Rock Mechanics
K. Abdolghanizadeh; M. Hosseini; M. Saghafiyazdi
Abstract
Natural and artificial materials including rocks and cement-based materials such as concrete and cement mortar are affected both physically and chemically by various natural factors known as weathering factors. The freeze-thaw process, as a weathering factor, considerably affects the properties of rocks ...
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Natural and artificial materials including rocks and cement-based materials such as concrete and cement mortar are affected both physically and chemically by various natural factors known as weathering factors. The freeze-thaw process, as a weathering factor, considerably affects the properties of rocks and concrete. Therefore, the effect of the freeze-thaw process on the physical and mechanical properties of materials should be taken into account in areas with the risk of this process. Given that few studies have been conducted on the effect of the freeze-thaw process on the fracture toughness, in this work, we aimed at investigating the effects of the freeze-thaw cycles and freezing temperature on the mode I and mode II fracture toughness of cement mortar. To this end, specimens were exposed to 0, 5, 10, 20, and 30 freeze-thaw cycles, and the mode I and mode II fracture toughness was determined in different cycles. The effect of freezing temperature in a freeze-thaw cycle on the mode I and mode II fracture toughness was also investigated. The damage factor was also defined based on the effective porosity of cement mortar, and its changes with the number of freeze-thaw cycles and mode I and mode II fracture toughness were studied. Finally, the decay function model provided by Mutluturk was investigated. According to the results obtained, the mode I and mode II fracture toughness of cement mortar decreased linearly with increase in the number of freeze-thaw cycles. The mode I and mode II fracture toughness decreased linearly with increase in the freezing temperature in a freeze-thaw cycle. The damage factor increased with increase in the number of freeze-thaw cycles, and, additionally, its relationship with mode I and mode II fracture toughness exhibited a linear behavior.
Rock Mechanics
M. Hosseini; A. R. Khodayari
Abstract
In an era of continued economic development around the globe, numerous rock-related projects including mining and gas/oil exploration are undertaken in regions with cold climates. Winters in the Iranian western and northwestern provinces are characterized by a high precipitation rate and a cold weather. ...
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In an era of continued economic development around the globe, numerous rock-related projects including mining and gas/oil exploration are undertaken in regions with cold climates. Winters in the Iranian western and northwestern provinces are characterized by a high precipitation rate and a cold weather. Under such conditions, rocks are exposed to long freezing periods and several freeze-thaw (F-T) cycles. It is thus necessary to examine the impact of these cycles on the physical and mechanical properties of rocks. Considering the abundant sandstone resources in Iran, in this work, we focused on the Lushan sandstone by investigating the effects of F-T cycles and freezing temperatures on the uniaxial and triaxial compressive strengths, cohesion, internal friction angle, and elastic modulus of the rocks. To study the impact of the number of F-T cycles on the strength of rocks, the specimens frozen at -16 °C were subjected to 1, 4, 8, 16, and 32 F-T cycles. Similar tests were also carried out on the specimens frozen at -24 °C. Furthermore, a number of tests were undertaken at the ambient temperature (25 °C) on specimens that did not undergo an F-T cycle. According to the results obtained, an increase in the number of F-T cycles and freezing temperatures reduced the uniaxial and triaxial compressive strengths, cohesion, internal friction angle, and elastic modulus due to the growth of the existing cracks and the nucleation of new cracks in the rock. Consequently, the effective porosity increased, whereas the dry specific gravity decreased with more F-T cycles and lower freezing temperatures.
