Experimental Testing and Analytical Modeling of Strip Footing in Reinforced Sandy Soil with Multi-Geogrid Layers Under Different Loading Conditions

Aram Mohammed Raheem

doi:10.11648/j.ajce.20160401.11

Abstract

In this study, large-scale physical models with dimensions of (0.9m * 0.9m * 0.55m) have been designed and constructed to investigate the behavior of strip footing in reinforced sandy soil with multi-geogrid layers under inclined and eccentric loading conditions. The effect of several parameters such as geogrid layers (N), soil relative density (RD), depth of the topmost geogrid layer (U/B), load inclination angle () and load eccentricity ratio (e/B) on the bearing capacity ratio (BCR) of reinforced soil have been investigated through 120 experimental tests. As the number of the geogrid layers increased from 0 to 4, the BCR increased by 255% for 15o load inclination angle and by 470% for 0.05 load eccentricity ratio in 60% RD. When the RD of the soil increased from 60% to 80%, the average decreases in horizontal displacement and footing tilting angle were about 35% and 21% respectively. Hyperbolic analytical model was used to predict the relationships of most of the studied parameters. However, p-q analytical model was suggested to model the relationship between the BCR versus U/B. Both suggested models (hyperbolic and p-q) were in a very good agreement with the experimental results.

Highlights

A strip footing is used to transfer loads from superstructures to the supporting soils
The overall behavior implied that having higher number of geogrid layers increased the bearing capacity ratio (BCR) of sandy soil while the load inclination effect was more at higher relative density (RD)
As the geogrid layer increased from 0 to 4, the BCR increased by 210%, and 250% for zero load inclination and by 255%, and 100% for 15o load inclination for RD of 60% and 80%

Summary

Introduction

A strip footing is used to transfer loads from superstructures to the supporting soils. Meyerhof [4] pointed out that the average bearing capacity of footing decreases parabolically with an increase in eccentricity. Different types of reinforcement layers have been used to reinforce the underneath soil such as galvanized steel strips, geotextiles, and geogrids [10]. The response of footings loaded over a reinforced soil bed by metal strips has been investigated by Binquet and Lee [12] and Fragaszy and Lawton [13]. Binquet and Lee [12] pointed out that the bearing capacity of shallow foundations could increase by (2 to 4) times when the underneath soil reinforced by galvanized steel strips. Laboratory model tests on square footing to quantify the bearing capacity of foundations reinforced with geogrids and geotextiles have been conducted by Guido et al [7]. Khing et al [14] examined the

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