A New Analytical Approach for Determination of the Bearing Capacity of a Strip Foundation on a Granular Trench

Abstract

The limit equilibrium method that considered the concept of lateral earth pressures exerted on retaining walls has been applied to determine a closed-form solution for the bearing capacity in a foundation on cohesive soils that were improved by a granular trench (column). The improvement factor (IF) as a design criterion was defined by the bearing capacity ratio with the trench to that without it. The terms of the obtained bearing capacity expression and values of the IF were explored by varying a wide range of width ratios (W/B) where the width of the trench was W, and the loading area was B. The results showed that the IF increased significantly with an increase in W/B and further improved with increases in the friction angle (ϕ) of the trench and decreases in Cu/γB, where the undrained cohesion was Cu and the unit weight of the cohesive in situ soil was γ. Moreover, the improving rate increased with increasing ϕ and for W/B<1 was more effective. In addition, the optimum depth of the trench (H) depended on W/B and ϕ. When W/B increased ≤1, H/B linearly increased from 0.5 to a certain value regarding the value of ϕ and afterward remained approximately constant. In this study, the effect of γ on the bearing capacity was highlighted. To ensure the improvement in the bearing capacity, the minimum required values of ϕ were determined through lower bound limit analysis.