Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the...Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.展开更多
Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage ex...Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage experi-ments were carried out. Horizontals flow are regarded as phreatic plan flows without penetration. Its seepage law sati-fies the Dupuit equation. With parallel lay seepage model,the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum. An unsaturated flow ap-peared in the vertical experiment,with a hydraulic gradient of 1. The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient. That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic co-efficient between 63 and 155,which is 25 to 100 times larger than that of a homogeneous body.展开更多
The stability of unsaturated soil slope has been the hot point recently. Especially, the seeping rainfall makes losing stability of unsaturated soil slope, and causes enormous loss to the producation and safety of oth...The stability of unsaturated soil slope has been the hot point recently. Especially, the seeping rainfall makes losing stability of unsaturated soil slope, and causes enormous loss to the producation and safety of other people. The seeping rainfall makes volumetric water content of unsaturated soil slope changing, and the volumetric water content has directly relationship with matric suction. And matric suction also has directly relationship with the stability of unsaturated soil slope. So the change of matric suction influence the stability changing, that is, safety coefficient has decided relationship with volumetric water content. The profile of dangerous volumetric water content curves of unsaturated soil slope has been obtained. If a volumetric water content curve of some unsaturated soil slope belongs to one of these dongerous curves, the unsaturated soil slope could be in danger. So this is called DVWCCP(dangerous volumetric water content curves profile). By monitoring the volumetric water content curves can obtain the stability information of some soil slope to serve producing and safety.展开更多
Some of the characteristics of post-modernism, such as opposition centers, denial of holism, identity, differences and uncertainties, have had a great impact on the view of education. Because the purpose of education ...Some of the characteristics of post-modernism, such as opposition centers, denial of holism, identity, differences and uncertainties, have had a great impact on the view of education. Because the purpose of education is the starting point and end-result of education, which is related to the general orientation of education development, we have to re-examine the concept of modem educational purpose in the post-modernism thought. The author holds that compared with the modem education view, the educational purpose view of the post-modem period shows the following characteristics： Maintaining the diversification and difference of individuahty, paying attention to cultivating social consciousness and critical ability, learning to understand and respect ecological harmony.展开更多
基金Project(2013CB035401) supported by the National Basic Research Program of ChinaProject(51174228) supported by the National Natural Science Foundation of China+1 种基金Project(71380100003) supported by Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(201304) supported by Open Research Fund of Hunan Province Key Laboratory of Safe Mining Techniques of Coal Mines(Hunan University of Science and Technology),China
文摘Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.
基金Projects 2004CB619205 supported by the National Basic Research and Development Program of China50321402 by the National Science Fund for Distingui- shed Young Scholars of China50574099 by the National Natural Science Foundation of China
文摘Ore dumps are heterogeneous bodies with anisotropic seepage characteristics because of the ore segregation. In an indoor experiment,a dump was constructed with three strata,where the horizontal and vertical seepage experi-ments were carried out. Horizontals flow are regarded as phreatic plan flows without penetration. Its seepage law sati-fies the Dupuit equation. With parallel lay seepage model,the equivalent seepage coefficient in the horizontal flow was obtained and was equivalent to the weighted mean of the seepage coefficient of each stratum. An unsaturated flow ap-peared in the vertical experiment,with a hydraulic gradient of 1. The vertical flow was equivalent to the seepage model that moved in vertical bedding; its equivalent seepage coefficient depended on the stratum with the minimum seepage coefficient. That the experiment showed clear anisotropy in a heterogeneous body was obvious with an anisotropic co-efficient between 63 and 155,which is 25 to 100 times larger than that of a homogeneous body.
文摘The stability of unsaturated soil slope has been the hot point recently. Especially, the seeping rainfall makes losing stability of unsaturated soil slope, and causes enormous loss to the producation and safety of other people. The seeping rainfall makes volumetric water content of unsaturated soil slope changing, and the volumetric water content has directly relationship with matric suction. And matric suction also has directly relationship with the stability of unsaturated soil slope. So the change of matric suction influence the stability changing, that is, safety coefficient has decided relationship with volumetric water content. The profile of dangerous volumetric water content curves of unsaturated soil slope has been obtained. If a volumetric water content curve of some unsaturated soil slope belongs to one of these dongerous curves, the unsaturated soil slope could be in danger. So this is called DVWCCP(dangerous volumetric water content curves profile). By monitoring the volumetric water content curves can obtain the stability information of some soil slope to serve producing and safety.
文摘Some of the characteristics of post-modernism, such as opposition centers, denial of holism, identity, differences and uncertainties, have had a great impact on the view of education. Because the purpose of education is the starting point and end-result of education, which is related to the general orientation of education development, we have to re-examine the concept of modem educational purpose in the post-modernism thought. The author holds that compared with the modem education view, the educational purpose view of the post-modem period shows the following characteristics： Maintaining the diversification and difference of individuahty, paying attention to cultivating social consciousness and critical ability, learning to understand and respect ecological harmony.
