An engineered method used to stabilize existing slopes or excavation utilizing “top down” construction sequencing. This passive reinforcement system remediates unstable natural slopes or construct new or existing over-steepened slopes using closely spaced steel inclusions. The practice involves drilling solid or hollow bars to depths specified by a geotechnical engineer. GeoStabilization’s innovative Soil Nail Launcher™ utilizes compressed air to blast up to 20-foot-long nails into the slope at speeds reaching 250-mph.
Soil nails are reinforced bars installed in soil mass. Soil nails can be installed in a variety of methods including drilled, driven, or launched nails and can be installed in a wide range of soil conditions accommodating changes in ground conditions. Soil nails perform well under seismic loading due to coupling with the ground. Each installed nail is a soil probe which can aid in design refinement during construction. Soil nails are part of a soil-structure system, consisting of the following elements: earth materials, tendons, grout, facing, connections, and drainage.
Self-drilling soil nails are uniquely suited for collapsing soil or actively moving landslides. This nail type can be used for rock or soil masses. Self-drilling nails have a high installation rate and high pullout capacity.
Open hole soil nails use the nail itself to drill the hole, using grout as the drilling fluid. The nails are hollow in the center and the grout travels down the bars and out from holes in a sacrificial drill bit. Once a nail has been drilled, it is detached from the drill and left in place. This technology combines the three-step installation of a soil nail (drilling, installing bar, and grouting) into one. Its primary advantage is not only the grout keeps the drillhole open during drilling, but the rotation from the drill bit mixes grout with the soil surrounding the drillhole, resulting in a rough, irregular effective grout column that is larger than the diameter of the drill bit.
Unlike traditional drilled and grouted soil nails, launched soil nails have a high shear capacity to axial capacity ratio. Shear capacities of up to 20% or more of axial pullout capacity have been observed. Because of this divergence, the shear component of a launched soil nail is not ignored as it would be in traditional soil nail design using grouted soil nails. The general design procedure of a launched nail wall is similar to other soil reinforced retaining structures. The design has to satisfy three types of stability requirements: internal stability(including failures due to nail shear or tensile failure, pullout, and head strength or facing failures); external stability (overturning, sliding, and bearing capacity failure); and global stability.
When the requirement arises to stabilize slope erosion and slope failure so they don’t endanger personnel and infrastructure, GeoStabilization International® provides innovative technologies, fast action, and comprehensive solutions. For over twenty years, our teams have been mitigating landslides and providing residential slope stabilization, slope monitoring, slope protection, and landslide prevention services.
Using tensile elements to stabilize landslides is both practical and cost-efficient. However, the process of installing tensile elements in actively moving landslides challenges traditional technologies. For example, conventionally drilled soil nails (developed initially to stabilize cut slopes and excavations) are not generally suited for landslide repair. The Federal Highway Administration, in their Geotechnical Engineering Circular No. 7 (Soil Nail Walls), notes that the “application of [conventional solid bar] soil nails as a means to stabilize landslides is not often used in the current U.S. practice and is therefore not discussed in this document.” Collapsing holes, active ground movement, and grout loss and migration are primary problems with using these kinds of conventional technologies for geohazard mitigation.
GeoStabilization’s founders and engineers developed and patented the SuperNail™ series of tensile elements to solve this problem. As specified in the SuperNail™ services, launched nails are installed faster than any other soil nail technology (over 250 20-foot nails per day is possible). Some types of nails can be installed using specialized drilling techniques. Unlike conventional solid bar soil nails, the SuperNail™ nails can be installed in collapsing holes, areas with voids, actively moving landslides, and at depths of up to 120 feet in soil, rock, or a combination of soil and rock. Depending on the design services specified, anywhere from 1-4 corrosion protection layers will protect the tensile element for permanent application. In very aggressive soil conditions or coastal environments, fiberglass can be used instead of steel to construct SuperNail™.
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