Squeezing rock conditions at phyllite-slate zone in Golab water conveyance tunnel, Iran: A case study

Rahmati Asghar, Faramarzi Lohrasb, Darbor Mohammad

Department of Mining Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran

Doi:10.1007/s11771-017-3659-6 

Abstract: Squeezing ground in tunneling is associated with large deformation of the tunnel face. In this study, squeezing characteristics of the ground and rock conditions in Golab water conveyance tunnel, Iran, are discussed and the classification of squeezing behavior around zones where the problems occurred is presented. The squeezing conditions were investigated using empirical and semi empirical methods. In the next step, creep convergence of the tunnel with Burger’s model was simulated by the numerical method. Numerical analysis showed that wall displacement (64.1 mm) of the Golab tunnel was more than allowable strain (1% of the tunnel diameter), therefore, it was found that squeezing phenomenon could exist, leading to the failure of the support system. Numerical analysis at the phyllite-slate zone also showed squeezing conditions due to the weakness of rock mass and high overburden that this situation cause failure in the segmental lining. In this research, failure in segmental lining in phyllite-slate zone verified the results of the numerical modeling.

Keywords: squeezing; large deformation; Burger’s model; numerical analysis; failure; segmental lining