b'IntroductionBefore one can begin a discussion of soil nailing, One common way to do this is with a retaininga clear understanding of the difference between wallandtiebackanchors.Thetiebacksworksoilnailsand tiebackanchorsisrequired. togetherwiththestructuralretainingwalltoMany times one hears the term Soil Nail and providesufficientlateralsupporttoretaintheTiebacksusedinterchangeablyandthis unstable soil mass.The retaining wall must bedemonstratesalackofunderstandingofthe designedandconstructedtoproviderigidproducts. supportforthesoilmassoverthedistanceSuppose that a construction project requires an betweenthetiebackanchorplacements.Oneexcavation where the side of a soil cut cannot be often sees tieback anchors spaced eight to twelveprovided with a stable slope.Figure 1 illustrates feet apart along the length of the retaining wall.the soil cut and excavation for this project. Thespacingandnumberofanchorsdependsuponthewallheight,surchargeloadsandORIGINAL properties of the retained soil.Tieback anchorsGRADE mustbedrivenintothesoiltoadepththatissufficienttoprovidetensionresistanceintheFACE OF CUT anchorshaftthatisequaltothesoilforcespushing against the retaining wall.A typical soilcut with a retaining wall is illustrated in Figure 3.BOTTOM OFEXCAVATIONORIGINALGRADEFigure 1 TIEBACK ANCHORRETAINING WALLOnecaneasilyunderstandthatwithoutsomekind of containment of the soil at the face of the BOTTOM OFcut, a collapse of the soil along a failure plane is EXCAVATIONlikelytooccur.Thisfailurecanhappenveryquickly and without warning.The failure mightlook something like Figure 2.The unstable soilmoves to the bottom of the excavation leaving anatural and stable slope for the remaining soil. Figure 3Thisinterfacebetweenthestableandunstable Inmany construction projects soil nails can besoil is called a slip plane. used to retain the unstable soil mass.Soil Nails mustbeinstalledinacloseevenlyORIGINALGRADE spaced,geometricpattern.ExcavationdepthsFAILURE PLANE must be small increments, typically measuring 4to6feet deep untilthefinaldepthofcutisreached. No massive retaining wall structure isrequired.Usuallyonlyonedepthincrementcanbecompleted per day.Immediately following theincrementalexcavationofthesoilandtheinstallation of the soil nails, the vertical face ofFigure 2 thesoilcutiscoveredwithsteelmeshreinforcement and a coating of shotcrete.The most common way to prevent this kind of Soil nails are passive structural elements andsoilfailureistoprovidelateralsupporttothe are not tensioned after installation.The soilunstable soil situated in front of the slip plane.ECP Helical Torque Anchors Technical Service Manual2021 Earth Contact Products, L.L.C.2021-09 Chapter 3 - Page 51 All rights reserved'