Abstract：To provide references for stability analysis of Niba mountain tunnel construction，based on the actual stress environment and the uniaxial compression test，a series of triaxial compression and unloading tests are carried out. The rhyolite specimens are sampled from deep boreholes. The complete stress-strain curves of rhyolite specimens are analyzed and contrasted under different conditions，and the following results have been drawn. Microcracks develope in deep-buried rock mass. With the increase of buried depth，the peak strength becomes higher gradually. Integral rhyolite specimens have high compression strengths and obvious brittleness. Under triaxial compression conditions，the rhyolite specimen has obvious yield character，but macro failure happens after large plastic deformation. The failure forms turn from splitting failure to shear failure with the confining pressure increasing，and the obliquity of the fracture plane becomes gentle. Under unloading condition，the rhyolite specimens will be damaged more easily；the cohesion c is 48% lower than that under conventional compression condition，while internal friction angle  is 11% greater than that under conventional compression condition.
