The hollow cylinder test as an alternative to true triaxial loading of prismatic rock specimens

In the domain of Rock Mechanics, most laboratory tests do not simulate the triaxial states of stress that exist in rock masses involved in engineering workings. In fact, a conventional triaxial compression experiment is performed using a lateral confining pressure which is constant in all directions; therefore, only a 2-D state is created. The same thing happens in common shear tests, where a biaxial stress state is obtained, which is far from the field conditions where "in situ" shearing occurs. A description of the hollow cylinder test technique is presented, emphasizing the application of loadings along three surfaces, thus inducing true 3-D states of stress within rock samples. Results obtained using this method are shown and further applications are suggested.