عنوان مقاله [English]
Use of shells in foundations can be economically beneficial due to the increase in the columnar load and decrease in soil allowable stress. Shell foundation would be, therefore, a proper alternative to the shallow footings in soils with low allowable stress magnitude. Shell foundations are proper patterns with optimal design to obtain higher bearing capacity. Shell foundations enjoy a larger area of contact with soil due to their geometry. Shell footings are capable of carrying a larger load through more area contact with the soil. In this paper, the elasto-plastic behavior of the sandy soil, located under some shape of folded plate shell strip foundation, is studied. The Drucker Prager theory and experimental results are used in this analysis. Four geometrical models (A, B, C and D models) of shell foundation with different depths are located in sand with different densities (loose and dense sands). The experiment process includes foundation installation over the soil surface and embedded 50-100\% of the foundation width. Also, to carry out a perfect analysis of foundations, a powerful three- dimensional finite element program (ABAQUS 6.9-1) was used. This investigation shows that the predictions made by the developed model are found to be in good agreement with those of experimental data obtained from laboratory.Results of these analyses are compared with the same width in strip foundation (model E). This investigation shows that using (D) model of folded plate shell foundations is preferable to the common strip footings and other folded plate models. The contact soil stresses adjacent to the shell are non-uniform. Increasing the foundation depth of embedment and density, leads to the increase in the bearing capacity of foundations. The effect of improving sand geotechnical properties on bearing capacity is more than changes in shells patterns. The results show that bearing capacity is 2.5 to 4.8 times more in dense sand in comparison with the loose one. The maximum increase in bearing capacity for different shapes of shell foundations is about 72 percent.