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Explicit extension of the p–y method to pile groups in sandy soils

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Abstract

The method of “p–y” curves has been extensively used, in conjunction with simplified numerical methods, for the design and response evaluation of single piles. However, a straightforward application of the method to assess the response of pile groups is questionable when the group effect is disregarded. For this reason, the notion of p-multipliers has been therefore introduced to modify the “p–y” curves and account for pile group effect. The values proposed for p-multipliers result from pile group tests and are limited to the commonly applied spacing of 3.0 D and layout less than 3 × 3, restricting the applicability of the method to specific cases. With the aim of extending the applicability of the “p–y” method to pile groups, the authors have already proposed a methodology for estimating the “p G–y G” curves of soil resistance around a pile in a group for clayey soils. A complementary research allowing for the estimation of the “p G–y G” curves for sandy soils is presented in this paper. The well-known curves of soil resistance around the single pile in sandy soils are appropriately transformed to allow for the interaction effect between the piles in a group. Comparative examples validate the applicability and the effectiveness of the proposed method. In addition, the method can be straightforwardly extended to account for varying soil resistance, according to the particular location of a pile in a group. It can therefore be used in a most accurate manner in estimating the distribution of forces and bending moments along the characteristic piles of a group and therefore to design a pile foundation more accurately.

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Abbreviations

A :

Area associated with an interface node

d :

Normalized centre to centre pile spacing defined as s/D

D :

Pile diameter

E i :

Initial soil modulus of elasticity

E p :

Pile modulus of elasticity

F n :

Normal force (interface element)

F si :

Shear force (interface element)

F smax :

Limiting shear force (interface element)

H j :

Horizontal load carried by pile j

H m :

Mean horizontal load

K a :

Active earth pressure coefficient

K Gi :

Initial stiffness of the piles in a group

K i :

Initial soil stiffness

K i,j :

Initial stiffness of pile j in a group

K 0 :

Earth pressure coefficient at rest

k n :

Normal stiffness (interface element)

k s :

Shear stiffness (interface element)

lw j :

Location weighting factor for pile j

L :

Pile length

n :

Number of piles

n x :

Number of piles in the direction of loading

n y :

Number of piles in the direction perpendicular to the loading

p :

Pore pressure

p :

Lateral soil resistance to a single pile

p G :

Lateral soil resistance to piles in a pile group

p Gult :

Ultimate lateral soil resistance of the piles in a pile group

p ult :

Ultimate lateral soil resistance

p ult,j :

Ultimate lateral soil resistance to pile j in a pile group

R a :

Deflection amplification factor

R aj :

Deflection amplification factor for pile j

s :

Centre to centre pile spacing

u n :

Interface absolute normal penetration

y :

Deflection

y G :

Deflection of a pile in group

y mG :

Group deflection at the pile cap

y nG :

Group deflection at the pile cap normalized to pile diameter

y ns :

Single pile deflection at the pile head normalized to pile diameter

y s :

Single pile deflection at the pile head

z :

Depth from soil surface

γ′:

Effective soil unit weight

γ sat :

Saturated soil unit weight

Δu si :

Incremental relative shear displacement vector

ν :

Poisson’s ratio

σ n :

Interface normal stress

σ si :

Interface shear stress

φ :

Soil angle of friction

φ i :

Interface angle of friction

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Authors and Affiliations

  1. Department of Civil Engineering, University of Thessaly, Pedion Areos, 383 34, Volos, Greece

    Mello C. Papadopoulou & Emilios M. Comodromos

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  1. Mello C. Papadopoulou
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  2. Emilios M. Comodromos
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Correspondence to Emilios M. Comodromos.

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Papadopoulou, M.C., Comodromos, E.M. Explicit extension of the p–y method to pile groups in sandy soils. Acta Geotech. 9, 485–497 (2014). https://doi.org/10.1007/s11440-013-0274-z

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