The researchers used computer software to analyze how the stability of a tunnel in layered rock is affected by the angle and thickness of the rock layers. They found that as the angle of the rock layers increases, the displacement and stress on the surrounding rock first go up and then down. Also, thicker rock layers lead to less displacement and stress on the surrounding rock. Specifically, at a 30° angle, vertical displacement is highest; at a 45° angle, horizontal displacement is highest; and at a 45° angle, the rock experiences the most stress.