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In 1990 and 1991, a tire
shred beneficial use project was completed on U.S. Route 42 near Roseburg,
Oregon. As part of a highway improvement project, an embankment was
raised, causing the reactivation of an old landslide. The slide had to be
stabilized, and tire shreds were chosen as a lightweight fill material.
These shreds were placed at the head of the slide, and a counter balancing fill
was added at the toe of the slide. Figures 1 and 2 below show the location
of the two different fill areas at the site.
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Figure 1. Plan view of Oregon tire shred field trial (Upton and
Machan,
1993)
Figure 2. Cross section through Oregon tire shreds field trail (Upton and
Machan, 1993)
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Minnesota DOT specifications
were followed for the tire shreds:
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80% passing the 8-in size
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50% larger than the 4-in size
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maximum size in any direction -
24 in
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any metal particles had to be
contained within the rubber of the shreds
The shreds were
placed in 3-ft lifts, and compacted with a D-8 bulldozer. The maximum
thickness of the compacted tire shred fill was 14 feet, and geotextiles were
used at the site to separate these layers of tire shred material from the
surrounding soil.
After the tire
shreds were compacted, 36 inches of soil, 23 inches of aggregate base course,
and 8 inches of pavement were placed over the fill. Before these layers
were added, the tire shred unit weight was 45 pcf. After the soil,
aggregate, and pavement was added, and compression of the tire shreds occurred,
the estimated unit weight was 53 pcf.
Most of the
pavement didn't experience problems with cracking or rutting. One 50-ft
section did require some repair, as a mistake caused the soil cover to be 1 to 1.5 ft thinner than
had been specified. Measured pavement deflections were about 0.25 mm. Figure 3
below gives deflection results.
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Figure 3. Deflectometer test data: left, October 30, 1990; middle, January
7, 1991; right, December 12, 1991 (Upton and
Machan, 1993)
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For this project,
the cost of the tire shreds was $30/ton, and the placement of the fill cost
another $8.33/ton. The total cost was $27/c.y., minus state subsidy.
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