Abstract: In order to explore the mechanical properties and failure mechanism of fractured composite rock mass,the mechanical
response,crack propagation and damage evolution of composite rock samples under different fracture configurations
were systematically studied by combining indoor mechanical test with acoustic emission and digital image technology. The results
show that the mechanical properties of composite rock samples are dominated by sandstone,but the response of peak stress
and elastic modulus to fractures is controlled by local lithology and fracture spatial configuration. The crack position controls the
crack propagation path:sandstone cracks induce single-wing butterfly failure,central cracks induce ′Y′-shaped failure,and
limestone cracks induce butterfly penetration failure ;the mode of rock bridge penetration controlled by fissure dip angle can be
divided into three typical types. The acoustic emission ringing count characteristics are affected by the fracture position and dip
angle. The first peak time decreases first and then increases with the increase of dip angle,and there are obvious differences in
the dominant damage stage under different fracture positions. The proportion of tensile cracks decreases first and then increases
with the increase of inclination angle. The damage constitutive model based on acoustic emission energy characteristics effectively
reveals the damage evolution law of rock samples under uniaxial compression:the damage develops slowly in the initial
compaction stage,the damage level increases gradually in the elastic deformation stage,the damage amount increases sharply in
the pre-peak failure stage,and the damage variable tends to be stable in the post-peak stage. The research results reveal the
control mechanism of fracture geometric parameters on the mechanical behavior and failure mode of composite rock mass,and
provide a theoretical basis for the stability evaluation of fractured rock mass engineering.