Abstract: The delayed rock burst in the tunnel excavation of hydropower station and the delayed collapse hazards of surrounding rock mass after the excavation were laboratory studied using conventional triaxial compression test equipment on marble rock samples form Pingjing Hydropower Station construction site.  The marble of Jinping Hydropower Station is selected as the research object. Uni-axial compression and conventional triaxial compression tests of marble were carried out by using THMC multifunctional coupling testing machine. The mechanical properties and failure mechanism of marble under external load are studied. The test results show that,1. With the increase of confining pressure, the brittleness of marble decreases and the ductile increases gradually, that is to say, the plastic deformation of marble increases gradually.2. the failure of rock samples in conventional triaxial compression tests is achieved by the increase φ internal friction angle and the decrease of cohesion c.3. The influence mechanism of different confining pressure on the mechanical properties of marble is discussed from the angle of the failure mode of the conventional three-axis compression test marble.

Key words: conventional triaxial compression tests, marble rock samples, plastic deformation, brittle failure, ductile failure, failure mode