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Soil nailing is a construction technique that can be used as a remedial measure to treat unstable natural soil slopes or as a construction technique that allows the safe over-steepening of new or existing soil slopes. The technique involves the insertion of relatively slender reinforcing elements into the slope – often general purpose reinforcing bars (rebar) although proprietary solid or hollow-system bars are also available. Solid bars are usually installed into pre-drilled holes and then grouted into place using a separate grout line, whereas hollow bars may be drilled and grouted simultaneously by the use of a sacrificial drill bit and by pumping grout down the hollow bar as drilling progresses. Kinetic methods of firing relatively short bars into soil slopes have also been developed. Bars installed using drilling techniques are usually fully grouted and installed at a slight downward inclination with bars installed at regularly spaced points across the slope face. A rigid facing (often pneumatically applied concrete, otherwise known as shotcrete) or isolated soil nail head plates may be used at the surface. Alternatively a flexible reinforcing mesh may be held against the soil face beneath the head plates. Rabbit proof wire mesh and environmental erosion control fabrics and may be used in conjunction with flexible mesh facing where environmental conditions dictate. Soil nail components may also be used to stabilize retaining walls or existing fill slopes (embankments and levees); this is normally undertaken as a remedial measure. Since its first application using modern techniques in Versailles in 1972,〔"Construction d'un mur de soutènement entre Versailles-Chantiers et Versailles-Matelots", S. Rabejac and P. Toudic, General review of the railways, 93rd edition, pp 232-237.〕 soil nailing is now a well-established technique around the world. One of the first national guideline publications for soil nailing was produced in Japan in 1987. The U.S. Federal Highway Administration issued guideline publications in 1996〔U.S. Federal Highway Administration (FHWA). ("Manual for Design and Construction Monitoring of Soil Nail Walls." ) Publication no. FHWA-SA-96-069. Revised October 1998.〕 and 2003.〔FHWA (2003). ("Geotechnical Engineering Circular No. 7: Soil Nail Walls." ) Publication No. FHWA-IF-03-017.〕 == Preliminary Analysis == Four main points to be considered in determining if soil nailing would be an effective retention technique are as follows. First, the existing ground conditions should be examined. Next, the advantages and disadvantages for a soil nail wall should be assessed for the particular application being considered. Then other systems should be considered for the particular application. Finally, cost of the soil nail wall should be considered.〔FHWA (2003). ("Geotechnical Engineering Circular No. 7: Soil Nail Walls." ) Publication No. FHWA-IF-03-017. pp.13,14.〕 Soil nail walls can be used for a variety of soil types and conditions. The most favorable conditions for soil nailing are as follows: The soil should be able to stand unsupported one to two meters high for a minimum of two days when cut vertical or nearly vertical. Also all soil nails within a cross section should be located above the groundwater table. If the soil nails are not located above the groundwater table, the groundwater should not negatively affect the face of the excavation, the bond between the ground and the soil nail itself.〔FHWA (2003). ("Geotechnical Engineering Circular No. 7: Soil Nail Walls." ) Publication No. FHWA-IF-03-017. pp.14,15.〕 Based upon these favorable conditions for soil nailing stiff to hard fine-grained soils which include stiff to hard clays, clayey silts, silty clays, sandy clays, and sandy silts are preferred soils. Sand and gravels which are dense to very dense soils with some apparent cohesion also work well for soil nailing. Weathered rock is also acceptable as long as the rock is weathered evenly throughout(meaning no weakness planes). Finally, glacial soils work well for soil nailing.〔 A list of unfavorable or difficult soil conditions for soil nailing can include dry, poorly graded cohesion-less soils, soils with a high groundwater table, soils with cobbles and boulders, soft to very soft fine-grained soils, highly corrosive soils, weathered rock with unfavorable weakness planes, and loess.〔FHWA (2003). ("Geotechnical Engineering Circular No. 7: Soil Nail Walls." ) Publication No. FHWA-IF-03-017. pp.15,16.〕 Other difficult conditions include prolonged exposure to freezing temperatures, a climate that has a repeated freeze-and-thaw cycle, and granular soils that are very loose.〔FHWA (2003). ("Geotechnical Engineering Circular No. 7: Soil Nail Walls." ) Publication No. FHWA-IF-03-017. pp.16.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「soil nailing」の詳細全文を読む スポンサード リンク
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