Forecasting and controlling two main failure mechanisms in the Middle East’s longest highway tunnel

Abstract

One of the fundamental requirements in tunnel design is the prediction of failure mechanisms. Besides, analyzing the ground hazards and their conditions is essential when choosing a support system. More than 72 km of highway tunnels have been designed in Iraqi-Kurdistan. The existing variable strength of host rocks from soft to hard and high overburden in some zones necessitates studying two main failure mechanisms including squeezing and rockburst. In this among, the Korek twin tunnels will be the longest in the Middle East. Because of the high overburden of 1100 m, the length of 6740 m, and the complex geotechnical conditions, evaluating these failures becomes even more important. In this study, Firstly, empirical and semi-empirical methods were used to predict rockburst and squeezing in the Korek tunnels. Then, the predicted values were compared to numerical modeling. Finally, the stability of the tunnels was provided by using composite support systems including steel ribs embedded in shotcrete and rock bolts with over-excavation techniques. The results show that the mentioned techniques are highly effective in controlling squeezing and rockburst failures.