ABSTRACT
The stability of underground caverns is one of the most critical engineering and technical issues in the construction of pumped storage power stations (PSPs). During Taitai PSPs construction, the change of anchor stress gauge in the transformer chamber was between −0.90 MPa~147.23 MPa (abnormally large increment) this March. After the site investigation, there were no faults or structures in the surrounding rock mass around the monitoring point. The numerical analysis with FLAC3D has been performed, which revealed that the lagged support during construction would increase the anchor stress on the arch left of the cavern. Also, according to a lot of monitoring results of bolt stress gauge regarding some built underground caverns in China, its regularity is much worse than that of multi-point extensometer, and the representative of a bolt stress gauge in evaluating the safety of supporting structures is relatively poor. The multi-point extensometer data showed that the current excavation response increment is within a reasonable range. Therefore, the potential reason for the abnormal stress change would be that the construction team has not implemented support in time, and the rock mass stress release has influenced the monitoring point after the excavation of the transformer chamber. Based on the analysis, the transformer chamber is generally stable, and the deformation monitoring results need to be fed back in time during the excavation process for further analysis. When there is a stress relaxation phenomenon of the surrounding rock, the initial support must be implemented in time to control the stress release and deformation.
