Study on displacement measurement methods in geomechanical model testing of an underground cavern group for hydropower station

Taking the Shuangjiangkou Hydropower Station as a prototype, geomechanical model test was conducted to investigate the stability of an underground cavern group. To measure small displacements in the surrounding rock masses, a digital photogrammetric technique, displacement sensing bars using Fiber Bragg Grating (FBG) technology, and mini multi-point extensometers with high-precision grating scales were developed for measuring deformation. The variation process and curves of the law of displacements in the surrounding rock masses and at key points in the side walls can be obtained. The results show that the research and application of displacement measurement methods used in the geomechanical model test have achieved statisfactory results.