Geotechnical Illustration of Fereshteh Alley in Tabriz City

The consolidation settlement is one of the main geotechnical problems in areas with saturated fine grained layers. This phenomenon evaluation is carried out by borehole drilling, preparation of intact specimens, determination of geotechnical properties of soil and doing consolidation test. The subject of consolidation settlement does not sufficiently studied due to the considerable cost and time, especially in large areas. Sothe major damage of structures caused by this phenomenon. Types of clay and marl soil layers have spread in different parts of Tabriz city. In the north Fereshteh alley (located in the northeastern part of Tabriz city), the silty clay layers are outcrop. This layers have a significant consolidation settlement potential due to the drainage seepage of the sub-surface waters of the northern mountains of Tabriz. A significant number of buildings in this area have been seriously damaged in recent years. In this research, a geotechnical properties of soil samples (physical, plasticity, strength and consolidation properties), Obtained from drilling machine borehole and test pit, were determined. Initially, geotechnical conditions of layers is described. The allowable bearing capacity of the existing strip foundation, based on Hansen criteria, standard penetration test results and consolidation settlement, were calculated. This results were plotted for several of foundation widths and ratios of length to width. Based on this study results, the consolidation settlement criterion dictates allowable bearing capacity of foundations. So, the allowable bearing capacity of usual shallow foundation is not enough for usual structures in this area. Adequate geotechnical investigations and the use of deep foundations are recommendations and suggestions of this study.