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In order to improve the Hoek-Brown strength criterion not considering the influence of intermediate principal stress on rock strength, the evolutions of rock strength were investigated according to the results of the rock true triaxial compression test. The intermediate principal stress coefficient was introduced to quantify the effect on rock strength. Considering the relationships between the parameter of the Hoek-Brown strength criterion and the rock stress levels, the modified Hoek-Brown strength criterion for the true triaxial stress was then established with the Lagrange interpolation method. The spatial envelope characteristics of the modified strength criterion were analyzed. The best-fitting errors of seven rocks with true triaxial test results were finally compared with the three other three-dimensional strength criteria to verify the rationality of the modified strength criterion. The research results indicate that the rock strength increases gradually with the increase of minimum principal stress, and increases first and then decreases with the increase of intermediate principal stress, which presents a significant interval effect. The modified strength criterion not only has the advantage of the Hoek-Brown strength criterion in the nonlinear characteristics of the meridian plane but also describes the basic characteristics of rock strength in stress space. The spatial envelope surfaces for the modified strength criteria with the linear and quadratic interpolation are the non-equilateral hexagonal pyramidal surfaces and conical surfaces, which can meet the requirement of continuous smoothness in the tension-compression meridian plane interval. The modified strength criterion can better predict the true triaxial strength of rocks and reasonably reflect the influence of intermediate principal stress on the rock strength. The modified strength criterion with the quadratic interpolation improves the prediction accuracy of rock strength by about 1.2 to 2.0 times compared to the criterion with linear interpolation. The modified strength criterion has good agreement with the true triaxial test results of different hard and brittle rocks compared with other true triaxial strength criteria, which shows the applicability and reliability of the modified strength criterion.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the damage evolution of rock mode I crack, a method is proposed to solve the damage variable field in the crack tip region. In the experiment, a Brazilian half disk specimen with mode I prefabricated crack was used to carry out three-point bending loading and the strain field in the crack tip region was obtained by digital image correlation method and finite element method respectively. The objective function containing damage variables was established and the damage variables were solved by using the least square method. The results show that the damage field of crack tip can be obtained by using digital image correlation method and finite element method. The geometric characteristics and evolution of the localization zone of the crack tip damage field are consistent with the strain localization zone and are related to the crack propagation process. The length of localized zone of damage field can represent the length of fracture process zone, which can be used to analyze precursor of rock crack instability propagation. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to explore the similarities and differences between the mechanical properties and fracture evolution of rock-like materials and natural rocks during loading process, the mechanical characteristics and acoustic emission characteristics of limestone, sandstone and rock-like materials under uniaxial compression were studied by using rock pressure testing machine and full-waveform acoustic emission monitoring system. The results show that the limestone and sandstone fail instantaneously after reaching the peak stress, which is brittle failure. However, there is still residual strength after the peak stress of similar rock, which is plastic failure. In the former, the absence of low event rate of acoustic emission, which marks the precursor of the failure, will occur before the near failure, while in the latter, it is not apparent. The acoustic emission (AE) event rate of rocks is low before and then high, while that of similar rocks is 'high-low-high', and the corresponding AE energy rate shows a high degree of consistency. The distribution of acoustic emission bands is different in different deformation stages, reflecting the difference internal fracture evolution between the two. The research results provide a theoretical basis for distinguishing the failure characteristics of rock and rock-like materials in rock engineering. [ABSTRACT FROM AUTHOR]

BACKGROUND Fluorine is an essential trace element that exists in the natural environment, and its deficiency or excess in the environment can cause health problems. OBJECTIVES To summarize the research progress of sources of fluorine in the environment and to assess the risk to health. METHODS The sources of fluorine in the natural atmosphere, rocks, soils, water, and plants, were reviewed, and the factors affecting its form and content by the environment were analyzed, such as topography, rain leaching, soil parent material, soil pH, soil organic matter and geochemical behavior. RESULTS Fluorine has a wide range of sources. At present, more than 260 million people in the world have been affected by environmental problems caused by fluorine. Therefore, it is of great significance to carry out a health risk assessment. The common health risk assessment models of fluorine include Hazard Quotient and Hazard Index. Probabilistic methods are often used in risk analysis. At present, there are also applications of multi-channel exposure assessment methods to assess fluorine. The feasibility and limitations of traditional models were compared. CONCLUSIONS It is necessary to consider the uncertainty and sensitivity of the health risk assessment models, determine the fluorine enrichment pathway, improve the combined exposure assessment models, and consider the bioavailability of fluorine intake for health risk assessment of fluorine. The next step of research on health risk assessment of fluorine can use models to predict the risks of fluorine. It is still necessary to have a deep understanding of the source, occurrences, migration path and content influencing factors of fluorine to assess the health risks.

BACKGROUND The detection of trace mercury in rocks typically provides biased and non-reliable results because of the complex internal unit cell structure, incomplete hot water bath acid hydrolysis extraction, volatilization loss, and contact pollution. OBJECTIVES To establish a more effective method for the determination of trace mercury concentrations in rocks. METHODS Dual-channel atomic fluorescence spectrometry (AFS) and domestic solid sampling-cold atomic absorption spectrometry (AAS) were used to detect the total concentration of trace mercury in rocks. RESULTS Under the optimized conditions of dual-channel AFS, the samples were extracted in a boiling water bath with 80% aqua regia solution for 50min. The current was 30mA, the negative high voltage was 280V, the carrier gas flow was 600mL/min, and the shielding gas flow was 1000mL/min. The concentration range was 0.05-2μg/L, and the linear correlation coefficient was greater than 0.999. The sample weight was 0.2g, method detection limit was 0.285μg/kg, and relative standard deviation was 7.3%-15.3%. For domestic solid sampling-cold AAS, the sample was determined by direct injection without chemical digestion. The carrier gas flow was 180mL/min, pyrolysis process was conducted for 60s at 700℃. The concentration range was determined to be 0.05-5ng, and the linear correlation coefficient was greater than 0.999. The sample weight was 0.1g, method detection limit was 0.046μg/kg, and relative standard deviation was 1.3%-4.2%. CONCLUSIONS The solid sampling-cold AAS was found to be more effective than dual-channel AFS in terms of operation, detection limit, and stability. It is more suitable for the determination of trace mercury in rocks.

The durability of rock is not only related to its own properties, but also to the service environment in which it is located. This paper briefly introduces MDE method. Through a specific project, the residual mass percentage of rock in a certain design life is calculated, the service life of rock in the current service environment is quantified, and the properties of such rock are judged by taking into full consideration the nature of rock itself and the service environment. It is concluded that the residual mass percentage of such rocks calculated based on MDE method meets the use requirements after the designed service life, which can provide reference for the evaluation of rock durability in other projects. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to truly reveal the mechanism of rock deformation and failure and the nature of rock material damage, based on the analysis of rock material deformation law and mechanical characteristics, a rock damage constitutive model based on elastic energy release rate is established using the energy principle. Taking the damage variable as an internal variable that affected the change of rock performance, a new type of statistical damage constitutive model for rock is established based on the effective stress principle and statistical damage theory. It further improves the theoretical system of rock damage constitutive model and mades up for the shortcomings that traditional damage models cannot reasonably explain the causes of rock failure. The parameters of the damage model are determined using the rock test data, and the feasibility and applicability of the damage model are verified through a comparative analysis of the model curve and the test curve. The damage evolution model is substituted into the elastic energy-strain model to analyze the law of rock elastic energy change during loading. The results show that the model curve and the test curve almost coincide in the deformation phase before the peak, indicating that the damage model perfectly reflects the linear elastic deformation characteristics of the rock. The model curve and the test curve do not agree well at the post-peak stage, but they also have a good description of the nonlinear deformation law of the rock. The damage model also better reflectes the relationship between the accumulation and release of elastic energy and the damage and destruction of rocks, and the characteristics of the degree of rock damage increases with the increasing confining pressure. At the same time, in the initial loading stage, the damage variable of the rock increases with the increasing axial strain. This shows that under the load, the internal cracks in the rock gradually develop, so that the damage of the rock material is gradually accumulated. When the confining pressure reaches above 10 MPa, the damage-strain curves basically coincide. The growth rate of the damage-strain curve rises sharply at the moment of initial loading. When the strain of the rock is about 0.01%, the damage-strain curve changes from rapid growth to steady growth. Because the damage quickly accumulates near the peak stress point of the rock, the damage variable rapidly increases to 1 in value.

BACKGROUND The sampling weight can be as low as milligram level when the contents of rare earth elements in rock and soil samples are determined by inductively coupled plasma-mass spectrometry (ICP-MS). However, the size of 200 mesh samples requires 100mg to ensure representativeness, which makes it difficult for ICP-MS to make full use of its advantages of high sensitivity and small sampling volume. OBJECTIVES To establish the method for the determination of rare earth elements in ultra-fine rock and soil samples by ICP-MS with microwave digestion. METHODS A method was developed for the determination of rare earth elements in ultra-fine rock and soil samples by ICP-MS with microwave digestion. The ultra-fine rock and soil samples were prepared by the planetary superfine pulverizing machine with wet grinding. Some parameters influencing the preparation of ultra-fine rock and soil samples, including grinding method, grinding time and the proportion of grinding balls were optimized. Microwave digestion of ultrafine-grained rock and soil samples in a nitric acid-hydrofluoric acid-hydrogen peroxide solution system, the sampling amount was reduced to 5mg, the total acid amount was reduced to 0.25mL and the digestion time was reduced to 25 minutes. RESULTS The results indicated that the samples were best refined when the wet-milling was adopted with ethanol as a dispersant and the milling time was 10 minutes and 15 minutes for 200 mesh soil and rock samples, respectively. The material ratios were 7g materials, 500 grinding balls, 45mL dispersants for the preparation of ultra-fine soil samples, whereas 5g materials, 500 grinding balls, 45mL dispersants for the preparation of ultra-fine rock samples. The particle size distribution D95 of soil standard substance GBW07404 and GBW07447 can be as low as 7.51μm and 7.05μm, and the D95 of rock standard substance GBW07104 and GBW07121 can be 8.42μm and 8.30μm under the optimized conditions. Microwave digestion of ultrafine-grained rock sample GBW07104 in a nitric acid-hydrofluoric acid-hydrogen peroxide solution system, the sampling amount was reduced to 5mg, the total acid amount was reduced to 0.25mL, the digestion time was reduced to 25 minutes, and the measured value of rare earth elements was consistent with the certified value with the relative standard deviation is between 1.64% and 5.21%. CONCLUSIONS This method was used for the detection of rare earth elements in other ultra-fine standard materials (GBW07404, GBW07447 and GBW07121), which yielded the relative standard deviation of 0.17%-6.60%, meeting the first criterion of Geology and Minerals Laboratory Testing Quality Management Standards.

BACKGROUND: Fluorine is an essential trace element that exists in the natural environment, and its deficiency or excess in the environment can cause health problems. OBJECTIVES: To summarize the research progress of sources of fluorine in the environment and to assess the risk to health. METHODS: The sources of fluorine in the natural atmosphere, rocks, soils, water, and plants, were reviewed, and the factors affecting its form and content by the environment were analyzed, such as topography, rain leaching, soil parent material, soil pH, soil organic matter and geochemical behavior. RESULTS : Fluorine has a wide range of sources. At present, more than 260 million people in the world have been affected by environmental problems caused by fluorine. Therefore, it is of great significance to carry out a health risk assessment. The common health risk assessment models of fluorine include Hazard Quotient and Hazard Index. Probabilistic methods are often used in risk analysis. At present, there are also applications of multi - channel exposure assessment methods to assess fluorine . The feasibility and limitations of traditional models were compared. CONCLUSIONS: It is necessary to consider the uncertainty and sensitivity of the health risk assessment models, determine the fluorine enrichment pathway, improve the combined exposure assessment models, and consider the bioavailability of fluorine intake for health risk assessment of fluorine. The next step of research on health risk assessment of fluorine can use models to predict the risks of fluorine. It is still necessary to have a deep understanding of the source, occurrences, migration path and content influencing factors of fluorine to assess the health risks. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: The detection of trace mercury in rocks typically provides biased and non - reliable results because of the complex internal unit cell structure, incomplete hot water bath acid hydrolysis extraction, volatilization loss, and contact pollution. OBJECTIVES: To establish a more effective method for the determination of trace mercury concentrations m rocks. METHODS: Dual - channel atomic fluorescence spectrometry ( AFS) and domestic solid sampling - cold atomic absorption spectrometry (AAS) were used to detect the total concentration of trace mercury in rocks. RESULTS: Under the optimized conditions of dual - channel AFS, the samples were extracted in a boiling water bath with 80% aqua regia solution for 50min. The current was 30mA, the negative high voltage was 280V, the carrier gas flow was 600m1/ min, and the shielding gas flow was lOOOml/ min. The concentration range was 0. 05 - 2µ.g/L, and the linear correlation coefficient was greater than 0. 999. The sample weight was 0. 2g, method detection limit was 0. 285 µg/kg, and relative standard deviation was 7. 3 % - 15. 3 % . For domestic solid sampling - cold AAS, the sample was determined by direct injection without chemical digestion. The carrier gas flow was 180m1/min, pyrolysis process was conducted for 60s at 700°C. The concentration range was determined to be 0. 05 - 5ng, and the linear correlation coefficient was greater than 0. 999. The sample weight was 0. 1 g, method detection limit was 0. 046µ.g/kg, and relative standard deviation was 1. 3% - 4. 2%. CONCLUSIONS: The solid sampling - cold AAS was found to be more effective than dual - channel AFS in terms of operation, detection limit, and stability. It is more suitable for the determination of trace mercury in rocks. [ABSTRACT FROM AUTHOR]

In order to explore the propagation and penetration law of non-coplanar overlapping fractures, a computational model with noncopaanar overlapping double fractures is established based on damage theory. The crack propagation process under uniaxial compression is described. The rationality of numerical simulation is vented by comparison with the experimental results. The stress tram relationship is explained. The crack difference of different inclination angle is explained from a mesa-view point of VIEW. Finally, the mechanism of wing crack is deduced based on fracture mechanics theory. The results show that the crack tip produces "wing-shaped crack at the crack tip, the stress-strain curve with coplanar no-overlapping cracks presents three typical stages: elastic stage, damage stage and failure stage. the number of acoustic emission events in the elastic stage less, the number of acoustic emission events on the damage stage Increases gradually, and the failure concentration occurs in the failure stage; for the case of smaller fracture dip angle, the maximum tensile stress occurs near the crack tip,not at the crack tip. [ABSTRACT FROM AUTHOR]

BACKGROUND Beijing is a typical geographical distribution area of selenium deficiency. However, some research results in recent years indicate that the soils in some areas reaches the level of selenium enrichment. It is important to study the characteristics of selenium distribution in these areas for the research of a selenium-rich environment in Beijing and the development of selenium-rich land resources. OBJECTIVES To discuss the characteristics of selenium content in soil and crops, the source of selenium and the relationship between selenium in soil and other elements such as carbon, iron and phosphorus, and to evaluate the safety of selenium-rich land. METHODS Samples of 1297 topsoil, 25 sets of corn and corresponding root soil and 15 rock samples were collected from an eco-conserving division of the Daqinghe River watershed. The content of selenium in these samples was determined by atomic fluorescence spectrometry. Methods of correlation analysis and multivariate statistical analysis and GIS technology were used to study the characteristics of selenium content in soil and crops, the source of selenium enrichment, and the relationship between soil selenium and other elements such as carbon, nitrogen, phosphorus and sulfur, and the safety of selenium-rich land was evaluated. RESULTS The results showed that the soil selenium content ranged from 0.055 to 0.465mg/kg and that the background value was 0.257mg/kg, which show selenium-rich characteristics. 360.4km2 selenium-rich land resources was identified. The selenium content of corn ranged from 0.028 to 0.70mg/kg, and the geometric mean was 0.20mg/kg. 80% of the corn samples were selenium-rich products. The selenium-rich soil and the selenium-rich crops had the same spatial distribution, which indicated that the soil was an important source of selenium in crops. CONCLUSIONS Geological background and soil parent material are the key control factors affecting the distribution of selenium-rich land resources. Dark rock series of fluvial deposition are a crucial source of selenium in soil. The overall environmental quality of selenium-rich land is clean and safe, and only 0.2% of the area (3.23km2) contains soil heavy metal (Cd, Hg, Pb) content, which exceeds the level of risk management control. Due to these findings, attention needs to be paid during selenium-rich land development.

BACKGROUND Polymerized silicic acid cannot be quantitatively complexed with molybdate in geological sample, therefore the silicon is determined by silicon-molybdenum blue colorimetric spectrophotometry. The key of this method is how to digest the solid sample to prepare a solution and ensure that the silicic acid occurs as a single molecule. OBJECTIVES To completely digest the geological samples by high-pressure acid digestion without loss of silicon and polymerization of silicic acid. To improve the stability of silicon-molybdenum yellow by adding a stabilizing agent. METHODS Hydrofluoric acid-nitric acid was used to digest the geological samples, so that the silicon in the sample was completely converted into fluorosilicic acid and was stably present in the solution. Boric acid and ammonium molybdate were added to make the excess hydrofluoric acid and boric acid to form stable BF4- dosing ion, which replaced the evaporation and removal of hydrofluoric acid, thus avoiding the volatilization loss of silicon and fluoride ions converted into gaseous SiF4 during the acid removal process. Under the action of ammonium molybdate, silicon was fully converted into silicon molybdenum heteropolyacids. In the color development process, the stability of silicon-molybdenum yellow was significantly improved by adding acetone, and the absorbance was increased to some extent, thereby improving the color development effect of silicon by silicon-molybdenum blue pectrophotometry. RESULTS The method avoided the problem that the silicic acid was easy to be polymerized during the acidification process when using the conventional alkali fusion digestion. A large amount of flux was introduced to cause a high blank. The validity of the method was evaluated by analyses of rock, soil, sediment and quartzite reference materials. The results of SiO2 were in good agreement with certified values and the relative standard deviation (n=10) was less than 1%. CONCLUSIONS This method is suitable for the rapid and accurate analysis of silica in common geological samples.

BACKGROUND Traditional inductively coupled plasma-mass spectrometry (ICP-MS) determination of trace elements such as Ag and Cd in geochemical samples is seriously affected by the matrix effect and multiple polyatomic ions, making it difficult to measure these elements accurately. OBJECTIVES To compare the results of ICP-MS standard mode (STD) and kinetic energy discrimination mode (KED), and determine the valid determination modes of each element. METHODS The samples were digested by HNO3-HF-HClO4, and the residue was dissolved in aqua regia. Under the KED mode, the isotopes with less interference were selected as the determination isotopes. Rh was used as the internal standard element to correct the signal drift, and the sample solution was diluted by 1000. Under these conditions, the matrix effect was minimized. RESULTS The productivity of matrix elements such as Zr and Nb oxides was reduced, and the interference of oxides on Ag and Cd was minimized under the KED mode. The KED mode improved the signal-to-noise ratio and reduced the detection limits of this method with Ag and Cd, detection limits of 0.004mg/kg and 0.005mg/kg, respectively. The detection limits of the other 12 elements were also lower than those of 76 element analysis schemes in a multi-objective geochemical survey. The accuracy of determination of trace elements was significantly better than that of the STD mode. CONCLUSIONS The method has been verified by the first-class national reference material and the analytical results are in good agreement with the certified values. The method provides high-quality data for exploration geochemistry.

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BFS and XSBRI,were used as mud cake curing agent, and the influence of curing agent compound on the compressive strength of mud cake,vas studied. The interface cementation mechanism of mud cake and rock,vas studied by modern analysis method. The results showed that the combined use of BFS and XSBRI had a synergistic effect on the curing of mud cake and could obviously improve the compressive strength of mud cake. The - COO absorption peak in the mud cakes modified by the curing agent can be seen clearly by using FTIR. This indicated that XSBRI participated in the reaction during the curing process of mud cake. XRD analysis indicated that hydration products are formed in mud cake, such as CaAL2Si2O8 • '1H20 and Ca(Si04 )2 ( OH)2,. The SEM diagram and EDS analysis of mud cake showed that the netlike hydration products are filled in the clay minerals, and the latex covered the surface of mud cake and rock, it is realized the integrating cementation of mud cake and rock. The study showed that the combination of BFS and XSBRI using as mud cake curing agent can be helpful to improve the cementation quality of the interface between mud cake and rock. [ABSTRACT FROM AUTHOR]

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Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the ability of profile control and water shutoff ? carboxylic acid polymer microemulsion was prepared by free radical polymerization with the styrene ? butyl acrylic acid，acrylamide，methacrylic acid asmonomers and the polyvinyl alcohol as dispersing agent. The polymer microemulsion was characterized by infrared spectroscopy ? transmission electron microscope and scanning electron microscope. The sealing performance of polymer microemulsion in porous rock media was investigated by core sealing evaluation experiment. The results show that the highest water blocking rate is 95. 49 %，he lowest is 93. 03 %. The water blocking rates are all above 90%. Moreover,the highest oil blocking rate is 4. 96% and the lowest is 3. 59%. The oil blocking rates are all less than 5%. The results show that the carboxylic acid polymer microemulsion have good sealing performances for porous rock media. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: The sampling weight can be as low as milligram level when the contents of rare earth elements in rock and soil samples are determined by inductively coupled plasma-mass spectrometry (ICP-MS). However, the size of 200 mesh samples requires 100mg to ensure representativeness, which makes it difficult for ICP-MS to make full use of its advantages of high sensitivity and small sampling volume. OBJECTIVES: To establish the method for the determination of rare earth elements in ultra-fine rock and soil samples by ICP-MS with microwave digestion. METHODS: A method was developed for the determination of rare earth elements in ultra-fine rock and soil samples by ICP-MS with microwave digestion. The ultra-fine rock and soil samples were prepared by the planetary superfine pulverizing machine with wet grinding. Some parameters influencing the preparation of ultra-fine rock and soil samples, including grinding method, grinding time and the proportion of grinding balls were optimized. Microwave digestion of ultrafine-grained rock and soil samples in a nitric acid-hydrofluoric acid-hydrogen peroxide solution system, the sampling amount was reduced to 5mg, the total acid amount was reduced to 0.25mL and the digestion time was reduced to 25 minutes. RESULTS: The results indicated that the samples were best refined when the wet-milling was adopted with ethanol as a dispersant and the milling time was 10 minutes and 15 minutes for 200 mesh soil and rock samples respectively. The material ratios were 7g materials, 500 grinding balls, 45mL dispersants for the preparation of ultra-fine soil samples, whereas 5g materials, 500 grinding balls, 45mL dispersants for the preparation of ultra-fine rock samples. The particle size distribution D95 of soil standard substance GBW07404 and GBW07447 can be as low as 7.51μm and 7.05μm, and the D95 of rock standard substance GBW07104 and GBW07121 can be 8.42μm and 8.30μm under the optimized conditions. Microwave digestion of ultrafine-grained rock sample GBW07104 in a nitric acid-hydrofluoric acid-hydrogen peroxide solution system, the sampling amount was reduced to 5mg, the total acid amount was reduced to 0.25mL, the digestion time was reduced to 25 minutes, and the measured value of rare earth elements was consistent with the certified value with the relative standard deviation is between 1.64% and 5.21%. CONCLUSIONS: This method was used for the detection of rare earth elements in other ultra-fine standard materials (GBW07404, GBW07447 and GBW07121), which yielded the relative standard deviation of 0.17%-6.60%, meeting the first criterion of Geology and Minerals Laboratory Testing Quality Management Standards. [ABSTRACT FROM AUTHOR]

The study of crack propagation through the cracked rock specimen is an important research direction of rock mechanics and geotechnical engineering.In this paper, a single axis compression test of a class of rock samples with two non-parallel cracks is carried out by using the numerical simulation software PFC2D.By means of statistical crack model, two kinds of coalescence modes are found, which are different from the modes of two parallel cracks.The two crack coalescences occurred when the origin inclined crack and another crack have the overlap part in the horizontal direction.From the mechanical response of the specimen, the peak stress of the specimen is the largest when the horizontal cracks are in the same level and the horizontal cracks located in below or above of the origin inclinedcrack, and the peak stress of the two sides are approximately symmetric.The coalescence of cracks occurred in the stress has reached or not reached its peak value, and the number of the micro-cracks changes regularly when the stress and strain curves of the specimens are from the plastic to the failure of the specimens.The coalescences of cracks and the number of micro-cracks can predict or reflect the failure of the specimen to a certain extent.By the laboratory tests, we found the same coalescence modes that exist in the numerical simulation and it demonstrates the feasibility of numerical simulation.

Currently,the damage constitutive model based on D-P（Drucker-Prager） criterion of rock has occupied dominant position in the field of damage constitutive model of rock.its advantages have become increasingly prominent.This paper mainly analyzes the results of the experimental data based on Drucker-Prager Criterion and finds some fatal errors.Poisson’ratio is key factor in it.Poisson’ratio of rock is variable value from the experimental observation.Since the Poisson’s ratio is used in the full damage constitutive model,We propose a new conception of"quasi-poisson’ratio",derived the formula of quasiPoisson’s ratio and introduce it to the constitutive model of rock based on Drucker-Prager Criterion in order to revise it.The new modified model is a new breakthrough for numerical analysis and software application.We believe the conception of "QuasiPoisson’Ratio"will lead to many aspects of the improvements in rock mechanics and has long-term meanings.

BACKGROUND:Beijing is a typical geographical distribution area of selenium deficiency. However, some research results in recent years indicate that the soils in some areas reaches the level of selenium enrichment. It is important to study the characteristics of selenium distribution in these areas for the research of a selenium-rich environment in Beijing and the development of selenium-rich land resources. OBJECTIVES:To discuss the characteristics of selenium content in soil and crops, the source of selenium and the relationship between selenium in soil and other elements such as carbon, iron and phosphorus, and to evaluate the safety of selenium-rich land. METHODS:Samples of 1297 topsoil, 25 sets of corn and corresponding root soil and 15 rock samples were collected from an eco-conserving division of the Daqinghe River watershed. The content of selenium in these samples was determined by atomic fluorescence spectrometry. Methods of correlation analysis and multivariate statistical analysis and GIS technology were used to study the characteristics of selenium content in soil and crops, the source of selenium enrichment, and the relationship between soil selenium and other elements such as carbon, nitrogen, phosphorus and sulfur, and the safety of selenium-rich land was evaluated. RESULTS:The results show that the soil selenium content ranged from 0.055 to 0.465mg/kg and that the background value was 0.257mg/kg, which show selenium-rich characteristics. 360.4km2 selenium-rich land resources was identified. The selenium content of corn ranged from 0.028 to 0.70mg/kg, and the geometric mean was 0.20mg/kg. 80% of the corn samples were selenium-rich products. The selenium-rich soil and the selenium-rich crops had the same spatial distribution, which indicates that the soil is an important source of selenium in crops. CONCLUSIONS:Geological background and soil parent material are the key control factors affecting the distribution of selenium-rich land resources. Dark rock series of fluvial deposition are a crucial source of selenium in soil. The overall environmental quality of selenium-rich land is clean and safe, and only 0.2% of the area (3.23km2) contains soil heavy metal (Cd, Hg, Pb) content, which exceeds the level of risk management control. Due to these findings, attention needs to be paid during selenium-rich land development. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When determining the ratio of cadmium isotopes in rock, problems of low cadmium content and interference of isotopes (106Pd, 108Pd, 110Pd, 112Sn, 113In, 114Sn and 116Sn) were discovered. However, the existing separation methods have high chemical yield for cadmium but low removal rate for isotopic. Therefore, a separation and purification method with high yield for cadmium and high removal force for palladium and stannum is necessary. A N256-N256-P204 three-column separation method was developed for separation and purification of cadmium in rocks. Verified by standard rock samples,the recovery of Cd is more than 99% and the removal factor of Pd and Sn is more than 4.0 x 10³. The separation process meets the requirements of isotope ratio determination of trace cadmium in rocks, and is especially suitable for the isotope ratio measurement of cadmium in some samples with unknown Pd and Sn isotope abundance. [ABSTRACT FROM AUTHOR]

BACKGROUND: Traditional Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) determination of trace elements such as silver and cadmium in geochemical samples is seriously affected by the matrix effect and multiple polyatomic ions, making it difficult to measure these elements accurately. OBJECTIVES:To compare the results of ICP-MS standard mode (STD) and kinetic energy discrimination mode (KED), and determine the valid determination modes of each element. METHODS: The samples were digested by HNO3-HF-HClO4, and the residue was dissolved in aqua regia. Under the KED mode, the isotopes with less interference were selected as the determination isotopes. Rh was used as the internal standard element to correct the signal drift, and the sample solution was diluted by 1000. Under these conditions, the matrix effect was minimized. RESULTS: The productivity of matrix elements such as Zr and Nb oxides was reduced, and the interference of oxides on Ag and Cd was minimized under the KED mode. The KED mode improved the signal-to-noise ratio and reduced the detection limits of this method with Ag and Cd, detection limits of 0.004mg/kg and 0.005mg/kg, respectively. The detection limits of the other 12 elements were also lower than those of 76 element analysis schemes in a multi-objective geochemical survey. The accuracy of determination of trace elements was significantly better than that of the STD mode. CONCLUSIONS: The method has been verified by the first-class national reference material and the analytical results are in good agreement with the certified values. The method provides high-quality data for exploration geochemistry. [ABSTRACT FROM AUTHOR]

In order to explore the failure mode of rock under explosive load in blasting engineering, six groups of rock specimens with 74 mm diameter and 0.5 aspect ratio were tested with Hopkinson compression bar test apparatus. The test results show that the strain rate effect of rock material is very sensitive under dynamic impact loading. As long as the strain rate changes very little, the compressive strength will increase significantly. The strain rate of rock specimen is not a fixed value, but changes continuously with time. The damage form of rock failure is mainly caused by the lateral tensile strain. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on typical characteristics and teaching features of exploration technology and engineering specialty, a comprehensive experiment of rock physics was designed to investigate the effects of pressure, temperature and fluid on velocities of the rock. The rock that was placed in a reactor with loading axial pressure and confining pressure and heated by the heating ring was used to measure P-and S-wave velocities under high temperature and high pressure. The results indicated that P-and S-wave velocities of the rock increase with pressure increase and decrease with temperature increase, and P-wave velocity of water saturated rock is higher than that of gas saturated rock while S-wave velocity of water saturated rock is less than that of gas saturated rock. This exploratory research will help students to understand theoretical knowledge of the textbooks, and cultivate their practical abilities and innovation abilities. [ABSTRACT FROM AUTHOR]

The accuracy of the certified values of the national reference materials plays an important role in instrument calibration, and therefore quality control for analysis data. In order to test the accuracy of the certified values of the Chinese National Standard Reference Materials, 36 trace elements were determined for 18 National Standard Reference Materials of rock (from GBW 07103 to GBW 07125), 19 National Standard Reference Materials of sediment (from GBW 07301 to GBW 07318) and 19 National Standard Reference Materials of soil (from GBW 07401 to GBW 07430) by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). These National Standard Reference Materials were digested by using the pressurized acid digestion technique. The relative standard deviation (RSD) of most trace elements in these materials were typically better than 10%, except for Ni, Cr, Pb, Co, Cu, Sc, Yb and Lu in several reference materials. Most of the results were consistent with the certified values in the literature, and with a relative error of less than 10%. Results given here indicate that a few certified values of some reference materials should be revised. In addition, content values of some trace elements in the National Standard Reference Materials of sediment or National Standard Reference Materials of soil, such as Ni for GBW 07306, Be, Hf and Ta for GBW 07313, Li and Be for GBW 07314, Hf and Ta for GBW 07409, GBW 07410 and GBW 07411, Gd and Ta for GBW 07426 are provided here.

The physical and mechanical parameters of rock are the basic data for numerical simulation, similar simulation, key layer judgment, roof classification, support selection. Therefore, the test drilling holes were drilled from the ground to the floor of coal seam in the coal mine of the Bulianta, Daliuta and Buertai. Brazil splitting, uniaxial compression and three axis compression tests were earned out. Finally, the parameters of density, RQD value, tensile strength, compressive strength, elastic modulus, cohesion and internal friction angle in different sedimentary periods were analyzed. The results indicate that the strata of three test mines can be divided into eight depositional periods, cretaceous and Jurassic diazepam group, Jurassic Zhiluo formation, Jurassic Yanan group 1-2 coal Jurassic Yanan group 2-2 coal, Jurassic Yanan group siltstone, Jurassic Yanan group 4 coal and at the bottom of Jurassic Yanan group,respectively. The sandstone is the main rock in the strata of Shendong coal field, especially in Cretaceous, sandy mudstone and mudstone did not appear. With the increase of deposition time,the density of the rock has an increasing trend. However,the increase is not obvious. The tensile strength, compressive strength, elastic modulus and cohesion of the rock show a positive relationship with the deposition time. But there is no significant relationship among the RQD value,the internal friction angle and the deposition time. The deposition time has great influence on the mechanical parameters of the rock. The effect of deposition time on the tensile strength of mean-grained sandstone is the largest. The maximum value is 31.2 times of the minimum value. The effect of deposition time on the compressive strength and elastic modulus of mean-grained sandstone is the largest. The maximum value of compressive strength is 12. 4 times of the minimum value. The maximum value of elastic modulus is 32. 8 times of the minimum value. The physical and mechanical parameters of lock m the Cretaceous and Jurassic diazepam group are much smaller than other sedimentary periods. [ABSTRACT FROM AUTHOR]