Formation mechanism of extension fractures induced by excavation of a gallery in soft sedimentary rock, Horonobe area, Northern Japan

Abstract

a b s t r a c tThis paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan. Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone (EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks. The EDZ fractures terminate against pre-existing shear fractures. Therefore, even for excavations in soft sedimentary rocks, formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes.

A micromechanical analysis of the fracture properties of saturated porous media

“…Under external loadings, the fracture of porous media is typically multiphysics coupled (Rice and Simons, 1976;Rudnicki, 2001;Exadaktylos, 2012). Furthermore, the microstructures, such as pores and micro cracks, have been found to have great effects on the mechanical behavior of porous media, especially the fracture behavior (Shafiro and Kachanov, 1997;Cramer and Sevostianov, 2009;Ponson, 2009;Nara et al, 2011Nara et al, , 2014Ryvkin and Aboudi, 2011;Tokiwa et al, 2013;Tsusaka and Tokiwa, 2013;Zybell et al, 2014). A mutual understanding of the fracture behavior of porous media is of fundamental importance in fulfilling their applications and has received an increasing interest in recent years (Kovalyshen, 2010).…”