ISRM suggested methods for determining the creep characteristics of rock

摘要

It is important to note that creep is only one aspect of thetime-dependent behavior of rocks. In Fig. 1, three cases areillustrated with respect to the complete stress–strain curve:creep, i.e., increasing strain when the stress is held constant;stress relaxation, i.e., decreasing stress when thestrain is held constant; and a combination of both, when therock unloads along a chosen unloading path. This ISRMsuggested method deals only with the case of creep, whichis particularly relevant for cases where the applied load orstress is kept constant.Creep tests have also been carried out on soft rocks such astuff, shale, lignite, and sandstone, medium-hard rocks such as marble, limestone, and rock salt, and hard rocks such asgranite and andesite (i.e., Akagi 1976; Akai et al. 1979,1984; Ito and Akagi 2001; Berest et al. 2005; Doktan 1983;Passaris 1979; Serata et al. 1968; Wawersik 1983; Okuboet al. 1991, 1993; Masuda et al. 1987, 1988; Ishizuka et al.1993; Lockner and Byerlee 1977; Boukharov et al. 1995;Fabre and Pellet 2006; Aydan et al. 1995; Chan 1997;Cristescu and Hunsche 1998; Hunsche 1992; Hunsche andHampel 1999; Ito et al. 1999; Mottahed and Szeki 1982;Perzyna 1966; Slizowski and Lankof 2003; Yang et al.1999). These experiments were mostly carried out undercompressive loading conditions.There are few studies on rocks using creep tests under atensile loading regime (Ito and Sasajima 1980, 1987; Itoet al. 2008; Aydan et al. 2011). In particular, shallowunderground openings may be subjected to a sustainedtensile stress regime, which requires the creep behavior ofrocks under such conditions.