Abstract：In analyzing excavation engineering，it is of great importance to determine rock strength parameters by unloading stress path. However，strength values determined by conventional unloading tests are often with great divergence. Obviously，among all the factors，divergence of rock specimens is important. To determine unloading strength parameters of rock by a single specimen，multiple failure state method is introduced into unloading stress path；and a special loading procedure based on unloading multiple failure method is put forward for triaxial tests. In conventional multiple failure state tests，it is believed that strain control is the only feasible way to carry out loading control. However，for some confining unloading tests，of which stress-controlled loading approaches are necessary，it is difficult to realize multiple failures by a stress-controlled loading approach. In stress-controlled tests performed by a MTS 815.02 triaxial testing machine for rock mechanics，several critical difficulties such as judging the peak strengths during the tests and controlling the axial deformation during each failure state are investigated；and solutions of these difficulties are proposed. Several multiple failure tests on marble specimens under confining unloading procedures are successfully conducted in the end. It is observed that strength values obtained from this approach matched well with those from conventional unloading tests. It is shown that the proposed approach is feasible and reliable，which not only considers the stress path，but also avoids the divergence of the specimens. It is a practicable and effective method for rock unloading strength parameters determination.
