| Fractured rock mass widely exists in nature.The existence of cracks will make the stress environment in the rock body more complex,and have an impact on the bearing capacity and failure mode of rock mass.When subjected to external loads,cracks will further develop,expand and even connect,causing rock mass instability and damage,thus causing many engineering disasters,such as underground chamber collapse,wall extrusion,slope collapse,deep cracks in the dam body,etc.Therefore,the study of fractured rock mass has important reference significance for guiding the engineering related to rock mass.According to the real rock mechanical parameters measured in the experiment,rock-like samples with similar mechanical properties are prepared according to the corresponding proportion.The indoor test is carried out by using the YAD-2000microcomputer controlled full-automatic pressure testing machine and DS2 series A-type acoustic emission instrument.At the same time,the PFC software is used for numerical simulation to study the crack propagation and strength characteristics of fractured rock mass under different conditions.The main research contents and results of this paper are as follows:（1）The disc specimen was loaded by Brazilian splitting test at different angles.The failure mode of Brazilian splitting test is mostly splitting failure along the loading direction,and the effect of increasing the loading angle on the prefabricated crack increases first and then decreases.（2）Ten groups of rock-like samples with two groups of intersecting cracks were prepared,and uniaxial compression tests with different inclination combinations were carried out,and the crack propagation process in the samples was analyzed.It was concluded that when the sample combination included 30°inclination,the general strength was higher than other combinations,and the change trend was different only at 45°,so the combination of 45°and 45°was selected to change the fracture length for research,The influence of inclined crack length on sample strength is greater than that of horizontal crack.（3）The increase of each crack length will have a greater impact on the strength of the sample,and the increase of the horizontal crack length will have a greater impact on the sample at the same angle.When the horizontal crack length is less than the inclined crack length,the sample failure is mainly affected by the wing crack generated by the inclined crack,and the final sample failure mode is diagonal shear failure.When the horizontal crack length is greater than the inclined crack length,the crack after the sample failure is antisymmetric.（4）A PFC2D numerical model is established to change the dip angle of a single group of intersecting fractures and the dip angle of two groups of intersecting fractures.The change value of peak stress when only one group is changed is less than that when both groups are changed at the same time,and the fracture phenomenon of contact force chain is more obvious when the dip angle of fractures is changed at the same time.The PFC3D is used to establish a model that changes the different angles of the prefabricated crack deflection along the cylinder model circumferential and axial directions to explore the influence of the three-dimensional plane crack on the sample.When rotating along the cylinder circumferential direction,the peak stress gradually decreases with the increase of the offset angle.When the angles of the upper and lower groups of intersecting cracks are perpendicular to each other,the peak strength is the lowest,and the axial deflection along the cylinder,the peak stress gradually increases with the increase of the deflection angle of the lower group of intersecting cracks. |
