Any prestressed anchor intended for permanent use, generally with a service
life greater than 24 months.

Post Grouting: Grouting an anchor a second time after primary grout has set.

Prestressing Steel:

A group of steel strands that combine to form a tendon or a high strength steel

bar.

Primary Grout: Portland cement grout that is injected into an anchor hole before or after the
installation of the anchor tendon to transfer force to the surrounding ground along the bonded length
of the tendon.

Proof Test Load:

An incremental load applied to an anchor while recording the total movement

of the anchor at each increment.

Temporary Anchor:

A prestressed anchor intended for temporary use, generally with a service life

of less than 24 months. Temporary anchors installed in corrosive environments may require
corrosion protection.

Test Anchor: An anchor installed before the installation of the production anchors to which load is
applied to verify design parameters.

Test Load (TL):

Maximum load to which an anchor is subjected during testing.

Total Anchor Length:

A total of a tendon’s unbonded length plus its bond length.

19.2

Reference Standards and Codes

Standards and codes for Ground Anchors 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;

•

ADQCC (TR-516)

Road Structures Design Manual;

ASTM American Society for Testing and Materials.Table 19-1 presents AASHTO and American
Society for Testing and Materials (ASTM) standards that are related to materials for ground anchors.
It includes designations and titles.

Table 19-1: Designations and titles for AASHTO and ASTM standards that apply to ground

anchors works

AASHTO
DESIGNATION

ASTM
DESIGNATION

TITLE

AASHTO M 203M/M
203-12

Standard Specification for Steel Strand, Uncoated
Seven-Wire for Concrete Reinforcement

ASTM A416/A416M-
12a

Standard Specification for Steel Strand, Uncoated
Seven-Wire for Prestressed Concrete

ASTM A886/A886M-
10

Standard Specification for Steel Strand, Indented,
Seven-Wire Stress-Relieved for Prestressed
Concrete

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AASHTO
DESIGNATION

ASTM
DESIGNATION

TITLE

ASTM A882/A882M-
04a(2010)

Standard Specification for Filled Epoxy-Coated
Seven-Wire Prestressing Steel Strand

AASHTO M85-12

ASTM C150-12

Standard Specification for Portland Cement

ASHTO M 270M/M
270-12

ASTM A709/A709M-
11

Standard Specification for Structural Steel for
Bridges

ASTM

A536-

84(2009)

Standard Specification for Ductile Iron Castings

ASTM A53/A53M-12

Standard Specification for Pipe, Steel, Black and
Hot-Dipped, Zinc-Coated, Welded and Seamless

ASTM A500-10a

Standard Specification for Cold-Formed Welded
and Seamless Carbon Steel Structural Tubing in
Rounds and Shapes

ASTM D3350-12

Standard Specification for Polyethylene Plastics
Pipe and Fittings Materials

ASTM D4101-11

Standard Specification for Polypropylene Injection
and Extrusion Materials

AASHTO M 252-09

Standard

Specification

for

Corrugated

Polyethylene Drainage Pipe

AASHTO M 317M/M
317-03(2007)

ASTM
D3963/D3963M-
01(2007)

Standard

Specification

for

Epoxy-Coated

Reinforcing Bars: Handling Requirements for
Fabrication and Job Site

19.3

Working Drawings for Ground Anchor

At least four weeks before work is to begin, the Contractor shall submit to the Engineer for review
and approval complete working drawings and design calculations that describe a ground anchor
system or systems intended for use. Such submittals shall include the following information:

A ground anchor schedule that includes the following details:

•

Ground anchor number

•

Ground anchor design load

•

Type and size of tendon

•

Minimum total anchor length

•

Minimum bond length for ground anchors

•

Minimum length of bonded tendon

•

Minimum length of unbonded tendon

•

Inclination

•

Failure mechanism

A drawing of a proposed ground anchor tendon and its corrosion protection
system, including the following details:

•

Spacers for separating tendon elements, with planned locations for such spacers

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•

Centralisers, spacers, and their locations

•

Corrosion protection system for unbonded length of tendon

•

Corrosion protection system for bonded length of tendon

•

Anchorage and trumpet

•

Anchorage corrosion protection system

•

Drilled or formed hole size

•

Level of each stage of grouting

•

Any revisions to structure details that are necessary to accommodate the ground

anchor system intended for use

The grout mix design and placement procedures

The Contractor shall not begin any work on ground anchors until the Engineer has provided written
approval of the working drawings. Such approval shall not relieve the Contractor of any responsibility
defined in the Contract documents for successful completion of the work.

19.4

Materials for Ground Anchor

Materials for ground anchor shall comply with the standards and requirements outlined in this
section.

19.4.1

Prestressing Steel for Ground Anchor

Ground anchor tendons shall consist of single or multiple elements of prestressing steel, anchorage
devices, and, if required, couplers, all of which shall conform to the applicable requirements of
Section 22.7 of Chapter 22, Prestressing Systems. To be acceptable for use as ground anchor
tendons, materials shall comply with the standards listed in Table 19-1.

19.4.2

Grout for Ground Anchor

Cement shall be Type I, II, or V Portland cement that conforms to the Standard Specification for
Portland Cement (AASHTO M 85) or (ASTM C150). Cement used for grouting shall be fresh and
shall not contain any lumps or other indications of hydration or pack set.

A cement shall conform to the applicable requirements mentioned at Section 4.3.1 of Chapter 4,
Concrete Works, of the

Standard Specifications

With the approval of the Engineer, grout may include admixtures. Expansive admixtures may only
be added to grout for filling sealed encapsulations, trumpets, and anchorage covers. Grout shall not
include accelerators.

Water for mixing grout shall be potable, clean, and free of injurious quantities of substances known
to be harmful to Portland cement or prestressing steel.

The grout requirements shall comply with the applicable requirements mentioned at Section 22.7.2
of Chapter 22, Prestressing Systems.

19.4.3

Steel Elements for Ground Anchor

Bearing plates shall be steel of at least AASHTO grade 36 or ASTM grade 250 that conforms to the

Standard Specification for Structural Steel for Bridges

(AASHTO M 270M/M 270) or (ASTM

A709/A709M). Bearing plates may also be ductile cast iron that conform

s to ASTM’s

Standard

Specification for Ductile Iron Castings

(ASTM A536).

Trumpets that provide a transition from the anchorage to the unbonded length corrosion protection
shall be fabricated from a steel pipe that conforms to the requirements of

ASTM’s

Standard

Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless

(ASTM

A53/A53M) or steel tubing that conforms to

ASTM’s

Standard Specification for Cold-Formed Welded

and Seamless Carbon Steel Structural Tubing in Rounds and Shapes

(ASTM A500).

A trumpet’s

wall shall be at least 5.0 mm thick.

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Covers that enclose exposed anchorages shall be at least 2.5 mm thick. Such covers shall be
fabricated from one of the following materials:

•

AASHTO grade 36 steel (AASHTO M 270M/M 270)

•

ASTM grade 250 steel (ASTM A709/A709M)

•

Steel pipe (ASTM A53/A53M)

•

Steel tubing (ASTM A500)

•

Ductile cast iron (ASTM A536)

19.4.4

Corrosion Protection Elements for Ground Anchor

Corrosion-inhibiting grease shall conform to the requirements outlined in section 3.2.5 of the

Specification for Unbonded Single Strand Tendons

, published by the Post-Tensioning Institute (PTI

M10.2-00).

A Sheath for an unbonded length of a tendon shall consist of one of the following materials:

a. Seamless polyethylene (PE) tube with a minimum wall thickness of 1.5 mm ± 0.25 mm.

Polyethylene shall be classified

in accordance with ASTM’s

Standard Specification for

Polyethylene Plastics Pipe and Fittings Materials

(ASTM D3350).

b. Seamless polypropylene tube with a minimum wall thickness of 1.5 mm ± 0.25 mm.

Polypropylene shall be classified

in accordance with ASTM’s

Standard Specification for

Polypropylene Injection and Extrusion Materials

(ASTM D4101).

c. Heat-shrinkable tube of a radiation cross-linked polyolefin tube that is internally coated with

an adhesive sealant. Walls for such tubes, before shrinking, shall be at least 0.6 mm thick.
Adhesive sealant shall be at least 0.5 mm thick.

d. Corrugated polyvinyl chloride (PVC) tube with a minimum wall thickness of 0.8 mm.

Encapsulation for a length of bonded tendon shall consist of one of the following:

1. Corrugated high-density polyethylene (HDPE) tube

that conforms to AASHTO’s

Standard

Specification for Corrugated Polyethylene Drainage Pipe

(AASHTO M 252). Such tubing shall

have a minimum wall thickness of 0.8 mm.

2.  Deformed steel tube or pipe with a minimum wall thickness of 0.63 mm.
3.  Corrugated PVC tube with a minimum wall thickness of 0.8 mm.
4.  Fusion-bonded  epoxy  that  conforms  to  the  requirements  of

AASHTO’s Standard

Specification for Epoxy-Coated Reinforcing Bars: Handling Requirements for Fabrication and
Job Site (AASHTO M 317M/M 317

) or ASTM’s Standard Specification for Fabrication and

Jobsite Handling of Epoxy-Coated Steel Reinforcing Bars (ASTM D3963/D3963M). In
variance from these standards, however, such epoxy shall have a film thickness of 0.4 mm.

19.4.5

Miscellaneous Elements for Ground Anchor

A bond-breaker for a tendon shall consist of a smooth plastic tube or pipe that is resistant to aging
by ultraviolet light and that can withstand abrasion, impact, and bending during handling and
installation.

Spacers for separation of elements of a multi-element tendon shall permit the free flow of grout. They
shall be fabricated from plastic, steel, or material that is not detrimental to the prestressing steel.
Such spacers shall not be wood.

Centralisers shall be plastic, steel, or other material that is not detrimental to either the prestressing
steel or any tendon corrosion protection element. Centralisers shall not be wood. A centraliser shall
be able to maintain the position of the tendon so that at least 12 mm of grout can cover it or its
encapsulation.

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19.5

Fabrication of Ground Anchor

Tendons for ground anchors may be fabricated either in a shop or the field from materials that
conform to the requirements outlined in Section 19.4, Materials. Tendons shall be fabricated as
shown on the approved working drawings.

Each tendon

’s size shall ensure that its maximum test load does not exceed 80 percent of its

minimum guaranteed ultimate strength.

19.5.1

Tendon Bond Length for a Ground Anchor

The Contractor shall determine the tendon bond length that satisfies load test requirements. A
tendon for a ground anchor shall have a bonded section that is at least 3.0 metres long in all cases,
at least 4.5 metres in soil, or the minimum length shown in the Contract documents, if such exceeds
3.0 metres.

A tendon bond length shall be encapsulated by a grout-filled corrugated plastic or deformed steel
tube, or by a fusion-bonded epoxy coating. A tendon shall be grouted inside the encapsulation either
before or after it is inserted into the drill hole. The Contractor shall not punch holes in this
encapsulation or allow grout to flow between the encapsulation and the drill hole.

To provide an average of 5.0 mm of grout covering for the prestressing steel, a tendon shall be
centralized within the encapsulation and a tube shall be of an effective size. For ground anchor
tendons that are protected by grout, the Contractor shall use spacers and centralisers that satisfy
the requirements outlined in Section 19.6.3, Grouting. An anchorage device for tendons protected
with fusion-bonded epoxy shall be electrically isolated from the main structure under construction.

19.5.2

Spacers and Centralisers for a Ground Anchor

Spacers along a tendon

’s bond length shall ensure that prestressing steel will bond to grout. Such

spacers shall be located at centres no greater than 3.0 metres. An uppermost spacer shall reside no
more than 1.5 metres from the top of the anchor tendon

’s bonded length and a bottommost spacer

shall reside no more than 1.5 metres from the bottom of the tendon

’s bonded length.

Centralisers shall reside along the

tendon’s bonded length at centres no greater than 3.0 metres. An

uppermost centraliser shall reside no more than 1.5 metres from the top of the bonded length and a
bottommost centraliser shall reside no more than 300 mm from the bottom of the bonded length.
Centralisers are not required on tendons that have been installed using a hollow-stem auger if such
a tendon is grouted through the auger and its drill hole is full of a stiff grout with a slump of 225 mm
or less during extraction of the auger. The Contractor may use a combination centraliser-spacer.

Centralisers are not required on tendons that have been installed in coarse-grained soils using a
pressure injection system and grouting pressures greater than 1.0 MPa.

Centralisers shall ensure a minimum grout cover of 13 mm over the tendon

’s bonded length or its

encapsulation, as appropriate. The Contractor shall use centralisers that do not impede the free flow
of grout up the bore hole. Centralisers

’ centre-to-centre spacing shall not exceed 3 meters.

19.5.3

Tendon Unbonded Length for a Fround Anchor

A ground anchor

’s tendon shall have an unbounded section that is at least 4.5 metres long or as

long as indicated in the Contract documents or approved working drawings.

Either a sheath completely filled with corrosion-inhibiting grease or grout or a heat-shrinkable tube
shall provide corrosion protection. If a protective sheath contains grease, the Contractor shall prevent
grease from escaping at the sh

eath’s ends. Grease shall completely coat the tendon and fill the

interstices between the wires of seven-wire strands.

Continuity of corrosion protection

shall be provided at the transition from the tendon’s bonded length

to its unbonded length.

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If a protective sheath is not a smooth tube, then a separate bondbreaker shall prevent the tendon
from bonding to anchor grout

that surrounds the tendon’s unbonded length.

19.5.4

Anchorage and Trumpet for a Ground Anchor

A ground anchor may use nonrestressable anchorages, unless the Contract documents specify the
use of restressable anchorages.

Bearing plate sizes shall ensure that bending stresses in the plate and the average bearing stress
on concrete, if applicable, do not exceed the nominal resistances described in Article 5.10.9.7.2 of
the

AASHTO LRFD Bridge Design Specifications

(9). Bearing plates shall not be smaller than the

sizes indicated in the Contract documents.

The Contractor shall weld a trumpet to the bearing plate. This trumpet shall have an inside diameter
at least 6 mm greater than the diameter of the tendon at the anchorage.

A trumpet shall be long enough to accommodate movements of the main structure during testing
and stressing. For strand tendons with encapsulation over the unbonded length, a trumpet shall be
long enough to enable the ten

dons to make a transition from the tendon’s unbonded length to the

anchor head without damaging the encapsulation.

Trumpets filled with corrosion-inhibiting grease shall have a permanent Buna-N rubber seal or a seal
of an approved equivalent between the trumpet and the corrosion protection elements for the
tendon’s unbonded length. Trumpets filled with grout shall have a temporary seal between the
trumpet and

the corrosion protection elements for the tendon’s unbonded length.

19.5.5

Tendon Storage and Handling

Storage and handling of tendons shall avoid damage and corrosion.

The Engineer shall reject any prestressing steel with abrasions, cuts, nicks, welds, and weld splatter.
A slight rusting, if it does not cause pits that are visible to the unaided eye, shall not cause the
Engineer to reject prestressing steel for a tendon. Before inserting a tendon into the drilled hole, the
Contractor shall examine its corrosion protection elements for damage and shall repair any damage
found in a manner approved by the Engineer.

Repairs to encapsulation shall comply with the recommendations of the tendon

’s supplier.

19.6

Installation of a Ground Anchor

The Contractor shall select the drilling method, grouting procedure, and grouting pressure to be used
for the installation of the ground anchor as necessary to satisfy load testing and durability
requirements.

19.6.1

Drilling for Anchor Installation

As the drilling method for ground anchor installation, the Contractor may use core drilling, rotary
drilling, percussion drilling, auger drilling, or driven casing. Whatever method the Contractor selects
shall prevent loss of ground above the drilled hole that may be detrimental to the main structure or
existing structures in the vicinity. The Contractor shall remove any casings for anchor holes, unless
the Engineer

authorises leaving them in place. Each drilled hole’s location, inclination, and alignment

shall comply with the Contract documents. Inclination and alignment shall be within ±3 degrees of
the planned angle at the bearing plate and within ±300 mm of the planned location at the point of
entry on the ground surface.

19.6.2

Tendon Insertion for Anchor Installation

The Contractor shall insert the tendon for a ground anchor into the drilled hole to the desired depth.
When a tendon cannot be completely inserted, the Contractor shall remove it and either clean or re-
drill the drill hole to permit insertion. Partially inserted tendons shall not be driven or forced into the
hole.

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19.6.3

Grouting for Anchor Installation

Ground anchor systems shall use a neat cement grout or sand cement grout that conforms to the
specifications in this section. Admixtures, if used, shall be mixed in quantities that do not exceed
manufacturers’ recommendations.

Grouting equipment shall produce grout without lumps or cement that is not dispersed. A positive-
displacement grout pump shall have a pressure gauge to monitor grout pressures. This pressure
gauge shall be capable of measuring pressures of at least 1.0 MPa or twice the actual grout
pressures used, whichever is greater.

Grouting equipment sizes shall enable grout to be pumped in one continuous operation. A mixer
shall be able to agitate grout continuously.

Grout shall be injected from the lowest point of a drill hole. The Contractor may pump grout through
grout tubes, casings, hollow-stem augers, or drill rods. The Contractor may place grout either before
or after inserting the system’s tendon. During installation, the Contractor shall record quantities of
grout used and grout pressures. To prevent excessive ground heaving or fracturing of rock
formations, the Contractor shall control grout pressures and grout quantities.

Except where indicated in these specifications, the Contractor may plane grout

for both a tendon’s

bonded length and above the top of the bonded length at the same time. Such placement, however,
shall not be under pressure.

Grout at the top of a drill hole shall stop 150 mm from the back of the main structure or 150 mm from
the bottom of the trumpet, whichever is lowest.

If the ground anchor is installed in a fine-grained soil in a drilled hole with a diameter that is larger
than 150 mm, then the Contractor shall place grout above the top of the bonded length after the
ground anchor has been load-tested. The Contractor may grout an entire drill hole at the same time
if the ground anchor system does not derive a significant portion of its load resistance from the soil
above the

ground anchor’s bonded length.

If ground anchors in rock use grout-protected tendons, the Contractor shall use pressure grouting
techniques. Pressure grouting requires sealing a drill hole and injecting grout until a 0.35 MPa grout
pressure can be maintained on the grout within the

tendon’s bonded length for a period of 5 min.

If the Contractor fills a grout tube with grout, it may remain in the drill hole. After grouting, a tendon
shall not be loaded for at least three days.

19.6.4

Trumpet and Anchorage for Anchor Installation

Corrosion protection that surrounds a

tendon’s unbounded length shall extend into an anchor

system’s trumpet at least 150 mm beyond the trumpet’s bottom seal.

Corrosion protection that surround

s a tendon’s unbounded length shall not contact the bearing plate

or the anchor head during load testing or stressing.

A bearing plate and anchor head shall be perpendicular to

a tendon’s axis.

A trumpet shall be completely filled with corrosion inhibiting grease or grout. Such grease may be
placed any time during construction. Grout placement, however, shall occur after a ground anchor
has been load-tested. The Contractor shall demonstrate that the procedures selected for placement
of either grease or grout will completely fill a trumpet.

19.7

Testing and Stressing for a Ground Anchor

The Contractor shall test each ground anchor using either a performance test or a proof test, as
outlined in this section. No load greater than ten percent of the design load may be applied to a
ground anchor before load testing. Load testing shall occur simultaneously for an entire tendon.

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19.7.1

Equipment for Ground Anchor Testing

The Contractor shall use a dial gauge or vernier scale that can measure displacements to an
accuracy of 0.025 mm to measure ground anchor movement. Such testing equipment shall travel
sufficiently to measure total ground anchor movement without being reset.

A hydraulic jack and pump shall apply test loads. The Contractor shall use a calibrated pressure
gauge to measure applied loads. This pressure gauge shall be graduated in increments no greater
than 0.7 MPa. When an anchor under its maximum test load has a theoretical elastic elongation that
exceeds the

jack’s ram travel, working drawings shall include the procedure for recycling the jack

ram. Each increment of test load shall be applied as rapidly as possible.

A calibrated reference pressure gauge shall be available at the site. A separate reference gauge
shall be calibrated with the test jack and pressure gage.

For creep testing, the Contractor shall use an electrical resistance load cell and readout.

Placement of stressing equipment over a ground anchor

’s tendon shall ensure that the jack, bearing

plates, load cells, and stressing anchorage are axially aligned with the tendon and that the tendon is
centred within the equipment.

19.7.2

Performance Testing for Ground Anchors

The Contractor shall conduct performance testing, in accordance with the details in this section, on
at least five percent of all ground anchors and no fewer than three ground anchors, whichever is
greater. The Engineer shall select the ground anchors for performance testing. All remaining anchors
shall be proof-tested as outlined in Section 19.7.3.

Performance testing shall involve incrementally loading and unloading a ground anchor in
accordance with the schedule shown in Table 19-2 unless the Contract documents indicate a
different maximum test load and schedule. During Performance testing, the Contractor shall take the
following actions:

a. Raise the load from one increment to another immediately after recording a ground anchor

’s

movement.

b. Measure and record each tested ground anchor

’s movement to the nearest 0.025 mm with

respect to an independent fixed reference point at the alignment load and at each incremental
load.

c. Use a pressure gauge to monitor load.
d. Place the reference pressure gauge in series with the testing pressure gauge during each

performance test.

If loads indicated by the reference pressure gauge and testing pressure gauge differ by more than
ten percent, the Contractor shall recalibrate the jack, the testing pressure gage, and the reference
pressure gauge. At load increments other than the maximum test load, the Contractor shall hold the
load just long enough to obtain the movement reading.

Table 19-2: Performance load test schedule

Load

Observation

Period

min

Remarks

10 minutes

0.25 DL*

10 minutes

0.25 DL

10 minutes

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Load

Observation

Period

min

Remarks

0.50 DL*

10 minutes

0.25 DL

10 minutes

0.50 DL

10 minutes

0.75 DL*

10 minutes

0.25 DL

10 minutes

0.50 DL

10 minutes

0.75 DL

10 minutes

1.0 DL*

10 minutes

0.25 DL

10 minutes

0.50 DL

10 minutes

0.75 DL

10 minutes

1.00 DL

10 minutes

1.20 DL*

10 minutes

0.25 DL

10 minutes

0.50 DL

10 minutes

0.75 DL

10 minutes

1.00 DL

10 minutes

1.20 DL

10 minutes

1.33 DL*

10 minutes

If T

-T

>1.0 mm, the holding time to be extended

for an additional 50 minutes

Reduce to lock-off
load

10 minutes

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Load

Observation

Period

min

Remarks

AL = Alignment load (The alignment load is a small load, normally less than ten percent of the
design load, applied to the ground anchor in order to keep the testing equipment in position during
testing)

DL = Design load for ground anchor

= Ground anchor movement at 10.0 minutes

= Ground anchor movement at 1.0 minute

* = Graph required, as specified herein

For performance testing, the Contractor

shall hold an anchor’s maximum test load for 10 minutes,

pumping the jack as necessary to maintain a constant load. This load hold period shall start as soon
as the maximum test load is applied. During this period, the Contractor shall measure and record a
ground anchor

’s movement at 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, and

10 minutes. If a tested ground anchor moves more than 1.0 mm from the first measurement (at 1
minute) and the last measurement (at 10 minutes), the Contractor shall hold the maximum test load
for an additional 50 minutes.

When extending a performance test by 50 minutes, the Contractor shall measure and record the
ground anchor

’s movement again at 15 minutes, 20 minutes, 25 minutes, 30 minutes, 45 minutes,

and 60 minutes. Based on the results, the Contractor shall construct a graph that plots the ground
anchor

’s movement for each load increment marked in with an asterisk (*) in Table and a plot of the

residual ground anchor movement of the tendon at each alignment load versus the highest
previously applied load. Graph format shall be approved by the Engineer prior to use.

19.7.3

Proof Testing for Ground Anchors

The Contractor shall perform proof testing, as outlined in this section, on every anchor that was not
subjected to performance testing.

A  proof test shall be performed by incrementally loading  a ground anchor in accordance with the
schedule  shown  in Table 19-3,  unless  the  Contract  documents  indicate  a  different maximum  test
load  and  schedule.  During  proof  testing,  the  Contractor  shall  increase  the  applied  load  by  one
increment  immediately  after  recording  the  tested  anchor

’s movement. Ground anchor movement

shall be measured and recorded to the nearest 0.025 mm with respect to an independent fixed
reference point at the alignment load and at each increment of load.

The Contractor shall use a calibrated pressure gauge to monitor load. At load increments other than
the maximum test load, the Contractor shall hold a load just long enough to obtain and record the
tested anchor’s movement.

Table 19-3: Proof load test schedule

Load

Observation
Period min

Remarks

10 minutes

0.25 DL

10 minutes

0.50 DL

10 minutes

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Load

Observation
Period min

Remarks

0.75 DL

10 minutes

1.00 DL

10 minutes

1.20 DL

10 minutes

1.33 DL

10 minutes

If T

-T

>1.0 mm, the holding time to be extended for an

additional 50 minutes

Reduce to lock-off
load

10 minutes

AL = Alignment load

DL = Design load for ground anchor

= Ground anchor movement at 10.0 minutes

= Ground anchor movement at 1.0 minute

For proof testing, the Contractor

shall hold an anchor’s maximum test load for 10 minutes, pumping

the jack as necessary to maintain a constant load. This load hold period shall start as soon as the
maximum test load is applied. During this period, the Contractor shall measure and record a ground
anchor’s movement at 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, and 10
minutes. If a tested ground anchor moves more than 1.0 mm from the first measurement (at 1 minute)
and the last measurement (at 10 minutes), the Contractor shall hold the maximum test load for an
additional 50 minutes.

When extending a proof test by 50 minutes, the Contractor shall measure a record the ground
anchor’s movement again at 15 minutes, 20 minutes, 25 minutes, 30 minutes, 45 minutes, and 60
minutes. Based on the results, the Contractor

shall construct a graph that plots the ground anchor’s

movement for each load increment in the proof test. Format for such graphs shall comply with
directions from the Engineer.

19.7.4

Creep testing for Ground Anchors

The Contractor shall perform Creep tests in accordance with specifications in the Contract
documents. The Engineer shall select which ground anchors shall be subjected to creep testing.
When the Contract mandates creep testing, at least two ground anchors shall be so tested.

A creep test shall be made by incrementally loading and unloading a ground anchor in accordance
with the performance test schedule. At the end of each loading cycle, the load shall be held constant
for the observation period indicated in Table 19-4, unless the Contract documents indicate a different
maximum test load and schedule. The Contractor shall read and record the tested ground anchor

’s

movement during each observation period at 1 minute and thereafter at 2, 3, 4, 5, 6, 10, 15, 20, 25,
30, 45, 60, 75, 90, 100, 120, 150, 180, 210, 240, 270, and 300 minutes, as appropriate.

Each load-hold period shall start as soon as the test load is applied. In a creep test, the Contractor
shall use a calibrated pressure gage and reference pressure gage to measure the applied load and
a load cell to monitor small changes of load during a constant load-hold period. The Contractor shall
pump the jack as necessary to maintain a constant load.

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Table 19-4: Creep test schedule

Load

Observation Period min

0.25DL

0.50DL

0.75DL

1.00 DL

1.20 DL

1.33 DL

300

Based on the results of creep testing, the Contractor shall construct a graph that plots ground anchor
movement and residual movement as described in Section 19.7.2 for performance tests. The
Contractor shall also construct a graph that plots a creep-tested ground anchor

’s movement for each

load-hold as a function of the logarithm of time. Format for such graphs shall comply with directions
from the Engineer.

19.7.5

Acceptance Criteria for Ground Anchor Testing

A performance-tested or proof-tested ground anchor with a 10-minute load-hold shall be deemed to
be acceptable if all of the following conditions apply:

•

A tested ground anchor resists the maximum test load with less than 1.0 mm of movement

between 1 minute and 10 minutes.

•

A tested anchor’s total movement at the maximum test load exceeds eighty percent (80%) of
the theoretical elastic elongation of the

anchor’s unbonded length.

•

Total movement of a ground anchor in competent rock that is performance-tested under the

maximum test load does not exceed the theoretical elastic elongation of the

anchor’s

unbonded length

plus

50 percent of the theoretical elastic elongation of the

anchor’s bonded

length.

•

Elongation measurements are within calculated tolerances.

A performance-tested or proof-tested ground anchor with a 60-minute load-hold shall be deemed to
be acceptable if all of the following conditions apply:

•

A tested ground anchor resists the maximum test load with a creep rate that does not exceed

2.0 mm in the last log cycle of time.

•

A tested anchor’s total movement at the maximum test load exceeds eight percent (80%) of
the theoretical elastic elongation of the

anchor’s unbonded length.

•

For a performance-tested ground anchor in competent rock, the total movement at the

maximum test load shall not exceed the theoretical elastic elongation of the

anchor’s

unbounded length plus 50 percent of the theoretical elastic elongation of the

anchor’s bonded

length.

A creep-tested ground anchor shall be deemed to be acceptable if all of the following conditions
apply:

•

A tested ground anchor carries the maximum test load with a creep rate that does not exceed

2.0 mm in the last log cycle of time.

•

A tested anchor’s total movement at the maximum test load exceeds eighty percent (80%) of
the theoretical elastic elongation of the

anchor’s unbonded length.

•

Total movement of a ground anchor in competent rock that is performance-tested under the

maximum test load

does not exceed the theoretical elastic elongation of the anchor’s

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unbonded length

plus

50 percent of the theoretical elastic el

ongation of the anchor’s bonded

length.

a ground anchor’s total movement when tested under the maximum test load does not exceeds

80 percent of the theoretical elastic elongation of the

anchor’s unbonded length, the Contractor shall

replace the ground anchor without further expense to the Owner.

A ground anchor has a creep rate greater than 2.0 mm per log cycle of time can be incorporated into
the structure, but its design nominal resistance shall be equal to one-half of its failure load. An
anchor’s failure load is the load it can resist after the load has been allowed to stabilize for 10
minutes.

When a ground anchor fails, the Contractor shall modify the design, the installation procedures, or
both. Such modifications may include, but are not limited to, installing a replacement ground anchor,
reducing  the  design  load  by  increasing  the  number  of  ground  anchors,  modifying  the  installation
methods,  increasing  the  bond  length,  or  changing  the  ground  anchor  type.  Any  modification  that
requires changes to the main structure under construction shall be approved by the Engineer. Any
modifications of design or construction procedures shall be without additional cost to the Owner and
without extension of the time schedule defined in the Contract documents.

Repeating tests for any ground anchor shall not be permitted, except ground anchors have been re-
grouted.

19.7.6

Lock-Off

Upon successful completion of load testing, the Contractor shall reduce the loads on ground anchors
to the lock-off load that is indicated in the Contract documents and transfer load to anchorage
devices. The Contractor may completely unload a ground anchor before lock-off. After transferring
the load and before removing the jack, the Contractor shall take a lift-off load reading. A lift-off load
measurement shall be within 10% of the specified lock-off load.

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NDEX

abrasion, 7
Bearing plates, 6, 8
bending stresses, 8
bond length, 4, 5, 7, 8, 14
bond-breaker, 7

Cement

, 4, 6

cement-grouted ground anchors, 3
Centralisers, 5, 7, 8
corrosion protection, 3, 4, 5, 6, 7, 8
corrugated, 7
Creep tests, 12
dial gauge, 10
displacements, 10
drilled hole, 3, 8, 9
existing structures, 9
exposed anchorages, 6
grease, 6, 8, 10
grout, 3, 4, 6, 7, 8, 9, 10

Grouting equipment, 9
lock-off load, 11, 12, 14
maximum test load, 7, 10, 11, 12, 13, 14
movement, 3, 4, 10, 11, 12, 13, 14
nonrestressable, 8
performance testing, 10, 11, 12
performance-tested, 13
pressure gauge, 9, 10, 12
prestressing steel, 3, 6, 7, 8
proof testing, 12
proof-tested, 10, 13
restressable anchorages, 8
sand cement, 9
Sheath, 6
Spacers, 5, 7, 8
Trumpets, 6, 8
ultraviolet light, 7
unbonded length, 4, 5, 6, 8, 13, 14
vernier scale, 10

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Chapter 20: Earth Retaining Systems

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STANDARD CONSTRUCTION SPECIFICATIONS

PART 2

ROAD STRUCTURES

CHAPTER 20 - EARTH RETAINING SYSTEMS

DOCUMENT NO: TR-

FIRST EDITION

JANUARY 2018

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Chapter 20: Earth Retaining Systems

ABLE OF

ONTENTS

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

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

Earth Retaining Systems ........................................................................................................ 1

20.1

Reference Standards and Codes ........................................................................................ 1

20.2

Working Drawings for Earth Retaining Systems .................................................................. 2

20.3

Materials for Earth Retaining Systems ................................................................................ 2

20.3.1

Concrete for Earth Retaining Systems ......................................................................... 2

20.3.2

Reinforcing Steel for Earth Retaining Systems ............................................................ 3

20.3.3

Structural Steel for Earth Retaining Systems ............................................................... 3

20.3.4

Timber for Earth Retaining Systems ............................................................................ 3

20.3.5

Drainage Elements for Earth Retaining Systems ......................................................... 3

20.3.6

Backfill Material ............................................................................................................ 4

20.4

Earthwork for Earth Retaining Systems ............................................................................... 5

20.4.1

Structure Excavation .................................................................................................... 5

20.4.2

Foundation Treatment .................................................................................................. 5

20.4.3

Structure Backfill .......................................................................................................... 5

20.5

Drainage for Earth Retaining Systems ................................................................................ 5

20.5.1

Concrete Gutters .......................................................................................................... 5

20.5.2

Weep Holes .................................................................................................................. 6

20.5.3

Drainage Blankets ........................................................................................................ 6

20.5.4

Geocomposite Drainage Systems ................................................................................ 6

20.6

Construction for Earth Retaining Systems ........................................................................... 6

20.6.1

Concrete, Masonry Gravity, and Reinforced Concrete Retaining Walls ....................... 7

20.6.2

Sheet-pile, Soldier-pile and Secant Pile walls .............................................................. 9

20.6.3

Crib and Cellular Walls ............................................................................................... 13

20.6.4

MSE Walls .................................................................................................................. 14

Index ............................................................................................................................................. 25

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IST OF

ABLES

Table 20-1: Designations and titles for AASHTO and ASTM standards that apply to earth retaining
works ................................................................................................................................................. 1

Table 20-2: Backfill requirements ..................................................................................................... 4

Table 20-3: Backfill material for crib and cellular walls ..................................................................... 4

Table 20-4: Reinforced (infill) soil for MSE walls .............................................................................. 4

Table 20-5: Materials for reinforced concrete walls .......................................................................... 7

Table 20-6: Construction tolerances for reinforced concrete walls ................................................... 8

Table 20-7: Materials for soldier-pile and soldier-pile tie-back walls ............................................... 10

Table 20-8: Safety factors ............................................................................................................... 17

Table 20-9: Pervious Backfill Gradation .......................................................................................... 20

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EARTH RETAINING SYSTEMS

This chapter provides specifications and requirements for the designing, furnishing, and installing
earth-retaining systems. Such work shall comply with the Contract documents and the specifications
outlined in this chapter.

20.1

Reference Standards and Codes

Standards and codes for Earth Retaining System 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;



ADQCC (TR-516)

Road Structures Design Manual



ASTM American Society for Testing and Materials.

Table 20-1 presents AASHTO and American Society for Testing and Materials (ASTM) standards
that are related to materials for earth retaining systems. It includes designations and titles.

Table 20-1: Designations and titles for AASHTO and ASTM standards that apply to earth

retaining works

AASHTO
DESIGNATION

ASTM
DESIGNATION

TITLE

ASTM C1372-11

Standard Specification for Dry-Cast Segmental
Retaining Wall Units

ASTM C140-12a

Standard Test Methods for Sampling and Testing
Concrete Masonry Units and Related Units

ASHTO M
270M/M 270-12

ASTM
A709/A709M-11

Standard Specification for Structural Steel for Bridges

AASHTO T 27-11

ASTM C136-06

Standard Test Method for Sieve Analysis of Fine and
Coarse Aggregates

AASHTO T 236-
08

ASTM D3080-11

Standard Test Method for Direct Shear Test

AASHTO M
202M/M 202-08

ASTM
A328/A328M-
07(2012)

Standard Specification for Steel Sheet Piling

ASTM
A690/A690M-
07(2012)

Standard Specification for High-Strength Low-Alloy
Nickel, Copper, Phosphorus Steel H-Piles and Sheet
Piling with Atmospheric Corrosion Resistance for Use
in Marine Environments

AASHTO M
232M/M 232-10

ASTM
A153/A153M-09

Standard Specification for Zinc Coating (Hot-Dip) on
Iron and Steel Hardware

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20.2

Working Drawings for Earth Retaining Systems

Working drawings and design calculations shall be submitted to the Engineer for review and approval
at least four weeks before work begins. Such submittals shall be required for the following:

a. For each alternative proprietary or non-proprietary earth-retaining system proposed, as

permitted or specified in the Contract documents.

b. Complete details for the system to be constructed are not included in the Contract

documents.

c. When otherwise required by the Contract documents or these specifications. Working

drawings and design calculations shall include the following:

1. Existing ground elevations that have been verified by the Contractor for each location

involving construction wholly or partially in original ground

2. Layout of wall that will effectively retain the earth as indicated in the Contract

documents

3. Complete design calculations substantiating that the proposed design satisfies the

design parameters in the Contract documents

4. Complete details of all elements required for the proper construction of the system,

including complete material specifications

5. Earthwork requirements, including specifications for material and compaction of

backfill

6. Details of revisions or additions to drainage systems or other facilities required to

accommodate the system

7.  Other information required in the Contract documents or requested by the Engineer
8.  Assumption made in design and construction loading
9.  Life span for the constructed element
10. Any drainage system required during construction and in service
11. Proprietary systems
12. Compaction method

Work shall not begin on any earth retaining system for which working drawings are required until
such drawings have been approved by the Engineer. Approval of the Contractor's working drawings
shall not relieve the Contractor of any responsibility under the Contract documents for the successful
completion of the work.

20.3

Materials for Earth Retaining Systems

Materials for earth retaining systems shall comply with the standards and requirements outlined in
this section.

20.3.1

Concrete for Earth Retaining Systems

Concrete for earth retaining systems shall comply with the requirements outlined in this section.

20.3.1.1 Cast-in-Place Concrete

Cast-in-place concrete shall conform to the requirements of Chapter 4, Concrete Works, of the

Standard Specifications

. The concrete shall be Class C50/20 or stronger unless otherwise indicated

in the Contract documents.

20.3.1.2 Shotcrete

Shotcrete shall conform to the requirements of Section 4.3.10.5 of Chapter 4

Concrete Works of

these

Standard Specifications

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20.3.1.3 Elements

Precast Concrete

Precast concrete element materials, manufacturing, storage, handling, and erection shall conform to
the requirements of Section 21.13 of Chapter 21, Concrete Structures, of these

Standard

Specifications

Unless otherwise shown in the Contract documents, or in the approved working drawings, Portland
cement (OPC and SRC) concrete used in precast elements shall conform to Class C50/20.

20.3.1.4 Segmental

Concrete Facing Blocks

Masonry concrete blocks used as wall-facing elements shall have a minimum compressive strength
of 50 MPa and a water absorption limit of 5 percent.

Facing blocks shall meet the requirements of the American Society for Testing and Materials (ASTM)
C1372, except that acceptance regarding durability under this testing method shall be achieved if
the weight loss of four of the five specimens at the conclusion of 150 cycles does not exceed 1
percent of its initial weight.

Blocks shall also meet the additional requirements of ASTM C140.

20.3.2

Reinforcing Steel for Earth Retaining Systems

Reinforcing steel shall conform to the applicable requirements of Chapter 5, Reinforcing Steel, of
these

Standard Specifications

20.3.3

Structural Steel for Earth Retaining Systems

Structural steel shall conform to the American Association of State Highway and Transportation
Officials (AASHTO) M 270M/M 270 (ASTM A709/A709M), Grade 36 (Grade 250) or equivalent,
unless otherwise specified in the Contract documents.

20.3.4

Timber for Earth Retaining Systems

Timber  shall  conform  to  the  requirements  of  Chapter  16,  Timber  structures  of  the  American
Association  of  State  Highway  and  Transportation  Officials  (AASHTO)  LRFD  Bridge  Construction
Specifications,  3

Edition, 2010 and Chapter 7 of the

Standard Specifications,

Incidental

Construction.

20.3.5

Drainage Elements for Earth Retaining Systems

Drainage elements for earth retaining systems shall comply with the requirements outlined in this
section.

20.3.5.1

Pipe and Perforated Pipe

Pipe and perforated pipe shall conform to Subsection 708, Concrete, Clay, and Plastic Pipe; and
Section 709, Metal Pipe, of the AASHTO Guide Specifications for Highway Construction.

20.3.5.2 Filter

Fabric

Filter fabric shall conform to the requirements of Section 2.5.2.9 of Chapter 2, Earthworks, of the

Standard Specifications

20.3.5.3 Pervious

Backfill

Pervious backfill material shall conform to the requirements of Section 2.5.2.5 of Chapter 2,
Earthworks, of the

Standard Specifications,

unless otherwise specified in the Contract documents or

in the approved working drawings.

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20.3.5.4 Geocomposite Drainage Systems

Geocomposite drainage systems shall conform to the requirements specified in the Contract
documents or the approved working drawings.

20.3.6

Backfill Material

All backfill material shall consist of material free from organic material or other unsuitable material,
as determined by the Engineer. Gradation shall be determined by AASHTO T 27 (ASTM C136).
Grading shall be as shown in Table 20-2, unless otherwise specified.

Table 20-2: Backfill requirements

Sieve size

Percent passing

75 mm

100

No. 4 (4.75 mm)

35 – 100

No. 30 (600 μm)

20 – 100

No. 200 (75 μm)

0 - 15

20.3.6.1 Crib

and Cellular Walls

Backfill material for crib and cellular walls shall be of such character that it will not sift or flow through
wall openings in accordance to

Table 20-2

. For wall heights more than 6.0 m, following grading, as

shown in Table 20-3, shall be required.

Table 20-3: Backfill material for crib and cellular walls

Sieve size

Percent passing

75 mm

100

No. 4 (4.75 mm)

25 – 70

No. 30 (600 μm)

5 – 20

No. 200 (75 μm)

0 – 5

20.3.6.2 Mechanically

Stabilised Earth Walls

Reinforced (infill) soil for mechanically stabilised earth (MSE) walls shall conform to the grading,
internal friction angle, and soundness requirements shown in Table 20-4.

Table 20-4: Reinforced (infill) soil for MSE walls

Sieve size

Percent passing

75 mm

100

No. 40 (425 μm)

5 – 60

No. 200 (75 μm)

0 – 10

*Plasticity index (PI), as determined by AASHTO T 90, shall not exceed 6%.

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Materials shall exhibit an angle of internal friction of not less than 36 degrees, as determined by the
Standard Direct Shear Test, AASHTO T 236 (ASTM D3080), on the portion finer than the No. 10 (2-
mm) sieve, utilising a sample of the material compacted to 95 percent of AASHTO T 99, Methods C
or D at optimum moisture content. No testing is required for reinforced (infill) material where 80
percent of sizes are greater than 19 mm.

Materials shall be substantially free of shale or other soft, poor durability particles; and shall have a
magnesium sulphate soundness loss of less than 30 percent after five cycles.

Additionally, reinforced (infill) material shall meet the following electrochemical requirements when
using steel soil reinforcement:

a.  pH of 6 to 10
b.  Resistivity not less than 30 ohm.m
c.  Chlorides not greater than 100 parts per million
d.  Sulphates not greater than 200 parts per million
e.  No recycled aggregate material shall be used

20.4

Earthwork for Earth Retaining Systems

Earthwork for retaining systems shall comply with the requirements outlined in this section.

20.4.1

Structure Excavation

Structure excavation for earth-retaining systems shall conform to the requirements of Section
2.4.2.11 of Chapter 2

Earthworks, of the

Standard Specifications

and as provided below.

20.4.2

Foundation Treatment

If sub-excavation of foundation material is required, the Contractor shall perform the excavation to
the limits shown. Material excavated shall be replaced with structure backfill material meeting the
requirements for the particular earth-retaining system to be constructed, unless a different material
is specified in the Contract documents.

Foundation soil shall be proof rolled and compacted to 95% Modified Proctor density and inspected
by the Engineer prior to placement of levelling pad materials, or as per bearing capacity required
shown on the Contract plans.

20.4.3

Structure Backfill

Placement of structure backfill material shall conform to the requirements of Section 2.5.2.4 of
Chapter 2, Earthworks, of the

Standard Specifications

and Section 20.6. Material used shall conform

to the requirements of Section 20.3.6.

20.5

Drainage for Earth Retaining Systems

Drainage facilities shall be constructed in accordance with the details shown in the approved working
drawings or in the Contract documents and these specifications.

20.5.1

Concrete Gutters

Concrete gutters shall be constructed to the profile indicated in the Contract documents or in the
approved working drawings. Shotcrete shall conform to the requirements of Section 4.3.10.5 of
Chapter 4

Concrete Works of these

Standard Specifications

. Outlet works shall be provided at sags

in the profile, at the low ends of the gutter, and at other indicated locations.

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20.5.2

Weep Holes

Weep holes shall be constructed by the Contractor at the locations shown in the Contract documents
or in the approved working drawings. A minimum of 0.06 m

of pervious material as specified in

Article 20.3.5.3 encapsulated with filter fabric shall be placed at each weep hole.

Joints between precast concrete retaining-wall face panels that function as weep holes shall be
covered with filter fabric. The filter fabric shall be bonded to the face panels with approved adhesive.
Face panels that are to receive the filter fabric shall be dry and thoroughly cleaned of dust and loose
materials.

20.5.3

Drainage Blankets

Drainage blankets consisting of pervious material encapsulated in filter fabric, collector pipes, outlet
pipes, and cleanout pipes shall be constructed as specified in the Contract documents or in the
approved working drawings.

Subgrade receiving the filter fabric shall conform to the compaction and elevation tolerance specified
and shall be free of loose or extraneous material and sharp objects that may damage the filter fabric
during installation.

The fabric shall be stretched, aligned, and placed in a wrinkle-free manner. Adjacent borders of the
fabric shall be overlapped from 300 mm to 450 mm. should the fabric be damaged, the torn or
punctured section shall be repaired by placing a piece of fabric that is large enough to cover the
damaged area and to meet overlap requirements.

Pervious materials shall be placed in horizontal layers and thoroughly consolidated along with and
by the same methods specified for structure backfill. Ponding and jetting of pervious material or
structure backfill material adjacent to pervious material shall not be permitted.

During spreading and compaction of the pervious material and structure backfill or embankment
material, a minimum of 150 mm of such material shall be maintained between the fabric and the
Contractor's equipment.

Perforated collector pipes shall be placed within the pervious material to the flow line elevations
shown.

Outlet pipes shall be placed at sags in the flow line, at the low end of the collector pipe, and at other
locations shown or specified in the Contract documents. Rock slope protection, when required at the
end of outlet pipes, shall conform to the details in the Contract documents, or approved working
drawings, and the applicable requirements in Chapter 7 of the

Standard Specifications,

Incidental

Construction.

Cleanout pipes shall be placed at the high ends of collector pipes and at other locations, as specified
in the Contract documents.

20.5.4

Geocomposite Drainage Systems

Geocomposite drainage systems shall be installed at the locations shown in the Contract documents
or in the approved working drawings. Geocomposite drainage material shall be placed and secured
tightly against the excavated face, lagging, or back of wall as specified in the Contract documents.
When concrete is to be placed against geocomposite drainage material, the drainage material shall
be protected against physical damage and grout leakage.

20.6

Construction for Earth Retaining Systems

Earth-retaining system construction shall conform to the lines and grades indicated in the Contract
documents, on the working drawings, or as directed by the Engineer.

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20.6.1

Concrete, Masonry Gravity, and Reinforced Concrete
Retaining Walls

Stone and Reinforced concrete block masonry construction shall conform to the applicable
requirements of Section 6.2 of Chapter 6

Masonry, of these

Standard Specifications

Vertical precast concrete wall elements with cast-in-place concrete footing support shall be
adequately supported and braced to prevent settlement or lateral displacement until the footing
concrete has been placed and has achieved sufficient strength to support the wall elements.

The exposed face of concrete walls shall receive a Class 2 finish as specified in Section 21.12 of
Chapter 21, Concrete Structures, of these

Standard Specifications

, unless a special architectural

treatment is specified in the Contract documents, or in the approved working drawings.

20.6.1.1 Materials

Concrete shall be of the compressive strength shown on the Contract plans, typically Class C30/20.
Materials shall conform to the requirements of the Contract plans, the Engineer, and these standard
specifications, including those sections specifically noted in Table 20-5. Other materials required
shall be as specified in the particular specifications.

Table 20-5: Materials for reinforced concrete walls

Material

Standard specification
section

Portland cement concrete and its constituent materials;

steel reinforcing bar and epoxy-coated steel reinforcing bar;

premoulded joint filler and water stops.

Chapter 4, Materials

Chapter 5, Reinforcing Steel

Chapter 4, Water stops

Backfill

Chapter 2, Structural backfill

Pipe underdrains

Chapter 11, Pipe underdrains

20.6.1.2 Construction Requirements

Excavation and Foundation Preparation

Excavation and backfill shall be in accordance with the requirements of applicable Sections of
Chapter 2, Earth Works, of the

Standard Specifications.

Excavation shall conform to the requirements of Section 2.4.2.11 of Chapter 2, Earth Works, and to
the limits and construction stages shown in the Contract plans. Foundation soils found to be
unsuitable shall be removed and replaced in accordance with the applicable Sections of Chapter 2,
Earth Works.

Precast Concrete Wall Stem Panels

Unless otherwise indicated on the Contract plans, the Contractor may fabricate precast concrete
wall stem panels. Precast concrete wall stem panels may be used for construction of retaining walls,
if allowed by the Contract plans or the particular specifications. Precast concrete wall stem panels
shall conform to Chapter 4, Precast concrete panels, and shall be cast with Class C30/20 or stronger
concrete. Formwork shall comply with Chapter 4, Formwork.

Precast concrete wall stem panels shall conform to the following:

1. Be fabricated per the dimensions and details shown in the Contract plans, except as modified

in the shop drawings or as approved by the Engineer

2. Be fabricated full height

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3. Conform to the construction tolerances as stated in Table 20-6
4. Include a mating shear key between adjacent panels as follows:



Beveled corners



Thickness of 40 mm



Continuous with uniform width over the entire height of the wall stem, with a minimum

width of 90 mm and a maxium width of 140 mm

5. Receive the surface finish specified in the Contract plans to the limits shown in the Contract

plans in conformance with Chapter 21, Concrete finishing or as supplemented in the
particular specifications. Rolled on textured finished shall not be used.

6.  Be cast in a vertical position if a form liner texture is required on both sides of the panel.
7.  Be rigidly held in place during placement and curing of the footing concrete.
8.  Be placed a minimum of 25 mm into the footing to provide a shear key.
9.  Be constructed so that the base of the precast concrete wall stem panel is sloped 40 mm per

metre to facilitate proper concrete placement.

Maximum allowable tolerances or deviations from dimensions shown on the Contract plans or the
approved shop drawings shall be as described in

Table 20-6

Table 20-6: Construction tolerances for reinforced concrete walls

Parameter

Tolerance

Height of precast wall stem panel

±6 mm

Width of precast wall stem panel

±6 mm

Thickness of precast wall stem panel

+6 mm, -3 mm

Concrete cover for steel reinforcing bar

+10 mm, -3 mm

Width of precast concrete wall stem panel joints

±6 mm

Offset of precast concrete wall stem panels

(Deviation from a straight line extending 1.5 m on
each side of the panel joint)

Across panel face

Across top of wall

±6 mm

±10 mm

Footing cross sectional dimensions

+50 mm, -13 mm

Variation in footing thickness

+no limit, -5 % of specified thickness up to
a maximum of 13 mm

Average levels of footings

±25 mm

Position of wall

10 mm

Alignment of wall

2 minutes

Average levels of wall

+10 mm

Verticality of wall

1 in 400. Maximum 25 mm

Surface regularity of wall

3 mm

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Soil bearing pressure beneath the formwork supports for the precast concrete wall stem panels shall
not exceed the maximum design soil pressure shown in the Contract plans for the retaining wall.

To ensure an even flow of concrete under and against the base of the wall panel, a form shall be
placed parallel to the precast concrete wall stem panel, above the footing, to allow a minimum 300
mm head to develop in the concrete during concrete placement.

Minimum clear cover to the erection block-outs shall be 40 mm.

All precast concrete wall stem panel joints shall be constructed with joint filler installed on the backfill
side of the wall. Joint filler material shall extend from 0.6 m below the final ground level in front of
the wall to the top of the wall. Joint filler shall be a nonorganic flexible material meeting the
requirements for joint filler in Chapter 4 and shall be installed to create a waterproof seal at panel
joints.

Cast-in-Situ Concrete Construction

Cast-in-situ concrete for concrete retaining walls shall be formed, reinforced, cast, cured, and
finished in accordance with Chapter 4, Concrete Works, and the details shown in the Contract plans.
All cast-in-situ concrete shall be Class C30/20. Formwork shall comply with Section 1.20.8 of
Chapter 1, General Requirement, of these

Standard Specifications

Cast-in-situ concrete for adjacent wall stem sections between vertical expansion joints shall be
formed and placed separately, with a minimum 12-hour time period between concrete placement
operations or as approved by the Engineer.

Premoulded joint filler, 12 mm thick, shall be placed at the full height of all vertical wall stem
expansion joints. When the Contract plans call for premoulded joint filler, the Contractor shall fasten
it with galvanised wire nails to one side of the joint. Nails must be no more than 150 mm apart and
shall be 40 mm from the edges over the entire joint area. Nails shall be at least 40 mm longer than
the thickness of the filler.

Nails may be substituted by the Contractor with any adhesive approved by the Engineer. This
adhesive, however, shall be compatible with ASTM D 1751

(29)

materials and capable of bonding the

filler to portland cement concrete (PCC).

Backfill, Weepholes, and Gutters

Backfill, weepholes, and gutters shall be constructed as shown on the Contract plans. Unless
otherwise shown in the Contract plans, structural backfill conforming to the requirements of Section
2.5.2.4 of Chapter 2, Earth Works, backfill, shall be installed in the zone between the back of wall
and a vertical plane extending up from the back of the footing or from the back of the wall drain,
whichever is farther from the back of the wall. Structural backfill shall extend the full height of the
wall or to 200 mm below the concrete gutter, if present, unless otherwise shown on the Contract
plans.

Backfill and compaction in bridge approach zones shall be done for each layer. For other areas,
backfill and compaction shall only be required for the top 600 mm of depth. All backfill and
compaction shall be performed in accordance with Section 2.5.3.4 of Chapter 2, Earth Works, of the

Standard Specifications.

Weepholes are typically 75-mm-diameter openings placed in the wall panel above the ground level
at the face of wall and sloped down toward the face of wall, as shown in the Contract plans.

20.6.2

Sheet-pile, Soldier-pile and Secant Pile walls

This work constructs continuous walls of timber, steel, or concrete sheet piles, and constructs
soldier-pile (H-Beam/King Post) walls with horizontal facing elements of timber, steel, or concrete.

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20.6.2.1 Description

This work constructs sheet pile, soldier-pile walls, soldier-pile tie-back walls, concrete soldier-pile
walls, and secant pile walls.

Soldier-pile walls consist of steel piles, which may be wide flanges or pipes, embedded into the
ground along the wall alignment with timber lagging installed to retain soil between the piles. Soldier-
pile tie-back walls are soldier-pile walls with ground anchors installed between piles.

Concrete soldier-pile walls use reinforced concrete shafts instead of steel piles, and the unsupported
length of wall between concrete piles is retained by reinforced shotcrete facing in place of timber
lagging.

Secant pile walls consist of closely spaced concrete shafts with no unreinforced space between the
constructed shafts.

20.6.2.2 Materials

Materials shall meet the requirements of Table 20-7 and as described herein.

Table 20-7: Materials for soldier-pile and soldier-pile tie-back walls

Material

Specification section

PCC and its constituent materials;

Steel reinforcing bar and epoxy-coated steel reinforcing bar;

Premoulded joint filler and waterstops.

Chapters 4 and 5, Materials

Backfill

Chapter 2, Structural backfill

Pipe underdrains

Chapter 11, Pipe underdrains

Controlled density fill (CDF)

Chapter 4, Controlled density fill

Permanent ground anchors

Chapter 19, Ground Anchors

Paints

Chapter 24, Painting

Shotcrete

Chapter 7, Shotcrete facing

Timber lagging for soldier-pile walls shall be structural grade material of the size, species, and grade
shown on the Contract plans, or as directed by the Engineer. Grades shall be as established by the
United Kingdom Timber Grading Committee, or equivalent international timber grading certification
organisation, as approved by the Engineer

. Unless otherwise specified, timber lagging in walls with

concrete fascia panels shall be untreated. Timber lagging for all other walls shall be treated.

Material for steel piling and pile splices shall conform to ASTM A 36M or ASTM A 992M, except the
material for steel pipe piling and splices shall conform to the requirements of ASTM A 252, Grade 2.
Steel soldier-piles, and associated steel bars and plates, shall conform to ASTM A 36M or ASTM A
992M, except as otherwise noted in the Contract plans. All steel piling material may be accepted by
the Engineer based on the manufacturer’s certificate of compliance.

Other materials required shall be as specified in the particular specifications.

20.6.2.3 Sheet-pile

Walls

Steel sheet piles shall be of the type and weight (mass) specified in the Contract documents. Steel
sheet piles shall conform to the requirements of AASHTO M 202M/M 202 (ASTM A328/A328M),

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AASHTO M 270M/M 270 (ASTM A709/A709M) Grade 50 (Grade 345), or to the specifications for
Piling for Use in Marine Environments in ASTM A690/A690M.

Painting of steel sheet piles, when required, shall conform to the requirements of Section 24.5 of
Chapter 24, Painting, of the

Standard Specifications

Timber sheet piles, unless otherwise specified or permitted in the Contract documents, shall be
treated in accordance with American Association of State Highway and Transportation Officials
(AASHTO) LRFD Bridge Construction Specifications, Chapter 17, Preservative treatment of wood.
Piles shall be of the dimensions, species, and grade of timber specified in the Contract documents.
Piles may be either cut from solid material or made by building up with three planks securely fastened
together.

Piles shall be drift sharpened at their lower ends so as to wedge adjacent piles tightly together during
driving.

Concrete sheet piles shall conform to the details specified in the Contract documents or the approved
working drawings. Manufacture and installation of sheet piles shall conform, in general, to the
requirements for precast concrete bearing piles in Chapter 18 of the

Standard Specifications,

Driven

Piles.

Concrete sheet piles detailed to have a tongue and groove joint on the portion below-ground and a
double-grooved joint on the exposed portion shall, after installation, have the upper grooves cleaned
of all sand, mud, or debris and grouted full. Unless otherwise provided in the Contract documents,
or approved in writing by the Engineer, grout shall be composed of one part cement and two parts
sand. The grout shall be deposited through a grout pipe placed within a watertight plastic sheath
extending the full depth of the grout slot formed by the grooves in two adjacent pilings and which,
when filled, completely fills the slot.

Sheet piles shall be driven to the specified penetration or bearing capacity in accordance with the
requirements of Chapter 18 of the

Standard Specifications,

Driven Piles.

After driving, the tops of sheet piles shall be neatly cut-off to a straight line at the elevation specified
in the Contract documents, or as directed by the Engineer.

Sheet-pile walls shall be braced by wales or other bracing system, as shown in the Contract
documents, or directed by the Engineer.

Timber waling strips shall be properly lapped and joined at all splices and corners. The wales shall
preferably be in one length between corners and shall be bolted near the tops of the piles.

When specified in the Contract documents, or in the approved working drawings, reinforced concrete
caps shall be constructed in accordance with Chapter 4, Concrete Works, of these

Standard

Specifications

20.6.2.4 Soldier-pile

Walls

Soldier-piles (H-Beam/King Post) shall be either driven piles or piles constructed in a drilled shaft
excavation to the specified penetration or bearing capacity indicated in the Contract documents.

Driven piles shall be furnished and installed in accordance with the requirements of Chapter 18 of
the

Standard Specifications,

Driven Piles. Piles shall be of the type indicated in the Contract

documents.

Piles constructed in a drilled shaft excavation shall conform to the details shown in the Contract
documents.

Construction of the shaft excavation and placement of concrete or lean concrete backfill shall be in
accordance with Chapter 17, of the

Standard Specifications,

Drilled Piles. Structural components of

the soldier-pile placed in the shaft excavation shall be as specified in the Contract documents.
Reinforced concrete, either cast-in-place or precast, shall conform to the requirements of Chapter 4
of the

Standard Specifications,

Concrete Works.

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Timber members shall conform to the requirements of the American Association of State Highway
and Transportation Officials (AASHTO) LRFD Bridge Construction Specifications, 2010, Chapter 16,
Timber structures and Chapter 17, Preservative treatment of wood of and Chapter 7 of the

Standard

Specifications,

Incidental Construction.

Steel members shall conform to the requirements of Chapter 23 of the

Standard Specifications,

Steel

Structures. Painting of steel members, if required, shall conform to the requirements of Section 24.5
of Chapter 24, Painting, of the

Standard Specifications.

Concrete backfill placed around precast concrete, timber, or steel pile members in the drilled shaft
excavation shall be of class C20/20 or as shown in the Contract plans. The limits for placement of
concrete and lean concrete shall be specified in the Contract documents.

The facing spanning horizontally between soldier-piles shall conform to the materials and details in
the Contract documents or in the approved working drawings. Timber lagging shall conform to the
requirements of the American Association of State Highway and Transportation Officials (AASHTO)
LRFD  Bridge  Construction  Specifications,  Chapter  16,  Timber  structures,  and  Chapter  17,
Preservative  treatment  of  wood.  Precast  concrete  lagging  or  facing  panels  and  cast-in-place
concrete  facing  shall  conform  to  the  requirements  in  Chapter  4  of  the

Standard Specifications,

Concrete Works.

Concrete anchors, welded connections, and bolted connections for securing facing elements to the
soldier-piles shall conform to the details in the Contract documents.

Exposed surfaces of concrete wall facing shall receive a Class 1 finish, as specified in Chapter 4 of
the

Standard Specifications,

Concrete Works, unless a special architectural treatment is specified in

the Contract documents or in the approved working drawings.

20.6.2.5 Secant-Pile Walls

Secant pile walls shall be constructed in the same manner as concrete soldier-pile walls, except that
the sequence of shaft construction shall be as indicated in the particular specifications. Primary
shafts are installed first and allowed to cure undisturbed for the minimum time established in the
particular specifications before secondary piles are constructed in the intermediate areas.

20.6.2.6 Anchored

Sheet-pile and Soldier-pile Walls

Anchored wall construction shall consist of constructing sheet-pile and soldier-pile walls anchored
with a tie-rod and concrete anchor system or with ground anchors. Sheet-pile and soldier-pile wall
construction shall conform to the requirements of Articles 20.6.2.3 and 20.6.2.4, respectively.

Wales

Wales consisting of timber, steel, or concrete shall conform to the details in the Contract documents,
or in the approved working drawings. The alignment of wales shall be such that tie-rods or ground
anchors can be installed without excessive bending. Steel wales shall conform to the requirements
of Chapter 23 of the

Standard Specifications,

Steel Structures. Concrete wales shall conform to the

requirements of Chapter 4 of the

Standard Specifications,

Concrete Works.

Concrete Anchor System

Concrete anchor systems, consisting of drilled shafts or reinforced concrete shapes placed within
the limits of soil or rock excavation, with or without pile support, shall conform to the details in the
Contract documents or in the approved working drawings.

Battered anchor piles shall be driven to the proper batter shown. The tension anchor piles shall be
furnished with adequate means of anchorage to the concrete anchor block.

Drilled shaft concrete anchors shall conform to the details in the Contract documents or in the
approved working drawings and be constructed in conformance with Chapter 17 of the

Standard

Specifications,

Drilled Piles.

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Tie-rods

Tie-rods shall be round-steel bars conforming to AASHTO M 270M/M 270 (ASTM A709/A709M),
Grade 36 (Grade 250), unless otherwise specified in the Contract documents.

Corrosion protection shall be provided as specified in the Contract documents. Care shall be taken
in the handling and backfilling operations to prevent damage to the corrosion protection or bending
of the tie-rod itself.

Tie-rod connections to the soldier-piles, wales, wall faces, and concrete anchors shall conform to
the details specified in the Contract documents.

Ground Anchors

Ground anchors shall be constructed in conformance with the requirements of Chapter 19 of the

Standard Specifications,

Ground Anchors.

Ground anchor connections to soldier-piles, wales, or wall faces shall conform to the details in the
Contract documents, or in the approved working drawings. Anchor elongation shall be monitored
and approved before final cutting of strands.

Earthwork

Earthwork shall conform to the requirements in Section 20.4.

Unless otherwise specified in the Contract documents, excavation in front of the wall shall not
proceed more than 900mm below a level of tie-rods or ground anchors until tie-rods and anchors, or
ground anchors, are completed and accepted by the Engineer.

Placement of lagging shall closely follow excavation in front of the wall such that loss of ground is
minimized.

20.6.3

Crib and Cellular Walls

This work constructs timber, concrete, or steel crib walls; and concrete monolithic cell walls,
complete with backfill material, within the cells formed by the members.

20.6.3.1 Foundation

In addition to the requirements of Section 20.4.2, the foundation or bed course material shall be
finished to exact grade and cross slope so that the vertical or battered face alignment shall be
achieved.

When required, timber mud sills, concrete levelling pads, or concrete footings shall conform to the
details specified in the Contract documents. Timber mud sills shall be firmly and evenly bedded in
the foundation material.

Concrete for levelling pads, or footings, shall be placed against the sides of excavation in the
foundation material.

20.6.3.2 Crib

Members

Unless otherwise specified in the Contract documents, timber headers and stretcher members shall
conform  to  the  requirements  of  the  American  Association  of  State  Highway  and  Transportation
Officials (AASHTO) LRFD Bridge Construction Specifications, Chapter 16, Timber structures, and
shall  be  the  same  as  for  caps,  posts,  and  sills.  Preservative  treatment  shall  conform  to  the
requirements of the American Association of State Highway and Transportation Officials (AASHTO)
LRFD  Bridge  Construction  Specifications,  Chapter  17,  Preservative  treatment  of  wood.  Member
sizes shall be as shown in the Contract documents.

Concrete header and stretcher members shall conform to the requirements of Chapter 4 of the

Standard Specifications,

Concrete Works, for precast concrete members. Member dimensions and

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minimum concrete strengths shall be as specified in the Contract documents, or in the approved
working drawings.

Steel crib members consisting of base plates, columns, stretchers, and spacers shall be fabricated
from  sheet  steel  conforming  to  AASHTO  M  218.  Member  thickness  shall  be  as  specified.  Crib
members shall be so fabricated that members of the same nominal size and thickness shall be fully
interchangeable.  No  drilling,  punching,  or  drifting  to  correct  defects  in  manufacture  shall  be
permitted.  Any  members  having  holes  improperly  punched  shall  be  replaced.  Bolts,  nuts,  and
miscellaneous hardware shall be galvanized in accordance with AASHTO M 232M/M 232 (ASTM
A153/A153M).

20.6.3.3 Concrete

Monolithic Cell Members

Concrete monolithic cell members consisting of four-sided cells of uniform height and various depths
shall be cast in conformance with the requirements set forth for precast members in Chapter 21 of
the

Standard Specifications,

Concrete Structures. Minimum concrete compressive strengths shall

be of class C30/20.

Exposed cell faces shall have a Class 1 finish; faces not exposed to view shall have a uniform surface
finish free of open pockets of aggregate or surface distortions in excess of 6mm. Protruding keys
and recesses for keys on the tops and bottoms of the side walls of the cells shall be accurately
located.

20.6.3.4 Member

Placement

Timber and concrete crib members shall be placed in successive tiers at spacing conforming to the
specified details for the particular height of the wall being constructed.

Drift bolts at the intersection of timber header and stretcher members shall be accurately installed
so that minimum edge distances are maintained. At the intersection of concrete header and stretcher
members, asphalt felt shims, or other approved material, shall be used to obtain uniform bearing
between the members.

Steel column sections, stretchers, and spacers shall conform to the proper length and weight, or
mass, as specified in the Contract plans. These members shall be accurately aligned to permit
completing the bolted connections without distorting the members. Bolts at the connections shall be
torque to not less than 34000 N.mm.

Concrete monolithic cell members of the proper sizes shall be successively stacked in conformance
with the layout specified in the Contract documents or in the approved working drawings. Care shall
be exercised in placing the members to prevent damage to the protruding keys. Damaged or ill-fitting
keys shall be repaired using a method approved by the Engineer.

20.6.3.5 Backfilling

Cells formed by the wall members shall be backfilled with structure backfill material conforming to
the requirements in Section 20.3.6. Backfilling shall progress simultaneously with the erection of the
members forming the cells. Placement of backfill material shall not disturb or damage the members.
Overall stability shall be considered, including construction loading and surcharge.

Placement of backfill shall be in uniform layers not exceeding 300mm in thickness, unless otherwise
proposed by the Contractor and approved by the Engineer. Compaction shall be to a density of at
least 95 percent of the maximum density, as determined by AASHTO T 99, Method C.

Backfilling behind the wall to the limits of excavation shall conform to the same requirements, unless
otherwise indicated or approved.

20.6.4

MSE Walls

This Section specifies construction of retaining walls using a proprietary reinforced soil wall system
using either Precast Concrete Facing Panels or Modular Block Facing Units, constructed in

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accordance with the supplier's drawings and specifications and in conformity with the alignment,
grades and dimensions shown on the Contract plans or as established by the Engineer.

MSE wall construction shall consist of constructing a facing system to which polymeric soil
reinforcement is connected and the placement of reinforced infill material surrounding the soil
reinforcement.

20.6.4.1 Terminology

Inclusion: is a generic term that encompasses all man-made elements incorporated in the soil to
improve its behaviour. Examples of inclusions are geotextile sheets, or polymeric grids. The term
reinforcement is used only for those inclusions where soil-inclusion stress transfer occurs
continuously along the inclusion.

Mechanically Stabilized Earth Wall (MSEW): is a generic term that includes reinforced soil (a term
used when multiple layers of inclusions act as reinforcement in soils placed as fill).

Reinforced Soil Slopes (RSS): are forms of reinforced soil that incorporate planar reinforcing
elements in constructed earth-sloped structures with face inclinations of less than 70 degrees.

Geosynthetics: is a generic term that encompasses flexible polymeric materials used in geotechnical
engineering such as geotextiles, geomembranes, geonets, and grids (also known as geogrids).

Facing:  is  a  component  of  the  reinforced  soil  system  used  to  prevent  the  soil  from  ravelling  out
between  the  rows  of  reinforcement.  Common  facings  include  precast  concrete  panels,  dry  cast
modular  blocks,  shotcrete,  wood  lagging  and  panels,  and  wrapped  sheets  of  geosynthetics.  The
facing also plays a minor structural role in the stability of the structure. For RSS structures it usually
consists of some type of erosion control material.

Retained Soil: is the fill material located between the mechanically stabilized soil mass and the
natural soil.

Reinforced (Infill) Soil: is the fill material in which the reinforcements are placed.

20.6.4.2 References

All work shall conform to the latest edition of all applicable standards and codes. The following is a
representative list of applicable codes and standards however is not an all inclusive list.

a. American Concrete Institute (ACI):

1. 318/318R, Building Code Requirements for Reinforced Concrete.

b. American Society for Testing and Materials (ASTM):

1. A615/A615M, Standard Specification for Deformed and Plain Billet-Steel Bars for

Concrete Reinforcement.

2. A775/A775M, Standard Specification for Epoxy-Coated Reinforcing Steel Bars.
3. ASTM 4595 , Tensile tests for geotextiles and geogrids.

c. American Association of State Highway and Transportation Officials (AASHTO):

1. AASHTO-LRFD "Bridge Design Specifications
2. (AASHTO) LRFD Bridge Construction Specifications,.

d. U.S Federal Highway Administration publications:

1. FHWA No. FHWA-NHI-10-024 and FHWA-NHI-10-025.

20.6.4.3 General

Requirements

a. The Contractor shall provide a complete set of drawings issued for construction and complete

specifications of the proposed wall system for the approval of the Engineer prior to ordering
materials to construct these walls.

b. Any particular requirements of the approved detailed specifications for the approved

proprietary system shall govern over any conflicting or incompatible requirement contained
within these Specifications.

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