ABSTRACT
Ramsey and Chester (2004) carried out confined triaxial extension tests on dog-bone shaped Carrara marble that showed a continuous transition from extension fracture to shear fracture with increasing compressive stress. On the other hand, in engineering geology fields, the stress state, when generating core disking and when excavating an underground open space, is assumed to be an extensional stress state where the three principal stresses are compressive and maximum and the intermediate principal stresses are always equal. However, there is insufficient data related to the confined triaxial extension test. Confined triaxial compression tests and confined triaxial extension tests under different loading paths, and a true triaxial test under an extension stress state, were conducted using Kimachi sandstone. We show the differences in deformation characteristics between the three different types of extension tests and the compression test.
