Prediction of tunnel squeezing in soft sedimentary rocks by geoelectrical data

Squeezing is time-dependent deformation that can cause technical difficulties and financial consequences in underground structures. This study employs electrical resistivity data to predict squeezing intensity along the Beheshtabad tunnel in the Sanandaj–Sirjan zone in Iran. For comparison analysis, a semi-empirical approach was correlated with numerical modeling to predict tunnel squeezing at the design stage. The squeezing intensity obtained for the Beheshtabad tunnel was then compared with the instability observations along the Golab tunnel excavated in sedimentary rocks of the same zone. We developed a relationship between electrical resistivity and strains and provided a new strain-based squeezing classification system. The calibrated electrical data produced more accurate results for predicting tunnel squeezing than the conventional methods. The results show that rock type, joint properties, and water saturation impact squeezing.