With the application of TBM in the construction of tunnels, increasing simulations are taken on TBM tunnels. This paper first proposes the concept of utilizing Block Theory to simulate TBM tunnels in discontinuous rock masses and analyze the stability of surrounding rock blocks in TBM tunnels. Therefore, block classification for TBM tunnels is set up according to the main differences between TBM tunnels and tunnels using traditional methods, which has laid the foundation of simulating a TBM tunnel. What' more, the identification of Influenced Block and the simulation procedure of a TBM tunnel are both illustrated in flowchart. Also, a simple example of a double shield TBM tunnel excavation is implemented based on BLKLAB and the corresponding removable blocks are analyzed. Moreover, a representative excavation step is picked out to illustrate the removable blocks around the TBM, which meets the block classification for TBM tunnels.
As one type of complex discontinuous medium, rock masses in nature are split into rock blocks by finite and infinite discontinuous geological planes. Recently, the block theory  has developed rapidly as a stability analysis method of discontinuous rock masses. Applying the block theory, researchers have carried out various analyses on the stability of blocks in the excavation of slopes, caverns and tunnels, from which reliable results have been achieved as well [2-7].
Compared with traditional approaches of D&B (Drilling and Blasting) method and NATM (New Austrian Tunneling Method) in tunnel excavation, TBM method has the following advantages of fast heading rate, short construction period, favorable working environment, eco-friendliness and high comprehensive benefits, making it become the preferred choice at home and abroad. In recent years, researches on the simulation of TBM tunnels mainly focus on FEM  and FDM , while the block theory has not ever been applied in the simulation of TBM tunneling.