3-D stability analysis and design of the primary support of Karaj metro Tunnel: Based on convergence data and back analysis algorithm

Design and construction of underground structures are usually being performed based on an approximate understanding of geotechnical parameters, which are essential for selection of construction method and support system. The main purpose of this study is to determine the geotechnical parameters using back analysis based on convergence data, and also to adopt an appropriate primary support system. By installation of suitable support structure, the amount of tunnel ceilingʹs settlement was reduced to a number lower than the allowable limits. Back analysis was conducted throughout the alternative univariate method by PLASIX 3D Tunnel. The research showed that performed analysis based on convergence data and back analysis can be utilized as a more economical and time-saving method in comparison to consultant Engineers design based on soil mechanic tests. In addition, the parameters obtained from back analysis were greater than soil mechanic test method. Thus, the evaluations show that measurement error in soil mechanic tests is likely the source of this difference.