Piled Raft Foundations for Tall Structures – At a Glance

Volume 7 Issue 2 March - May 2017

Case Study

Piled Raft Foundations for Tall Structures – At a Glance

O. Eswara Reddy*, S. B. Mohammed Aejas**, R. Bharath***

* Professor, Department of Civil Engineering, Sree Vidyanikethan Engineering College (Autonomous), Tirupati, India.

**-*** UG Student, Department of Civil Engineering, Sree Vidyanikethan Engineering College (Autonomous), Tirupati, India.

Reddy, E.O., Aejas, M.S.B., and Bharath, R. (2017). Piled Raft Foundations for Tall Structures – At a Glance. i-manager’s Journal on Civil Engineering, 7(2), 41-52. https://doi.org/10.26634/jce.7.2.13427

Abstract

In the modern society of technology, construction of tall structures has been increased all over the world. Stability of the tall structure depends mainly upon the type of foundation. Combined piled raft foundation has been used throughout the world for several years to support tall structures as it has the advantages of both shallow foundation and deep foundation. Piled raft foundation is considered most economical. In this foundation system, the structural loads are carried partly by the raft and partly by the piles. This type of foundation system is considered as more effective because the raft is able to provide a reasonable measurement of both stiffness and load resistance. The method involves limit state design approach for designing a piled raft foundation for tall structures and requires three analyses like serviceability of the structure, overall stability of the structure, and analysis for obtaining foundation loads, moments, and shear forces for designing the foundation system. The concept of combined piled raft foundation usage is that it should be able to resist applied axial load with an appropriate factor of safety and at working load, the settlements of combined foundation should be limited. In case of poor soil conditions, grouting is done at the bottom of the pile which increases the bearing capacity of the soil, reduces the settlements and improves the properties of the soil. This paper describes the design principles of foundation, the approach for limit state design method, finite element method, and the concept of soil-structure interaction. Application of piled raft foundation system is explained with the help of a case study. It is opined that the piled raft foundation system can be effectively adopted for construction of tall structures.