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1.
The evolution of porosity and changes in wave velocity in granite after high-temperature treatment has been experimentally investigated in different studies. Statistical analysis of the test results shows that there is a temperature threshold value that leads to variations in porosity and wave velocity. At a temperature that is less than 200 °C, the porosity of granite slowly increases with increases in temperature, while the wave velocity decreases. When the temperature is greater than 200 °C (especially between 400 and 600 °C), the porosity quickly increases, while the wave velocity substantially decreases. The temperature ranges of room temperature to 200 and 200–400 °C correspond to the undamaged state and the micro-damage state, respectively. The results confirm that there is an important link between the variations of physical and mechanical properties in response to thermal treatment. By studying the relationships among rock porosity, wave velocity and temperature, this provides the basis for solving multi-variable coupling problems under high temperatures for the thermal exploitation of petroleum and safe disposal of nuclear waste.  相似文献   

2.
Variations in the mechanical properties (compressive strength, elastic modulus, tensile strength, and fracture toughness) of granite were analyzed as functions of temperature. It was found that above 200 °C, tensile strength and fracture toughness tended to decrease with temperature, while variations in the compressive strength and elastic modulus demonstrated decreasing trends when the heating temperature exceeded 400 °C. The temperature ranges of room temperature—200 and above 600 °C—corresponded to an undamaged state and strongly/completely damaged state, respectively. It is suggested that 400 °C might be a critical threshold of thermal damage to granite. Based on results of statistical tests, a sharp decrease in mechanical properties can be recognized, accompanied by a drastic growth in peaking strain and acoustic emission rate. This phenomenon may be associated with the α/β phase transition of quartz.  相似文献   

3.
Open burning of waste at dumpsites sites may alter many physical and chemical properties of underlining soil layers including its ability to retard the migration of potential contaminants, such as lead, through the vadose zone. In this study, lead sorption onto soil samples from Irbid that were subjected to high temperatures has been investigated. These samples were collected from ground surface and heated to temperatures of 25, 70, 100, 200, 225, 250, 275, 300, 400, and 550°C. Based on these temperatures the soil was divided into ten different groups. Each group was first characterized by conducting a set of experiments to estimate the Atterberg limits (liquid limit, plastic limit, and plasticity index), the organic carbon content, and a set of batch experiments to study lead adsorption. Results indicate that the LL, PL, total organic carbon are slightly affected by high temperatures less than 200°C, show an abrupt change between temperature from 200 and 300°C, and then slight change above 300°C. Sorption of lead onto heated samples, however, was not significantly changed. This may be explained by the fact that adsorption of heavy metals mainly occurs onto the soil mineral parts which are slightly affected by the temperature range used in this study.  相似文献   

4.
The in situ Raman spectra of a hydrous anorthoclase at temperatures of 20–800 °C have been measured using a LABRAM-HR spectrometer and Linkam TS 1500 heating stage. The frequencies of modes at 54, 99, 130 and 162 cm?1 related to M–O vibrations decrease sharply and then increase drastically or keep steady at temperatures above 200 °C. A knee point can be clearly seen at about 200 °C for those modes. The frequency of the mode at 282 cm?1 shows little temperature dependence. However, for the two strongest modes at 471 and 512 cm?1, the frequencies decrease linearly with increasing temperature. From evolution of the frequencies of modes at 54, 99, 130 and 162 cm?1 with temperature, the following conclusions can be drawn: (1) The distance of the local M–O bond shortens rather than lengthens at temperatures above 200 °C; (2) The abrupt changes of the local structure of M site induce a collapse of the framework structure and displacive phase transition at 200 °C; and (3) The H atoms incorporated in anorthoclase are located at the M site. These results are indicative for the structure and properties of anorthoclase at deep earth conditions.  相似文献   

5.
Impacts of subsurface heat storage on aquifer hydrogeochemistry   总被引：3，自引：3，他引：0  
The use of shallow aquifers for subsurface heat storage in terms of energy management and building climatisation can lead to a temperature rise in the aquifer to 70 °C and above. The influence of temperature changes on individual mineral and sorption equilibria, reaction kinetics and microbial activity is largely known. However, the impact of heating to temperatures as high as 70 °C on the aquifer overall system has not been quantified yet. Temperature-related changes in sediment ion exchange behaviour, dimension and rates of mineral dissolution and precipitation as well as microbially enhanced redox processes were studied in column experiments using aquifer sediment and tap water at 10, 25, 40, and 70 °C. At 70 °C, a change in sediment sorption behaviour for cations and organic acids was postulated based on temporal changes in pH, magnesium, and potassium concentration in the experimental solution. No clear changes of pH, TIC and major cations were found at 10–40 °C. Redox zoning shifted from oxic conditions towards nitrate and iron(III) reducing conditions at 25 and 40 °C and sulphate reducing conditions at 70 °C. This was attributed to (a) a temperature-related increase in microbial reduction activity, and (b) three times higher release of organic carbon from the sediment at 70 °C compared to the lower temperatures. The findings of this study predict that a temperature increase in the subsurface up to 25 °C and above can impair the usability of ground water as drinking and process water, by reducing metal oxides and thus possibly releasing heavy metals from the sediment. Generally, at 70 °C, where clear cation and organic carbon desorption processes were observed and sulphate reducing conditions could be achieved, a site-specific assessment of temperature effects is required, especially for long-term operations of subsurface heat storage facilities.  相似文献   

6.
Fluorine in coal is important because of not only its association with indicators of mineralization, but also environmental concerns relevant to the health of plants, animals and humans. In order to analyze the fluorine emission characteristics, this paper summarizes the laboratory data from a number of Chinese literatures of fluorine emission of coal and clay minerals for high-temperature heating. The range of temperature to which specimens have been exposed is room temperature to 1200 °C. The variation of fluorine emission has a significant increase with increasing temperature between the ranges 400–1200 °C, especially above 600 °C. Besides, environmental humidity has obvious influence on fluorine releasing.  相似文献   

7.
Aquifer thermal energy storage may result in increases in the groundwater temperature up to 70 °C and more. This may lead to geochemical and microbiological alterations in the aquifer. To study the temperature effects on the indigenous microbial community composition, sediment column experiments at four different temperatures were carried out and the effluents were characterized geochemically and microbiologically. After an equilibrium phase at groundwater temperature of 10 °C for 136 days, one column was kept at 10 °C as a reference and the others were heated to 25, 40 and 70 °C. Genetic fingerprinting and quantitative PCR revealed a change in the bacterial community composition and abundance due to the temperature increase. While at 25 °C only slight changes in geochemical composition and gene copy numbers for bacteria were observed, increasing concentrations of total organic carbon in the 40 °C column were followed by a strong increase in bacterial abundance. Thermophilic bacteria became dominant at 70 °C. Temporary sulfate reduction took place at 40 and 70 °C and this correlated with an increased abundance of sulfate-reducing bacteria (SRB). Furthermore, a coexistence of SRB and sulfur-oxidizing bacteria (SOB) at all temperatures indicated an interaction of these physiological groups in the sediments. The results show that increased temperatures led to significant shifts in the microbial community composition due to the altered availability of electron donors and acceptors. The interplay of SRB and SOB in sedimentary biofilms facilitated closed sulfur cycling and diminished harmful sulfur species.  相似文献   

8.
The paper presents materials on the fabric of the western, southwestern, and southern exocontact zones of the Khibina alkaline pluton and metavolcanic rocks of the Il’mozerskaya Formation of the Paleoproterozoic Imandra-Varzuga riftogenic structure. The volcanics of the Imandra-Varzuga structure were originally metamorphosed to the greenschist facies (at temperatures of ≥300°C and pressures of ≥2.0–2.5 kbar) and were afterward metamorphosed to the pyroxene-hornfels facies under the thermal effect the Khibina pluton with the development of a hornfels zone 150–400 m thick. According to their composition, the hornfelses are subdivided into three zones: inner, intermediate, and outer. The inner zone is up to 30 m thick and consists of hornfelses of clinopyroxene-plagioclase composition with olivine as a typomorphic mineral and with variable amounts of amphibole. The intermediate zone occurs at a distance of 30–200 m from the pluton, is separated from the inner zone by the olivine isograde, and consists of amphibole-clinopyroxene-plagioclase hornfelses. The outer zone, 200–400 m away from the contact of the pluton, is made of fine-grained melanocratic hornblende hornfelses. The thermal transformations of the metavolcanics involved the gradual replacement of their low-temperature mineral assemblage (actinolite + albite) by a higher temperature one (clinopyroxene + amphibole + andesinebytownite ± olivine). Our data on the chemical composition of the rock-forming minerals of the hornfelses indicate that the olivine is ferrohortonolite-fayalite, the clinopyroxene belongs to the augite-ferroaugite series, and occasional orthopyroxene grains (which were found only in the intermediate zone) are ferrohypersthene. The amphibole in the hornfelses of the intermediate zone and the outermost (farthest from the contact) part of the inner zone is edenite, a Ca amphibole. The amphibole in hornfelses near the contact is kataphorite of the Na-Ca amphibole group. The plagioclase composition generally corresponds to andesine and bytownite and is albite-oligoclase near the contact with the pluton. The hornfelses adjacent to the contact bear rare sanidine grains. The mineral thermo-and barometry of the hornfelses yielded temperatures of 700–640°C and pressures of 1–1.5 kbar. The temperature determined for the zone exactly at the contact was approximately 700°C, which corresponds to the initial temperature of the rocks in contact with the magma and is close to the crystallization temperature of the nepheline syenites of the Khibina pluton.  相似文献   

9.
Wang  Fei  Konietzky  Heinz  Frühwirt  Thomas  Dai  Yajie 《Acta Geotechnica》2020,15(8):2259-2275

The knowledge about thermo-mechanical properties of granite is still limited to some extent. Individual measurements are necessary to obtain reliable properties for specific granite types. A reliable numerical model of thermal cracking behaviours of granite exposed to extreme high temperatures (e.g. 800–1000 °C) is missing. In this study, the impact of temperature up to 1000 °C on physical, mechanical, and thermal properties as well as thermo-mechanical coupled behaviour of Eibenstock granite was investigated by laboratory testing and numerical simulations. The physical properties including mineral composition, density, P-wave velocity, and open porosity are measured to be temperature dependent. Uniaxial compression and Brazilian tests were carried out to measure uniaxial compressive strength (UCS), Young’s modulus, stress–strain relationship, and tensile strength of Eibenstock granite before and after thermal treatment, respectively. Thermal properties including specific heat, thermal conductivity, thermal diffusivity, and linear thermal expansion coefficient are also measured and found to be temperature dependent, especially the expansion coefficient which shows a steep increase around 573 °C as well as at 870 °C. The numerical simulation code FLAC3D was used to develop a numerical scheme to simulate the thermal-induced damage of granite at high temperatures. Statistical methods combined with real mineral composition were used to characterize the heterogeneity of granite. The numerical model is featured with reliable temperature-dependent parameters obtained from laboratory tests. It can well reproduce the laboratory results in form of thermal-induced micro- and macrocracks, as well as the stress–strain behaviour and the final failure pattern of Eibenstock granite after elevated temperatures up to 1000 °C. The simulation results also reveal that the thermal-induced microcracks are randomly distributed across the whole sample. Although most thermal-induced damages are tensile failures, shear failure begins to develop quickly after 500 °C. The obvious UCS reduction in granite due to heating is mainly caused by the increase in shear failure. The simulation also shows that the dominant impact of α–β quartz transition is widening pre-existing cracks rather than the formation of new microcracks.

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10.
The influence of the intrusion of basaltic dykes and sills was investigated on sandstones and siltstones of the Atane Formation (Turonian-Coniacian) from the Sarqaq area (Nûgssuaq peninsula, central West Greenland).In the unaltered rock sequence, the siltstones are dominated by kaolinite, quartz and feldspar. No cementation was observed. The sandstones which are prevalent in this formation are arkoses and lithic arkoses with quartz/feldspar ratios of about 1, with variable contents of rock fragments and with minor amounts of matrix. The matrix consists mainly of kaolinite, less frequently of illite-muscovite and smectite or interstratified illite-smectite. Cement minerals include calcite, Fe-calcite, both mainly in concretions, and subordinate Fe-oxide hydrates.The porosity of the sandstones and siltstones indicates a former maximum depth of burial of 1000 m in the Sarqaq region.Adjacent to thin dykes and sills (1–2 m) the above-described rocks are altered as follows. In sandstones albite (fibrous), quartzine, smectite, goethite were all formed at the expense of kaolinitic matrix, and aragonite cement. In siltstones, interstratified illite-smectite, illite, smectite and low-cristobalite replaced kaolinite. These minerals, especially smectite, exclude temperatures above 200°C; they were probably formed during a cooling period.Adjacent to thicker basalt intrusions—only sills, over 5 m thick, and no dykes are known from this area—the following alterations are observed. In sandstones two textural types of albite were formed in addition to: (1) fibrous albite mentioned above; (2) undulose lath-shaped albite; (3) coarse-twinned non-undulose replacement albite. Moreover, brownish luminescing undulose quartz, muscovite, chlorite, epidote, nontronite and anatase occur. In siltstones the mineral association muscovite-chlorite-pyrophyllite-albite occurs, suggesting temperatures in the range of 250–500°C. Additionally a 22–26 Å mixed-layer mineral (chlorite-muscovite?) formed. At the contacts of thick as well as thin basalt intrusions the detrital grains directly adjoining the basalt are partly fractured; potassium feldspar grains show also a chemical disintegration.The temperatures calculated by application of a cooling model are higher than those indicated by the mineral alterations observed. Convective heat transfer by pore water is suggested as an explanation.  相似文献   

11.
Rare-metal granites of Nuweibi and Abu Dabbab, central Eastern Desert of Egypt, have mineralogical and geochemical specialization. These granites are acidic, slightly peraluminous to metaaluminous, Li–F–Na-rich, and Sn–Nb–Ta-mineralized. Snowball textures, homogenous distribution of rock-forming accessory minerals, disseminated mineralization, and melt inclusions in quartz phenocrysts are typical features indicative of their petrographic specialization. Geochemical characterizations are consistent with low-P-rare metal granite derived from highly evolved I-type magma in the late stage of crystallization. Melt and fluid inclusions were studied in granites, mineralized veins, and greisen. The study revealed that at least two stages of liquid immiscibility played an important role in the evolution of magma–hydrothermal transition as well as mineral deposition. The early stage is melt/fluid case. This stage is represented by the coexistence of type-B melt and aqueous-CO2 inclusions in association with topaz, columbite–tantalite, as well as cassiterite mineral inclusions. This stage seems to have taken place at the late magmatic stage at temperatures between 450 °C and 550 °C. The late magmatic to early hydrothermal stage is represented by vapor-rich H2O and CO2 inclusions, sometimes with small crystallized silicic melt in greisen and the outer margins of the mineralized veins. These inclusions are associated with beryl, topaz, and cassiterite mineralization and probably trapped at 400 °C. The last stage of immiscibility is fluid–fluid and represented by the coexisting H2O-rich and CO2-rich inclusions. Cassiterite, wolframite ± chalcopyrite, and fluorite are the main mineral assemblage in this stage. The trapping temperature was estimated between 200 °C and 350 °C. The latest phase of fluid is low-saline, low-temperature (100–180 °C), and liquid-rich aqueous fluid.  相似文献   

12.
This study investigates the origin and chemical composition of the thermal waters of Platystomo and Smokovo areas in Central Greece as well as any possible relationships of them to the neighboring geothermal fields located in the south-eastern part of Sperchios basin. The correlations between different dissolved salts and the temperature indicate that the chemical composition of thermal waters are controlled by, the mineral dissolution and the temperature, the reactions due to CO2 that originates possibly by diffusion from the geothermal fields of Sperchios basin and the mixing of thermal waters with fresh groundwater from karst or shallow aquifers. Two major groups of waters are recognized on the basis of their chemistry: thermal waters of Na–HCO3–Cl type and thermal waters mixed with fresh groundwater of Ca–Mg–Na–HCO3 type. All thermal waters of the study area are considered as modified by water–rock interaction rainwater, heated in depth and mixed in some cases with fresh groundwater when arriving to the surface. Trace elements present low concentrations. Lithium content suggests discrimination between the above two groups of waters. Boron geochemistry confirms all the above remarks. Boron concentration ranges from 60 μg L?1 to 10 mg L?1, while all samples’ constant isotopic composition (δ11B ≈ 10 ‰) indicates leaching from rocks. The positive correlation between the chemical elements and the temperature clearly indicates that much of the dissolved salts are derived from water–rock interactions. The application of geothermometers suggests that the reservoir temperature is around 100–110 °C. Chalcedony temperatures are similar to the emergent temperatures and this is typical of convective waters in fault systems in normal thermal gradient areas.  相似文献   

13.
Mineralogical and colour changes of quartz sandstones by heat   总被引：1，自引：0，他引：1  
Seven German and three Hungarian monumental sandstones have been tested in laboratory conditions to analyse the effect of heat. The studied quartz sandstones have a wide-range of cements and grain-sizes including silica-, carbonate-, clay- and ferrous mineral—cemented varieties of fine-, medium- to coarse-grained types. Cylindrical specimens were heated up to 150, 300, 450, 600, 750 and 900°C in an oven. The mineralogical and textural changes were recorded and compared by using microscopy, XRD, DTA-DTG and SEM. Colours and colour differences (a*, b*, L* values) were also measured and evaluated. Colour changes are related to mineral transformations. The most intense colour change is caused by the oxidation of iron-bearing minerals to hematite that takes place up to 900°C. When temperature increases the green glauconite becomes brownish while the chlorite changes to yellowish at first. The colour of burnt sandstone is not a direct indicator of burning temperature, since there are sandstones in which the burnt specimens are lighter and less reddish than the natural ones. Porosity increase is related to micro-cracking at grain boundaries (above 600°C) and within the grains (at and above 750°C) and mineral transformations. The clay mineral structure collapses at different temperatures (kaolinite up to 600°C, chlorite above 600°C) and leads to a slight increase in porosity. The most drastic change is observed in calcite cemented sandstones where the carbonate structure collapses at 750°C and CaO appears at 900°C. Subsequently it is transformed to portlandite due to absorption of water vapour from the air. This leads to the disintegration of sandstone at room temperature a few days after the heat shock.Special issue: Stone decay hazards  相似文献   

14.
The Mediterranean Sea has been identified as one of the hotspots for climate change. Intense warming in the Mediterranean Sea may have strong implications for biological activity and ecosystem functioning. To elucidate the effects of warming on planktonic and benthic metabolism, we performed experiments under different increasing temperature regimes, ranging from three to six different temperatures. The lowest range of temperatures assessed was of 2.6 °C and the maximum was 7.5 °C. Our results suggest that a 6 °C warming of the Mediterranean waters may yield a mean increment in planktonic respiration rates of coastal communities of 24 %, higher than the mean increase expected for planktonic gross primary production (9 %). These results confirm earlier theories, and agree with previous experiments, of a higher increase in respiration rates than in primary production with warming, with the subsequent consequences for the carbon cycle, resulting in a negative feedback to climate warming, as ocean communities will capture less CO2.  相似文献   

15.
Information from a database, which was compiled and continuously updated by the authors of this paper and now includes information from 19500 publication on fluid and melt inclusions in minerals, is used to summarize results on the physicochemical formation parameters of hydrothermal Au, Ag, Pb, and Zn deposits. The database provides information on fluid inclusions in minerals from 970 Pb-Zn, 220 Au-Ag-Pb-Zn, and 825 Au-Ag deposits in various settings worldwide. Histograms for the homogenization temperatures of fluid inclusion are presented for the most typical minerals of the deposits. In sphalerite, most homogenization temperatures (1327 measurements) of fluid inclusions lie within the range of 50–200°C with a maximum at 100–200°C for this mineral from Pb-Zn deposits and within the range of 100–350°C (802 measurements) with a maximum at 200–300°C for this mineral from Au deposits. Data are presented on fluid pressures at Au (1495 measurements) and Pb-Zn (180 measurements) deposits. The pressure during the preore, ore-forming, and postore stages at these deposits ranged from 4–10 to 6000 bar. The reason for the high pressures during preore stages at the deposits is the relations of the fluids to acid magmatic and metamorphic processes. More than 70% of the fluid pressures values measured at Pb-Zn deposits lie within the range of 1–1500 bar. Au-Ag deposits are characterized by higher fluid pressures of 500–2000 bar (61% of the measurements). The overall ranges of the salinity and temperature of the mineral-forming fluid at Au-Ag (6778 measurements) and Pb-Zn (3395 measurements) deposits are 0.1–80 wt % equiv. NaCl and 20–800°C. Most measurements (～64%) for Au-Ag deposits yield fluid salinity <10 wt % equiv. NaCl and temperatures of 200–400°C (63%). Fluids at Pb-Zn deposits are typically more saline (10–25 wt % equiv. NaCl, 51% measurements) and lower temperature (100–300°C, 74% measurements). Several measurements of the fluid density fall within the range of 0.8–1.2 g/cm3. The average composition of volatile components of the fluids was evaluated by various techniques. The average composition of volatile components of fluid inclusions in minerals is calculated for hydrothermal W, Au, Ag, Sn, and Pb-Zn deposits, metamorphic rocks, and all geological objects. The Au, Ag, Pb, and Zn concentrations in magmatic melts and mineral-forming fluids is evaluated based on analyses of individual inclusions.  相似文献   

16.
This study reports the kinetic experimental results of albite in water and in KCI solution at 22 MPa in the temperature range of 25 to 400℃. Kinetic experiments have been carried out in an open flow-through reaction system (packed bed reactor). Albite dissolution is always incongruent in water at most temperatures, but becomes congruent at 300℃ (close to the critical point 374℃). At temperatures from 25 to 300℃, the incongruent dissolution of albite is reflected by the fact that sodium and aluminum are easily dissolved into water; from 300 to 400℃ it is reflected by silicon being more easily dissolved in water than Al and Na. Maximum albite dissolution rates in the flow hydrothermal systems have been repeatedly observed at 300℃, independent of flow rates.The kinetic experiments of albite dissolution in a KCl aqueous solution (0.1 mol KCl) indicate that the dissolution rate of albite increases with increasing temperature. Maximum silicon release rates of albite have been observed at 400℃, while ma  相似文献   

17.
Groundwater at the Azores archipelago is a strategic resource for the freshwater supply. Freshwater, mineral and thermal water discharges occur in the archipelago, and especially at the Fogo and Furnas volcanoes (São Miguel). These discharges provide data for case studies of groundwater chemistry from volcanic monitoring due to the stable composition of the sampled waters. The mineral and thermal discharges are mainly of sodium bicarbonate types and present a large range of temperatures, from cold springs to waters at about 90 °C. Some boiling discharges have a sulfate-dominated composition, suggesting a steam-heating mechanism. Geochemical studies on these mineral and thermal waters began in the 19th century. Data gathered since these earlier studies provide a baseline for pH, temperature, CO2 and major-element composition. Weekly measurements of pH and temperature also denote a rather stable behavior.  相似文献   

18.
Aquifer thermal energy storage in urban and industrial areas can lead to an increase in subsurface temperature to 70 °C and more. Besides its impacts on mineral and sorption equilibria and chemical reaction kinetics in an aquifer, temperature sensitively influences microbial activity and thus redox processes, such as sulphate reduction. Microorganism species can only operate within limited temperature ranges and their adaptability to temperature is a crucial point for the assessment of the environmental consequences of subsurface heat storage. Column experiments with aquifer sediment and tap water at 10, 25, 40, and 70 °C showed that under the constant addition of acetate sulphate reduction could be initiated after 26–63 pore volumes exchanged at all temperatures. Fastest initiation of sulphate reduction with the highest reduction rates was found at 40 °C. Maximum rate constants during experimental run-time were 0.56 h?1 at 40 °C and 0.33, 0.36, and 0.25 h?1 at 10 and, 25, and 70 °C, respectively. Hence, microbial activity was enhanced by a temperature increase to 40 °C but was significantly lowered at 70 °C. At 25 °C methane was found in solution, indicating the presence of fermenting organisms; at 10, 40, and 70 °C no methane production was observed. It could be shown that redox processes in an aquifer generally can adapt to temperatures significantly higher than in situ temperature and that the efficiency of the reduction process can be enhanced by temperature increase to a certain limit. Enhancement of sulphate reduction in an aquifer due to temperature increase could also allow enhanced degradation of organic ground water contaminants such as BTEX, where sulphate is an important electron acceptor.  相似文献   

19.
Temperature is one of the variables that influence the elasto-plastic behavior and integrity of rock outcrops. Fluctuations in temperature can trigger alteration of some of the mineral properties and impact the brittle-plastic transition. Initiation and propagation of thermally induced tension cracks tend to weaken most rock types. The principal goal of this study was to anticipate impacts of thermal stress-strain cycles on the dynamic response of representative rock units exposed in the Khewra Gorge of the Salt Range Punjab of Pakistan. Ten types of sedimentary rock units were sampled, including marl, dolomite, three types of limestone, and five different sandstones exhibiting varying characteristics in outcrop. Boulder specimens were collected from the field and transported to the laboratory to prepare 50 drill cores that could be subjected to thermal cycling between 50 and 200 °C in increments of 50 °C. Room temperature core samples were tested using an Erudite resonance frequency meter to measure their Q-factors and the resonance frequency (Fr) at an applied loading frequency of 7 KHz with 0.01 V output voltage. Results suggest that thermal cycling tends to reduce the dynamic Young’s modulus (Ed) and Q-factor. Other parameters, such as damping ratio (ξ), specific damping capacity (Ψ), and loss factor (?) appeared to increase with increasing temperature cycles, likely as a result of developing thermally induced tensile fractures. The resultant values of the null hypothesis (t-critical and t-stats) suggests that the null hypothesis can be discarded because there was no observable difference between the measured and expected values for the cores tested. The observations and data emanating from this study might be useful in designing low-level radioactive waste landfills, nuclear waste repositories, and deep underground excavations where the increased temperature could alter the mechanical behavior of the parent rock mass.  相似文献   

20.
Using the method of pyrolysis—gas chromatography, the composition of fluid inclusions in Brazilian carbonado and associating monocrystalline diamonds were investigated for the first time. Temperature trends were obtained for the composition of the released gas phase; based on this data, it was concluded that the diamonds include two generations of inclusions: those decrepitating at temperatures below 500°C and above 500°C. It was found that the fluid released from carbonado at high temperatures is anomalously enriched in carbon monoxide, which is strongly different from the characteristics of both the products of intracrustal mineral, rock, and ore formation and the results of crust—mantle interaction.  相似文献   

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