The stability of a twin-tube highway tunnel is analyzed using improved discontinuous deformation analysis (DDA) method. By employing advancing front method
the triangular DDA blocks are automatically generated in the computational area. In this process
numerous artificial joints whose strength is higher than that of real joints come into being. In addition,the reinforcing effect of prestressed bolt on the surrounding rock is also taken into account. The numerical results are compared with the measured data
and they show pretty good agreement; therefore
it is shown that the improved DDA method is capable of analyzing stability of underground tunnels.