Double Nickel Slide, South Pass, Wyoming

In 1985, a highway alignment on State Highway 28 in Wyoming initiated a landslide.  Rock drains and berms were installed at the toe of the slide to help stabilize it.  In 1993, more movement of the slide was noticed.  Figure 1 below shows the slide area.

Figure 1. Plan view showing outline of slide area (Dahill, 1994)

Measures had to be taken to stabilize the landslide to prevent further movement and damage.  A combination of four different repair options were used.  They are listed below and shown in figure 2 as well. shift alignment away from the head of the slide lower the grade to reduce the slide's driving force create additional toe berms use a lightweight fill material like tire shreds

Figure 2. Cross section through slide area with slide plane used for analysis (Dahill, 1994)

The tire shred layer was approximately 6 feet thick, and the fill was placed in 1-ft lifts compacted with a bulldozer.  The tire shred layer was separated from the soil by geotextiles.  Figure 3 shows that the tire shred layer was covered with 36 inches of subbase aggregate, 12 inches of crushed base aggregate, and 6 inches of pavement.

Figure 3. Typical section through pavement and base and subbase courses at the Double Nickel Slide

10,032 c.y. of tire shreds were used.  The material had a unit weight of 35 pcf, and was the least expensive lightweight fill option at $4/c.y.  Approximately 470,000 to 630,000 tires were used in the project.