Assessing the effect of governing parameters of bearing capacity determination of small piled rafts on clay soil

Baleshwar Singh,Shivanand Mali

doi:10.1007/s12517-021-08609-8

Baleshwar Singh, Shivanand Mali

Open Access

https://doi.org/10.1007/s12517-021-08609-8

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Abstract

In the present study, a small piled raft foundation has been simulated numerically through PLAXIS 3-D software. The objective of this study was to investigate the effect of governing parameters such as pile length, pile spacing, pile diameter, and number of piles on the settlement and load-bearing behavior of piled raft, so as to achieve the optimum design for small piled raft configurations. An optimized design of a piled raft is defined as a design with allowable center and differential settlements and satisfactory bearing behavior for a given raft geometry and loading. The results indicated that, with increase in pile length, pile spacing, pile diameter, and number of piles, both the center settlement ratio and differential settlement ratio decreased. The load-bearing capacity of piled raft increased with increase in pile length, pile spacing, pile diameter, and number of piles. Furthermore, the percentage load carried by the piles increased as the pile length, pile spacing, pile diameter, and number of piles increased. The bending moment and shear force in corner pile are noted to be more, and they decreased towards the center pile. With increase in pile length, the maximum raft bending moment decreased, whereas the maximum shear force in the raft increased. Further, with increase in pile spacing, pile diameter, and number of piles, the maximum bending moment and maximum shear force in the raft increased. The optimum parameters for the piled raft foundation can be selected efficiently with the consideration of maximum bending moment and maximum shear force while designing the piled raft foundation. Thus, the results of this study can be used as guidelines for achieving optimum design for small piled raft foundation.

Highlights

Foundation is the most important part of the structure, and it should be analyzed and designed in order to provide safety, reliability, and serviceability of the structure
The piled raft can be classified into two categories, as “small piled raft” when the raft width is lesser than the pile length (Br < Lp), and as “large piled raft” when the raft width is greater than the pile length (Br > Lp) (Viggiani 2001)
Seo et al (2003) carried the parametric study of the piled raft by PLAXIS 2-D software and reported that the total settlement of piled raft in clay soil decreased as the pile length increased

Summary

Introduction

Foundation is the most important part of the structure, and it should be analyzed and designed in order to provide safety, reliability, and serviceability of the structure. If the shear strength of clay soil is very poor, long load-bearing piles are required to transfer the entire load to deeper and stiffer soil layers. If the shear strength of clay soil is adequate, load can be supported by the raft foundation. When the clay layer has intermediate strength, raft foundation may not be feasible, as the bearing capacity. In a small piled raft, the primary reason to add the piles is to achieve a sufficient factor of safety against bearing failure. In a large piled raft, piles are added essentially to reduce the settlement. The piled raft has been used for supporting a high rise buildings and offshore structures because it is very efficient in reducing settlement and improving the load-bearing capacity of soil. Ahmed et al (2014) evaluated the soil-foundation-structure interaction of buildings

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