Modelling tunnel squeezing using gene expression programming: a case study

Squeezing is a well-known geotechnical phenomena when excavating underground spaces, especially tunnels. It occurs under different geotechnical conditions in weak rock masses. A study was carried out to develop a mathematical and practical model to predict squeezing so that risk mitigation measures can be taken if necessary. A mathematical model based on the gene expression programming algorithm was developed using a database including 115 squeezing case histories. Four model performance evaluation criteria - specificity, sensitivity, accuracy and Matthew's correlation coefficient - were then used based on the test database and receiver operating characteristic curve. The accuracy of the model was also compared with previously developed models. The results showed that model can determine the squeezing with acceptable accuracy. It was then used to investigate squeezing-prone areas in the Beheshtabad water conveyance tunnel of Iran.