An investigation on the mechanical behavior of geogrid reinforced stone column groups

Increasing trend in the population density of the cities causes rising demand on high rise construction projects. High-rise structures bring high vertical loads on foundation soils. Especially in shallow foundations built on weak soils, large amounts of soil settlements may occur due to high vertical loads, which can cause varying levels of damage to the superstructural load bearing elements. In weak soils accommodating high liquefaction potential, settlement and stability problems, it becomes generally necessary to establish piled foundations or to use soil improvement methods under the building foundations since sole application of shallow foundations may not be sufficient to transfer superstructure loads to the soils. At this point, stone columns appear as one of the economical and efficient soil improvement solutions. However, stone columns which are unreinforced contrary to reinforced concrete bored piles, may be insufficient to resist high structural loads safely. Within the scope of this study, the stress-deformation behavior of stone column groups under vertical loads and the effect of geosynthetic reinforcement were investigated. For this purpose, a series of loading tests were carried out on standard and geogrid reinforced stone column groups, to investigate the effect of geosynthetic wrapping reinforcement on settlement amounts and bearing capacities of in the improved soil cell. The physical and mechanical properties of the granular bedding material used in the model tests, aggregate utilized for stone column formation and reinforcement geogrids were determined through laboratory tests and by considering the material parameters available in the previous studies in the literature. The bearing capacity stone column groups installed in different configurations under a rigid foundation plate was investigated besides the settlement behavior of the foundation under vertical loads were discussed in detail within the scope of the study. As a result of the study, important findings on the effect of geosynthetic reinforcement on the mechanical properties of group stone columns were obtained. It is thought that the results of the study can contribute for the development of a new technology regarding the design of stone columns that can be more efficient in terms of both strength and economy.