Influence of 3D cavern on the failure characteristics of adjacent tunnel
To address the special condition of cavities in the tunnel surrounding rock in Guizhou Zijin golden mine(caves in geological bodies often lead to unstable and even violent damage of underground engineering rock enclosures),the deformation and secondary damage behavior of the surrounding rock were monitored by acoustic emission and tunnel endoscope cameras based on true triaxial compression tests of simplified rock specimens containing tunnels and cavities.The study shows that the prefabrica-ted cavern leads to a 25%decrease of z-axis peak stress of samples,the secondary failure shows earlier appearance time,and the dominant secondary failure concentrates during the final peak stress period.Prefabricated cavern located on the right top side of the tunnel contributes to a new type of splitting failure,which starts in the middle rock between the tunnel and cavern,develops vertically along the surface field of the tunnel sidewall,finally forms a divided rock plate and move inwards;the above characteristics are different from that of the traditional splitting failure.The compressive force and the corresponding shear failure play the dominant role in the construction of splitting failure;the prefabri-cated cavern shows a slight influence on the bottom and left surrounding rocks of the tunnel because of the location(right-top outside the tunnel).The prefabricated cavern contributed to the dense distribu-tion of secondary tensile and shear cracks in the rock between the tunnel and cavern,and the corre-sponding destruction level of this region is relatively higher than rock at other positions.
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