Abstract: Instrumental Neutron Activation Analysis (INAA) was done to determine the abundances of rare earth elements (REE) of 58 samples of Late Palaeozoic Carboniferous-Permian coals and related rocks in North China...Abstract: Instrumental Neutron Activation Analysis (INAA) was done to determine the abundances of rare earth elements (REE) of 58 samples of Late Palaeozoic Carboniferous-Permian coals and related rocks in North China. Detailed study of REE geochemistry shows that the ?REE of most coals studied in this paper is in a normal range between 30×10?6 and 80×10?6 with a mean of 56×10?6. The REE in the Taiyuan Formation in the northern part of North China are much richer than those in the southern part. This is due to the shorter distance to the source area in the north. Moreover, the ?REE is in positive correlation to coal ash, especially closely related to the content of clay minerals <2 μm in size. This reveals that most REE were carried by terrigenous clastic materials, especially fine clay minerals. In the coals the light REE (LREE) are much richer than the heavy REE (HREE), and the LREE/HREE ratio in coals generally varies from 2 to 8. The LREE/HREE ratio of high-ash, low-sulphur coals is higher than that of low-ash, high-sulphur coals, and is even higher in the roof and floor rocks, reaching 12 with the highest (up to 21) in pyrite concretions, which shows that the HREE have a stronger affinity to organic matter in a reducing environment influenced by seawater. Furthermore, Eu is generally depleted in coals. The REE chondrite-normalized distribution patterns are very similar in coals of the whole of North China. From the REE geochemical characteristics it can be concluded that during the formation of Late Palaeozoic Carboniferous-Permian coals in North China, the supply of terrigeneous materials remained quite stable. The ?REE in low-ash, high-sulphur coals is relatively low and the REE are mainly carried by fine-grained minerals and organic matter and a certain percentage of REE are adsorbed by organic matter; while the ?REE in high-ash, low-sulphur coals is higher and the REE are mainly present in detritus. The ?REE of magmatism-influenced coals is the highest, which suggests that the introduction of magmatic substances may increase the ?REE, thus causing the REE distribution patterns to show an abnormal feature. Moreover, some harmful elements such as U, W and As usually increase when the coals are influenced by magmatism.展开更多
The study of the creep properties of coal and its adjacent mudstone is very important for understanding the mechanism of delay outburst coal. The samples of delay outburst coal and its adjacent mudstone collected from...The study of the creep properties of coal and its adjacent mudstone is very important for understanding the mechanism of delay outburst coal. The samples of delay outburst coal and its adjacent mudstone collected from Yongshanqiao mine were used to carry out triaxial creep tests. The influence of confining pressure and axial compression on the creep test was analyzed. An accelerated creep model was constructed in parallel with a nonlinear viscous component and plastic component. It is connected with the traditional Burges creep model in series. A creep model which can describe the nonlinear viscoelastic-plastic creep model of rock was established and the corresponding creep equation was derived.According to the results of the creep test, the related parameters of the equation were fitted. The results show that, under the same confining pressure, instantaneous creep strain, creep strain of deceleration phase and constant rate creep of the coal and its adjacent mudstone are increased with an increase in the deviatoric stress. But at the same axial pressure, all of the above decrease with an increase of confining pressure. The duration time of the deceleration creep phase increases with the increase in the deviatoric stress. The theoretical values of the creep equation are in good agreement with the experimental results. It indicates that the creep properties of the delayed outburst coal and its adjacent mudstone can be well described by the creep model established in this paper.展开更多
文摘Abstract: Instrumental Neutron Activation Analysis (INAA) was done to determine the abundances of rare earth elements (REE) of 58 samples of Late Palaeozoic Carboniferous-Permian coals and related rocks in North China. Detailed study of REE geochemistry shows that the ?REE of most coals studied in this paper is in a normal range between 30×10?6 and 80×10?6 with a mean of 56×10?6. The REE in the Taiyuan Formation in the northern part of North China are much richer than those in the southern part. This is due to the shorter distance to the source area in the north. Moreover, the ?REE is in positive correlation to coal ash, especially closely related to the content of clay minerals <2 μm in size. This reveals that most REE were carried by terrigenous clastic materials, especially fine clay minerals. In the coals the light REE (LREE) are much richer than the heavy REE (HREE), and the LREE/HREE ratio in coals generally varies from 2 to 8. The LREE/HREE ratio of high-ash, low-sulphur coals is higher than that of low-ash, high-sulphur coals, and is even higher in the roof and floor rocks, reaching 12 with the highest (up to 21) in pyrite concretions, which shows that the HREE have a stronger affinity to organic matter in a reducing environment influenced by seawater. Furthermore, Eu is generally depleted in coals. The REE chondrite-normalized distribution patterns are very similar in coals of the whole of North China. From the REE geochemical characteristics it can be concluded that during the formation of Late Palaeozoic Carboniferous-Permian coals in North China, the supply of terrigeneous materials remained quite stable. The ?REE in low-ash, high-sulphur coals is relatively low and the REE are mainly carried by fine-grained minerals and organic matter and a certain percentage of REE are adsorbed by organic matter; while the ?REE in high-ash, low-sulphur coals is higher and the REE are mainly present in detritus. The ?REE of magmatism-influenced coals is the highest, which suggests that the introduction of magmatic substances may increase the ?REE, thus causing the REE distribution patterns to show an abnormal feature. Moreover, some harmful elements such as U, W and As usually increase when the coals are influenced by magmatism.
基金provided by the National Natural Science Foundation of China (Nos.41172138, 41472235, and 51474008)the Natural Science Foundation of Anhui Province (No.1508085QE89)
文摘The study of the creep properties of coal and its adjacent mudstone is very important for understanding the mechanism of delay outburst coal. The samples of delay outburst coal and its adjacent mudstone collected from Yongshanqiao mine were used to carry out triaxial creep tests. The influence of confining pressure and axial compression on the creep test was analyzed. An accelerated creep model was constructed in parallel with a nonlinear viscous component and plastic component. It is connected with the traditional Burges creep model in series. A creep model which can describe the nonlinear viscoelastic-plastic creep model of rock was established and the corresponding creep equation was derived.According to the results of the creep test, the related parameters of the equation were fitted. The results show that, under the same confining pressure, instantaneous creep strain, creep strain of deceleration phase and constant rate creep of the coal and its adjacent mudstone are increased with an increase in the deviatoric stress. But at the same axial pressure, all of the above decrease with an increase of confining pressure. The duration time of the deceleration creep phase increases with the increase in the deviatoric stress. The theoretical values of the creep equation are in good agreement with the experimental results. It indicates that the creep properties of the delayed outburst coal and its adjacent mudstone can be well described by the creep model established in this paper.
