Interaction analysis of two floating granular piled raft units

ABSTRACT

The pile–soil–raft interactions remain a daunting problem in the study of piled-raft foundations. A simple analytical continuum approach is implemented in the present research to analyse the interaction between two granular floating piled-rafts. The formulation uses the equations of Mindlin and Boussinesq for the estimation of the displacements for forces in the interior and on the surface of the continuum. Settlement influence factor, interaction factor, the normalised shear stresses along the granular pile (GP)-soil interface, the percentage load shared by GP, the percentage load transferred to the GP base, and the normalised contact pressure distribution underneath the raft are evaluated and presented for design.

KEYWORDS:

• Granular piled raft (GPR)
• settlement influence factor (SIF)
• interaction coefficient
• contact pressure
• loads transferred to the granular pile

Acknowledgements

The first author is highly grateful to the late Dr. Vaibhaw Garg and would like to acknowledge the suggestions and discussion. His appreciation and positive attitude about the research work have played a significant role.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Jitendra Kumar Sharma and Ashish Solanki formulated the original idea, which was also discussed by Madhira R. Madhav. After his valuable suggestions all authors agreed with the concept of the paper. Ashish Solanki performed analysis. Ashish Solanki wrote the manuscript with the help of Jitendra Kumar Sharma, which is further, edited and reviewed by Madhira R. Madhav and extended the work as per his instructions.

Nomenclature

GPR	=	Granular piled raft
SIF	=	Settlement influence factor
L	=	Length of GP
d	=	Diameter of GP = (2a)
s/d	=	Spacing of GPs
n	=	Number of elements of GP
L/d	=	Relative length of GP
D	=	Diameter of raft
D/d	=	Relative size of raft
P	=	Load on granular piled raft
q	=	Loading intensity
Egp,νgp	=	Deformation modulus and Poisson’s Ratio of GP material
Es,νs	=	Deformation modulus and Poisson’s Ratio of soil
Kgp= (Egp/Es)	=	Relative stiffness of GP
τ	=	Shear stresses at GP-soil interface
τ*= τ(πdL)/P	=	Normalized shear stress of a GP w.r.t. total load
pr	=	Raft stresses
pb	=	Pile base pressure
Z =(z/L)	=	Normalized depth of GP
I2GPR	=	Settlement Influence factor (SIF)
IZ	=	Settlement Influence factor for any depth
PP	=	Load on pile
PR	=	Load on raft
PB	=	Load on base of GP
(PP/P)×100	=	Percentage load transfer to the pile
(PR/P)×100	=	Percentage load transfer to the raft
(PB/P)×100	=	Percentage load transfer to the base
$\left\{S^{\mathit{ps}}\right\}$	=	Vertical soil displacement vector at GP nodes
$\left\{{\rho }^{\mathit{ps}}\right\}$	=	Normalized vertical soil displacement vector at GP nodes
$\left[I^{\mathit{ppf}}\right]$	=	Displacement influence coefficients for the effect of GP element shear stresses and base pressure on settlement of nodes of pile elements
$\left[I^{\mathit{prf}}\right]$	=	Displacement influence coefficients for the effect of raft stresses on settlement of nodes of pile elements
$\left\{S^{\mathit{rs}}\right\}$	=	Vertical soil displacement vector at raft nodes
$\left\{{\rho }^{\mathit{rs}}\right\}$	=	Normalized vertical soil displacement vector at raft nodes
$\left[I^{\mathit{rpf}}\right]$	=	Displacement influence coefficients for the raft nodes due to elemental shear stresses on GP
$\left[I^{\mathit{rrf}}\right]$	=	Displacement influence coefficients for the raft nodes due to raft stresses
α2 r	=	Interaction coefficient for two group granular piled raft system

Additional information

Funding

No funding was received to assist with the preparation of this manuscript.