Improvement Separation Layer of Disconnected Piled Raft Foundations using Geogrid and Geocell Layers

Ayat I Khalil,Mahmood R Mahmood,Husam H Baker,M Karkush,M Fattah,D Choudhury

doi:10.1051/e3sconf/202131801017

Abstract

To control the problems of high stresses and applied moments in the piled raft foundations disconnected piled were used and the piles considered as reinforcement to the soil rather than as structural members, the gap (separation layer) between the piles and the raft can be filled with stabilized granular material which distributes the stresses below the raft and decreases the concentration stresses at the pile heads. Fifteen model tests were performed using three precast concrete pile models embedded within soft clayey soil of undrained shear strength 30kPa. Flexi-Force sensors were used fixed on piles head and the surrounding soil to measure the sharing load transmitted to piles and the surrounding soil. Geogrid and geocell materials were used in different depths and in multilayers to reinforce the separation layer and increase its stiffness. The results show that when reinforcing the separation layer with geogrid at different depths, an increase in depth over the top of the piles reduced the bearing pressure. When used, geocell reinforcement significantly increases in load carrying capacity, and a significant reduction in footing settlement occurs.

Highlights

In the presence of such geotechnical /structural factors, the raft and pile foundations can be combined productively to increasing the ultimate bearing capacity and decreasing settlements, as Burland et al initially suggested [1]
For all model tests, Terzaghi's proposal, which described the load corresponding to the displacement of 10% of the width f footing, has been adopted to define the failure criteria raft and the disconnected piled raft foundation system
The results show that the highest bearing pressure equal to (1860 N) for using a cushion layer of thickness B and (1500 N) for a raft on clay only without cushion

Summary

Introduction

In the presence of such geotechnical /structural factors, the raft and pile foundations can be combined productively to increasing the ultimate bearing capacity and decreasing settlements, as Burland et al initially suggested [1]. Liang et al [4] suggested that the sand-gravel mixture compacted into the layers between the raft and top of the piles plays a major role in mobilizing the load-transfer mechanism of the subsoil, as well as in modifying the pile load transmission. Since it has been described by many authors, Fioravante et al [5] found that the stiffness and thickness of the interposed cushion layer governed this mechanism. They showed that using the cushion will adjust the piles' load-sharing ratios and subsoil and among the piles

Methods

Findings

Discussion

Conclusion