A large number of rockburst cases happened in deep tunnels of JinpingⅡhydropower station revealed that the slab failure of surrounding rock has a strong relationship with rockburst. Model specimens that meet the architectural feature of slab failure are made by using high-strength gypsum. Instability destruction process

strength and deformation characteristics

crack propagation signature of model specimens are researched under the condition of one lateral side restraint uniaxial loading mode. The results show that (1) the instability destruction process of the slab model specimens shows the characteristics of strain rockburst. A typical failure process can be described as follows: initiation and propagation of extension crack from the tip of pre-existing fissure

splitting into slabs

flexure deformation of slabs

buckling of slabs and ejection of slices. (2) The peak strength

elastic modulus of model specimens containing one

two and three pre-existing fissures show a steady decline law

but the peak axial strain decreases and then increases. (3) The emergence of extension crack will result in: a sudden change of the lateral strain near the tip of adjacent fissures and a significant increase in the amount and the rate of lateral deformation of the specimens. (4) Due to the affect of the free surface

extension crack will enter into unstable propagation stage in a short time after its initiation from the tip of pre-existing fissure that near the free surface of specimens and this will lead to the overall instability of the model specimen. At last

acoustic emission characteristics of specimen in the overall stage of compression deformation are analyzed. The research results are of important significance for the reveal of the instability destruction law of slabbing surrounding rock and the rockburst formation mechanism of deep tunnel in hard rock.