Taking the underground caverns of Shuangjiangkou (SJK) Hydropower Station as an engineering background, a largescale true 3D physical model test is performed to study the stability of the enclosing rock masses, including the analogous material, the steel structure frame, fabrications of rock bolts and cables, development of the measuring
techniques, fabrication of the physical model, excavations and the overload test. The developed steel structure can simulate the complicated circumstances just like high in-situ stress and high overburden depth. It also can apply the true 3D loading on six surfaces of the physical model. Many combinational ball sliding blocks are installed between model surface and the structural wall to reduce the friction between the contact surfaces. During the model construction, precast blocks are used and monitoring holes are predefined before the analogous material is piled up. A unique grouting technique and prestressed cables are adopted in the model test. A digital photogrammetric technique, displacement
sensing bars based on Fiber Bragg Gratings (FBG) technology, and mini extensometers are developed and adopted for measuring the deformation in the process of excavations. The overload tests are accomplished under the conditions of different overburden depths. The results of this research will make certain guiding significance to the practical engineering.