EXPERIMENTAL INVESTIGATION ON FRACTURE OF THREE TYPES OF UNDERGROUND CAVERNS
SONG Yimin1，PAN Yishan2，ZHANG Mengtao2，SHI Huiji1
(1. Department of Mechanics and Engineering，Tsinghua University，Beijing 100084，China；2. College of Mechanics and Engineering，Liaoning Technical University，Fuxin，Liaoning 123000，China)
Abstract：To explore the fracture process and mechanism of underground caverns，three types of fractures which include primary and remote fracture，V-shape notches and zonal disintegration，have been studied by model experiments. The prefabrication cavern models were loaded under biaxial compressive loading and triaxial compressive loading. The fracture extension of the surrounding rock of model caverns are monitored by the white light digital speckle correlation method and acoustic emission. Based on laboratory test results，three types of fracture mechanisms were analyzed. The experimental results of primary and remote fracture show that the remote-fracture mechanical mechanism is the tensile strain concentration，and the tensile strain is the main focus and the combined effect of tension and compression. The experimental results of V-shape notches show the surrounding rock fractures of underground caverns form in the local area of the border of the model caverns，then extend to form the V-shaped fracture zones. The follow-up fracture in the tip of V-shape notches of model caverns expands to the surrounding rock of model caverns. The experimental results of zonal disintegration show the circular fracture of the deep surrounding rock of model caverns forms in the tip of the local fracture area of the border of model caverns，and extend to the deep surrounding rock. At the same time，a non-fracture zone has formed intermediately in the border of underground caverns and the circular fracture of surrounding rock.
