b'Design Example 1BHeavy Weight New ConstructionWeak SoilIn this variation, the same construction load and In this design example there exists just under thesoilconditionsprevailasstatedinDesign surface afivefootlayer ofveryweakClass8Example 1 with the exception that five feet of soilconsistingofloosesandandsoftorganicextremely weak soil now exists directly below clay.These very weak soils overlay inorganicthe surface. clay that is able to provide sufficient lateral shaftAdditional Design Details: support for the required load. The soil data revealed a least five feet of very The AxialCompressiveLoadLimitof100,000loose sand fill and very soft clay organic soil near pounds (Table 2 - Chapter 1) is not valid whenthe surface. this2-7/8inchdiametertubularshaftpasses StandardPenetrationTestvaluesforthisweak through Class 8 soil with reported SPT values,layer were reported to be N = 1 to 3 blows perfoot - Soil Class = 8 N = 1 to 3 bpf. Below 5 feet the soil profile is the same as shown One must understand that the weak upper layerin Design Example 1. ofsoilisnotabletoprovidesufficientlateralECP Torque Anchor Design: The soil data support to the shaft to prevent bucking.here suggests that below the initial five feet of In Chapter 1 - Table 15, Conservative Criticalvery weak soil, the soil profile is similar to the BucklingLoadEstimates (Reproducedbelow)soil in Design Example 1.Referring to Example demonstratesthis shaftweakness quiteclearly1, it can be recalled that the pile configuration for various soil strengths and types.Referring torequiredsupportingthe60,000poundultimate Table 15 below, it can be seen that the estimatedload on pile using an 8-10-12 inch diameter plate bucklingstrengthforthe2-7/8inchdiameter,configuration.The 2-7/8 inch diameter tubular 0.276 inch wall standard helical Torque Anchor shaft,with0.276inchwallthickness,hada shaftwhenitpassesthroughsoilconsistingofsufficient AxialCompressiveLoadLimitto very loose sand fill and soft organic clay havingsupportthedesignloadandsufficient Useable SPT values that range from N = 1 to 3 blowsTorsionalStrength toinstall thepileunderthe per foot is only 48,000 pounds.soil conditions represented in Design Example 1. This layer of weak soil is not capable of lateral Knowing that there exists a layer of extremely shaftsupport whena60,000poundweaksoilnearthesurfaceonthissiteis compressiveloadisapplied.Shaftbucklingimportant information because helical piles have withintheweakupperlevelsoil mustbeslender shafts and require sufficient lateral soil considered.supportagainsttheshafttopreventshaft 2. Select a Pile Shaft with Suitable Bucklingbuckling under full load. (See Table 9, Chapter Strength. Theaxialultimatecompressive1 - Class 8 soil) capacityrequirementforthisprojectis60,0001.Determine theBucklingStrength.Please pounds on the pile shaft.note that Chapter 1Table 2provides AxialCompression Table 15Conservative Critical Buckling Load EstimatesLoadLimitsforhelicalpileshafts whentheshaftsare Uniform Soil Conditioninstalledintosoilthat Shaft Size Organics Very Soft Clay Soft Clay Loose Sandprovidessufficientlateral N 1 N = 1- 2 N = 2 - 4 N = 2 - 4support along the pile shaft. 1-1/2 Sq 13,000 lb 16,000 lb 23,000 lb 19,000 lbTestinghassuggestedthat 1-3/4 Sq. 19,000 lb 24,000 lb 48,000 lb 28,000 lbshaft buckling is not an issue 2 Sq. 28,000 lb 35,000 lb 96,000 lb 43,000 lbwhen the soil has a SPT value, 2-7/8 Dia x 0.203 36,000 lb 44,000 lb 62,000 lb 51,000 lbN 4blowsperfootfor 2-7/8 Dia x0.276 39,000 lb 48,000 lb 69,000 lb 56,000 lbtubularshaftsand N 5 3-1/2 Dia x 0.300 63,000 lb 78,000 lb 110,000 lb 90,000 lbblows per foot for solid square 4-1/2 Dia x 0.337 113,000 lb 139,000 lb 160,000 lb 160,000 lbshafts.ECP Technical Design ManualTorque Anchor Design Examples2021 Earth Contact Products, L.L.C.2021-09 Chapter 5Page 83 All rights reserved'