Strainburst Control in Deep Tunnels Using a Slotted Excavation Method

Abstract

Strainburst is the most common type of rockburst in deep excavations, which sometime result in heavy losses. This research studies the feasibility of a conceptualized destressing method for strainburst control. In this method, the rock is destressed by cutting slots at the excavation boundary. First, a circular tunnel is modeled and the stress distribution around the tunnel is calculated. In a separate model, a slot is added to the tunnel wall. Results show that when the slot is added to the model, the rock at the tunnel wall destresses, and the stress concentration zone transfers to a distance farther away from the wall. Also, the analysis of the failure zone around the tunnel and the velocities of the failed element nodes show that the failure in the slotted tunnel is less violent compared with the tunnel without the slot. Secondly, a parametric study is conducted to find the optimum dimensions of the slot. Finally, the rockburst damage in Jinping II drainage tunnel is simulated and then the application of the proposed destressing method for strainburst prevention in this tunnel is studied. Comparison of the modeling results with the field rockburst observations of the drainage tunnel shows that the proposed destressing method can be considered as a potential tool for strainburst control in deep excavations.