02832Mse Backfill

MSE BACKFILL

PART 1 GENERAL

1.1SECTION INCLUDES

retaining walls and Reinforced Soil Slopes (RSS).

1.2RELATED SECTIONS

1.3REFERENCES

Rammer and a 305-mm (12 in.) Drop

Magnesium Sulfate

Conditions

Ignition

Aggregate by Nuclear Methods (Shallow Depth)

MSE Backfill

Reinforcements for Mechanically Stabilized Earth Walls and Reinforced Soil Slopes

1.4DEFINITIONS

units, and within 2 ft of obstructions such as driven piles and drilled shafts.

1.5SUBMITTALS Not Used

1.6QUALITY CONTROL

construction.

PART 2 PRODUCTS

2.1MSE BACKFILL

determined by AASHTO T 267 on the portion of the material finer than the No. 10 sieve.

according to AASHTO T 104:

when using a sodium sulfate solution.

when using a magnesium sulfate solution.

27.

MSE Backfill

Table 1 MSE Backfill Gradation (percent passing) Sieve Size Metal Reinforcement Geogrid Reinforcement 4 inch 100 –

¾ inch – 100

No. 40 0 – 60 0 – 60

No. 200 0 –15 0 –15

be used with geogrid reinforcement under the following conditions:

installation damage testing using a representative sample of the proposed MSE backfill material. 1) Refer to FHWA-NHI-09-087 for testing protocols.

test is not less than 1.2. 1) Refer to FHWA-NHI-09-087 for determination of the installation damage reduction factor.

licensed in the State of Utah.

installation damage testing when a change in the backfill characteristics from the original tested representative sample is suspected.

AASHTO T 90.

determined by AASHTO T 236.

density at optimum moisture content as determined by AASHTO T 99, Method D.

has at least 80 percent of the material retained on the 3/4 inch sieve.

MSE Backfill

Table 2 Electrochemical Properties Geogrid Property Metal Reinforcement Test Method Reinforcement Minimum 3000 ohm- Resistivity N/A AASHTO T 288 cm, at 100% saturation*

pH 6.0 – 10.0 5.5 – 10.0** AASHTO T 289

AASHTO T 291 or Chlorides Maximum 100 ppm N/A ASTM D 4327 AASHTO T 290 or Sulfates Maximum 200 ppm N/A ASTM D 4327

* Do not follow Note 6 of AASHTO T 288 to find lowest possible resistivity (where soil is in a slurry state). Saturate soil to 100% saturation where a sheen of water is observed at the top surface of the sample in the soil box. ** Maximum pH value for polyester geogrid is 9.0 unless long-term immersion testing performed according to FHWA-NHI-09-087 shows acceptable performance. For pH > 8.0, use a durability reduction factor (RFD) of 1.3 for polyester geogrid.

2.2MSE FREE DRAINING BACKFILL

27.

MSE Backfill

Table 3 MSE Free Draining Backfill Gradation (percent passing) Sieve Size Metal Reinforcement Geogrid Reinforcement 2 inch 100 –

1 1/2 inch 90 – 100 – /4 inch – 100

/8 inch 20 – 75 20 – 75

No. 4 0 – 15 0 – 15

No. 200 0–5 0–5

PART 3 EXECUTION

3.1BACKFILL PLACEMENT

(concrete panel, modular block, or welded wire) with backfill placement.

wall materials, misalignment of facing panels or modular blocks, and damage to soil reinforcement and facing members.

beneath the soil reinforcing elements.

compaction.

specified density.

away from the wall when placing backfill over the soil reinforcement to prevent the soil reinforcement from bunching towards the wall face.

MSE Backfill

subsequent backfill layers.

face.

at speeds less than 5 mph. 1) Avoid sudden braking and sharp turning.

compacting backfill within the limits of the soil reinforcement.

soil reinforcement has been installed and one lift of MSE backfill has been placed and compacted over the reinforcement layer to avoid pushing the facing units out of alignment.

the reinforcement connection from a point approximately 24 inch behind the back face of the wall facing element to the end of the soil reinforcement zone, unless otherwise shown at specific locations in the authorized retaining wall drawings.

reinforcement and overlying lift of MSE backfill until the Engineer indicates and records that MSE backfill placement and density requirements (including in the light equipment zone) have been met.

of two-stage walls before backfilling behind the wall more than 6 ft above the bottom of the wall.

thickness before compaction.

density, according to AASHTO T 99.

soil reinforcement layer is covered with at least 16 inch of MSE backfill.

at least 18 inch.

requirements.

density, according to AASHTO T 99, Method D.

MSE Backfill

by the type of compaction equipment used, but not greater than 8 inch before compaction.

lightweight or medium-weight (hand-held or hand-guided) mechanical roller, tamper, or vibratory compactor.

800 lb within this zone when compacting a thin leveling lift along the reinforcement connections level.

misalignment of the facing units.

or between optimum moisture and four percent below optimum moisture.

AASHTO T 99, Method D.

excess of the optimum moisture content. 1) MSE backfill may be reused, provided it is aerated or otherwise reworked until the moisture content is uniform and acceptable throughout the entire lift.

throughout each layer during placement and compaction.

3.2PROTECTION OF THE WORK

excavation at least 24 hours before placing MSE backfill.

first stage of two-stage walls) is complete, and

direct runoff of rainwater away from the wall face.

the wall construction site, including at the front face of the wall.

END OF SECTION

MSE Backfill