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Helical Pile Design Verification - Pipe Section Pile

RS2875.165 (2.875 in Pipe Section) with 8''-10''-12'' Helixes


A. Project description


This example presents a detailed example for calculating the ultimate axial capacity of a helical pile according to Vesic 1974 and Meyerhoff/Hansen method. Table 1 below presents assumed soil properties, Table 2 summarizes the soil stratigraphy, while Table 3 describes assumed helical pile properties.


Table 1: Soil properties


Table 2: Stratigraphy (Boreholes)


Table 3: Helical pile properties


Soil Properties and Model in HelixPile


Pile Section Properties and Helix Configuration


B. Ultimate bearing capacity calculations – Cylinder failure method


B1. Manual calculations


For the cylinder lateral pressures factor, we will use the Mitch – Clemence method:


K = 0.09e(0.08fr) = 0.09


Table 4:  Ultimate shear stress line force calculations.



Figure: Ultimate shear stress line force on cylinder body.


Cylinder strength: Fcylinder = A1 + A2 = 14375 + 9420 = 23795 lbs = 23.8 kips


Vesic method


Tip: Fult = 0.86 kips (compression)


Plate 1: Fult = 5.85 kips (compression)


Plate 3: Fult = 13.89 kips (tension)


So, the utimate cylinder compression capacity is Fult, comp =  23.8 + 0.86 + 5.85= 30.51 kips


The utimate cylinder tension capacity is Fult, tension =  23.8 + 13.89 = 37.69 kips


Meyerhoff/Hansen


Tip: Fult = 0.81 kips


Plate 1: Fult = 5.58 kips


Plate 3: Fult = 13.32 kips


So, the utimate cylinder compression capacity is Fult, comp =  23.8 + 0.81 + 5.58 = 30.19 kips


The utimate cylinder tension capacity is Fult, tension =  23.8 + 13.32 = 37.12 kips


B2. Calculations with HelixPile


The following images present the calculated compression and tension cylinder capacities with the Vesic and Meyerhoff/Hansen methods respectively. The analysis has been performed with HelixPile software.


Figure: Cylinder Capacities in HelixPile - Vesic Method


Figure: Cylinder Capacities in HelixPile - Meyerhoff/Hansen Method


Table 5:  Comparison between manual calculations and HelixPile results.


 

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