Abstract: Based on self-designed pressure-tension conversion device and the RMT150C rock mechanics test system, the direct tension tests of the bilateral asymmetric cracked rock-like plate specimen have been carried out with the digital speckle correlation method (DSCM); and then the tensile stress-strain curves, the evolution of the surface strain fields and the crack propagation modes are obtained correspondingly. The results show that the tensile stress-strain curve of rock-like specimen can be roughly divided into four stages: (1) The approximate linear stage, the prefabricated crack basically do not work, the stress increases rapidly with strain, and the specimen surface strain field distribution is mainly affected by the internal pores and particles. (2) The whole slowly increasing stage, the two prefabricated cracks and the pores and particles in the specimen affect the distribution of the surface strain field; and the stress increases with strain on the whole. (3) The short peak transitional stage, one prefabricated crack plays a decisive role in the distribution of the surface strain field. (4) The final failure stage, the crack initiation is located in the relatively concentrated area of the strain field, and which cause the specimen damaged. For the bilateral asymmetric cracked plate specimen under direct tension, one of the cracks will propagate first, and is away from and then close to the front crack, which have great significance for the study of the propagation law of multi-crack interaction under tension stress state by using numerical simulation method.

Key words: pressure/tension conversion device, prefabricated cracks, direct tension, strain field, stress-strain curve, crack path