STANDARD SPECIFICATIONS FOR CONSTRUCTION OF ROADS AND BRIDGES ON FEDERAL HIGHWAY PROJECTS (FP-14) - page 5

 

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STANDARD SPECIFICATIONS FOR CONSTRUCTION OF ROADS AND BRIDGES ON FEDERAL HIGHWAY PROJECTS (FP-14) - page 5

 

 

Section 213
213.07 Mixing. Keep traffic, except mixing equipment off the spread material. Use a rotary mixer.
(a) Lime mixtures.
(1) Preliminary mixing. Adjust the moisture content of the mixture to optimum plus necessary
hydration moisture. Use the mix design hydration moisture rate. Thoroughly mix the lime, soil,
and water to obtain a homogeneous friable mixture. Complete the mixing on the same day lime
is applied. Check to ensure lime is fully hydrated and add additional water if necessary.
Mellow the mixture for 1 to 4 days at a moisture content of 2 to 3 percent above optimum as
directed by the CO.
(2) Final mixing. Remix until 95 percent of the mixture, except hard and durable particles,
passes a 1½-inch (37.5-millimeter) sieve and at least 50 percent of the soil portion of the mixture
passes a No. 4 (4.75-millimeter) sieve when tested according to AASHTO T 27 in the non-dried
condition.
(b) Lime/fly ash mixtures. Mix according to Subsection 213.07(a)(1). Use either a pre-blended
lime/fly ash mixture or mix the lime and fly ash in separate operations.
If the lime and fly ash are mixed separately, mix the lime first and mix the fly ash within 2 days of
lime mixing. Adjust the moisture content of the lime/fly ash mixture to 2 to 3 percent above
optimum. Mix the material to prevent formation of fly ash balls. Complete the mixing within 2 hours
after adding the fly ash.
(c) Cement, fly ash, or cement/fly ash mixtures. Add water to adjust the moisture content of the
mixture to 2 to 3 percent above optimum. Mix the material until 95 percent of the soil portion of the
mixture hard and durable particles passes a 1½-inch (37.5-millimeter) sieve and at least 50 percent
of the soil portion of the mixture passes a No. 4 (4.75-millimeter) sieve when tested according to
AASHTO T 27 in the non-dried condition. Complete the mixing within 2 hours after the cement, fly
ash, or both are added.
213.08 Compacting and Finishing. Immediately after final mixing, spread and compact the mixture. Use
a vibratory sheep-foot roller to achieve compaction. Use pneumatic-tire and smooth-drum rollers for finish
rolling.
Compact the mixture to at least 95 percent of maximum dry density from the approved mix design.
Complete compaction operations within 2 hours of completion of mixing.
Finish the compacted subgrade to within plus or minus 0.10 foot (30 millimeters) of the staked line, grade,
and cross-section. Check the surface with a 10-foot (3-meter) straightedge.
Add or remove material to correct surface deviations in excess of ¾ inches in 10 feet (19 millimeters in
3 meters) between two contacts of the straightedge with the surface. When adding material, scarify the
subgrade to at least 6 inches (150 millimeters). Recompact the area to restore the required density and
strength. For Subsection 213.07(b) or (c) mixtures, complete compaction operations within 2 hours of
adding the cement, fly ash, or both.
145
Section 213
213.09 Curing. Keep the subgrade continuously moist and within 3 percent of optimum moisture content
until the next course is placed. Apply water under pressure through a spray bar equipped with nozzles,
which produce a fine, uniform spray. Place the next course within 14 days after compacting and finishing.
If the subgrade deforms, loses density, or ravels before placement of the next course; correct the damaged
subgrade.
Traffic may be allowed on the stabilized subgrade 24 hours after compaction and finishing if approved by
the CO.
213.10 Acceptance. See Table 213-2 for sampling, testing, and acceptance requirements.
Material for chemical admixtures, fly ash, lime, hydraulic cement, and water will be evaluated under
Subsections 106.02 and 106.03.
Subgrade stabilization work will be evaluated under Subsections 106.02 and 106.04.
Reconditioning of subgrade will be evaluated under Section 303.
Measurement
213.11 Measure the Section 213 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable.
Measure width horizontally to include the top of subgrade width and allowable widening. Measure length
horizontally along the centerline of the roadway.
Payment
213.12 The accepted quantities will be paid at the contract price per unit of measurement for the Section
213 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
146
Section 213
Table 213-2
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Mix Design
Subgrade
Measured and
Proportioning
Subsection
1 per
Existing
Yes
30 days
stabilization
tested for
213.03
submitted
roadbed /
before
conformance
mix design
subgrade
production
(106.04)
Production
Stabilized
Measured and
Moisture-density
AASHTO
1 per
Processed
Yes, when
Before
material
tested for
T 99, Method C(1)
soil type, but
material behind
requested
using
conformance
not less than
mixer
in work
(106.04)
1 for each day
of production
Gradation
AASHTO
1 per
"
"
T 27 & T 11
3500 yd2
(3000 m2),
but not less
than 1 per layer
Density
AASHTO
"
In-place
No
Before
T 310 or other
placing
approved procedures
next layer
Compressive
ASTM
"
Processed
Yes, when
"
strength
D5102(2), D1633(3)
material behind
requested
(7-day cure)
as applicable
mixer
(1) Minimum of 5 points per proctor.
(2) At 7-day cure at 105°F (40 °C). Compact sampled material immediately according to Procedure B. Do not complete the proportioning and mixing of
Sections 10.2 and 10.3. Report average unconfined compressive strength from at least three specimens.
(3) At 7-day cure. Report average unconfined compressive strength from at least three specimens.
147
148
DIVISION 250
SLOPE REINFORCEMENT
AND RETAINING WALLS
149
Section 251
Section 251. — RIPRAP
Description
251.01 This work consists of furnishing and placing riprap for bank protection, slope protection, drainage
structures, and erosion control.
Riprap acceptance methods are designated according to Table
251-1. If no acceptance method is
designated, use Method A.
Riprap classes are designated according to Table 705-1.
Geotextile filters are designated according to Table 714-1.
Material
251.02 Conform to the following Subsections:
Geotextile
714.01
Neat hydraulic cement grout
725.13(a)(2)
Riprap
705.02
Construction Requirements
251.03 General. Perform the work under Section 209. Dress the slope to produce a smooth surface. If
geotextile filter is required, place according to Section 207.
251.04 Placed Riprap. Placed riprap is rock placed on a prepared surface to form a well-graded mass.
Place riprap to its full thickness in one operation to avoid displacing the underlying material. Do not place
riprap material by methods that cause segregation or damage to the prepared surface. Place or rearrange
individual rocks by mechanical or hand methods to obtain a dense uniform blanket with a reasonably
smooth surface.
251.05 Keyed Riprap. Keyed riprap is rock placed on a prepared surface and set into place by impact
pressure.
Place rock for keyed riprap according to Subsection 251.04. Set the riprap into place by exerting impact
pressure with a hydraulic-powered bucket or an approximate 5000-pound (2000-kilogram) flat-faced mass.
Repeated impacts should be made until the rock is firmly seated and forms a reasonably uniform surface
without reducing the effective sizes of the rocks. Do not use impact pressure on riprap below the water
surface.
251.06 Grouted Riprap. Grouted riprap is rock placed or keyed on a prepared surface with the voids
filled with grout.
150
Section 251
Place rock for grouted riprap according to Subsection 251.04 or 251.05. Thoroughly moisten the rocks and
wash excess fines from the riprap or to the underside of the riprap. Do not place grout unless the air
temperature is at or above 35 °F (1 °C) within the near-surface voids of the riprap. Place the grout in a
manner to prevent segregation. Begin placing grout at the lowest elevation of the riprap. Fill voids without
unseating the rocks. Do not exceed 5-foot (1.5-meter) thickness for each layer of grouted riprap. Allow
3 days curing time before adding the next layer of riprap and grout. Provide weep holes through the
grouted riprap as required. Keep the grouted riprap moist for 3 days after the work is completed and
protect it from freezing for at least 7 days after grouting.
251.07 Acceptance. See Table 251-1 for sampling, testing, and acceptance requirements.
Rock for riprap will be evaluated under Subsections 106.02 and 106.04.
Material for grout will be evaluated under Subsections 106.02 and 106.03.
Acceptance Method A riprap construction will be evaluated under Subsection 106.02.
Acceptance Method B riprap construction will be evaluated under Subsections 106.02 and 106.04.
Placing grout will be evaluated under Subsection 106.02.
Geotextile filters will be evaluated under Section 207.
Structure excavation and backfill will be evaluated under Section 209.
Measurement
251.08 Measure the Section 251 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring riprap by the cubic yard (cubic meter), measure in place.
Payment
251.09 The accepted quantities will be paid at the contract price per unit of measurement for the Section
251 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
151
Section 251
Table 251-1
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Source
Riprap
Measured and
Apparent
-
AASHTO
1 per
Source
Yes
Before
-
(705.02)
tested for
specific gravity
T 85
material
of
using in
conformance
& absorption
type
material
work
(106.04 & 105)
Soundness
-
AASHTO
"
"
"
"
-
using
T 104
sodium sulfate
LA abrasion
-
AASHTO
"
"
"
"
-
T 96
Production
Riprap
Process control
Size
-
See Note (2)
1 per
In-place
"
"
-
(705.02)
(153.03)
Methods
100 yd3
A & B
(80 m3)
per Class
Measured and
Gradation(1)
-
FLH
1 per
Stockpile
No
24
-
tested for
Method B
T 521
1000 yd3
or
hours
conformance
(800 m3)
in-place(3)
(106.02 & 106.04)
per Class
(1) Notify CO at least 7 days before performing test.
(2) Verify riprap class by confirming that the largest accessible rock has an intermediate dimension greater than the upper limit of the D85 size range
specified in Table 705-1.
(3) Point of sampling to be approved by CO.
152
Section 252
Section 252. — ROCKERY, SPECIAL ROCK EMBANKMENT,
AND ROCK BUTTRESS
Description
252.01 This work consists of constructing rockeries, special rock embankments, and rock buttresses.
Geotextile filters are designated according to Table 714-1.
Material
252.02 Conform to the following Subsections:
Foundation fill
704.01
Geotextile
714.01
Granular rock backdrain
703.17
Neat hydraulic cement grout
725.13(a)(2)
Rock for buttresses
705.05
Rock for rockeries
705.06
Rock for special rock embankment
705.04
Construction Requirements
252.03 Rockery. Verify the limits of the rockeries. Notify the CO if planned rockery lengths, heights, or
both are inadequate to intersect with adjacent slopes. Submit cross-sections verifying intersections for
approval.
Construct rockeries as follows:
(a) Excavation. Perform the work under Sections 204 and 209 as required. Do not excavate more
areas for rockeries than can be replaced with rockery construction in one shift unless shoring is
provided. Protect backslopes from damage by surface water.
(b) Erection. Remove sharp objects from the backslope before installing geotextile filter. Anchor
geotextile filter to the excavation backslope to withstand backfilling operations. Overlap the
geotextile filter at least 24 inches (600 millimeters) at seams. Reinforce damaged fabric with a patch
of the same type of geotextile filter by overlapping the patch 36 inches (900 millimeters) beyond the
damaged area in all directions.
Furnish and install drain systems according to Section 605 when specified. Do not connect collector
pipes to storm water retention systems unless approved by the CO.
Seat rocks firmly on a prepared foundation.
153
Section 252
Place rocks to avoid continuous joints in either the vertical or horizontal direction. Locate at least
one bearing point a distance no greater than 6 inches (150 millimeters) from the face of the rockery.
Place each rock to ensure it bears on at least two rocks below. Place incrementally smaller rocks as
construction proceeds in successive lifts. Slope the top surface of each rock towards the back of the
rockery at an inclination of at least 5 percent.
Choke voids from the drain side of the rockery in each successive lift. Choke voids greater than
6 inches (150 millimeters) with a rock large enough to fill the void.
Backfill with granular rock backdrain concurrent with rock placement until level with the top of
rock. Place granular rock backdrain in horizontal layers not to exceed 12 inches (300 millimeters)
compacted depth. Compact each layer according to Subsection 204.11. Compact areas not accessible
to rollers with other approved methods.
252.04 Special Rock Embankment and Rock Buttress. Verify the limits of embankments and
buttresses. Notify the CO if the embankment or buttress lengths, heights, or both are inadequate to
intersect with adjacent slopes. Perform the work under Sections 204 or 209 as required. When specified,
place geotextile filter according to Section 207.
Place rocks in a stable orientation with minimal voids to produce a random pattern. Construct the
exposed face of the rock mass reasonably uniform with projections beyond the line of the slope that are
no greater than 12 inches (300 millimeters) for mechanically-placed rock or 6 inches (150 millimeters)
for hand-placed rock.
Use rock smaller than the minimum rock size to choke the larger rock solidly in position and to fill voids
between the large rocks.
252.05 Acceptance. See Table 252-1 for sampling, testing, and acceptance requirements.
Material for rockeries, special rock embankments, and rock buttresses will be evaluated under
Subsections 106.02, 106.03, and 106.04.
Construction of rockeries, special rock embankments, and rock buttresses will be evaluated under
Subsections 106.02 and 106.04.
Roadway excavation will be evaluated under Section 204.
Geotextile filters will be evaluated under Section 207.
Structure excavation and backfill will be evaluated under Section 209.
Measurement
252.06 Measure the Section 252 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring rockeries by the square feet (square meter) of rockery front face; measure the rockery
from the bottom of the base rock elevation to the top of the cap rock elevation. Measure front face on a
plane parallel to the rockery face.
154
Section 252
When measuring special rock embankment and rock buttress by the cubic yard (cubic meter), measure in
place.
Payment
252.07 The accepted quantities will be paid at the contract price per unit of measurement for the Section
252 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
155
Section 252
Table 252-1
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Source
Rock for
Measured and
Rock breadth
Subsection
1 per
Source of
No
Before
buttresses
tested for
and thickness
705.05(a)(1)
rock type
material
using
(705.05)
conformance
in work
(106.04 & 105)
Apparent
AASHTO T 85
"
"
Yes
"
Not required
specific
when using
gravity
Government
-provided
source
Absorption
"
"
"
"
"
"
Durability index
AASHTO T 210
"
"
"
"
"
(course)
Rock for
"
Apparent
"
1 per
Source of
Yes
Before
Not required
rockeries
specific gravity
rock type
material
using
when using
(705.06)
in work
Government
-provided
source
Absorption
"
"
"
"
"
"
LA abrasion
AASHTO T 96
"
"
"
"
"
Durability index
AASHTO T 210
"
"
"
"
"
(course)
Soundness
AASHTO T 104
"
"
"
"
"
using
sodium sulfate
156
Section 252
Table 252-1 (continued)
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Production
Rock for
Process control
Size
See Note (1)
1 per
In-place
No
24
special rock
(153.03)
100 yd3
hours
embankment
(80 m3)
(705.04)
Rock for
"
"
"
1 per
"
"
"
buttresses
100 yd3
(705.05)
(80 m3)
Rock for
"
"
See Note (2)
2 per
"
"
"
rockeries
lift of rock
(705.06)
per rockery
(1) For mechanically placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension greater than the D50 size
specified in Table 705-2. Also confirm that the smallest accessible rock has an intermediate dimension within the lower D50 size range specified in Table 705-2.
For hand placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension greater than the D75 size specified in
Table 705-3. Also confirm that the smallest accessible rock has an intermediate dimension within the D25 size range specified in Table 705-3.
(2) Verify rock size by confirming that the largest accessible rock has a width greater than the minimum width specified in the Rockery Design Table and Rockery
Detail Sheets in the plans.
157
Section 253
Section 253. — GABIONS AND REVET MATTRESSES
Description
253.01 This work consists of constructing rock filled gabion structures and revet mattresses.
(a) Gabions baskets. A rock filled wire enclosure having a height of 12 inches (300 millimeters) or
more.
(b) Revet mattresses. A rock filled wire enclosure having a thickness of less than
12 inches
(300 millimeters).
Geotextile filters are designated according to Table 714-1.
Material
253.02 Conform to the following Subsections:
Backfill material
704.03
Gabion and revet mattress material
720.02
Gabion and revet mattress rock
705.01
Geotextile
714.01
Structural backfill
704.04
Construction Requirements
253.03 General. Verify the limits of the structure. Submit drawings according to Subsection 104.03. See
Section 257 for Contractor-designed gabion walls.
Perform excavation and backfill according to Section 209.
253.04 Basket Assembly. Furnish twisted wire or welded wire baskets. Do not damage wire coatings
during basket assembly, structure erection, cell filling, or backfilling. Rotate the basket panels into position
and join the vertical edges with fasteners according to Subsection 253.05. Temporary fasteners may be
used for basket assembly if they are supplemented during structure erection with permanent fasteners
according to Subsection 253.05.
Rotate the diaphragms into position and join the vertical edges according to Subsection 253.05.
253.05 Structure Erection. Place the empty gabion baskets on the foundation and interconnect the
adjacent baskets along the top and vertical edges using permanent fasteners.
Where lacing wire is used, wrap the wire with alternating single and double loops every other mesh
opening and not more than 6 inches (150 millimeters) apart. Where spiral binders are used, crimp the ends
to secure the binders in place. Where alternate fasteners are used, space the fasteners in every mesh
opening and not more than 6 inches (150 millimeters) apart.
158
Section 253
Interconnect each vertical layer of baskets to the underlying layer of baskets along the front, back, and
sides. Stagger the vertical joints between baskets of adjacent rows and layers by at least one-half the cell
length.
253.06 Cell Filling. Remove kinks and folds in the wire mesh, and properly align the baskets. Place rock
carefully in the basket cells to prevent bulging of the baskets and to minimize voids in the rock fill.
Maintain the basket alignment.
Place stiffeners in each unrestrained exterior basket cell greater than 12 inches (300 millimeters) in height.
This includes interior basket cells left temporarily unrestrained. Place stiffeners concurrently with rock
placement.
Fill the cells in a row or layer to ensure no cell is filled more than 12 inches (300 millimeters) above an
adjacent cell. Repeat this process until the basket is full and the lid bears on the final rock layer.
Secure the lid to the sides, ends, and diaphragms according to Subsection 253.05. Make exposed basket
surfaces smooth and neat with no sharp rock edges projecting through the wire mesh.
253.07 Backfilling. Place a geotextile filter over the back face of the gabion structure. Concurrently with
the cell filling operation, backfill the area behind the gabion structure with structural backfill according to
Subsection
209.09. Compact each layer according to Subsection 209.10, except use an acceptable
lightweight mechanical or vibratory compactor within 36 inches (900 millimeters) of the gabion structure.
253.08 Revet Mattresses. Place a geotextile filter according to Section 207. Construct revet mattresses
according to Subsections 253.04 through 253.06. Anchor the mattresses in place according to the
manufacturer’s recommendations. Place geotextile filter against the vertical edges of the mattress and
backfill against the geotextile filter using backfill material. Overfill revet mattresses by 1 to 2 inches (25 to
50 millimeters).
253.09 Acceptance. See Table 209-1 for sampling, testing, and acceptance requirements.
Material for gabion structures and revet mattresses will be evaluated under Subsections 106.02 and 106.03.
Construction of gabion structures and revet mattresses will be evaluated under Subsections 106.02 and
106.04.
Geotextile filters will be evaluated under Section 207.
Structure excavation, structural backfill, and backfill material will be evaluated under Section 209.
Measurement
253.10 Measure the Section 253 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring gabions by the cubic yard (cubic meter), measure in the structure.
Measure foundation fill under Section 208.
159
Section 253
Payment
253.11 The accepted quantities will be paid at the contract price per unit of measurement for the Section
253 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
160
Section 254. — RESERVED
161
Section 255
Section 255. — MECHANICALLY-STABLILIZED EARTH WALLS
Description
255.01 This work consists of constructing mechanically-stabilized earth (MSE) walls.
Geotextile filters are designated according to Table 714-1.
Reinforcement geotextile and geogrid are designated according to Tables 714-5 and 714-6.
Material
255.02 Conform to the following Section and Subsections:
Concrete masonry units
725.07(a)
Geotextile
714.01
Mechanically-stabilized earth wall material
720.01
Minor concrete
601
Reinforcement geotextile and geogrid
714.04
Select granular backfill
704.08
Unclassified borrow
704.06
Construction Requirements
255.03 General. Verify limits of the wall installation. Submit installation drawings according
to
Subsection 104.03. See Section 257 for Contractor-designed MSE walls.
Perform the work under Section 209. Grade the foundation for a width equal to the length of reinforcing
elements plus the additional width shown in the plans.
When required, as determined by the Contractor, design and construct temporary shoring with
consideration of maintenance of traffic requirements in Section 156. See Section 208 for temporary
shoring.
For concrete panel and block-faced walls, provide a precast reinforced or a non-reinforced cast-in-place
concrete leveling pad. Cure cast-in-place leveling pads at least 12 hours before placing wall panels.
255.04 Wall Erection. Erect the wall according to the drawings and manufacturer’s recommendations.
Have an field representative from the wall system manufacturer on site during the startup of wall
erection. Construct MSE walls to the tolerance requirements of Table 255-1.
162
Section 255
Table 255-1
Construction Tolerance
Facing Type
Vertical
Horizontal
Horizontal
Tolerance(1)
Tolerance(2)
Straight Edge
Point Check(3)
Precast concrete panel,
±0.6 inch
±0.6 inch
±0.6 inch
masonry block units
(±15 mm)
(±15 mm)
(±15 mm)
±1½ inch
±1½ inch
±3 inch
Welded wire, gabions
(±38 mm)
(±38 mm)
(±75 mm)
(1) Wall vertical tolerance at top of wall for every 10 feet (3 meters) of wall height. For
example 65 feet (20 meter) wall height multiply 6.5×value.
(2) Wall horizontal tolerance at top of wall for every 10 feet (3 meters) of wall height.
(3) Maximum horizontal deviation at a point in the wall from a 10-foot (3-meter) straightedge
placed horizontally or vertically on the theoretical plane of the design face.
(a) Precast concrete panel-faced. Erect panels by lifting devices connected to the upper edge of the
panel.
Make the joint openings ¾±¼ inch (19±6 millimeters) wide. Install joint material according to the
drawings. Cover joints on the backside of the panels with a 12-inch (300-millimeter) wide strip of
geotextile filter. Overlap geotextile filter splices at least 4 inches (100 millimeters).
Hold the panels in position with temporary wedges or bracing during backfilling operations.
(b) Wire-faced. Place backing mats in successive horizontal lifts as backfill placement proceeds.
Connect, tighten, and anchor soil reinforcement elements to the wall facing units before placing
backfill. Do not place reinforcing elements below the corresponding connection elevations. Pull and
anchor the reinforcement mesh taut before placing additional backfill. Do not use hardware cloth or
geosynthetic material to retain backfill at the face of the wall.
(c) Gabion-faced. Place the first lift of backfill before filling the gabion baskets. Construct gabion
structures according to Section 253. Lay reinforcement mesh horizontally on compacted fill and
normal to the face of the wall. Connect the gabion facing unit to reinforcement mesh with spiral
binders or tie wire at 4-inch (100-millimeter) nominal spacing with alternating single and double
locked loops. Pull and anchor the reinforcement mesh taut before placing additional backfill.
(d) Concrete masonry block-faced. Place the first course of modular block wall units on top of and
in full contact with the leveling pad. Place units side by side for the full length of the wall such that
adjoining blocks are located according to the manufacturer’s recommendations. Place units to ensure
only the front face of the unit is visible. Check for proper elevation and alignment every two courses.
Install connection devices, alignment devices, or both as required by design. Fill voids in and around
units with unit fill as required by manufacturer’s installation guidelines to meet the required
connection strength. Place geotextile filter between unit fill and select granular backfill. If the unit
fill is required to meet connection strength specifications, completely fill each course of block before
proceeding to the next course. Place reinforcement no more than two times the block depth or
24 inches (600 millimeters), whichever is less. Remove excess material from the top of the units
before installing each succeeding block course.
163
Section 255
255.05 Backfilling. Backfill the stabilized volume with select granular backfill according to Subsection
209.09. Place select granular backfill material from the back of the wall face to the end of the
reinforcement. Ensure that no voids exist below the reinforcement. Compact each layer according to
Subsection 209.10, except use an acceptable lightweight mechanical or vibratory compactor within
36 inches (900 millimeters) of the wall face. Consolidate facing backfill by rodding or other approved
means to produce a uniform, tight facing fill. Where the stabilized volume supports spread footings for
bridges or other structural loads, compact the top 5 feet (1.5 meters) to at least 100 percent of the
maximum density.
Do not damage or disturb the facing or reinforcing elements. Do not operate equipment directly on top
of the reinforcing mesh or strips. Correct damaged, misaligned, or distorted wall elements.
Backfill and compact behind the stabilized volume with unclassified borrow according to Subsections
209.09 and 209.10. At the end of the day's operation, slope the last lift of backfill away from the wall
face to direct surface runoff away from the wall. Do not allow surface runoff from adjacent areas to
enter the wall construction area.
255.06 Acceptance. See Table 255-2 for sampling, testing, and acceptance requirements.
Material for mechanically-stabilized earth walls listed under Subsection 720.01 will be evaluated under
Subsections 106.02 and 106.03. Submit a production certification with each shipment of concrete face
panels.
Construction of mechanically-stabilized earth walls will be evaluated under Subsections 106.02 and
106.04.
Geotextile filters and reinforcement geotextile and geogrid will be evaluated under Section 207.
Structure excavation, select granular backfill, and unclassified borrow will be evaluated under Section 209.
Gabions will be evaluated under Section 253.
Concrete leveling pad will be evaluated under Section 601.
Measurement
255.07 Measure the Section 255 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring mechanically-stabilized earth walls by the square foot (square meter), measure the front
face of wall excluding footings.
When measuring select granular backfill within the stabilized volume by the cubic yard (cubic meter),
measure in place.
Measure foundation fill under Section 208.
164
Section 255
Payment
255.08 The accepted quantities will be paid at the contract price per unit of measurement for the Section
255 pay item listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
165
Section 255
Table 255-2
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Source
Select
Measured and
Gradation
AASHTO
1 per
Source of
Yes
Before
Not required
granular
tested for
T 27 & T 11
soil type
material
using
when using
backfill
conformance
in work
Government-
(704.08)
(106.04 & 105)
provided source
Angle of
AASHTO
"
"
"
"
"
internal
T 236 and
friction
Subsection
704.08(a)(2)
Soundness
AASHTO
"
"
"
"
"
using
T 104
sodium sulfate
Plasticity
AASHTO
"
"
"
"
"
index
R 58, T 89,
& T 90
Resistivity(1)
AASHTO
"
"
"
"
"
T 288
pH(1)(2)
AASHTO
"
"
"
"
"
T 289
Sulfate
AASHTO
"
"
"
"
"
content(1)(3)
T 290
Chloride
AASHTO
"
"
"
"
"
content(1)(3)
T 291
166
Section 255
Table 255-2 (continued)
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Production
Select
Measured and
Moisture-
AASHTO
1 per
Source of
Yes
Before
granular
tested for
density
T 99,
soil type
material
using
backfill
conformance
Method C(4)
in work
(704.08)
(106.04)
Density
AASHTO
2 per
In-place
No
Before
T 310 or
lift
placing
other approved
next layer
procedures
(1) Required for MSE walls with metallic reinforcements.
(2) Required for MSE walls with geosynthetic reinforcements.
(3) Tests for sulfate and chloride content are not required when resistivity is greater than 5000 ohm centimeters.
(4) Minimum of 5 points per proctor.
167
Section 256
Section 256. — PERMANENT GROUND ANCHORS
Description
256.01 This work consists of furnishing and installing permanent ground anchors.
Material
256.02 Conform to the following Subsections:
Anchor tendons
722.02
Neat hydraulic cement grout
725.13(a)(1)
Construction Requirements
256.03 Qualifications. Provide a professional engineer, on-site supervisor, and installation personnel
with experience installing and testing permanent ground anchors. Submit the following for approval at
least 30 days before starting work:
(a) Names of personnel; and
(b) A résumé for each individual describing their experience on at least five ground anchor projects
of similar complexity over the past
5 years. Include project names, locations, and contact
information for project owners.
256.04 Submittal. At least 30 days before starting ground anchor work, submit the following according to
Subsection 104.03:
(a) Start date;
(b) Method of excavation to ensure slope stability;
(c) Ground anchor construction sequence;
(d) Ground anchor types, sizes, spacings, depths, installation angles, bond zone lengths, and ultimate
tendon strengths for the range of material to be encountered;
(e) Tendons, couplers, bearing plates, facing items, and additional hardware with manufacturer’s
MSDS and product data sheets, specifications, catalog cuts, and mill certificates;
(f) Manufacturer recommendations for tendon and hardware handling, storing, assembly, and working
temperature ranges;
(g) Grout type, mix design, mixing equipment, placement procedures, and 7-day grout compressive
strength test results;
(h) Procedures and material for repairing corrosion protection coatings in the field;
(i) Drilling methods and equipment;
168
Section 256
(j) Drill hole diameters to achieve the specified pullout resistance;
(k) Alternative drilling and grouting methods such as grout additives;
(l) Additional material needed to achieve required bond capacities such as grout socks;
(m) Methods to ensure borehole stability during excavation and grout placement;
(n) Ground anchor testing methods and equipment including type and capacity of reaction load system,
drawings, supporting calculations for structural components of the ground anchor load test apparatus,
and calculations for soil bearing and settlement below the reaction frame; and
(o) Identification number and calibration test certification for each jack, pressure gauge, and electronic
load cell. Clearly indicate the serial number of each component of the testing assembly on calibration
graphs. Submit results from calibration tests conducted by an independent testing laboratory within the
previous 60 days.
Allow 10 days for submittal review.
256.05 Tendon Fabrication.
(a) General. Size tendons to ensure:
(1) The design load does not exceed 60 percent of the minimum ultimate tensile strength of the
tendon; and
(2) The maximum test load does not exceed 80 percent of the minimum ultimate tensile strength
of the tendon.
(b) Bond length. Determine the bond length necessary to develop the design load shown in the
drawings. Use a minimum bond length of 10 feet (3 meters) in rock and 15 feet (4.5 meters) in soil.
Provide corrosion protection of the tendon bond length with a cement grout cover.
Where encapsulation of the tendon is required, protect the tendon bond length from corrosion by
encapsulating it in a grout-filled corrugated plastic or deformed steel tube or by coating it with
fusion-bonded epoxy. Place the grout inside the tube either before or after the tendon is placed in the
drill hole. Centralize the tendon within the tube with a minimum ⅛-inch (3-millimeter) grout cover.
(c) Centralizers. Use spacers along the tendon bond length of a multi-element tendon to separate each
of the individual elements of the tendon. Use centralizers to ensure at least ½ inch (13 millimeters) of
grout cover over the tendon bond length or tendon bond length encapsulation as appropriate. Use
centralizers that do not impede the free flow of grout up the bore hole. Position centralizers within
5 feet (1.5 meters) from the top of the tendon bond length, within 12 inches (300 millimeters) from the
bottom of the tendon bond length, and so their center-to-center spacing does not exceed 10 feet
(3 meters).
Centralizers are not required on hollow-stem-augured tendons if the ground anchor is grouted through
the auger and the hole is maintained full of a stiff grout during extraction of the auger. A grout is
considered "stiff" if its slump is less than 9 inches (230 millimeters).
169
Section 256
(d) Unbonded length. Provide minimum unbonded length of 10 feet (3 meters) for steel bars and
15 feet (4.5 meters) for steel strands.
(1) If the entire drill hole is grouted in one operation, provide corrosion protection of the
unbonded length with a sheath completely filled with corrosion-inhibiting grease,
corrosion-inhibiting grout, or a heat-shrinkable tube internally coated with an elastic adhesive.
If grease is used under the sheath, completely coat the unbonded tendon length, fill spaces
between individual elements of multi-element tendon with grease, and provide measures to
prevent grease from escaping at the ends of the sheath.
If the sheath is grout filled, provide a separate bond-breaker along the unbonded length of the
tendon.
(2) If a grease-filled sheath corrosion protection is provided and the drill hole above the bond
length is grouted after the ground anchor is locked off, grout the tendon inside a second sheath.
Where restressable ground anchors are used, provide restressable anchorage compatible with the
post-tensioning system provided.
If multi-element tendons are used, properly seat the wedges as recommended by the manufacturer for
the post-tensioning system provided.
(e) Bearing plates. Size the bearing plates to ensure:
(1) The bending stresses in the plate do not exceed the yield strength of the steel when a load
equal to 95 percent of the minimum specified ultimate tensile strength of the tendon is applied;
and
(2) The average bearing stress of the bearing plate does not exceed that recommended in the PTI,
Guide Specification for Post-Tensioning Materials.
Weld trumpet to bearing plate. Make the inside diameter of the trumpet equal to or larger than the hole
in the bearing plate. Make the trumpet long enough to accommodate movements during stressing and
testing. For multiple or single element tendons with encapsulation over the unbounded length, make
the trumpet at least 24 inches (600 millimeters) beyond the structural fascia and soil backslope
interface to allow a transition from the unbounded length to the anchorhead without damaging
encapsulation. Fill the trumpet of restressable ground anchors with corrosion-inhibiting grease. Provide
a permanent Buna-N synthetic rubber seal or an approved equal between the trumpet and the unbonded
length corrosion protection.
Fill the trumpets of non-restressable ground anchors with grout. Provide a 12-inch (300-millimeter)
minimum tightly-fitting temporary seal between the trumpet and the unbonded length corrosion
protection.
256.06 Handling and Storing Material. Handle and store tendons in a manner to avoid damage or
corrosion. Replace tendons exhibiting abrasions, cuts, welds, weld splatter, corrosion, or pitting. Repair or
replace tendons exhibiting damage to encapsulation or sheathing. Degrease the bond length of tendons and
remove solvent residue before installation.
170
Section 256
256.07 Installation.
(a) Drilling. Drill ground anchor holes within 12 inches (300 millimeters) of the required location.
Drill the longitudinal axis of the drill hole parallel to the longitudinal axis of the tendon. Install the
ground anchor within three degrees of the required inclination from horizontal. Install the ground
anchor with a horizontal angle within three degrees of a line drawn perpendicular to the plane of the
structure. Do not extend ground anchors beyond the right-of-way or easement limits.
Insert the tendon in the drill hole to the required depth without driving or forcing. Where the tendon
cannot be completely inserted, remove the tendon, and clean or redrill the hole to permit insertion.
(b) Grouting.
(1) Equipment. Use a positive displacement grout pump equipped with a pressure gage capable of
measuring pressures of at least 150 pounds per square inch (1 megapascal) or twice the required
grout pressure, whichever is greater. Provide a secondary pressure capability of at least
1,000 pounds per square inch (7 megapascal) to clean out grout or dirt blockages in hoses, tremie
tubes, or casings. Use a high speed, high shear grout mixer with a minimum operating speed of
1,500 revolutions per minute to produce a well-mixed grout that is free of lumps or other
indications of prior cement hydration. Furnish holding tanks with a variable speed high-efficiency
paddle that maintains a thoroughly mixed grout for pumping.
(2) Procedures. Grout tendons into drill holes using a neat hydraulic cement grout placed in one
continuous operation. Inject the grout from the lowest point of the drill hole. The grout may be
placed either before or after insertion of the tendon. Record the quantity of the grout and the grout
pressure for each ground anchor. Control the grout pressures to avoid excessive heaving or
fracturing.
Except as indicated below, the grout above the top of the bond length may be placed at the same
time as the bond length grout, but do not placed it under pressure. Do not place grout at the top of
the drill hole in contact with the back of the structure or the bottom of the trumpet.
If the ground anchor is installed in a fine-grained soil using drill holes larger than 6 inches
(150 millimeters) in diameter, place the grout above the top of the bond length after the ground
anchor has been tested and stressed. The entire drill hole may be grouted at one time if it can be
demonstrated that the ground anchor does not derive a significant portion of its load-carrying
capacity from the soil above the bond length.
Use pressure grouting for grout protected tendons anchored in rock. After sealing the drill hole,
pressure inject grout until a 50-pound per square inch (0.3-megapascal) grout pressure at the top of
the drill hole is maintained for 5 minutes.
(c) Finishing. After grouting is complete, fill the grout tube with grout if it will remain in the hole.
Wait at least 3 days before loading the tendon.
Extend the corrosion protection surrounding the unbonded length up beyond the bottom seal of the
trumpet or 12 inches (300 millimeters) into the trumpet if no trumpet seal is provided.
Trim the corrosion protection surrounding the tendon so it does not contact the bearing plate of the
anchorhead during testing and stressing.
171
Section 256
Place the bearing plate and anchorhead so the axis of the tendon is within three degrees of
perpendicular to the bearing plate and the axis of the tendon passes through the center of the bearing
plate without bending the tendon.
If grout protected tendons or fusion-bonded epoxy encapsulations are used, electronically isolate the
bearing plate, anchorhead, and trumpet from the surrounding concrete, soldier pile, or metallic element
embedded in the structure.
Place trumpet grease during construction. Place trumpet grout after the ground anchor has been tested
and stressed.
Completely cover anchorages permanently exposed to the atmosphere with a corrosion-inhibiting
grease or grout.
Inspect the trumpet and anchorage grout levels 24 hours after initial grout placement. If needed, refill
the trumpet or anchorage with grout.
256.08 Testing and Stressing.
(a) Testing equipment. Conform to the following:
(1) Dial gauges. Use two dial gauges capable of measuring to 0.001 inch (0.025 millimeters) and
with sufficient travel to measure the theoretical elastic elongation of the total length at the
maximum test load without resetting, accounting for elongation in both the bonded and
unbonded zones. Align the gauges parallel to the axis of the anchor or pile and support the
gauges independently from the hydraulic jack, ground anchor, or reaction frame.
(2) Hydraulic jack, pressure gauge and load cell. Apply test loads with a hydraulic jack and
measure with a calibrated pressure gauge and electronic load cell. Use a hydraulic jack and
pressure gauge with a pressure range not exceeding twice the anticipated maximum test pressure
and calibrated as a unit by an independent firm within 45 days of the start of work. Use a
pressure gauge graduated in 100-pound per square inch (1-megapascal) increments or less. Use a
jack with ram travel sufficient to allow testing without resetting.
(3) Reference gauge. Have the reference gauge calibrated with the test jack and pressure gauge.
Keep the reference gauge at the project site.
(4) Reaction frame. Provide a reaction frame designed by a professional engineer to meet the
requirements of the site, resist the maximum test loads and prevent excessive deformation of the
bearing surface.
(b) Stressing. Place testing equipment over the ground anchor tendon to ensure the jack, bearing
plates, load cells, and stressing assembly are axially aligned with the tendon and the tendon is centered
within the equipment. Do not apply loads greater than 80 percent of the minimum ultimate tensile
strength of the tendon.
172
Section 256
Place the reference pressure gauge in series with the pressure gauge, jack, and load cell so they need
not be unloaded and repositioned during a test. Raise the load from one increment to another. Hold the
load just long enough to measure and record the ground anchor movement to the nearest 0.001 inch
(0.025 millimeters) with respect to an independent fixed reference point. Repump the jack as necessary
to maintain a constant load. Monitor the load with a pressure gauge. If the load measured by the
pressure gauge and the load measured by the reference pressure gauge differ by more than 10 percent,
recalibrate the jack, pressure gauge, and reference pressure gauge.
(1) Performance tests. The CO will designate locations for sacrificial ground anchors
for
performance tests. Test according to Tables 256-1 and 256-3.
Table 256-1
Performance Test Load Sequence
Test
Test Load Increment
Sequence
1.33D
Reduce to
AL
0.25D
0.50D
0.75D
1.00D
1.20D
(Load-Hold Test)
Lock-Off
Load
1
2
3
4
5
6
10 minutes*
AL = Alignment load (no greater than 5 percent of D (0.05D) applied to the ground anchor before setting the
movement recording devices. Zero dial gauges after the first setting of A).
D = Design load.
* Hold the load to within 2 percent and measure and record the ground anchor movement during the load-hold
test at 1, 2, 3, 4, 5, 6, and 10 minutes. When the ground anchor movement between 1 minute and 10 minutes
exceeds 0.04 inches (1 millimeter), maintain the maximum test load an additional 50 minutes and record the
movement at 20, 30, 40, 50, and 60 minutes.
(2) Proof tests. Test according to Tables 256-2 and 256-3.
Table 256-2
Proof Test Load Sequence
Test Load Increment
1.33D
Reduce to
AL
0.25D
0.50D
0.75D
1.00D
1.20D
(Load-Hold Test)
Lock-Off
Load
10 minutes*
AL = Alignment load. See alignment load note in Table 256-1.
D = Design load.
* Hold the load to within 2 percent and measure and record the ground anchor movement during the
load-hold test at 1, 2, 3, 4, 5, 6, and 10 minutes. When the ground anchor movement between 1 minute
and 10 minutes exceeds 0.04 inches (1 millimeter), maintain the maximum test load an additional
50 minutes, recording movement at 20, 30, 40, 50, and 60 minutes.
173
Section 256
(c) Lock off. Reduce the load to the specified lock-off load and transfer the load to the anchorage
device. After transferring the load and before removing the jack, measure the lift-off load. If the load is
not within 10 percent of the specified lock-off load, reset the anchorage and remeasure the lift-off load.
Repeat as necessary.
256.09 Test Results and Reporting. Plot the ground anchor movement versus the maximum load for each
test sequence in Tables 256-1 and 256-2, and plot the residual movement of the tendon at each alignment
load versus the highest previously applied load.
Provide preliminary results to the CO for each ground anchor tested before testing personnel leave the site.
Submit detailed verification and proof test load and deflection data in a tabular format. Submit a graph that
plots total ground anchor head movement versus load, the A-line, and the B-line. The A-line is defined as
0.8 multiplied by the theoretical free test length elastic elongation. The B-line is defined as the theoretical
free test length elastic elongation plus 0.50 multiplied by the theoretical bonded length elastic elongation.
Allow 5 days for the CO to conduct a review of the data and approve ground anchor installation.
256.10 Acceptance. See Table 256-3 for sampling, testing, and acceptance requirements.
Material for ground anchors will be evaluated under Subsections 106.02 and 106.03. Submit a production
certification for the ground anchor material.
Construction of ground anchors will be evaluated under Subsections 106.02 and 106.04.
Installed ground anchors will be evaluated based on one of the following performance or proof test results:
(a) After a 10-minute hold, the ground anchor carries the maximum test load with less than 0.04 inches
(1 millimeter) of movement between 1 and 10 minutes and the total movement at the maximum test
load exceeds 80 percent of the theoretical elastic elongation of the unbonded length.
(b) After a 60-minute hold, which is only conducted after 10-minute hold test fails, the ground anchor
carries the maximum test load with a movement rate that does not exceed 0.08 inch (2 millimeters) per
log cycle of time and the total movement at the maximum test load exceeds 80 percent of the
theoretical elastic elongation of the unbonded length.
Replace ground anchors with unacceptable performance or proof test results. Do not retest failed ground
anchors.
Measurement
256.11 Measure the Section 256 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
Measure performance tests that indicate acceptable installations.
Payment
256.12 The accepted quantities will be paid at the contract price per unit of measurement for the Section
256 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
174
Section 256
Table 256-3
Sampling, Testing, and Acceptance Requirements
Material or
Type of
Characteristic
Category
Test Methods
Sampling
Point of
Split
Reporting
Remarks
Product
Acceptance
Specifications
Frequency
Sampling
Sample
Time
(Subsection)
(Subsection)
Source
Aggregate
Measured and
Quality
-
AASHTO
1 per
Source of
Yes
Before
-
quality
tested for
M 6
material
material
producing
(fine)
conformance
type
(703.01)
(106.04 & 105)
Mix Design
Neat
Measured and
Flow
-
ASTM
1 per
"
Yes, when
"
-
hydraulic
tested for
C939
mix design
requested
cement
conformance
Compressive
-
AASHTO
"
"
"
"
-
grout (1)
(106.04)
strength
T 106
(725.13(a)(1))
(7-day)
ASTM C942
Production
Performance
Measured and
Deformation
-
Subsection
5%
Installation
No
5 days
-
test ground
tested for
256.08(b)(1)
or 3 min
anchor
conformance
(106.04)
Proof test
"
"
-
Subsection
Each
"
"
"
-
ground anchor
256.08(b)(2)
anchor
(1) Prepare and test grout cube specimens according to ASTM C942. Make grout cubes for testing from random batches of grout as directed. Normally, strength
testing for permanent ground anchors will not be required as system performance will be measured by load holding each anchor. Grout cube testing will be
required if admixtures are used or irregularities occur in anchor testing.
175
Section 257
Section 257. — CONTRACTOR-DESIGNED RETAINING WALLS
Description
257.01 This work consists of designing various types of retaining walls. Wall types include gabion,
mechanically-stabilized earth, permanent ground anchor, reinforced concrete, soil nail, reinforced soil
slopes, micropiles, and other wall systems.
Material
257.02 Conform to the following Sections:
Driven piles
551
Gabions
253
Mechanically-stabilized earth walls
255
Micropiles
567
Permanent ground anchors
256
Reinforced concrete retaining walls
258
Reinforced soil slopes
261
Reinforcing steel
554
Soil nail retaining walls
259
Structural concrete
552
Construction Requirements
257.03 General. The designer/supplier furnishing the proposed retaining wall is responsible for the
stability of the structure. Do not qualify the responsibility for the design or restrict the use of the
drawings or calculations for the proposed alternate. Indemnify the Government from claims for
infringement of proprietary rights by others without the consent of the patent holders or licensees.
Verify the limits of structure installation.
Arrange and conduct a pre-design conference following selection of the structure designer/supplier and
before design work starts to discuss structure selection, constructability, and design parameters, methods
and limitations. Include the CO, subcontractors, supplier, and the supplier’s design engineer.
257.04 Submittals. At least 90 days before starting construction, submit the following according to
Subsection 104.03:
(a) Plan and elevation drawings for each structure containing the following:
(1) A plan view of the structure showing:
(a) Horizontal offset from the construction centerline to the face of the structure at defining
points along the base, including start and end stations;
(b) Location, length, coverage ratio, and type of reinforcement/anchorage as applicable (such
as strip, mesh, grid, geosynthetic fabric, anchor);
176
Section 257
(c) Centerline and size of drainage structure or drainage pipe behind, passing through, or
passing under the structure; and
(d) Location, length and offset from the face of wall to guardrail or guardwall features or
parapet structures.
(2) An elevation view of the structure showing:
(a) Elevation and station at horizontal and vertical break points and at least every 50 feet
(15 meters) along the top of the structure at the face;
(b) Elevation and station at the top of leveling pads and footings, at the top and tip of piling,
and at least every 50 feet (15 meters) along the structure base;
(c) Length and type of reinforcement, anchorage, structure module, and lagging;
(d) Distance and elevation along the structure face to all steps in the base, footings, leveling
pads, or lagging;
(e) Distance along the structure face to where changes in reinforcement or anchor lengths
occur;
(f) Construction joints; and
(g) Original and final ground-line.
(3) A typical cross-section view showing:
(a) Type and depth of facing elements and structural connections to reinforcing and
anchorage elements;
(b) Structure batter or face slope;
(c) Length, spacing, and type of reinforcement, anchorage, structure module and
corresponding limits of excavation, and reinforced fill placement zones;
(d) Location of guardrail or guardwall features or parapet structures, including embedment
depths, offset from structure facing, and connection details with structure
reinforcement/anchorage;
(e) Original and final ground-line, including right-of-way limits; and
(f) Estimated or known location of subsurface soil and rock units.
(4) General construction notes.
(5) Horizontal and vertical curve data affecting the structure, including match lines or other
details to relate structure stationing to centerline stationing.
(6) Material list and summary of quantities. Include the gradation for facing rock. Facing rock
should be sufficiently sized to prevent migration of the rock through the facing basket for the
chosen wall system.
(b) Dimensions and schedules of reinforcing steel including reinforcing bar bending details, dowels,
studs, or both for attaching the facing.
177
Section 257
(c) Details and dimensions for foundations and leveling pads including steps in the footings or leveling
pads.
(d) Details and dimensions for:
(1) Panels, modules, soldier piles, and lagging necessary to construct the structure;
(2) Reinforcing steel in structural elements;
(3) Details of proposed splices in reinforcements;
(4) Location of mesh, strip attachment, or anchor devices embedded in facing panels; and
(5) Anchors and soldier piling including the spacing and size of piles and the spacing and angle
of anchors.
(e) Details for the installation of structure drainage features, including strip, sheet, edge, blanket and
underdrain systems, and associated piping;
(f) Details for constructing structures around drainage features, utilities, lighting foundations, traffic
barriers, and other obstructions.
(g) Details for terminating structures and adjacent slope construction.
(h) Architectural treatment details.
(i) Design notes including a description of symbols, terminology, and computer programs used in the
design of the structure. Specify the bearing pressure beneath the structure footing, stabilized earth
mass, or soldier piles.
(j) Verification of design criteria and soil, rock and reinforcement parameters for each structure.
Include results from creep, durability, construction induced damage, and junction strength tests as
applicable.
(k) Design calculations, including assessment of temporary excavation stability and internal and
external stability of earth retaining structures. Include joint, splice, and facing connection capacity
calculations.
Include a checklist showing each of the items specified in these requirements have been addressed in the
design. Submit 3 sets of drawings with the initial submission. One set will be returned with corrections if
necessary. If revisions are required, make corrections and resubmit three revised sets.
257.05 Design and Construction. Design and construct the wall according to the approved drawings and
the following Sections as applicable:
(a) Gabions. See Section 253.
(b) Mechanically-stabilized earth walls. See Section 255.
(c) Permanent ground anchor walls. See Sections 256, 551, and 552.
(d) Reinforced concrete retaining walls. See Section 258.
178
Section 257
(e) Soil nail retaining walls. See Section 259.
(f) Reinforced soil slopes. See Section 261.
(g) Micropiles. See Section 567.
Update drawings when plan dimensions are revised due to field conditions or for other reasons.
257.06 Acceptance. Design of the retaining walls will be evaluated under Subsection 106.02 and the
applicable Sections listed in Subsection 257.05.
Measurement
257.07 Measure the Section 257 pay items listed in the bid schedule according to Subsection 109.02.
Payment
257.08 The accepted quantities will be paid at the contract price per unit of measurement for the Section
257 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this
Section. See Subsection 109.05.
Progress payments for Contractor-designed retaining walls will be paid as follows:
(a) 50 percent of the pay item amount will be paid when the design submittal is approved.
(b) An additional 25 percent of the pay item amount will be paid when 50 percent of the retaining wall
construction is complete.
(c) Payment of the remaining portion of the pay item amount will be paid when 100 percent of the
retaining wall construction is complete.
179
Section 258
Section 258. — REINFORCED CONCRETE RETAINING WALLS
Description
258.01 This work consists of constructing reinforced concrete retaining walls.
Material
258.02 Conform to the following Sections and Subsections:
Forms and falsework
562
Reinforcing steel
709.01
Sealants, fillers, and seals
712.01
Structural backfill
704.04
Structural concrete
552
Construction Requirements
258.03 General. Verify the limits of the wall installation. Prepare and submit forms, falsework drawings,
and drainage provisions according to Section 562. See Section 257 for Contractor-designed reinforced
concrete retaining walls.
Perform the work under Section 209.
After excavation is complete, request approval as to the character and suitability of the foundation
material. Allow the CO 24 hours to review and approve the foundation before constructing the footing.
258.04 Reinforcing Steel. Submit order lists and bending diagrams according to Subsections 104.03 and
554.03. Fabricate reinforcing steel according to Subsection 554.05. Ship and protect material according to
Subsections
554.04,
554.06, and
554.07. Place, fasten, and splice reinforcing steel according to
Subsections 554.07, 554.08, and 554.09.
258.05 Structural Concrete. Design concrete mixture according to Subsection 552.03. Store, handle,
batch, and mix material and deliver concrete according to Subsections 552.04 through 552.08. Provide
quality control according to Section 153 and Subsection 552.09. Construct wall according to Subsections
552.10 through 552.16.
258.06 Backfilling. Backfill the area behind the wall with structural backfill according to Subsection
209.09. Compact each layer according to Subsection
209.10, except use an approved lightweight
mechanical or vibratory compactor within 36 inches (900 millimeters) of the wall.
Do not place structural backfill against concrete until 80 percent of the design strength is achieved.
258.07 Acceptance. Reinforced concrete retaining wall material, and construction will be evaluated as
follows:
Forms and falsework drawings will be evaluated under Section 562.
Structure excavation and backfill will be evaluated under Section 209.
180
Section 258
Structural concrete will be evaluated under Section 552.
Reinforcing steel will be evaluated under Section 554.
Material for joint fillers, sealants, tie bars, dowel bars, and hook bolts will be evaluated under Subsections
106.02 and 106.03.
Measurement
258.08 Measure the Section 258 pay items listed in the bid schedule according to Subsection 109.02 and
the following as applicable:
When measuring retaining walls by the square foot (square meter), measure by the front face of wall
excluding footings.
Measure foundation fill under Section 208.
Payment
258.09 The accepted quantities will be paid at the contract price per unit of measurement adjusted
according to Subsection 106.05 for the Section 258 pay items listed in the bid schedule. Payment will be
full compensation for the work prescribed in this Section. See Subsection 109.05.
Payment for reinforced concrete retaining wall will be made at a price determined by multiplying the
contract price by the material pay factor. The material pay factor is calculated as follows:
PFa =
1 - 0.5 (1-PF)
where:
PF = Pay factor for concrete as determined under Section 552.
181
Section 259
Section 259. — SOIL NAIL RETAINING WALLS
Description
259.01 This work consists of constructing soil nail retaining walls.
Material
259.02 Conform to the following Section and Subsections:
Bolts and nuts
717.01(d)
Centralizers and spacers
722.02(e)
Geocomposite drain
714.02
Neat hydraulic cement grout
725.13(a)(1)
Shotcrete
566
Soil nails
722.04
Structural backfill
704.04
Structural carbon steel (bearing plates)
717.01(a)
Welded stud sheer connectors
717.05
Construction Requirements
259.03 Qualifications. Provide a professional engineer, on-site supervisors, and installation personnel
with experience installing and testing soil nails. Submit the following for approval at least 30 days
before starting work:
(a) Names of personnel; and
(b) A résumé for each individual describing their experience on at least five soil nail retaining wall
projects of similar complexity over the past 5 years. Include project names, locations, and contact
information for project owners.
259.04 Submittal. At least 30 days before starting soil nail retaining wall work, submit the following
according to Subsection 104.03:
(a) Start date;
(b) Method of excavation to ensure wall and slope stability;
(c) Retaining wall construction sequence;
(d) Soil nail types, sizes, spacings, depths, and installation angles, bond zone lengths, and ultimate
tendon strengths for the range of material to be encountered;
(e) Tendons, couplers, bearing plates, facing items, and additional hardware with manufacturer’s
product data sheets, specifications, catalog cuts, and mill certificates;
(f) Manufacturer recommendations for tendon and hardware handling, storing, assembly, and working
temperature ranges;
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Section 259
(g) Grout type, mix design, mixing equipment, placement procedures, and 3-day and 28-day grout
compressive strength test results;
(h) Procedures and material for repairing corrosion protection coatings in the field and for applying
epoxy finish coatings on end hardware;
(i) Drilling methods and equipment;
(j). Drill hole diameter to achieve the specified pullout resistance;
(k) Alternative drilling and grouting methods such as grout additives;
(l) Additional material needed to achieve required bond capacities such as grout socks;
(m) Methods to ensure borehole stability during excavation and grout placement;
(n) Soil nail testing methods and equipment including type and capacity of reaction load system,
drawings, and supporting calculations for structural components of the soil nail load test apparatus; and
(o) Identification number and calibration test certification for each jack, pressure gauge, and electronic
load cell. Clearly indicate the serial number of each component of the testing assembly on calibration
graphs. Submit results from calibration tests conducted by an independent testing laboratory within the
previous 60 days.
259.05 General. See Section 257 for Contractor-designed soil nail retaining walls. Verify the limits of the
wall installation.
Clear the work area of vegetation and obstructions according to Sections 201 and 203.
Excavate according to Section 204. Excavate for the wall in staged lifts concurrent with soil nail
installation and shotcrete placement. Do not allow the exposed unsupported final excavation face cut
height to exceed the vertical soil nail spacing plus the required reinforcing lap or the short-term stand-up
height of the ground, whichever is less. Do not excavate to the next lower lift until soil nail installation,
reinforced shotcrete placement, attachment of bearing plates and nuts, and soil nail testing have been
completed and accepted for the current lift. Cure grout and shotcrete at least 72 hours or attain the
specified
3-day compressive strength before excavating the next underlying lift. Application of the
shotcrete may be delayed up to 24 hours if it can be demonstrated the delay will not adversely affect the
excavation face stability.
259.06 Tendon Fabrication. Provide tendons designed to carry loads consistent with the approved design.
Thread tendon ends so they are capable of withstanding the approved test loads in addition to
accommodating the attachment of the bearing plate, beveled washer, nut, or other appurtenances as
required by the manufacturer’s specifications and the contract.
183
Section 259
Limit coupling of tendons to two per installation. Use couplers manufactured with a center stop to ensure
equal length of thread connects each section. Do not use couplers that interfere with the flow of grout.
Protect couplings from corrosion using the same corrosion protection used on the soil nail tendon
assembly. Use centralizers to position the tendon within 1 inch (25 millimeters) of the center of the drill
hole. Use centralizers that do not impede the free flow of grout into the drill hole. Position centralizers
within 24 inches (600 millimeters) from the top and bottom of the tendon and so their center-to-center
spacing does not exceed 10 feet (3 meters). Secure centralizers to the tendon to prevent shift during
handling or inserting into the drill hole.
259.07 Handling and Storing Material. See Subsection 256.06.
259.08 Installation.
(a) Drilling. Drill soil nail holes at the required locations and orientations. Use drilling equipment and
methods suitable for the ground conditions. Do not use water, drilling slurry, or other fluids for drilling
or removing cuttings.
Insert the soil nail tendon into the hole. Clean or redrill drill holes where the tendon with centralizers
cannot be completely inserted without forcing or driving.
(b) Grouting. Use a positive displacement grout pump according to Subsection 256.07(b) (1).
Grout tendons into drill holes using a neat hydraulic cement grout. Mix grout as recommended by
the cement supplier at the specified water-to-cementitious material ratio. Inject grout within
45 minutes of adding the cement to the water or within 15 minutes after mixing when the ambient
temperature is 90 °F (32 °C) or higher. Do not allow the grout temperature to exceed 90 °F (32 °C).
Grout the drill hole within 2 hours of completing drilling.
Inject the grout at the lowest point of each drill hole. Place primary and secondary grout stages in one
continuous operations. Keep the outlet end of the grout tube below the surface of the grout as the tube
is withdrawn to prevent voids. Control grout pressures to avoid ground heaving or fracturing. Record
the quantity of injected grout and the grout pressure for each soil nail installation. After grouting is
complete, fill the grout tube with grout if it will remain in the hole.
Maintain the temporary unbonded length of proof test soil nails open for later grouting. If the
unbonded test length of production proof test soil nails cannot be satisfactorily grouted after testing,
install a new soil nail in its place.
Request approval for alternate soil nail installation methods, including grout socks, grout admixtures,
or both when conditions prove necessary. Provide the CO with an on-site demonstration as part of the
request.
259.09 Testing and Stressing.
(a) Testing equipment. See Subsection 256.08(a).
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