Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 9 FOUNDATION ENGINEERING
Notes:
1. For constant soil modulus with depth (e.g. stiff overconsolidated clay), pile stiffness factor
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R = E pI p
(in units of length) where E p I p is the bending stiffness of the pile, D is the
k h D
width of the pile, k h is the coefficient of horizontal subgrade reaction.
2. For soil modulus increases linearly with depth (e.g. normally consolidated clay & granular
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soils), pile stiffness factor, T = E pI p
where n h is the constant of horizontal subgrade
n h
reaction given in table below:
3. The criteria for behaviour as a short (rigid) pile or as a long (flexible) pile are as follows:
Pile Type
Short (rigid) piles
Long (flexible) piles
Soil Modulus
Linearly increasing
L 2T
L 4T
Constant
L 2R
L 3.5R
Figure 9.7 Failure Modes of Vertical Piles under Lateral Loads (Broms, 1914a)
9-30 March 2009