The Effects of the Process of Stresses on Mechanical Properties of Tuff Rocks

According to the actual process of stress changes in underground excavations, a triaxial test method, using a loading pattern in which confined pressure is being reduced when exerting an axial loading, is introduced. In order to be compared, the expe- riment using general loading patterns, namely, increasing axial loading under constant confined pressure, was performed.The result shows that for these two load processes the strength characters are basically the same while deformation properties and brittleness and ductility are quite different. It is necessary to employ such a triazial test of which the stress process is consistent with the stress changes in an actual engineering practice to determine the mechanical properties of rocks.