ZZZ DFNHUGULOO FRP PNYDVV#DFNHUGULOO FRP 16 AUGUST 2021 WorldWide Drilling Resource® Nailing It ~ Tendons of Steel Compiled the Editorial Staff of WorldWide Drilling Resource® According to the United States Geological Survey, landslides occur in all 50 states and U.S. territories, causing $1-2 billion in damages and more than 25 fatalities on average each year. Recently, the H.R. 8810 / S. 529 National Landslide Preparedness Act was introduced in Congress, and former President Trump signed the bill into law on January 19th. This new law includes a national strategy for landslide hazards, risk reduction, and response, including landslide hazard stabilization. There are several methods for slope stabilization to mitigate landslides, one of which is soil nailing. Soil nails transfer tension and compression loads and are passive anchoring components without free length and prestressing. These structural elements are used for reinforcing the ground/rock mass to stabilize slopes and reduce the chances of landslides. Each soil nail consists of a high-strength steel bar inserted deep into the slope in a drilled borehole. A highstrength mixture of grout is used to bond the soil nail into the borehole. Pumped into each borehole, the cementitious grout sets each nail, pinning back a small section of the face. Multiple soil nails are installed in a regular pattern to fully stabilize the slope, creating a composite mass similar to a gravity wall. High-tensile steel netting installed over the soil nails, along with a bearing plate attached to each nail to hold the mesh in position, prevents material between soil nails from slipping out. Advantages of soil nailing include versatility and a smaller environmental footprint. It is easy to shore along irregular curves and surfaces. Installation methods can be modified according to constrained access. When space for shoring is limited, especially for tall retaining structures, soil nailing produces a much smaller footprint than laying back a slope. Typically, soil nails are installed with standard rotary highimpact drill rigs or Caterpillar® vibrators. More recently, a new hero of stabilization, GeoStabilization International®’s (GSI®) Soil Nail Launcher™, armed with their SuperNail®, employs its power to launch tendons of steel into the earth. Originally developed by the British military, the Soil Nail Launcher is a compressed air cannon which can accelerate a 1.5-inch-diameter, 20-foot-long steel or fiberglass tube to 250 miles per hour in a single shot. As these high-speed projectiles enter the earth, they generate a shock wave, causing the soil particles to deform (jump away) from the nail tip. The bars enter without significant abrasion or loss of exterior corrosion protection. Soil particles then collapse onto the bar in a relatively undisturbed state, yielding pullout capacities up to ten times greater than driven or vibrated rods or tubes, and increasing soil density in the nailed area. Launched soil nails can also be perforated to allow for horizontal drainage and pore water pressure relief. Usually mounted on a modified tracked excavator, the launcher can also be mounted on vehicles, long reach excavators, or crane basket frames. Weighing about two tons, it is portable and able to reach remote locations. With full articulation, it can work around overhead wires, underground utilities, and guard rail. The launcher’s mitigation partner, the advanced SuperNail can be installed faster than any other soil nail technology at over 250 20-foot nails per day. These can be used in collapsing holes, areas with voids, actively moving landslides, and at depths of up to 120 feet in soil, rock, or a combination of the two. Depending on the design services specified, anywhere from one to four layers of corrosion protection will guard the tensile element for permanent application. In very aggressive soil conditions or coastal environments, GSI can also use fiberglass instead of steel to construct the nails. Landslides are natural geological hazards, proving to be catastrophic for people and property in many cases. To counter these destructive scenarios, it is important to create stabilizing slopes which last longer and become part of the infrastructure. As engineers of soil nailing technology continue to innovate, these new advances hold great promise for landslide mitigation. Photo of Soil Nail Launcher courtesy of GeoStabilization International. ENV October Editorial Focus All About Drilling
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