نوع مقاله : مقاله کامل پژوهشی
1 گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه شهید مدنی آذربایجان
2 دانشگاه شهید مدنی آذربایجان
3 دانشگاه تبریز
عنوان مقاله [English]
Soil conditioning involves the injection of improvement materials from the mechanized tunneling machine to the work field and excavated soils. This study aims to investigate the effect of foam characteristics on the shear strength of granular and mixed soils at four stations in line 2 of the metro of Tabriz city. In this study, two types of foam which known as KOMEYL (KF168B-KF159A), CHEMIC (UGC-N2), and a type of polymer (RHEOSOIL 211) have been used. Based on foam characteristic tests, it can be concluded that the main difference between these materials is their stability time that the foam KF168B exhibits more stability time than the others. Also, results show that there is no significant difference between these foams in terms of their effect on the final shear strength of soil and foam mixtures. Also, adding a small amount of polystyrene polymer to foam solution induces a significant increase in the foam stability time, but not significantly increases the FER. Also, the shear strength test results on foam- soil samples show that the injection of foam above a standard ratio did not significantly affect its shear strength and the use of FIR higher than the required level may cause disorientation in the homogeneity of the soil-foam mixture. Based on the results, the effect of foam on shear strength decreasing ratio is strongly influenced by soil aggregates, so that for the tested soils, in fine-grained soils, the effect of foam on shear strength is significantly more than coarse-grained soils.