b'Preliminary Design Guideline Using Site Specific Soil DataThefollowing equipment that can maintain accurate installationpreliminarydesign WORKING LOAD = angles.The spacing requirement of five timesinformationis the diameter of the largest plate is measured atintendedtoassist the target depth.It is normal practice to clusterwith the selection of PILE CAP several shafts at the same surface location withanappropriateECP eachshafthavingasuitableoutwardbattertoTorqueAnchorMINIMUM accomplish the required shaft to shaft spacing atsystemforagiven EXTENSION DEPTHTO the final installed depth.THEproject. UPPERMOSTHELICALPLATE Usingguidelinesdescribedabove,theultimateFROMTHE Deep Foundations SURFACE capacity of an ECP Torque Anchorsystem canMUSTEXCEED 6TIMESTHE be calculated from the following equation:TorqueAnchor DIAMETEROFsystemsmustbe THEHELICALPLATE Equation 1: Ultimate Theoretical Capacity:consideredasdeep P uor T u = A H(c N c+ q N q )foundation elements.EXTENSIONAs a rule of Where:thumb, helical P uor T u = Ult. Capacity of Torque Anchor- (lb)HELICAL A H = Sum of Projected Helical Plate Areas (ft 2 )piles must be PLATE c = Cohesion of Soil - (lb/ft 2 )installed deeper N c= Bearing Capacity Factor for Cohesionthan the CriticalSOIL q = Soil Overburden Pressure to h middepth(lb/ft 2 )Depth of six times REACTION N q= Bearing Capacity Factor for Granular Soil.the diameter of Theultimatecapacityisdefinedastheloadthatthe largest helix. HELICALThe depth isPLATE resultsinadeformationofoneinch.Ingeneralmeasured from ultimatecapacityistheworkingorserviceloadthe intended finalSOIL with a factor of safety of 2.0 applied.HELICAL If one has access to a soil report in which c, ,surface elevation LEAD SECTION REACTIONto the uppermost HELICAL andare given, then Equation 1 can be solvedhelical plate of the PLATE directly.Unfortunately, many soil reports often doTorque Anchor. notcontainthesevaluesandthedesignermust SOIL decide which soil type is more likely to control theREACTION ultimate capacity.Thecapacityofa Figure 1.Helical Pile Loadmulti-helixdeep and Reaction Diagram Whenoneisunsureofthesoiltypeorthesoilfoundationsystem behavior cannot be determined, we recommend thatassumes that the ultimate bearing capacity is the onecalculateloadsusingcohesivesoilbehaviorsum of the bearing support from each plate of the because the result will be conservative.system. Testing has shown that when the helical In all cases, we highly recommend field testing toplatesarespacedatthreetimesthediameter verifytheaccuracyofthepreliminarydesignaway from the adjacent lower helical plate, each load capacities.platewilldevelopfullefficiencyandsoilcapacity.Spacing the helical plates at less than Soil Behaviorthree diameters is possible, however, each plate The following information is provided to introducewill not be able to develop full capacity and the the reader to the field of soil mechanics.Explaineddesigner will have to include a plate efficiency arethetermsandtheoriesusedtodeterminesoilfactorintheanalysiswhenconductingthe behaviorandhowthisbehaviorrelatestoTorquedesign. Anchorperformance.ThisisnotmeanttoPile or anchor shaft spacing should be no closer substituteforactualgeotechnicalsoilevaluations.than five times the diameter of the largest plate at A thorough study of this subject is beyond the scopethe bearing depth.Pile shaft spacing as close as ofthismanual.Thevaluespresentedherearethreediametershasbeen successfullyinstalled, typical of those found in geotechnical reports.butthisworkrequiresspecialinstallationECP Helical Torque Anchors Technical Service Manual2021 Earth Contact Products, L.L.C.2021-09 Chapter 1 - Page 17 All rights reserve'