Influence of Spherical Caverns on the Failure Characteristics of Neighboring Tunnels under True Triaxial Conditions: Insights from an Experimental Test and Discrete Element Simulation

Caverns are generally formed by a combination of regional geological action and groundwater, their improper treatment will inevitably lead to dangerous conditions in underground works. To detect the specific failure mechanism tunnel-surrounding rock induced invisible caverns, true triaxial compression test is conducted, accompanied acoustic emission technology an internal borehole camera, for monitoring response visible secondary cracks, corresponding DEM simulation carried out reveal meso-mechanism. The results indicate following: (1) cavern demonstrates negative influence on stability tunnel leads 25.82% reduction peak z-axis load specimens. (2) show that relatively severe dominant failures mainly occur near stress all types specimens, speed intensity cavern-existing specimen significantly greater than cavern-free specimen. (3) cavity-free shows mirror-symmetric splitting left right sidewalls, while cracks appear earlier asymmetrical distribution specimen, volume broken blocks free surface larger. (4) directly changes process (intermediate occurs failure), principal stress, failures. (5) Application displacement velocity trend fields helped accurate procedures test.