Originally developed by the British military to launch chemical weapons, the Soil Nail Launcher™ is a compressed air cannon that can accelerate a 1.5 inch (38mm) diameter, 20 foot (6.5m) long steel or fiberglass tube to 250 miles per hour (400 kph) in a single shot.
The compressed air cannon induces tensile stresses in each tube as it penetrates the ground. This tension counteracts the compressive stresses induced by the displaced soil and thereby prevents nail buckling. The single impulse, high-installation velocity creates a shock wave at the nail tip, which displaces the adjacent soil as the nail penetrates. Nail penetration ceases when accumulated frictional resistance of the soil at the nail tip is sufficient to dissipate the installation energy imparted by the cannon. Bars enter the earth without significant abrasion or loss of exterior corrosion protection. The soil particles then collapse onto the bar in a relatively undisturbed state, yielding pullout capacities up to 10 times that of driven or vibrated rods or tubes. Lastly, soil nailing increases soil density in the nailed area. In contrast, conventional open-hole drilling techniques allow the soil to relax prior to installation, which can adversely affect bond capacity.
Advantages are immediate contribution to stability, high rate of production, low impact access and competitive costs. Tests confirm that the nail/soil bond is typically higher than nails installed with traditional drilling methods. Both ungalvanized and galvanized bar will survive for a very long time in most soil environments.
Research by the United States Forest Service, the Federal Highway Administration, and three state departments of transportation sponsored a 1992 demonstration project for the Soil Nail Launcher. Those agencies spent over $250,000 and concluded that this new tool was a faster and less expensive way to install soil nails in some situations. EM 7170-12A “Application Guide for Launched Soil Nails” contains some of their findings.
The second Strategic Highway Research Program (SHRP2) recently selected launched soil nailing as a technology that achieved their goals of providing: 1. Rapid renewal of transportation facilities; 2. Minimal disruption of traffic; and 3. Production of long-lived facilities. Their most recent work, titled “Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform” was sponsored by the Federal Highway Administration in cooperation with the American Association of State Highway and Transportation Officials (AASHTO), and was administered by the Transportation Research Board of The National Academies. Read more about the study at geotechtools.org.
Advantages are immediate contribution to stability, high rate of production, low impact access and competitive costs. Tests confirm that the nail/soil bond is typically higher than nails installed with traditional drilling methods. Both ungalvanized and galvanized bar will survive for a very long time in most soil environments.
GeoStabilization International® has released its new Remote Operated Launcher System, bringing even more advanced technology to slope stabilization. Slope stability is critical for maintaining safe and sustainable infrastructure. This launcher system increases crew capabilities and productivity by providing flexible and customizable carrier configurations for the launched soil nail stabilization method. Using the same air cannon technology as the company’s Soil Nail Launcher™, the remote launcher provides the same slope stabilization capabilities that GeoStabilization has utilized for more than two decades. The system can now be attached to smaller, more maneuverable equipment by decoupling the air compressor from the excavator. Doing so reduces the equipment footprint and impact on traffic flow, while providing crews more mobility to traverse steep slopes and safely access difficult-to-reach areas, often without the need for temporary benching.
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