Experimental research on the mechanical properties of alkali-resistant glass fiber concrete acting as tunnel seismic isolation layer under periodic cyclic dynamic loading

The installation of seismic isolation layer is an effective measure to ensure the safe operation of underground projects such as tunnels during extreme seismic activities. Material parameters, mechanical properties, and design patterns of the seismic isolation layer are key research topics in exploring effective reduction of seismic response. This study mainly focused on the dynamic performance of the seismic isolation layer in tunnels. A series of drop hammer impact tests and laboratory shaking table tests were performed to reveal the seismic features of the seismic isolation layer under periodic external loading. The test results indicated that all cracks in the specimen initiated from the center and dispersed outwards under the cycle impact of the drop hammer. The incorporation of alkali-resistant glass fibers in concrete (AR-GFRC) effectively provided "reinforcement " and "crack resistance" under cyclic loading of the drop hammer, and the minimum number and width of cracks were observed at a 0.75 % HD fiber content and a 0.5 % HP fiber content. In the x- and y-axis directions, the seismic isolation layer effectively mitigated peak acceleration, strain response, and displacement at the tunnel vault and invert, but significant nonlinearity was identified. When the thickness of seismic isolation layer was 10 mm, the peak seismic response of the lining were minimum at a 0.75 % HD fiber content and a 0.5 % HP fiber content. However, the thickness of the lining was not directly related to the destruction of the lining. The tunnel mainly experienced shear deformation in the x-axis direction, with significant deformations from the left arch waist to the right arch foot (45°-225°), resulting in transverse cracking. The tunnel primarily underwent tensile and compressive deformation in the y-axis direction, with significant deformations occurring in the inverted vault (0°-180°), resulting in tension and circumferential cracks. This research can provide valuable data support and reference for the design and construction of underground projects such as tunnels.