Study On The Cross Crack Extension

The rock mass has certain joint and crack under the natural state, rock mass will produce certain joints and fissures. These joints and fissures always play a decisive role on the strength of the rock mass. In order to exploring complex engineering geological conditions, the effect of fracture strength of rock mass must be explored at first. In this paper, crack initiation and propagation in unidirectional stress conditions was studied mainly. So the failure modes of rock mass can be found.Pre-existing crack specimens, with different angles and different distances between cracks, were made for the different status of fractured rock mass in paper. According to the principle of single variable, the pre-existing crack angle and crack spacing effect on the mechanical properties of specimens can be found.The main content of this paper is as follows:①The domestic and foreign researches of the pre-existing crack in the rock were summarizied, and explained the mechanism of crack extension theory based on fracture mechanics.②According to the related physical and mechanical properties of rock, the similar mechanical properties of materials were chosen. Through a lot of test about mechanical properties, material mixture ratio was finally determined. In this paper, the AGI-250 KN type electronic precision testing machine(servo testing machine) was carried out in uniaxial compression test, and the whole process of the pictures were collected by the RDT / 16 type high speed dynamic recording system.③Informations recorded by the compression test system were made. Twelve groups of graphics were drawn by ORIGIN, which include stress- strain curve, the crack angle and spacing effect on maximum stress.④Images of the crack and the crack extension were photographed by the RDT / 16 type high speed dynamic recording system. These images are used to analysis together with the experimental data. According to the principle of single variable, the pre-existing crack angle and crack spacing effect on the mechanical properties of specimens can be found. Then, make a discussion maximum stress and maximum strain.⑤ABAQUS is used to numerical simulation of the crack expansion under condition of different crack angles and spacing. The numerical simulation results were compared with experiment results to verify their reliability.