Investigating The Safety Level of Urban Deep Excavation Projects Stabilized by Method of Braced Excavations (struts) Using Methods Based on Risk Assessment and Failure Analysis

The expansion of cities and the increase in the price of land has caused an increase in the number of underground floors and the depth of excavation, and considering that ensuring safety in excavation workshops, in addition to ensuring the health of employees, leads to an increase in the quality of the project, therefore, one of the important issues in urban construction and structures. Is to create proper stability during excavation, excavation is one of the dangerous earth operations. According to available statistics, many people lose their lives every year in excavation projects due to non-compliance with safety principles. In this research, first by conducting library studies, a list of effective risks in sustainable urban deep pit projects was prepared using the strut method, and experts' opinions were collected through a questionnaire and analyzed in SPSS software. Then the decision matrix was formed based on the desired indicators and criteria and were ranked using a questionnaire and based on the criteria of "level of influence", "level of importance" and "existence of necessary tools." Execution for wide pits", "Execution limitation in projects with irregular geometry or geometry", "Inability to use to increase the depth of the pit during execution or after the completion of excavation", "Too much settling in the pit and causing disturbance to the implementation of the foundation and structure", "the possibility of equipment and machinery colliding with the elements and putting them at risk", "collapse of walls and elements falling", "increasing the cost of implementation in deep pits and large fields compared to usual methods", "increasing Implementation time in deep pits and large fields compared to usual methods", "Falling from a height during work on connections", "need for strict quality control to implement restraints, especially connections" have the highest impact, respectively.