Abstract:
The strength of coal, mudstone, sandstone and other common rocks in the surrounding rock of deep roadway is low and the fractures are developed. Dynamic disasters are prone to occur in the complex mechanical environment of deep roadway. The key to clarify the occurrence of dynamic disasters is to study the dynamic response and energy dissipation law of the internal fracture characteristics to the rock mass. In order to study the influence of internal fracture dip angle and fracture distribution on the dynamic mechanical response and energy dissipation law of rock-like mass, the rock-like mass samples with internal fractures were prepared by sand powder 3D printing. The dynamic compression test of the samples was carried out by split Hopkinson pressure bar (SHPB). The high-speed camera was used to observe the crack development, and the dynamic failure characteristics were analyzed by combining the energy dissipation principle and fractal theory. The results show that with the increase of the dip angle of the internal fracture, the dynamic peak stress and the dynamic elastic modulus of the samples decrease first and then increase, both of which are the lowest at 30º. With the increase of the number of fractures, the influence of vertical distribution fractures on the dynamic peak stress of the sample is greater than that of horizontal distribution fractures. The energy dissipation of sample failure decreases first and then increases with the increase of fracture dip angle. When the fracture dip angle is small, the existence of loose filling will aggravate the attenuation of stress wave and increase the energy dissipation. With the increase of fracture dip angle, the influence of filling on the energy dissipation of sample decreases gradually. Under the same crack inclination angle, with the increase of fracture number, the energy dissipation of vertical distribution fracture samples are less than that of horizontal distribution fracture, which is positively correlated with the dynamic peak stress of sample. With the increase of fracture dip angle, the fractal dimension of the sample increases first and then decreases. When the fracture dip angle is 30°, the fracture degree of the sample is the largest, and the fractal dimension of the sample is the largest. The increase of the number of cracks makes the fragmentation of the sample gradually uniform, and the fractal dimension of the sample shows an increasing trend. The research results reveal the influence of internal fractures on the dynamic characteristics and energy dissipation of rock mass, and provide an important basis for the dynamic test of complex internal fractured rock mass by using sand powder 3D printing technology. It is of great significance to further understand the fracture and instability mechanism of surrounding rock in deep soft rock roadway in practical engineering.