A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for...A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.展开更多
The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A...The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A1-AIN- 50SiB material （prepared by ball-milling powders） and AI- AIN-50SiM material （prepared by mixing powders） exhibited the semi-continuous Si structures and the isolated Si islands, respectively. Subsequently, the AI-AIN-50Si materials were selected as the model materials by phase identification and microstructure analysis. The dynamic microstructural evolu- tion of AI-AIN-50Si materials was investigated using the computational fluid dynamics （CFD） method. Mathematical models and simulation results showed that the in situ synthesis of AIN was strongly influenced by the structure and the flow- path （（Cg,N2/lg,N2）＋（Cs,AlN/ls,AiN））. The flow paths of AI-AIN-50Si^B material were restricted by the semi-continuous Si. These Si structures can promote the formation of the strong turbulence with gradually weakened fluctuation, so that the in situ synthesis of AIN was interconnected and surrounded by an interpenetrating Si network. In contrast, the flow paths of AI- AIN-50Si^B material can easily pass through the isolated Si due to its mild turbulence with linear relationship. As a result, AIN was separated by the isolated Si and agglomerated in the matrix. Overall, the present work provides new insights into dynamic microstructural evolution in in situ reaction sinter- ing systems.展开更多
文摘A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.
基金supported by the financial support of the National Natural Science Foundation of China (51171146 and 51101177)the Program for Key Science and Technology Innovative Research Team of Shaanxi Province (2013KCT-05)
文摘The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A1-AIN- 50SiB material （prepared by ball-milling powders） and AI- AIN-50SiM material （prepared by mixing powders） exhibited the semi-continuous Si structures and the isolated Si islands, respectively. Subsequently, the AI-AIN-50Si materials were selected as the model materials by phase identification and microstructure analysis. The dynamic microstructural evolu- tion of AI-AIN-50Si materials was investigated using the computational fluid dynamics （CFD） method. Mathematical models and simulation results showed that the in situ synthesis of AIN was strongly influenced by the structure and the flow- path （（Cg,N2/lg,N2）＋（Cs,AlN/ls,AiN））. The flow paths of AI-AIN-50Si^B material were restricted by the semi-continuous Si. These Si structures can promote the formation of the strong turbulence with gradually weakened fluctuation, so that the in situ synthesis of AIN was interconnected and surrounded by an interpenetrating Si network. In contrast, the flow paths of AI- AIN-50Si^B material can easily pass through the isolated Si due to its mild turbulence with linear relationship. As a result, AIN was separated by the isolated Si and agglomerated in the matrix. Overall, the present work provides new insights into dynamic microstructural evolution in in situ reaction sinter- ing systems.
