Numerical Analysis of Geosynthetic-Encased Stone Columns under Laterally Loads

Out of all methods for ground improvement, stone column became more popular these days due to its simple construction and economic consideration. Installation of stone column especially in loose fine graded soil causes increasing in load bearing capacity and settlement reduction. Encased granular stone columns (EGCs) are commonly subjected to vertical load. However, they may also be subjected to significant amount of shear loading. In this study, three-dimensional finite element (FE) analyses were conducted to estimate the shear load capacity of EGCs in sandy soil. Two types of different cases, stone column and geosynthetic encased stone column were studied at different normal pressures varying from 15 kPa to 75 kPa. Also, the effect of diameter in two cases was considered. A close agreement between the experimental and numerical curves of shear stress - horizontal displacement trend line is observed. The obtained result showed that, by increasing the normal pressure and diameter of stone column, higher shear strength is mobilized by soil; however, in the case of encased stone column, increasing the diameter had more dominated effect in mobilized shear strength

Injectability of colloidal nano-silica in Bushehr carbonate sand with different silt content

The diverse carbonate materials found in Iran exhibit varied physical, mechanical, and chemical behaviors, making their stabilization a subject of great interest. Further research is necessary to investigate their properties. The engineering properties of problematic soils, like carbonate sand, can be enhanced by using suitable chemical soil stabilizers. Colloidal nano-silica solution injection in carbonate soils is highly beneficial, especially in small pores where injecting cement slurry is not feasible. Colloidal nano-silica is a suspension of silica nanoparticles in water, having viscosity similar to water, facilitating injection into such soils. Moreover, it is environmentally and chemically non-toxic. In this study, carbonate soil with varying silt contents (0%, 10%, 20%, 30%, and 40%), different nano-silica concentrations (10%, 20%, and 30%) and an average density of 50% were investigated for injectability along the Persian Gulf coast (Bushehr port). Injection was possible at a pH of about 6.5 with all concentrations, especially at 30%. Unconfined compression tests were carried out at different silt contents, curing periods, and nano-silica concentrations to determine the optimal injection concentration. The results showed that the unconfined compression resistance increased with higher concentrations of nano-silica, with 30% concentration demonstrating the best performance. Injecting colloidal nano-silica in carbonate soils, particularly silty sand, can serve as a stabilizing agent in construction