Experimental and Numerical Investigation for Estimating Optimal Depth-Bearing Capacity of Randomly Fiber-Reinforced Sandy Soils

Reinforcing will lead to improved mechanical properties of soil. Using different additives can help to increase bearing capacity, strength, or other important properties. In this study, poorly graded sandy soil was improved by adding synthetic fiber, and a strip footing was placed and loaded on unreinforced and reinforced soil. Samples were prepared in two relative densities of 50% and 65% and the soil was reinforced in 1B, 2B, 2.5B, and 3B depths (B is width of model footing). Bearing capacity and shear failure surfaces of soil that were analyzed by the Particle Image Velocimetry (PIV) method at different settlement to footing width ratios were obtained and compared. At the same time, experimental conditions were modeled with finite element method, and the results of shear failure surfaces were compared with experimental modeling. Results showed that reinforcing the soil under the strip footing forwarded shear failure surfaces toward downer surfaces from 1B up to 3B. In soils with a relative density of 50%, the main reinforcing depth was 2B and after 2B reinforcing did not have a considerable effect on improving the soil. By increasing the relative density from 50% to 65%, the effective reinforcing depth increased from 2B to 2.5B. Experimental and numerical modeling of soil under strip footing showed that the optimum reinforcing depth was between 2B and 2.5B that by increasing the reinforcing depth, the general shear failure behavior went toward local shear failure surfaces. The results of the study can be used as a reinforcing method and applied to real soil improvement applications in industry depending on the purpose of soil reinforcing for economic and efficient improvement design.