Design of the Appropriate Primary Support System of Karaj Subway Tunnel Based on Convergence Data and Back Analysis Algorithm

Back analysis can be used as a reliable method for stability and support structure analysis. In Karaj subway project، primary design and analyses have been conducted by consultant engineers based on soil mechanics laboratory tests and without consideration of geomechanical parameters of each available layer on the rout of tunnel. Therefore، In this research، considering various layers of the surrounded soil mass of tunnel، achieved geomechanical parameters of these layers have been analyzed by back analysis based on instrumentation results. Then، according to the achieved results and calibrated models، numerical models of three-dimensional stability of tunnel has been used to modify and optimize the tunnel primary support system design.