Analytical and experimental study of the improvement of stone column composite foundations under shaking effect

Stone column technology is considered as one of the methods that plays an effective role in reducing the liquefaction of saturated sediments. Given the greater permeability of the materials employed in stone columns compared to that of the surrounding soil, stone columns can partially or completely rectify the liquefaction potential created under seismic loading by accelerating the drainage process of the maximum interstitial pore water pressure. Considering stone columns and the surrounding soil under their influence, in this study, a set of analytical solutions will be proposed in order to solve the problem of liquefaction of saturated soils during an earthquake. Considering the excess pore water pressure at the boundary of the zones, vertical and horizontal drainages will be influenced based on these analytical solutions. Under certain conditions, the centrifuge test is performed on the sandy soils improved with the stone columns. The total seepage flow is calculated based on the radial and vertical drainage analysis in the centrifuge model test in the soil improved by stone columns using the analytical solutions proposed in this study and is converted into a settlement based on the equivalent relationship between the drainage flow rate and the volumetric changes of the surrounding soil. It is found that the calculated settlement is in good agreement with the value measured in the centrifuge test, which confirms the correctness of the analytical formula for calculating the proposed settlement for the foundation with the stone columns. Moreover, the combination of the effects of the radial and vertical drainages in stone column foundations in this study with the analytical solutions derived for water drainage based on the test results are evaluated.