b'Hydraulic Torque MotorECP Torque Anchors are usually installed with Symbols Used In This Chapterahydraulicmotorandreductiongearbox d Deflection of pile under test loading in.assembly.Some motors offer a two speed gearbox,whichallowstheinstallertoincreasethe Empirical efficiency factor relating ultimate k capacity of a pile or tieback to the installationadvancementtheTorqueAnchor throughthe torque ft -1(k = P uor T u/ T)upperstrataofthesoil. When approximately75%ofthedesigninstallationtorquehasbeen Torque conversion factor that is used to determinereached,therotationalspeedisreducedto K torque motor output from pressure differentialbetween5and10rpmuntilthefinaltorqueis across motorachieved for the required embedment length. P u Ultimate pile or anchor capacity*lb.p Pressure differential measured across a torqueInstallation Torque motor p =p in - p out - psiInstallationtorqueontheshaft,the Soil T Installation orMotorOutput Torque ft-lbEfficiencyFactor(k)and Table1were T u orP u UltimateHelical Product Capacity lbintroducedanddiscussedinChapter1.These Estimatingtheultimatecapacityofhelicalitems are reproduced for reference below. foundationproductbasedupontheinstallationShafttorsionduringinstallationcanprovidea torque has been used for many years.reasonablyaccurateestimateoftheultimate Unless a load test is performed to create a sitecapacityoftheinstalledhelicalscrewproduct. specificvalueforthe SoilEfficiencyFactorThe relationship between the shaft torsion during (k), a value must be estimated when designing.installationandtheultimatehelicalproduct While values for k have been reported from 2capacityisempiricalandwasdevelopedfrom to 20, most projects will produce a value of kresultsfromthousandsoftests.Whenone inthe6to14range.EarthContactProductsapplies rotational torsion to the end of the shaft at offersarangeofvaluesfor SoilEfficiencygradelevel,someofthetorqueenergyislost Factors(k)in Table12below.These kbefore it reaches the helical plates at the bottom valuesmaybeusedforestimatingempiricalend of the shaft.This loss of torque is due to ultimate capacities of installed Torque Anchors.friction between the shaft and the soil. These values may be used until a field load testIn Figure 1 below, notice that not all of the canprovide amoreaccurate sitespecificvaluetorque applied to the shaft by the motor reaches for k. Table 2 lists typical values of k forgeneralestimationsofultimatecapacityofthe helical plates.The actual torque applied to Torque Anchors based upon the output torquethe helical plates is T Plates= T Motor - T Shaft .The at the installation motor shaft.friction generated between the surface area of the Understand that the value of the Soil Efficiencyshaft and the soil is directly related to the type Factor(k)isanestimationoffrictionlossand size of the shaft along with properties of the during installation.The amount of friction losssoil at the installation site.Because of this has a direct relationship to soil properties and thetransmission torque loss in transmitting the motor anchor shaft.torque to the plates, an empirical Soil EfficiencyFactor (k) must be employed to arrive at areasonable estimate of ultimate capacity expected Table 12.Soil Efficiency Factor kfrom the pile or anchor. Typically SuggestedTorque Anchor Type Encountered Average Value,Soil Efficiency Factork: Is the relationship Range k kbetweeninstallationmotortorqueandultimate 1-1/2 Sq. Bar 9 - 11 10capacityoftheinstalledTorqueAnchor. 1-3/4 Sq. Bar 9 - 11 10Shaft Friction Torque from 8.5(Compression ) 8.5= T shaft Motor Applied 2 Sq. Barto Shaft = T Motor 1011 (Tension) 102-7/8 Diameter 8 - 9 93-1/2 Diameter 7 - 8 84-1/2 Diameter 6 - 7 7Helical Plate Figure 1 .Friction = T platesECP Technical Design Manual - Installation & Testing2021 Earth Contact Products, L.L.C.2021-09 Chapter 4 - Page 61 All rights reserved'