b'havesuitable lengthtoprovidetherequired As a general rule of thumb, many designers usehorizontal embedment length. (See Figure 3.) six times the diameter of the largest helical plateTable 13 provides equations to obtain the shaft from the surface elevation to the top of largestlengthL at selected downward angles and helical anchorplate - (d) as Criticalgives a Horizontal Embedment and the Depth to Embedment Depth - D.the largest plate.Use the longestlength - L determined from the Table 13.Angular Embedment Lengthcells to the right of the installation IMPORTANT:angle . Use the cell with the longerL for the design.CriticalEmbedmentDepthInstallation Angle, Multiply the additionalD: Intensionapplications , Declination depth required from wall Length L required to reach theFrom Horizontal penetration to Critical Minimum Horizontalthereisashallowfailure Depth to obtain Tieback Embedment at the specifiedmechanism for screw piles.The LengthL. downward angle anchorfailswhenthesoilsuddenly erupts from insufficient 10 0 6 x additional depth L 10= [H + (10 d lg )] x 1.015soiloverburdenontheanchor. 15 0 4 xadditional depth L 15= [H + (10 d lg )] x 1.035To prevent such failures, TorqueAnchorsmustbeinstalledtoa 20 0 3 xadditional depth L 20= [H + (10 d lg )] x 1.064sufficient embedment depth to be 25 0 2.5 xadditional depth L 25= [H + (10 d lg )] x 1.104consideredadeepfoundation.This is illustrated in Figure 3 on H = Height of Backfill (ft) d lg= Largest Plate Dia. (ft)Page 29.Torque Anchor Installation LimitsShaft Strength: The data in Table 2 gives the to insure proper embedment and to prevent shaftstrength ratings for various shaft configurations impact fractures.in axial tension, compression and shaft torsion. ItisimportanttoalsounderstandthattheThevaluesarefrommechanicaltestingand empiricaltorsionalfactorkreducesthenotfromtestsinthesoil.BecauseTorque practical limit on the ultimate capacity that canAnchor products are installed by rotating them bedevelopedinthesoil.Thisisespeciallyinto the soil; the installation torsion can limit the importantwhendesigningwithlargertubularultimate strength of the product. productsbecauselargetubularshaftspassThe Useable Torsional Strength column in Table throughthesoillessefficientlythansmaller2 indicates the maximum installation torque that tubular shafts and solid square bars.shouldbeintentionallyappliedtotheTorque ShaftStiffness: WhenthetubularTorqueAnchorshaftduringinstallationin Anchorisinstalledthroughsoftsoilsthathomogeneous soil.The risk of product failure display a Standard Penetration Test value N dramaticallyincreaseswhenoneexceedsthese 4 blows per foot (N 5 for square shafts), thelimits. possibility of shaft buckling must be consideredWhenchoosingaproductforaproject,the in assessing the axial compressive capacity of thedesignershouldselectaproductthathasan pile.adequate margin of torsional strength above the Itisimportanttorememberthattubularshaftstorquerequiredforembedment.Thismargin provide superior resistance to buckling than solidwill allow for increases in torque during the final squarebarswhenusedinaxialcompressionembedmentlengthaftertheinitialtorsional applications.resistancecriterionhasbeenmet.Inaddition, Thisisbecausetubularshaftshavegreaterfracturesfromunexpectedimpactloadingcan flexural stiffness. (They have a larger moment ofand often occur during installation, especially in inertia.)Ingeneraltubularpileconfigurationsobstruction laden soils. thelargershaftdiameterwillprovidegreaterIt is recommended that a margin of at least 30% resistance to lateral deflection or buckling withinabove the required installation torque be allowed the soil.ECP Helical Torque Anchors Technical Service Manual2021 Earth Contact Products, L.L.C.2021-09 Chapter 1 - Page 32 All rights reserve'