Abstract: The fracture mode and velocity for the center of marble slab under the stress loading were studied in the experiment. The results are as follows.1. Most cracks cross veins at an angle of about 45° and some nearly 0°. Failures of the rock usually occurred at different time,with one of the cracks first going through the slab. There was shear strain before failure. The direction of the main fracture was in disagreement with the surface of minimum tensile strength. The hydraulic fracturing direction of main fracture is probably in disagreement with the direction of maximum horizontal principal compressive stress.2. logⅤ-L diagram (Ⅴ,velocitv of propagating cracks; L,ratio of crack's length L to (R₂-R₁):R₁ R₂,radius of the indenter and the marble slab,respectively) shows that three stages for the failure of the slab: in the initial,Ⅴ was relatively large (10mm/s) when cracks occurred and then exponentially decreased (0.05mm/s) with increasing L; in slowly fracturing,Ⅴ alternatively increased with increasing L(0.1-2mm/s); and in rapidly fracturing,Ⅴ increased abruptly and a noticed turning might be found,over which log Ⅴ increased exponentially (to 1 m/s) and then fractures occurred.

摘要： 本文叙述大理石板中心受压时的破裂形式及破裂传播速度:1.主破裂走向与大理石纹理多数成45°角,少数近似平行,破裂时总是一侧先断通;破裂前存在剪应变,主破裂方向不一定与最弱张裂面一致;2.1gⅤ—L图表明:始发段,刚出现裂纹时,Ⅴ较大(约10毫米/秒),随L增大,Ⅴ急剧减小(约0.05毫米/秒);缓裂段,随L增大,Ⅴ起伏式缓慢增长(0.1—2毫米/秒);速裂段,过一明显转折点后,随L增大,Ⅴ急剧增长(约1米/秒),破裂发生。