ABSTRACT
The hydraulic behavior and associated mechanical, physical, and chemical processes of geological formations and rock masses are one of the most important aspects of rock engineering applications, especially for underground excavations. Although the existence of groundwater around underground excavations presents advantageous engineering applications such as hydrocarbon or compressed air storages in unlined rock caverns (Javadi et al., 2014a, 2016b; Froise, 1987; Lee & Song, 2003; Yoshida et al., 2013), most underground excavations usually face different kinds of direct and indirect groundwater challenges (ITA, 1991; Tseng et al., 2001; Yang et al., 2009; Yoo et al., 2012; Gattinoni et al., 2013; Zarei et al., 2012). From the engineering point of view, these groundwater challenges can be categorized into four major groups including in-tunnel (mainly due to the groundwater inflow and construction problems), near zone around tunnel (i.e. instability, collapse, swelling), far zone around tunnel (mainly groundwater alteration and drawdown), and support system (i.e. deterioration, erosion) challenges that result in increasing time, cost, risk, and environmental hazards and decrease the safety and work efficiency. Successful and appropriate treatment of these challenges requires a problem statement and thorough understanding of the effective features.
