Physical Model Test on the Deformation and Fracturing Process of Underground Research Laboratory during Excavation and Overloading Test

Understanding the excavation-induced deformation and failure behaviors of the URL (underground research laboratory) for the geological disposal of HLW (high-level radioactive waste) before its construction is essential due to its high safety requirements. To reveal the interaction between structures, the effect of supporting and the characteristics of the overloading-induced damage and safety factor, we carried out a physical model test on the deep underground chamber groups consisting of one main roadway and two parking lots (one is supported, the other is not supported), and the engineering background is the URL of HLW for the geological disposal in Beishan. This type of geomechanical model test is still the first to be carried out so far. The test results confirm that the chamber group is generally stable during the excavation process. After the excavation, the displacement of the intersection is 7–33% larger than that of the non-intersection. The displacement of the supported chamber is reduced by 14–22% compared with that without support. The tension of the bolt at the vault top is greater than that at the waist of the cave. Without support, the safety coefficient of crack initiation is 1.7; the safety coefficient of local destruction is 2.1; and the safety coefficient of general demolition is 2.3. In contrast, the safety coefficient of crack initiation is 1.9; the safety coefficient of local destruction is 2.2; and the safety coefficient of general demolition is 2.4 when the rock mass is supported. The research results provide an important basis for optimizing design schemes and evaluating the safety of the construction process for URL.