Research Specifications

Urban development and rapid extension of cities have been accompanied by considerable growth in excavation projects. Soil nail walls have been found to be an economical solution to many soil reinforcement and excavation support problems. In order to overcome some of the intrinsic problems with the conventional grout soil nails, screw soil nails were developed in recent years that provide several advantages over grouted soil nails. Tabriz Marl outcrops at considerable parts of this city. Considering the rapid development of the Tabriz (as one of the biggest industrial cities of Iran) a large part of new urban areas and industrial zones will be located on marl soils. Therefore, it is necessary to evaluate the efficiency of the screw nailing method in Tabriz marl soils. In the present study, the performance of the walls reinforced by screw and grouted nails in different types of Tabriz marls were studied. For this purpose a three-dimensional (3D) modeling is performed for excavation depths of 8 and 17 m using the ABAQUS software. The results of the numerical analyses revealed that the failure zone of the screw and grout nailed walls are similar and consisting of parts entitled A and B. There is no significant difference between the characteristics of part B at both of the screw nailing and grout nailing methods. While, the A part of the failure zone and the maximum soil displacements in this part at the screw nailing method are smaller than those of the grout nailing method. At all types of the Tabriz marl, the lateral and vertical displacement of the reinforced walls by screw nails are smaller than those of grout nails, and in the case of yellow marl, the difference is considerable, while, at Brown marl it is negligible. The results of analyses show that the screw nail performs better than the pressurized cement grouted nail in terms of wall displacement. The efficiency of the screw nails increases in comparison to grouted nails by proceeding with the excavation proce