Numerical simulation of rock deformation for support design in tunnel intersection area

Passenger and vehicle adits and ventilation shafts are commonly used for emergency access and ventilation in long tunnels. Increasing support load and additional tunnel deformation may endanger tunnel stability during construction in the intersection of the access and main tunnels. To understand the mechanical behavior of rock masses in the intersection area, 75 cases of 3D numerical analysis were conducted. These analyses were conducted under various tunneling conditions including rock strength, rock mass rating, overburden depth, and intersection angle. Following analysis results, a criterion for assessing the effect of intersection angles on tunnel behavior has been established, and three categories of support design suggestions for different geological conditions have also been proposed.