Effect of Anisotropy on the Long-Term Strength of Granite

Abstract

Granite rock mass is used for various rock engineering purposes. To ensure long-term stability, information about the subcritical crack growth (SCG) and an estimate of the long-term strength (LTS) of the rock are necessary. The influence of the anisotropy of granite on its LTS has not yet been clarified. In this study, the anisotropy of the long-term rock strength was investigated for two types of granite rocks, Oshima granite and Inada granite. Specifically, the effect of the anisotropy in crack propagation on the LTS was examined. The results showed that the LTS of granite is anisotropic, as are the fracture toughness and Brazilian tensile strength measured in this study. The LTS was lowest when crack propagation occurred parallel to the rift plane, where most of the microcracks occur. For Inada granite, which has an anisotropic SCG index, the degree of anisotropy of the LTS increased as the time-to-failure increased. This suggests that the LTS of granite is anisotropic.

Influence of surrounding environment on subcritical crack growth in marble

“…Therefore, determining fracture toughness is important. Several researchers have measured the fracture toughness using DT tests (Atkinson, 1979;Meredith, 1983;Meredith and Atkinson, 1985;Nara, 2015;Nara et al, 2012). Since fracture toughness depends on the environmental conditions such as temperature (Meredith and Atkinson, 1985;Funatsu et al, 2004Funatsu et al, , 2014, relative humidity (Nara et al, 2012), water vapor pressure (Kataoka et al, 2015), and water (Vavro and Souček, 2013), it is necessary to conduct fracture toughness measurements under controlled environmental conditions.…”

“…The experimental apparatus used in this study was the same as that used by Nara andKaneko (2005, 2006) in air, and Nara et al (2009) in water. The apparatus was set in a room where the temperature and relative humidity could be controlled over ranges of 278-353 K, and 40-90%, respectively.…”

“…In particular, studies of time-dependent fracturing in rock have been conducted to examine the natural hazards related to failure in rock, such as the increase in seismicity seen prior to earthquake rupture, fault formation, growth, sliding, and volcanic eruption (Kilburn and Voight, 1998;Ciccotti et al, 2000aCiccotti et al, , 2001Heap et al, 2011;Brantut et al, 2013Brantut et al, , 2014aViolay et al, 2013). Additionally, several studies have evaluated the long-term strength and time-to-failure based on the measurement of time-dependent fracturing (Schmidtke and Lajtai, 1986;Jeong et al, 2007;Nara et al, 2013;Nara, 2015).…”

“…In addition, it is important to ensure the stability of rock slopes in open-pit mines for safety. Various studies have examined timedependent fracturing in rock to determine the time-dependency of rock stability (Atkinson, 1984;Swanson, 1984;Meredith and Atkinson, 1985;Sano, 1988;Nara andKaneko, 2005, 2006). In particular, studies of time-dependent fracturing in rock have been conducted to examine the natural hazards related to failure in rock, such as the increase in seismicity seen prior to earthquake rupture, fault formation, growth, sliding, and volcanic eruption (Kilburn and Voight, 1998;Ciccotti et al, 2000aCiccotti et al, , 2001Heap et al, 2011;Brantut et al, 2013Brantut et al, , 2014aViolay et al, 2013).…”

P-wave propagation in dry rocks under controlled temperature and humidity

“…2,3 In the case of granite, the preferred orientation of pre-existing cracks produces anisotropies in strength 4,5 and fracture toughness, 6 In particular, it has been shown that fracture toughness is lowest when fracturing occurs in the direction parallel to the rift plane in which most pre-existing cracks are distributed. 6 Humidity is known to affect strength and fracturing in rock. For example, Fujii et al 7 reported that the strength of sandstone in Kushiro Coal Mine in Japan (Kushiro sandstone) decreases as water content rises.…”