ABSTRACT: The conventional triaxial test is widely used and the stress path is usually the conventional triaxial compression (CTC). The stress distribution of CTC is the intermediate principal stress (σ2) equal to the minimum principal stress (σ3) and the increase in the mean stress. However, the stress distribution related to failure in the crust and around underground excavations is not only CTC but also other stress paths such as the reduced triaxial compression (RTC), the conventional triaxial extension (CTE) and the reduced triaxial extension (RTE). For example, the formation mechanism of a horizontal joint, which is formed by an uplift of a pluton, is probably RTC or RTE.