Shield TBM tunneling method along with other mechanized method is one of the preferred ways to make tunnel, especially for long tunnel with unfavorable ground condition. Shield method is well known to be effective and safe to make tunnel on shallow and poor ground condition. However, occasional troubles or accidents occurred because of mechanical or geological reasons, such as improper selection of equipment, malfunction, encounter with unexpected geologic layers and large infiltration of ground water.
Shield tunneling method constitutes open-end and closed-end type. Open-end type shield is used when the geological condition is fairly good and has enough stand-up time for at least one cycle. Closed-end type shield is used when the geological condition is so unfavorable that tunnel face becomes unstable without instant application of support pressure. Closed-end type shield constitutes earth pressure-balanced shield and slurry shield. Balance between acting earth pressure and resisting support pressure is important for the closed-end type. To prevent the undesirable event, not only maintenance of equipment and detailed geological investigation but also application of proper support pressure on the tunnel face is required. 

Both analytical solution and numerical simulation is combined to predict proper support pressure. An analytical solution, developed by Anagnostou and Kovari(1996), is used for calculation of support pressure of EPB shield tunnel. For numerical solution, finite difference method (FLAC) and distinctive element method (PFC) is used. The former is used for the ground reaction behavior of rock mass; the latter is used for large displacement behavior of ground when the ground support varies. With simple model test case for water saturated ground, analytic solution predicts that pressures 82 kPa and 66 kPa are necessary for non-cohesive and cohesive ground condition. For unsaturated ground, analytic solution predicts that pressures 46 kPa and 32 kPa are necessary for non-cohesive and cohesive ground condition. The results show consistency between analytic and numerical approaches, as latter show significant decline of displacement up to the predicted support pressure and minor decline is minute for more support pressure. With this study, systematic estimation methods of tunnel face stability using numerical and analytical solution is proposed and verified. This approach is expected to be easily adapted and to enhance the reliability of design and construction phase. Once the earth pressure is known, appropriate support pressure or stiffness can be applied for the excavation of shield tunnel.