Tools and Technologies
- The Soil Nail Launcher
- The Super Nailer
- Geosynthetically Confined Soil (GCS®)
- BioWall®
- Launched Horizontal Drains
- Launched Scour Micropiles
- High Capacity Steel Mesh
The Soil Launcher
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.
Dynamic installation results in distinct benefits over conventional nailing techniques. First, as these high speed projectiles enter the earth, they generate a shock wave that causes the soil particles to elastically deform or “jump away” from the nail tip. The 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, Launched Soil Nails increase 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.
Launched Soil Nails also can be perforated to allow for horizontal drainage and pore water pressure relief, or they can be pressure grouted with a variety of materials to increase bond capacity and soil properties throughout the nailed region.
The Soil Nail Launcher typically is mounted on a modified tracked excavator. However, it can be mounted on vehicles, long reach excavators, or crane basket frames. It weighs about 2 tons (1.8 metric tonnes), making it portable and able to reach remote locations. The launcher unit has full articulation, allowing it to work around overhead wires, underground utilities, and guard rail.
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 SuperNailer, SuperNails® and SuperMicropilesTM
Soil Nail Launcher, Inc. has developed tools and technologies to complement the Soil Nail Launcher. The patented SuperNail® series includes grouting and additional steel or fiberglass bars for higher capacity and increased service life. The new SuperNailer can augment installation with patented drilling capability for deeper slides or areas with shallow bedrock. Our SuperMicropilesTM can be used to support structures such as our GCS® (Geosynthetically Confided Soil) walls, the most advanced retaining wall system to date.
Geosynthetically Confined Soil (GCS®)
Federally Funded research shows that GeoSynthetically Confined Soil (GCS®) structures have bearing capacities up to 20 times those of traditional Mechanically Stabilized Earth (MSE) walls. Sate of the art GCS® technology translates into better retaining walls, bridge abutments, box culverts, foundations, rockfall barriers, avalanche and debris flow deflectors, and more.
Facing options include natural vegetation, wire mesh, natural stone, concrete block, or sculpted shotcrete.
The key to GCS® performance is close (8 inch/200mm) reinforcement spacing with compacted granular backfill. The reinforcement induces confining effects in the soil up to four inches (100mm) from each sheet. That confining effect explains why GCS® structures built with even the lightest fabrics can withstand loads up to 22.5 tons per square foot (2.2 MPa) while MSE structures can fail under self weight.
BioWall®
The BioWall® is a patented, environmentally friendly and aesthetically unobtrusive facing option for bare rock or mineral soil slopes that are too steep to revegetate on their own. The BioWall® can be planted with native vegetation—in the form of live stakes, sprigs, bare root, plugs or seeds—and installed with an irrigation system.
Launched Horizontal Drains
Launched Horizontal Drains allow for pore water pressure relief during transient high groundwater events and provide a tensile and shear contribution at the same time. Traditional drilled drains provide no tensile contribution and are often spaced in a single row between 10 and 30 feet on center. Launched Horizontal Drains can be installed rapidly (up to 200 drains per shift) and are spaced in multiple rows as densely as 2.5 feet on center. Landslide repair practitioners never have had the luxury of such a tightly spaced array of horizontal drains, and no system currently available today provides for both tensile and shear capacity in addition to drainage.
Launched Scour Micropiles
Traditional micropiles are small-diameter steel rods or pipes installed in concrete-filled drill holes. They are used most often in groups to transfer bearing loads to deeper regimes. Engineers at Soil Nail Launcher, Inc. have discovered that micropiles also can be used to prevent scour at new constructions and repair existing scour holes and degrading stream beds.
Beyond the basic benefits of cost-savings and avoiding or minimizing rip rap installations, this new micropile application—especially when combined with our GCS® technologies—encourages the use of aquatic- and terrestrial-friendly open bottom boxes and bridges. And because Launched Scour Micropiles are installed with our Soil Nail Launcher, stream encroachment and other collateral damage is restricted practically to those areas of future disturbance.
Moreover, with the Soil Nail Launcher, there is no need for polluting drill rigs or fresh concrete around the stream or riparian zone. Launched Scour Micropiles zip into the ground at 220 miles per hour and set up as if they are in concrete. They are instantly ready for work! Launched Nails achieve significantly higher pullout capacity than driven nails.
Once the Launched Scour Micropiles are installed, appropriately graded alluvium can be added to fill the scour hole and create a ramp, eliminating the waterfall. Fish passage can be maintained, even in severe conditions. The diagrams show that if a fraction of the alluvium is larger than the spacing of the Launched Scour Micropiles, the micropiles’ three-dimensional cage effect will contain the particles and create a barrier to scour. If the stream bed is fine grained, then placement of appropriately graded rock on the array and upstream is a solution. As the material scours, these rocks will migrate down and fill into the matrix, creating this scour barrier.
High Capacity Steel Mesh
High capacity, Galfan® coated or galvanized steel wire mesh (rockfall mesh) can be used with or without post-tensioning to provide heavy erosion protection and translate soil nail forces into problem rock and soil slopes. These systems can provide an economical and “green” alternative to shotcrete in many applications.
SNLI uses two main systems to stabilize slopes with high capacity mesh:
• Geobrugg’s TECCO® System: One of the strongest mesh systems available today, the TECCO® slope stabilization system stabilizes steep, weathered slopes in place of concrete or shotcrete surface treatment and conventional heavy net systems. After cleaning, trimming and leveling the problem slope, the surface is covered by a high capacity steel wire mesh which is tensioned at a defined additional torque force via previously launched or drilled nails and plates. The mesh fits tight to the slope, preventing shallow sloughing and erosion. Most importantly, with proper application of fertilizer, seed, and erosion matting or hydromulch, the TECCO® system allows for vegetation to establish on the slope, eventually covering much of the mesh. The TECCO® slope stabilization mesh owes its high mechanical strength to an alloyed, high-tensile 3mm steel wire with 12 individual meshes per meter.
• Macaferri’s MacMat®: MacMat® is a three-dimensional permanent erosion control mat composed of UV stabilized, non degradable synthetic fibers with an additional structural skeleton of Maccaferri double-twisted steel wire mesh within the polymer matrix. MacMat® immediately increases the soil’s resistance to erosion by providing an environment that enhances the growth of vegetation through the mat. Supplied in rolled form, MacMat® can be anchored to the slope surface using launched or drilled soil nails. Topsoil can be brushed into the voids within the matrix. Seed can be applied to the surface before or after MacMat® is installed as vegetation will develop unhindered by the matrix.
