Experiment Study on Three Point Bending Broken Features of Limestone Sample

Abstract：In order to master the broken features of limestone, a three point bending experiment with pre-slitting limestone samples was condueted. With the acoustic emission monitoring and measuring and the roughness measurement, the fracturing toughness of the lime- stone and the fracturing surface roughness were obtained analyzed. The experiment results showed that the fracturing toughness of the lime- stone was low and only about 20 -30 N/mm3/2. Thus the max load of the fracturing failure was low and only about 1 100 N. Therefore, the capacity of the anti fracturing and stability lost expansion of the limestone was poor. The fracturing surface of the sample was flat and the roughness coefficient was not over six. When the limestone fractured, the limestone would be quickly failed and the completed me- chanics performances of the fractured limestone would be depended on the roughness size of the fractured surface. Under the normal tem- perature and normal pressure, the smaller roughness of the fractured surface was, the smaller of the shearing strength would be and the fractured rock mass would be easy lost the stability sliding along the fractured surface. The low fracturing toughness of the limestone, the small roughness coefficient of the fracturing surface and other fracturing features set that the limestone and the rock strata mainly as the limestone would be easy fractured and would lost the stability when the rock was fractured.