Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nannin...Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.展开更多
Ventilation system is significant in underground metal mine of alpine region.Reasonable evaluation of ventilation effectiveness will lead to a practical improvement for the maintenance and management of ventilation sy...Ventilation system is significant in underground metal mine of alpine region.Reasonable evaluation of ventilation effectiveness will lead to a practical improvement for the maintenance and management of ventilation system.However,it is difficult to make an effective evaluation of ventilation system due to the lack of classification criteria with respect to underground metal mine in alpine region.This paper proposes a novel evaluation method called the cloud model-clustering analysis(CMCA).Cloud model(CM)is utilized to process collected data of ventilation system,and they are converted into cloud descriptors by CM.Cloud similarity(CS)based Euclidean distance(ED)is proposed to make clustering analysis of assessed samples.Then the classification of assessed samples will be identified by clustering analysis results.A case study is developed based on CMCA.Evaluation results show that ventilation effectiveness can be well classified.Moreover,CM is used alone to make comparison of evaluation results obtained by CMCA.Then the availability and validity of CMCA is verified.Meanwhile,difference of CS based ED and classical ED is analyzed.Two new clustering analysis methods are introduced to make comparison with CMCA.Then the ability of proposed CMCA to meet evaluation requirements of ventilation system is verified.展开更多
The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensi...The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensively developed in this HP belt. Compared with normal mid-ocean ridge basalt(N-MORB), the high-pressure veins and host rocks are enriched in light rare earth elements(LREE) and incompatible elements. But high-pressure veins show a larger variation than host rocks in total REE abundance. On the trace element spidergram, all the samples are enriched in incompatible elements and show strong positive Pb anomaly relative to N-MORB. The array tendency lines of plots of the HP rocks have apparent slopes on diagram of m(Sr) vs m(Sr)/m(Zr), m(Li) vs m(Li)/m(Y) and (m(Ce)) vs m(Ce)/m(Pb), which indicates that the enrichment in LREE and incompatible elements relative to N-MORB of the HP-metamorphic rocks from western Tianshan is not attributed to magma evolution process of the protolith. High field strength elements, such as Nb, Ta, Ti, Zr and Hf, do not show negative anomaly relative to N-MORB, which is dissimilar to that of island arc basalts. Therefore, the enrichment in LREE and incompatible elements of the HP rocks is not attributed to the enrichment of the source of the protolith. The mass ratios of Rb to Ba, Ce to Pb, Nb to U and Ta to U of high-pressure veins and host rocks are intermediate of mid-ocean ridge basalt or oceanic island basalt and continental crust. The fluids in western Tianshan paleosubduction zones are mixtures of two sources, dehydration or devolatilization of host rocks and of subducted sediments.展开更多
High-pressure(HP)veins were extensively developed in western Tianshan high-pressure(HP)metamorphic belt.The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids.Anal...High-pressure(HP)veins were extensively developed in western Tianshan high-pressure(HP)metamorphic belt.The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids.Analytical data show that the immediately adjacent host-rocks of the studied HP vein are eclogites and gradually turned into blueschist as the distance from the veins increases,which indicates that the vein-forming fluid was derived from adjacent host-rocks;the boundaries between the vein and the host-rocks are sharp,which indicates that the fracture of the host-rocks is brittle during the vein-forming process.It is suggested that this type of HP veins is precipitated from the liquid formed by the dehydration of the host-rocks during the prograde metamorphism from blueschist to eclogite facies,which results in hydrofracturing of the rocks and provides the space for the vein to precipitate.The width of the eclogite-facies host-rocks is usually 1-2 cm,which provides the direct evidence that the fluid flow is on centimeter-scale.展开更多
For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element an...For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1) the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2) the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually;however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m) in the scope of all filling height.展开更多
To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with...To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.展开更多
文摘Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.
基金Project(2018YFC0808404)supported by National Key Research and Development Program of China。
文摘Ventilation system is significant in underground metal mine of alpine region.Reasonable evaluation of ventilation effectiveness will lead to a practical improvement for the maintenance and management of ventilation system.However,it is difficult to make an effective evaluation of ventilation system due to the lack of classification criteria with respect to underground metal mine in alpine region.This paper proposes a novel evaluation method called the cloud model-clustering analysis(CMCA).Cloud model(CM)is utilized to process collected data of ventilation system,and they are converted into cloud descriptors by CM.Cloud similarity(CS)based Euclidean distance(ED)is proposed to make clustering analysis of assessed samples.Then the classification of assessed samples will be identified by clustering analysis results.A case study is developed based on CMCA.Evaluation results show that ventilation effectiveness can be well classified.Moreover,CM is used alone to make comparison of evaluation results obtained by CMCA.Then the availability and validity of CMCA is verified.Meanwhile,difference of CS based ED and classical ED is analyzed.Two new clustering analysis methods are introduced to make comparison with CMCA.Then the ability of proposed CMCA to meet evaluation requirements of ventilation system is verified.
基金Preoject(2001CB409803) supported by the National Key Fundamental Research and Development Program of China
文摘The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensively developed in this HP belt. Compared with normal mid-ocean ridge basalt(N-MORB), the high-pressure veins and host rocks are enriched in light rare earth elements(LREE) and incompatible elements. But high-pressure veins show a larger variation than host rocks in total REE abundance. On the trace element spidergram, all the samples are enriched in incompatible elements and show strong positive Pb anomaly relative to N-MORB. The array tendency lines of plots of the HP rocks have apparent slopes on diagram of m(Sr) vs m(Sr)/m(Zr), m(Li) vs m(Li)/m(Y) and (m(Ce)) vs m(Ce)/m(Pb), which indicates that the enrichment in LREE and incompatible elements relative to N-MORB of the HP-metamorphic rocks from western Tianshan is not attributed to magma evolution process of the protolith. High field strength elements, such as Nb, Ta, Ti, Zr and Hf, do not show negative anomaly relative to N-MORB, which is dissimilar to that of island arc basalts. Therefore, the enrichment in LREE and incompatible elements of the HP rocks is not attributed to the enrichment of the source of the protolith. The mass ratios of Rb to Ba, Ce to Pb, Nb to U and Ta to U of high-pressure veins and host rocks are intermediate of mid-ocean ridge basalt or oceanic island basalt and continental crust. The fluids in western Tianshan paleosubduction zones are mixtures of two sources, dehydration or devolatilization of host rocks and of subducted sediments.
基金Project(2001CB409803)supported by the Major State Basic Research Development Program of China
文摘High-pressure(HP)veins were extensively developed in western Tianshan high-pressure(HP)metamorphic belt.The HP vein and host-rocks were analyzed by electronic microprobe to trace the origin of vein-forming fluids.Analytical data show that the immediately adjacent host-rocks of the studied HP vein are eclogites and gradually turned into blueschist as the distance from the veins increases,which indicates that the vein-forming fluid was derived from adjacent host-rocks;the boundaries between the vein and the host-rocks are sharp,which indicates that the fracture of the host-rocks is brittle during the vein-forming process.It is suggested that this type of HP veins is precipitated from the liquid formed by the dehydration of the host-rocks during the prograde metamorphism from blueschist to eclogite facies,which results in hydrofracturing of the rocks and provides the space for the vein to precipitate.The width of the eclogite-facies host-rocks is usually 1-2 cm,which provides the direct evidence that the fluid flow is on centimeter-scale.
基金Project(200911MS01) supported by the Scientific Research Fund of Guangxi Provincial Education Department, China Project (XBZ100126) supported by the Scientific Research Foundation of Guangxi University, China Project(2009B005) supported by the Teaching Reform Foundation in the New Century Higher Education of Guangxi Province,China
文摘For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1) the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2) the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually;however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m) in the scope of all filling height.
基金Project(2015-29)supported by Jiangsu Distinguished Professor,ChinaProject(BRA2015311)supported by the Jiangsu Province Fourth 333 Engineering,China
文摘To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.
