Ultra fractal crack crack#

More and more geotechnical engineering such as mining, tunnel and deep ground, which makes the research on dynamic mechanical properties and crack propagation of rocks under medium and high strain rates become the frontier subject at present. This kind of research has been systematically and perfectly studied by rock mechanics workers, and many achievements have been achieved 16, 17, 18, 19, 20, 21. Existing studies on rock mechanical properties and crack propagation are mostly concentrated in the low strain rate range. Loading rate 6, 7, 8, material geometric characteristics 9, energy dissipation 10, 11, 12, 13, and the non-linear problem of crack distribution 14, 15 are intertwined, which makes it difficult to analyze the stability of surrounding rock mass. Research on dynamic response 1, 2, 3, 4, 5 of rock materials under impact loading is very complicated. Therefore, the research on the dynamic properties and fracture propagation behavior of rock materials with different fissures has important engineering background and scientific significance.

$ultra fractal crack$

The further development and expansion of cracks lead to the decrease of rock strength, thus affecting the stability of rock mass. faults and joints) in rock mass lose their initial equilibrium state. Especially under the disturbance of dynamic loads such as earthquake, blasting and excavation of underground engineering, the weak structural planes (e.g. Except for one fissure, 60° and 90° specimens, with the extension of time, the increase rate of fractal dimension is decreasing correspondingly.įracture and instability of rock mass usually begin with original defects such as initial fissures, cracks and holes in rock mass. The fractal dimensions of crack evolution tend to increase with time as a whole and assume as a parabolic. As the fissure dip increases and the number of fissures increases, the dynamic peak stress and dynamic elastic modulus of the fractured sandstone gradually decrease. But at the same height and different mass, the energy absorbed by the sandstone accounts for about 68.6% of the total energy.

$ultra fractal crack$

The results demonstrate that under impact test conditions of the same mass and different heights, the energy absorbed by sandstone accounts for about 26.7% of the gravitational potential energy.

$ultra fractal crack$

The box fractal dimension is used to quantitatively analyze the dynamic change in the sandstone cracks and a fractal model of crack growth over time is established based on fractal theory. To investigate the influence of the fissure morphology on the dynamic mechanical properties of the rock and the crack propagation, a drop hammer impact test device was used to conduct impact failure tests on sandstones with different fissure numbers and fissure dips, simultaneously recorded the crack growth after each impact.

$ultra fractal crack$