Reliability analysis of nailing method in stabilization of urban excavation - A case study of an Excavation in Tehran

In the present study, global stability, soil-nail pullout failure and nail tensile failure are chosen to study. Cohesion, unit weight and angle of internal friction of soil and ultimate bond strength along the soil nail and yield strength of nail are modeled as random variables. Computations of reliability are performed using Matlab and RT software. For better understanding, a case of soil nail wall constructed to support a vertical excavation in Tehran is considered for the study and its stability is evaluated for three failure modes. The purpose of this research is to firstly analyze the reliability of nailing walls and validate it using the Monte Carlo simulation method. In addition, the effect of correlation between soil parameters and distribution of random variables on reliability index was investigated. By sensitivity analysis, the importance of variables in reliability index was investigated. Then, the reliability index changes were evaluated with respect to the safety factors. Finally, changes in the reliability index were studied by changing the length of nails and the diameter of the nails. According to the assumptions, the correlation between the soil resistance parameters does not have much effect on the pullout mode, if the general failure and pulling modes of the nails have a significant effect and should be taken into account in analyzes as well as the type of distribution of variables affects the reliability index and the choice of distribution type is important.