Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure m...Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure mechanism still remains unclear. In this work, based on laboratory tests, numerical simulations with the particle flow code(PFC) were carried out to reproduce the micro-fracturing process of granite specimens. Shear and tensile cracks were both recorded to investigate the failure mode of rocks under different loading conditions. At the same time, a dynamic damage model based on the Weibull distribution was established to predict the deformation and degradation behavior of specimens. It is found that micro-cracks play important roles in controlling the dynamic deformation and failure process of rock under impact loadings. The sharp increase in the number of cracks may be the reason for the strength increase of rock under high strain rates. Tensile cracks tend to be the key reason for splitting failure of specimens. Numerical simulation of crack propagation by PFC can give vivid description of the failure process. However, it is not enough for evaluation of material degradation. The dynamic damage model is able to predict the stress-strain relationship of specimens reasonably well, and can be used to explain the degradation of specimens under impact loadings at macro-scale. Crack and damage can describe material degradation at different scales and can be used together to reveal the failure mechanism of rocks.展开更多
An integrated geophysical survey which combines vertical seismicprofile method, shallow reflection seismic method, electric sounding, soil temperature measurement and radioactive gas measurement was used to investigat...An integrated geophysical survey which combines vertical seismicprofile method, shallow reflection seismic method, electric sounding, soil temperature measurement and radioactive gas measurement was used to investigate Zhaoshuling landslide in the new site of Badong County and to assess the stability of the landslide. By rational use of these methods together with borehole geological profile and other geological information, the spatial distribution of the landslide body, the formations and structures within and without the landslide body were determined and the stability of the landslide was also assessed, thus making great contribution to the successful and rational investigation and assessment of the landslide.展开更多
This paper reports on a mixed method inquiry into the use of vocabulary learning strategies and their development as strategic vocabulary learners in a key middle school on the Chinese mainland. In the inquiry, 475 fi...This paper reports on a mixed method inquiry into the use of vocabulary learning strategies and their development as strategic vocabulary learners in a key middle school on the Chinese mainland. In the inquiry, 475 first year junior secondary school pupils (247 boys and 228 girls) were surveyed about their strategy use in learning English vocabulary. Sixteen pupils (8 boys and 8 girls) participated in paired semi-structured interviews about their experiences of learning English vocabulary. Drawing on socio-cultural perspectives on language learning, the inquiry established the interconnections between the participants' strategy use and beliefs and identified the roles that agency played in their vocabulary learning. The analysis of interview data further revealed that the participants' strategy use emerged from interaction between their agency and the mediation of contextual resources and social agents including parents and teachers. These findings suggest that it is important for language teachers to collaborate with social agents such as parents in their efforts to support young learners' strategic vocabulary learning.展开更多
基金Projects(51274254,51322403)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0528)supported by theProgram for New Century Excellent Talents in University,ChinaProject(2013SK2011)supported by Hunan Province Science andTechnology Plan,China
文摘Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure mechanism still remains unclear. In this work, based on laboratory tests, numerical simulations with the particle flow code(PFC) were carried out to reproduce the micro-fracturing process of granite specimens. Shear and tensile cracks were both recorded to investigate the failure mode of rocks under different loading conditions. At the same time, a dynamic damage model based on the Weibull distribution was established to predict the deformation and degradation behavior of specimens. It is found that micro-cracks play important roles in controlling the dynamic deformation and failure process of rock under impact loadings. The sharp increase in the number of cracks may be the reason for the strength increase of rock under high strain rates. Tensile cracks tend to be the key reason for splitting failure of specimens. Numerical simulation of crack propagation by PFC can give vivid description of the failure process. However, it is not enough for evaluation of material degradation. The dynamic damage model is able to predict the stress-strain relationship of specimens reasonably well, and can be used to explain the degradation of specimens under impact loadings at macro-scale. Crack and damage can describe material degradation at different scales and can be used together to reveal the failure mechanism of rocks.
基金The authors are indebted to the chief engineer of Bureau of Geotechnique of Changjiang WaterResources Commission, Cui Zhengquan and the academician of the Chinese Academy of Sciences Xu Houze for their support and help. We would like to express our gra
文摘An integrated geophysical survey which combines vertical seismicprofile method, shallow reflection seismic method, electric sounding, soil temperature measurement and radioactive gas measurement was used to investigate Zhaoshuling landslide in the new site of Badong County and to assess the stability of the landslide. By rational use of these methods together with borehole geological profile and other geological information, the spatial distribution of the landslide body, the formations and structures within and without the landslide body were determined and the stability of the landslide was also assessed, thus making great contribution to the successful and rational investigation and assessment of the landslide.
文摘This paper reports on a mixed method inquiry into the use of vocabulary learning strategies and their development as strategic vocabulary learners in a key middle school on the Chinese mainland. In the inquiry, 475 first year junior secondary school pupils (247 boys and 228 girls) were surveyed about their strategy use in learning English vocabulary. Sixteen pupils (8 boys and 8 girls) participated in paired semi-structured interviews about their experiences of learning English vocabulary. Drawing on socio-cultural perspectives on language learning, the inquiry established the interconnections between the participants' strategy use and beliefs and identified the roles that agency played in their vocabulary learning. The analysis of interview data further revealed that the participants' strategy use emerged from interaction between their agency and the mediation of contextual resources and social agents including parents and teachers. These findings suggest that it is important for language teachers to collaborate with social agents such as parents in their efforts to support young learners' strategic vocabulary learning.