Fractal Analysis Of Control Of Fracture And Damage Of Limestone In General Experiments

The rock, consisted of diversified mineral crystalline grain, includes many random micro-cracks and micro-pores. It is neither discrete nor continuous medium. Therefore, using traditional methods to treat rocks as a macroscopic continuous medium is not rational, which neglect the effects of the existence of micro-cracks and micro-pores on rocks’ mechanical properties. As we can see, the failure mechanism of rocks is the process of the birth of micro-cracks, expanding, cut-through and fracture.As is well-known, the fracture surface records the process of its failure, but its surface is rough, which can not be depicted by using classical geometry. The study of fractal geometry shows that the fracture of rocks has fractal character, and using fractal dimension can depict the roughness of fracture and analyze the macroscopic mechanical properties of the failure of rocks.By using SAW-2000Electro-hydraulic Servo-controlled Rock Mechanics Testing System, some general mechanics experiments can be done to limestone which are selected from Xin’an coal mines, and the curve of stress-strain, the fracture surface and the image of fracture surface can be gained. With the JSM-6510LV High and Low Vacuum Scanning Electron Microscope, we can get the mesoscopic scan images of fracture. Then make the images of fracture into grey-scale maps by using Photoshop. According to the fractal theory, use box counting method to calculate the fractal dimension of fracture.From the perspective of damage mechanics, combine the theory of Weibull statistical distribution and fractal geometry, and introduce the reduced parameter into the basic formula of continuous damage mechanics, we can deduce the models of uniaxial and tiraxial compression experiments, and compares these models with the results of experiments, which shows the rational of these theoretical models.The failure process of rocks is always accompanied with the energy absorption and release. Therefore, from the perspective of energy, connect the fractal dimension with rocks’macroscopic characters of failure, and study the fractal characters of rock failure is feasible.