• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.23-32
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• 2001

Rock masses are usually discontinuous in nature, as a result of various geological processes they have underdone and they contain rock joints and bridges. Crack propagation and coalescence processes mainly cause rock failures in tunnels. In this study, we focused on the crack initiation, propagation and coalescence process of rock materials containing two pre-existing open cracks arranged in different geometries. During uniaxial compression, wing crack initiation stress, wing crack propagation angle, and crack coalescence stress of Diastone gypsum and Yeosan Marble specimens were examined. And crack initiation, propagation, and coalescence processes were observed. Shear, tensile and mixed (shear+tensile) types of crack coalescence occurred. To compare the experimental results with Ashby & Hallam model, crack coalescence stress was normalized and it generally agreed with the experimental results.

• Tunnel and Underground Space
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• v.11 no.3
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• pp.217-224
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• 2001

Rock masses are usually discontinuous in nature due to various geological processes and contain rock joints and bridges. Crack propagation and coalescence processes in rock bridge mainly cause rock failures in slopes, foundations, and tunnels. In this study, we focused on the crack initiation, propagation and coalescence process of rock materials containing two pre-existing open cracks arranged in different geometries. Specimens of 120${\times}$60${\times}$25 mm in size, which were made of Yeoman Marble, were prepared. In the specimens, two artificial cracks were cut with pre-existing crack angle ${\alpha}$, bridge angle ${\beta}$, pre-existing crack length 2c and bridge length 2b. Wing crack initiation stress, wing crack propagation angle, and crack coalescence stress were measured and crack initiation, propagation and coalescence processes were observed during uniaxial compression. Crack coalescence types were classified and analytical study using Ashby and Hallam model (1986) was performed to be compared with the experimental results.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.171-174
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• 2001