TN1130 : Effect of crack geometry on the fracture mechanism of limestone building stone in laboratory
Thesis > Central Library of Shahrood University > Mining, Petroleum & Geophysics Engineering > MSc > 2023
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Abstract
The fracture process in a rock includes the propagation of the fracture from the crack already in the rock and the coalescence of the fractures with each other. Considering the effect of knowing the path of crack growth in optimizing the size of the parts created in stone and controlling the stability of rock structures, it is necessary to investigate the path of failure under different loading conditions. One of the failure mechanisms in rock under tensile stress is the creation of a tensile crack. Three-point bending loading can be used to create tensile stress in the rock. Important factors in determining the path of crack growth and rupture in rock include crack geometry and loading mode. In this study, using three-point bending tests for two crack lengths of 1.5 and 3 cm and angles of 0, 15, 30 and 45, the important parameters in the interpretation of the rupture mechanism including failure stress, failure strain and bending modulus as mechanical parameters and deformation Also, the topography of the fracture surface and the rupture pattern were investigated as the geometry of the fracture surface and the way of crack growth. Studies show that the effect of crack length on flexural strength is greater for defined angles to the loading axis. Flexural modulus decreases with increasing crack length and crack angle. Increasing the length of the crack and the angle of the crack provide the conditions for more deformation and the rock breaks in more strains. As the crack length increases, the amount of deformation and strain before failure increases. The fracture surface topography in samples with shorter initial crack length has a smoother surface. Also, the increase in crack angle increases the surface roughness due to the change of state from intergranular to intregranular fracture. The fracture pattern in samples with higher crack angle indicates an increase in the initial fracture angle. Using the obtained results will be very useful considering the importance of providing desired sizes for building rock.
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#Keywords: Rock failure #Crack #Lime building rock #Three-point bending test Keeping place: Central Library of Shahrood University
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