2.2 Experimental plan
Seven types of support conditions, namely, rough tunnel, systematic rock bolt support, systematic rock bolt, and shotcrete support, systematic rock bolt and shotcrete and steel arch support, steel pipe support, steel pipe, and shotcrete support, and steel pipe and shotcrete and steel arch support, are considered. The shotcrete is simulated by using the epoxy resin with a thickness of 2 mm. The steel arch is composed of 304 stainless-steel pipes with an inner diameter of 20 mm. During the installation process, the steel pipe was put into the reserved cavity, and then the epoxy resin was injected into the pores between the outer wall of the steel pipe and the surrounding rock by using a syringe. Each support mode has been tested by the rocks with beddings angles of 0° and 90°, and the mechanical properties of the rock with holes and the failure of the surrounding rock under different support methods have been studied. In order to reduce the dispersion effects, three specimens were prepared for each case, and the ids and the support methods of the specimens are shown in Table 1.
The MTS815 rock mechanics testing system was used for the uniaxial compression tests of the anchored specimens with holes. The displacement control method was used as the loading type of the specimens, and the loading speed was controlled at 0.1 mm/min. During the test, a high-definition camera was used for recording the development and penetration of the surface cracks of the specimens, and the development process of the internal cracks in the holes was recorded by using the industrial endoscope apparatus.
Before and after the test, a German Siemens SOMATOM Scope X-ray Spiral CT Scanner was used to perform the non-destructive scanning of the specimens in order to detect the development and distribution of the internal cracks of the specimens. The spatial resolution of the CT scanner was 0.35 mm × 0.35 mm, the contrast resolution was 3 Hu, and the layer thickness was 0.75 mm.