A Triaxial Compression and Triaxial Extension Test of Kimachi Sandstone

Stress state at generating a core disking and at excavating an underground open space is assumed to be the same as extensional stress state where three principal stresses are compressive and major principal stress and intermediate principal stress are always equal. To compare the deformation characteristic of Kimachi sandstone under confined triaxial compression and under confined triaxial extension, triaxial compression tests and triaxial extension tests were carried out. It was obvious that the extensional stress state showed higher maximum strength and shows more brittle behaviour than the compressional stress state. The plane of fracture of the specimen in the extension tests was almost per-pendicular to the axis.