Thermal Shock Effect on Strength Loss Properties of Rock Materials: An Experimental Study on Thermal Fatigue Durability (original) (raw)
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Effect of heat on the mechanical properties of selected rock types – a laboratory study
Harmonising Rock Engineering and the Environment, 2011
A laboratory study was conducted to study the effect of heat on the mechanical properties of diabase, granite and quartzitic schist at temperatures of 400 • C, 750 • C and 1100 • C. Unheated samples were also studied. The reasoning behind this study was to understand the effect of elevated temperatures on the rock mass, such as in the event of a fire in a rock tunnel. Samples from the aforementioned rock types were heat treated at temperatures shown above, cooled slowly to room temperature and then subjected to uniaxial compression and Brazilian tests. Thin sections were extracted from the heat treated samples for microscopic analyses, which assisted in explaining the reasons for the mechanical behaviour observed from the mechanical test results. The uniaxial compression test showed that the strength of the rock specimens increased by 6% for granite to 29% for diabase at 400 • C when compared to the UCS values of the unheated specimens. From 750 • C to 1100 • C the decay in the strength was very rapid. From the microscopic analyses it was concluded that the increase in the strength of the rock specimens at 400 • C is attributed to the initial reaction of the rock forming minerals, hence the rock specimens were less brittle but more plastic. The rapid drop in the strength from 750 • C to 1100 • C is attributed to the mineralogical changes, micro-cracking and dehydration due to the loss of crystal bound water. At 1100 • C the rocks were highly friable and crumbled very easily when tested mechanically. The effect of mineralogical changes was obvious in diabase where the physical appearance of the samples mimicked that of natural iron, which is believed to be due to the alteration of pyroxene. The result was an increase in strength by 29% at 400 • C compared to the unheated specimens. Even at 750 • C the strength was slightly higher than unheated specimens. In summary; the mechanical behaviour of the rock specimens depended on the temperature level and the mineralogical and physical changes that occur at that temperature. Subject: Rock material and rock mass property testing (laboratory and in-situ testing)
Effects of heat on the mechanical properties of selected rock types : A laboratory study
2011
A laboratory study was conducted to study the effect of heat on the mechanical properties of diabase, granite and quartzitic schist at temperatures of 400 • C, 750 • C and 1100 • C. Unheated samples were also studied. The reasoning behind this study was to understand the effect of elevated temperatures on the rock mass, such as in the event of a fire in a rock tunnel. Samples from the aforementioned rock types were heat treated at temperatures shown above, cooled slowly to room temperature and then subjected to uniaxial compression and Brazilian tests. Thin sections were extracted from the heat treated samples for microscopic analyses, which assisted in explaining the reasons for the mechanical behaviour observed from the mechanical test results. The uniaxial compression test showed that the strength of the rock specimens increased by 6% for granite to 29% for diabase at 400 • C when compared to the UCS values of the unheated specimens. From 750 • C to 1100 • C the decay in the strength was very rapid. From the microscopic analyses it was concluded that the increase in the strength of the rock specimens at 400 • C is attributed to the initial reaction of the rock forming minerals, hence the rock specimens were less brittle but more plastic. The rapid drop in the strength from 750 • C to 1100 • C is attributed to the mineralogical changes, micro-cracking and dehydration due to the loss of crystal bound water. At 1100 • C the rocks were highly friable and crumbled very easily when tested mechanically. The effect of mineralogical changes was obvious in diabase where the physical appearance of the samples mimicked that of natural iron, which is believed to be due to the alteration of pyroxene. The result was an increase in strength by 29% at 400 • C compared to the unheated specimens. Even at 750 • C the strength was slightly higher than unheated specimens. In summary; the mechanical behaviour of the rock specimens depended on the temperature level and the mineralogical and physical changes that occur at that temperature. Subject: Rock material and rock mass property testing (laboratory and in-situ testing)
Strength, Toughness, Damage And Fatigue Of Rock
2004
Assessment of rock mechanical properties depends on sample size and testing methodologies. Even for samples cored from the same rock outcrop the difference in properties appears to be sensitive to the local thermal and stress histories of the rock structure. Variations in the fracture toughness, unconfined compressive strength and tensile strength of a suite of granite samples, when tested using different procedures, are discussed in terms of experimental errors of the loading system as well as the thermal history.
Geophysical Research Letters, 2020
We present results from a series of thermal stressing experiments that used three igneous rocks of different composition, grain size, and origin and contemporaneously recorded acoustic emissions (AEs) with changing temperature. Samples were subjected to both a single heating and cooling cycle and multiple heating/cooling cycles to different peak temperatures. The vast majority of thermal crack damage is generated during heating in the coarser-grained (quartz rich) rock but during cooling in the two finer-grained (quartz poor) rocks. Our AE results also demonstrate the presence of a temperature-memory effect, analogous to the Kaiser stress-memory effect observed during cyclic mechanical loading, but only in the coarser-grained rock. We suggest that the total amount of crack damage induced during either heating or cooling is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock was exposed. We use our laboratory-scale results to suggest ways in which crustal-scale geophysical data may need to be reinterpreted to provide more accurate estimates of total, accumulated damage and the approach to macroscopic failure in crustal segments hosting magma chambers and geothermal reservoirs. Plain Language Summary We present results from a series of laboratory thermal stressing experiments using three igneous rocks of different composition, grain size, and origin: a Granophyre (SGP) from the Slaufrudalur pluton in Iceland, an Andesite from Santorini, Greece (SA), and a Basalt from the Seljadalur region of Iceland (SB), in which acoustic emissions (AEs) were recorded at the same time as the temperature of the samples was experimentally increased or decreased. Samples were subjected to both a single heating and cooling cycle and multiple heating and cooling cycles to different peak temperatures. The vast majority of thermal crack damage was generated during heating in the larger-grained SGP but during cooling in the smaller-grained SA and SB. Our AE results demonstrate the presence of a temperature-memory effect in SGP, analogous to the Kaiser stress-memory effect observed during cyclic mechanical loading, but no similar effect is observed in either SA or SB. We suggest that the total amount of crack damage is dependent on the mineral composition and, most importantly, the grain size and arrangement, as well as the maximum temperature to which the rock was exposed. The results should be considered in models that consider the distribution of damage in cyclically thermally stressed regions such as crustal segments hosting geothermal reservoirs and/or magmatic intrusions.
Experimental analysis on physical and mechanical properties of thermal shock d.PDF
The purpose of this study was to explore the changes of mechanical and physical properties of granite under different thermal loading effects. Uniaxial compression experiments studying the rules of the influence of temperature load on mechanical properties of granite were carried out. After high-temperature heating at above 600 °C, granite tended to have stronger ductility and plasticity as well as declined peak stress and compressive strength. Thermogravimetry -differential scanning calorimetry (TG-DSC) analysis results showed that, thermal load at different temperatures induced reactions such as water loss, oxidation and crystallization in the microstructure of granite, which led to physical changes of granite. Hence it is concluded that, heating can significantly weaken the mechanical performance of granite, which provides an important support for the optimization of heating assisted processing of granite. It also reveals that, heating assisted cutting technique can effectively lower energy consumption and improve processing efficiency.
A Comprehensive Study of Thermal Stress on Limestone Rocks Article Info
Petroleum resources continue to dominate the energy sectors with no sign of a decline. Petroleum reserves, however, are dwindling in view of fewer new discoveries and increased production level. It is important to determine petroleum reserves accurately in order to correctly forecast energy budget in the future. The most commonly used methods to describe the fluid flow in oil reservoirs employ constant rock properties. However, these methods are not applicable to reservoirs that undergo changes in the rock properties due to variation in pore pressure. Common characteristics of fractured reservoirs are sensitivity of permeability and porosity to effective stress. The in-situ stress, in itself, can be of mechanical or thermal origin. The thermal stress can be significant in thermal enhanced oil recovery schemes such as injection of cold fluid in hot formation during water flooding or wastewater disposal, or even during hydraulic fracturing. Unfortunately, the most commonly literature review reveals that the research in this area has been focused mainly on thermal recovery of heavy oil. Few investigation, however, have been done on the onset and propagation of fractures under thermal stress or mechanical stress. Consequently, this paper is devoted to investigate fracture development and propagation in carbonate formation under thermal and mechanical stress. A series of experiments were ingeniously designed to study the effect of thermal stress on fractured carbonate formation. Laboratory experiments were conducted to determine stress-strain relationship and the time dependence taking in account fracture formations and their propagation. A computer image analyzer was used to observe the fracture/fissures distribution for various cases of thermal stress on carbonate rocks. The role of thermal and mechanical stress in determining orientation and propagation of fractures was also studied.
Rock Mechanics and Rock Engineering, 2020
This paper presents an experimental procedure for the characterization of the granitic rocks on a Mars-like environment. To gain a better understanding of the drilling conditions on Mars, the dynamic tensile behavior of the two granitic rocks was studied using the Brazilian disc test and a Split Hopkinson Pressure Bar. The room temperature tests were performed on the specimens, which had gone through thermal cycling between room temperature and − 70 °C for 0, 10, 15, and 20 cycles. In addition, the high strain rate Brazilian disc tests were carried out on the samples without the thermal cyclic loading at test temperatures of − 30 °C, − 50 °C, and − 70 °C. Microscopy results show that the rocks with different microstructures respond differently to cyclic thermal loading. However, decreasing the test temperature leads to an increasing in the tensile strength of both studied rocks, and the softening of the rocks is observed for both rocks as the temperature reaches − 70 °C. This paper presents a quantitative assessment of the effects of the thermal cyclic loading and temperature on the mechanical behavior of studied rocks in the Mars-like environment. The results of this work will bring new insight into the mechanical response of rock material in extreme environments.
Mechanical Behaviors of Granite after Thermal Shock with Different Cooling Rates
Energies
During the construction of nuclear waste storage facilities, deep drilling, and geothermal energy development, high-temperature rocks are inevitably subjected to thermal shock. The physical and mechanical behaviors of granite treated with different thermal shocks were analyzed by non-destructive (P-wave velocity test) and destructive tests (uniaxial compression test and Brazil splitting test). The results show that the P-wave velocity (VP), uniaxial compressive strength (UCS), elastic modulus (E), and tensile strength (st) of specimens all decrease with the treatment temperature. Compared with air cooling, water cooling causes greater damage to the mechanical properties of granite. Thermal shock induces thermal stress inside the rock due to inhomogeneous expansion of mineral particles and further causes the initiation and propagation of microcracks which alter the mechanical behaviors of granite. Rapid cooling aggravates the damage degree of specimens. The failure pattern gradually ...
A Comprehensive Study of Thermal Stress on Limestone Rocks
Int J Petrochem Res, 2017
Petroleum resources continue to dominate the energy sectors with no sign of a decline. Petroleum reserves, however, are dwindling in view of fewer new discoveries and increased production level. It is important to determine petroleum reserves accurately in order to correctly forecast energy budget in the future. The most commonly used methods to describe the fluid flow in oil reservoirs employ constant rock properties. However, these methods are not applicable to reservoirs that undergo changes in the rock properties due to variation in pore pressure. Common characteristics of fractured reservoirs are sensitivity of permeability and porosity to effective stress. The in-situ stress, in itself, can be of mechanical or thermal origin. The thermal stress can be significant in thermal enhanced oil recovery schemes such as injection of cold fluid in hot formation during water flooding or wastewater disposal, or even during hydraulic fracturing. Unfortunately, the most commonly literature review reveals that the research in this area has been focused mainly on thermal recovery of heavy oil. Few investigation, however, have been done on the onset and propagation of fractures under thermal stress or mechanical stress. Consequently, this paper is devoted to investigate fracture development and propagation in carbonate formation under thermal and mechanical stress. A series of experiments were ingeniously designed to study the effect of thermal stress on fractured carbonate formation. Laboratory experiments were conducted to determine stress-strain relationship and the time dependence taking in account fracture formations and their propagation. A computer image analyzer was used to observe the fracture/fissures distribution for various cases of thermal stress on carbonate rocks. The role of thermal and mechanical stress in determining orientation and propagation of fractures was also studied.