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Geocentrix Repute - Onshore pile design and analysis

Six model piles in sand

This is a test case from the PIGLET User Manual [1], which compares analytical results with those obtained from model tests in sand [2]. It deals with a 2 x 3 pile group, with the end rows of piles raked at 1 in 3 outwards from the pile cap.

The piles (533mm long, 12.7mm diameter, 0.8mm wall thickness) are spaced at 127mm centres in the X-direction (Sx) and at 75mm centres in the Y-direction (Sy). The piles' equivalent solid Young's moduli are assumed to be 16.3GPa axially and 28.9GPa laterally. The bottom of the pile cap is in contact with the ground surface.

The sand has a shear modulus G = 4.2z MPa (where z is the depth below the ground surface) and Poisson's ratio = 0.25.

The loads applied to the pile cap are V = 222N, H = 138N, and M = 6Nm.


Results from Repute

Click the thumbnail images below to see bar graphs giving the results obtained from Repute, PIGLET, and the physical model tests.
Click to enlarge Click to enlarge
Axial loads Shear loads Bending moments

Comparison with benchmark

The axial loads predicted by Repute are within 5% of those predicted by PIGLET [1], which in turn differ from the measured loads [2] by up to 12%.

The shear loads predicted by Repute are typically 10% different from those predicted by PIGLET, which in turn are typically 15% less than the measured loads.

The bending moments predicted by Repute are typically 13% higher than those predicted by PIGLET, which in turn differ typically from the measured moments by 6%.

Comments

The agreement between Repute, PIGLET, and Davisson and Salley's model tests is remarkably good, given the different assumptions made in the two methods of analysis [1, 3] and the inherent inaccuracies in physical modelling.

Better agreement between PIGLET's predictions and the measured results is expected because the shear modulus adopted by Randolph [1] for the soil was backfigured from test results for a single pile.

Reference

[1] Randolph, M. F. (1996). PIGLET analysis and design of pile groups, University of Western Australia.

[2] Davisson, M.T. and Salley, J.R (1970). Model study of laterally loaded piles. J. Soil Mechanics and Foundation Engineering Division, American Society of Civil Engineers, vol 96, no SM5.

[3] Basile, F. (2003). Analysis and design of pile groups. In Numerical Analysis and Modelling in Geomechanics (ed. J. W. Bull), Spon press, London, Chapter 10, pp 278-315.

Downloads

Repute project for this example.

Note: this project was created by importing a PGroupN (PGN) data file. You cannot enter the data directly into Repute, since the user interface only allows you to model real-world (and not model) piles.

 

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