SONGKLANAKARIN JOURNAL OF SCIENCE & TECHNOLOGY

Volume 42, No. 02, Month MARCH, Year 2020, Pages 339 - 345

Effect of stress path on shearing resistance of sandstone fractures

Pakpoom Naphudsa, Thanittha Thongprapha, Kittitep Fuenkajorn

Abstract Download PDF

Triaxial and direct shear tests have been performed on rough (tension-induced) and smooth (saw-cut) fractures in Phra Wihan sandstone specimens. Two stress paths are used for the triaxial shear testing: constant confining stress and constant mean stress. It is found that under low confinement both stress paths show similar shearing resistance for the rough fractures. Under high confinement, however, the strengths under constant mean stress are notably lower than those of constant confining stress. The shear strengths of smooth fractures are independent of the stress path. This is supported by the shear strength results obtained from the direct shear testing, which suggests that under low normal stress and unconfined condition the stress path effect is insignificant. It is postulated that fracture roughness and non-linear behavior of fracture wall rock under high confinements are the main factors that cause stress path dependency of rock fractures.

Keywords

shear strength, strain energy density, Coulomb criterion, mean stress, triaxial test

---