This study investigates the effect of particles roundness and morphology on the shear failure mechanism of soil. A strip footing was modeled under laboratory conditions. Calcareous soil was tested with three roundness classes: angular, rounded and well-rounded shapes with sizes of 0.30 mm to 4.75 mm. These were divided into six different groups at three relative densities of 30%, 50% and 70%. A series of photographs was taken during the tests and analyzed using the particle image velocimetry (PIV) method to understand the soil-deformation mechanism. The results showed that increasing the sample sizes increased the affected area of the soil. At the same time, increasing the relative density caused a punching failure mechanism that went towards the general failure. The shear failure mechanism of the soil changed from general toward punching shear failure with increasing particle roundness. This effect was larger with the smaller materials. Underneath the affected layers of soil, the angular samples were deeper than the rounded and well-rounded samples. The affected depth in the angular soil was approximately 1.5B in the smallest size group. This was more than 3B and near 4B in the largest size group. Both the sides and the underlying soil layers should be considered on angular soils. The area under the footing becomes more important than the side parts after increasing the roundness of the particles.

No abstract

No abstract

Different methods can be applied to improve soil behavior to increase the bearing capacity or reduce the settlement of footings. These methods can be stabilization or improvement of soil by the use of different geosynthetics; injection; grouting; or placing weak soil with stronger materials. One of the materials that can be used for improving soil is placing a stone layer under the footing. In this study, a stone layer under a strip footing is simulated with the finite element method (FEM) to estimate the soil behavior at different conditions. A stip footing with a width of 1m and a length of 8m with a 100 kN/m2 uniform load was modelled. The different widths of stone layer from 1B to 3B (B was the strip footing width) with different depths of 0.5B, 1B, 1.5B, and 2B were modelled in Plaxis 3D and results were obtained from the simulation. By considering the results, it was found that the optimum dimension of the stone layer for putting under strip footing was 2B width and 1B depth. This result can be applied to real projects.