“…In consequence, shales exhibit a strong anisotropy in both physical and mechanical properties, which has been observed both at the field scale [ Alkhalifah and Rampton , ; Le Gonidec et al , ] and the laboratory scale [ Ibanez and Kronenberg , ; Masri et al , ; Ikari et al , ]. In particular, several experimental studies investigated the anisotropic strength of shales [ Niandou et al , ; Dewhurst et al , ; Shea and Kronenberg , ]. Including studies performed on other anisotropic rocks such as slates, mica schists, and gneiss [ Shea and Kronenberg , , ; Rawling et al , ], models of anisotropic failure criterions, either semiempirical [ Kronenberg et al , ; Cazacu and Cristescu , ; Tien and Kuo , ] or micromechanical [ Rawling et al , ], have been developed.…”