Effects of Lateral Loads on a Single Pile

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Abstract

Design of piles under lateral loads requires estimation of ultimate load carrying capacity of the pile and also, the pile deflections need to be evaluated to determine the allowable loads. For estimating the pile response, structural engineers invariably utilize the simplified method prescribed in the Indian code IS 2911-2002 (Indian Standard Code of Practice for Design of Pile Foundations, 2002). The method is based on replacing the pile soil system by an equivalent cantilever, the length of which is a function of subgrade reaction of the surrounding soil and the pile geometry. However, the method described is applicable only for flexible piles, where the maximum depth coefficient L/T is equal to or exceeds 4.0. To estimate the pile response for rigid piles, simplified procedures are not suggested and hence in the present study, an attempt has been made to evaluate the pile response under lateral loads using detailed soil–pile analysis. Parametric studies are carried out for various pile lengths and various soil stiffness. The pile responses thus obtained are compared with the method given in IS 2911-2002. It was observed that the pile response based on IS 2911-2002 compared reasonably well with the detailed soil–pile model even for L/T ≥ 2.5. However IS 2911-2002 underestimates the pile head deflections for L/T < 2.5 for both free headed and fixed head piles and hence detailed soil–pile analysis is essential for such situations. The variation of pile response with soil stiffness is also evaluated using these methods and the results are presented. The soil–pile analysis is carried out using subgrade modulus approach. The soil stiffness is assumed to vary linearly along the pile depth and hence the study is applicable for cohesionless soils which can be used for practical design of single pile subjected to lateral loads.

Keywords

Modulus of subgrade reaction Laterally loaded piles Pile–soil interaction 

List of variables

D

Pile diameter

Ep

Young’s modulus of pile material

Ip

Moment of Inertia of Pile material

kh

Modulus of subgrade reaction

y

Pile deflection at a depth ‘x’ below GL

kh

Value of kx at x = L (tip of pile)

ηh

Constant of subgrade reaction

L

Length of the pile

Le

Embedded pile in the soil medium (=L1 + Lf)

L1

Length of pile above ground

Lf

Equivalent cantilever length below ground level

m

Reduction factor

R

Characteristic length/stiffness factor for cohesive soils

T

Characteristic length/stiffness factor cohesionless soils

k1

Terzaghi’s modulus of subgrade reaction

H

Applied horizontal load at pile top

M

Moment applied at the pile head location

Mf

Fixed end moment in the pile

Zmax = L/T

Maximum depth coefficient

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Copyright information

© The Institution of Engineers (India) 2013

Authors and Affiliations

  1. 1.Bhabha Atomic Research CentreMumbaiIndia

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