Description: |
Missouri's rolling hills and streams have attracted the attention of visitors since the state’s first settlers. Unfortunately, the beauty also has a beast … soil erosion. Slope repairs along Missouri’s highways are labor intensive, costly, and often must be repeated. They also can be damaging to highway shoulders, pavements and can require lane closures for several days.
Soil nailing is a proven method of stabilizing slopes. However, traditional soil nailing is a slow process requiring extensive excavation and drilling to insert the steel rods. Slide repairs using tradition soil nailing often take weeks to complete.
The Soil Nail Launcher, provided by Soil Nail Launcher, Inc. can complete slide repairs in just a few days and provide added strength. Adapted from British military technology, the launcher uses compressed air to send 1.5-inch steel bars 20 feet or more into the soil. The bars traveling up to 220 miles per hour create a shock wave causing the soil to jump away and allowing the bar to pass. The soil then collapses around the bar creating a powerful bond. Tests have shown this bond to be much greater than percussion-driven nails. The bars can be solid, threaded or hollow and have plain, galvanized or epoxy coatings. Hollow bars can serve as horizontal drains. Depending upon soil characteristics and its penetration resistance, the Soil Nail Launcher application is appropriate for shallow to medium depth slide repairs.
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Result: |
District staff worked with the contractor to complete 300 feet of slope in only two working days. It’s estimated that the project would have required five to six weeks to complete with traditional repair methods. The project also saved about four to five weeks’ maintenance labor. The cost for the project was just under $125,000, which included nail installation (300 feet of slope with two to three rows of rods every three feet) and mobilization costs. A manual fix would have cost about $400,000 to $500,000. The manual fix would have required a rock wedge repair at the top and a toe buttress along the foot of the slope. The Soil Nail Launcher resulted in minimal traffic disruptions. The launcher required only one lane of traffic to be closed at a time. It’s also possible to set the work site to avoid any lane closures.The launcher may be a good choice when there is limited working room or where closing the road is not an option. The launcher is also less intrusive than traditional methods, which can damage surrounding soil and vegetation.
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