Some kinds of Soil nails

17/ago/2016 09:46:31 sinorocksoilnailing Contatta l'autore

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Soil nailing is a technique used to reinforce and strengthen existing ground. • Soil nailing consists of installing closely spaced bars into a slope or excavation as construction proceeds from top down. • It is an effective and economical method of constructing retaining wall for excavation support, support of hill cuts, bridge abutments and high ways. • This process is effective in cohesive soil, broken rock, shale or fixed face conditions.

Origins • Soil nailing evolved from the New Austrian Tunneling method which is a system for underground excavations in rock. • This concept of combining passive steel reinforcement and shotcrete has also been applied to the stabilization of rock slopes since the early 1960s. • The first application of soil nailing was implemented in 1972 for a railroad widening project near Versailles, France. • The technique included installing high-density, grouted soil nails into a 60-ft.-high wall and facing it with reinforced concrete. • The United States first used soil nailing in 1976 for the support of a 13.7 m deep foundation excavation in dense silty sands.

Applications • Stabilization of railroad and highway cut slopes • Excavation retaining structures in urban areas for high-rise building and underground facilities • Tunnel portals in steep and unstable stratified slopes • construction and retrofitting of bridge abutments with complex boundaries involving wall support under piled foundations • Stabilizing steep cuttings to maximize development space. • The stabilizing of existing over-steep embankments. • Soil Nailing through existing concrete or masonry structures such as failing retaining walls and bridge abutments to provide long term stability without demolition and rebuild costs. • Temporary support can be provided to excavations without the need for bulky and intrusive scaffold type temporary works solutions.

Driven soil nails • Generally small-diameter nails (15-46 mm) with a relatively limited length (to about 20 m) made of mild steel (about 50 ksi) that are closely spaced in the wall (two to four nails per square meter). • Nails with an axial channel can be used to permit the addition of grout sealing. • Driven nails are the quickest (four to six per hour) and most economical to install (with a pneumatic or hydraulic hammer).

 Grouted soil nails • Steel bars, with diameters ranging from 15 to 46 mm, stronger than driven nails (about 60 ksi). • Grouted nails are inserted into boreholes of 10-15 cm and then cementgrouted. • Ribbed bars are also used to increase soil adhesion. • Corrosion-protected nails • For aggressive soils as well as for permanent structures.

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