Compressibility of Tire Shreds
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Tire shreds are a
compressible material. This has an effect on the settlement and unit
weight of the tire shreds, as well as the settlement and deflection caused by
temporary loads after construction. Figure 1 shows the compressibility of
type A tire shreds at low stresses and figure 2 shows compressibility at high
stresses. In general, it appears that compressibility of tire shreds
decreases as the stress level increases. Further compressibility data from
different projects is given in table 1.
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Figure 1. Compressibility of 3-in. minus tire shreds at low stresses (Nickels, 1995)
Figure 2. Compressibility of 3-in. minus tire shreds at high stresses (Manion and Humphrey, 1992)
Table 1. Compressibility on initial loading
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Particle
size (in.)
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Tire
shred
type
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Tire
shred source
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Initial
dry unit
weight
(pcf)
|
Vertical
strain (%) at indicated vertical stress (psi)
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Reference
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1.45
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3.63
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7.25
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14.5
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29.0
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3
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Mixed
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Palmer
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Compacted
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7
to 11
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16
to 21
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23
to 27
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30
to 34
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38
to 41
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(2)
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2
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Mixed
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Pine
State
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Compacted
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8
to 14
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15
to 20
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21
to 26
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27
to 32
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33
to 37
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(2)
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1
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Glass
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F
& B
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Compacted
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5
to 10
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11
to 16
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18
to 22
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26
to 28
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33
to 35
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(2)
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2
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Mixed
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Sawyer
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Compacted
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5
to 10
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13
to 18
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17
to 23
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22
to 30
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29
to 37
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(1)
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Mixed
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Compacted
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4
to 5
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8
to 11
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13
to 16
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18
to 23
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27
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(3)
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3
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Mixed
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Pine
State
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32
to 42
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12
to 20
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18
to 28
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----
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----
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----
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(5)
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2
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Mixed
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Pine
State
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Loose
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18
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34
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41
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46
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52
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(2)
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1
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Mixed
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F
& B
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Loose
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8
|
18
|
28
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37
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45
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(2)
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----
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Loose
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9
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12
to 17
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17
to 24
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24
to 31
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30
to 38
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(4)
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Reference:
(1)
Manion & Humphrey (1992)
(2) Humphrey, et al. (1992)
(3) Ahmed (1993)
(4) Drescher & Newcomb (1994)
(5) Nickels (1995)
Procedures
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Compressibility has
been determined by measuring vertical strain while vertical stress is increased on
samples of tire shreds in various sized containers. Special precautions
have to be taken, or vertical stress will be transferred to the walls of the
container by friction, resulting in underestimated compressibility. The
container that is used has to have a sufficient diameter relative to the particle sizes
of the tire shreds; the inside of the container should be lubricated to reduce
friction; and the vertical stress at the top and bottom should be measured and
used to compute an average vertical stress.
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Figure
3. Compressibility
apparatus used by Nickels
(1995)
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