The pressure tunnel is an important underground structure in the hydropower station and generally lined by concrete. According to the present design principle, the cracks are allowed to occur in the concrete lining during the operation period. However, the crack width should be controlled to be an acceptable value (Hao et al., 2004; Panthi, 2014). Cracks with large width may lead to unacceptable leakage in the pressure tunnel. Moreover, they may lso endanger the safety of pressure tunnel structure and the seepage stability of the surrounding rock. Therefore, the study of the lining cracking process in the pressure tunnel is of great significance. Previous studies have shown that as the pressure tunnel is an underground structure, the mechanical properties and crack mechanism of the concrete lining of the pressure tunnel are quite different from the structures above the ground. Considering the action of the surrounding rock mass, several theoretical and analytical studies on the lining cracking problem have been carried out (Simanjuntak et al., 2013; Amorim et al., 2014; Fernandez, 1994; Seeber, 1985a, 1985b). Many scholars have developed different analytical formulas to describe the cracks in pressure tunnels (Darwin and Scanlon, 1986; Schleiss, 1997a, 1997b, 1998). Compared with the analytical method, the numerical method reflects the various complicated factors in actual engineering practice (Mang et al., 2015; Zhang and Bui, 2015). Thus, in recent years, researchers mostly use numerical methods to study the pressure tunnels (Lin et al., 2007; Feist et al., 2009; Olumide and Marence, 2012; Wang et al., 2013). Because of the complexity of the engineering practice, the cracking behavior of the pressure tunnel lining has been simulated in only a few studies (Bian et al., 2016). In these studies, the cracks were simulated implicitly by an equivalent model (Zhou et al., 2015; Cividini et al., 2012) or a damage model (Bian et al., 2009). One of the disadvantages of these models is that the actual crack distribution cannot be described, and thus the crack number and the crack width cannot be determined directly. As mentioned above, the crack width is an important parameter in pressure tunnel design. Moreover, after the lining cracks, the internal water in the pressure tunnel will penetrate into the cracks and generate the water pressure on crack surfaces (WPCS).