The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnect...The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength.展开更多
Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entra...Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entrapped network structure in thickener,which is detrimental to underflow concentration.In this study,the continuous thickening experiment was carried out for ultra-fine tungsten tailings to study the influence of rake shearing on underflow.The micro pores structure and seepage flow in tailings bed before and after shearing are studied by CT and simulation approach to reveal the shearing enhancement mechanism of thickening process.The results shown that,the underflow concentration is increased from 61.4 wt%to 69.6 wt%by rake shearing in a pilot scale thickener,the porosity decreased from 46.48%to 37.46%.The entrapped water discharged from sticks structure more than sphere spaces.In items of seepage,after shearing,the seepage flow channel of tailings underflow is becoming longer,which caused the decreasing average flow rate decreases and absolute permeability.The absolute permeability is negatively correlated with tortuosity.The rake shearing can destroy the flocs structure;change the effective stress to increase the concentration.Higher underflow concentration improves the waste recycling and water recovery rate,especially for arid areas.展开更多
Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected...Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected by blood vessels.However,the change of pores structure in cortical bone under microgravity was still unclear.In this study,in order to clear the changes of pore structure with cortical vascular pores and its effect on bone mechanical properties,rat tail-suspension was used to simulate microgravity and the changes of the microstructure in rat tibia cortices were investigated by high-resolution micro-CT(3μm)while the bone mechanical properties were measured via three point bending test.The results showed the bone mineral density of cortical bone didn't change in tail-suspended rats.However,the pore structure of cortical bone in tail-suspended rats changed significantly,the proportion of pores greater than 15μm(cortical vascular pores)increased while that less than 15μm decreased.The mechanical properties of bone(such as maximum load and maximum stress)in tail-suspended rats deteriorated.And the volume ratio of pore vessels(vessel volume/tissue volume)was negatively correlated with the mechanical properties.In conclusion,the increase of cortical vascular pores in rats caused by the simulated microgravity contributes to the decrease of mechanical properties.展开更多
基金Project(41672298) supported by the National Natural Science Foundation of ChinaProject(2017YFC0602901) supported by the National Key Research and Development Program of China
文摘The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength.
基金This work was supported by funding from the National Natural Science Foundation of China Projects(51834001,51704094,U170420041)the China Postdoctoral Science Foundation(2020M672226)+2 种基金Program for Science&Technology Innovation Talents in Universities of Henan Province(19HASTIT047)Key Science Research Project in Universities of Henan Province(19B620001,20A620004)Henan Polytechnic University Science Fund for Distinguished Young Scholars(J2020-3).
文摘Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entrapped network structure in thickener,which is detrimental to underflow concentration.In this study,the continuous thickening experiment was carried out for ultra-fine tungsten tailings to study the influence of rake shearing on underflow.The micro pores structure and seepage flow in tailings bed before and after shearing are studied by CT and simulation approach to reveal the shearing enhancement mechanism of thickening process.The results shown that,the underflow concentration is increased from 61.4 wt%to 69.6 wt%by rake shearing in a pilot scale thickener,the porosity decreased from 46.48%to 37.46%.The entrapped water discharged from sticks structure more than sphere spaces.In items of seepage,after shearing,the seepage flow channel of tailings underflow is becoming longer,which caused the decreasing average flow rate decreases and absolute permeability.The absolute permeability is negatively correlated with tortuosity.The rake shearing can destroy the flocs structure;change the effective stress to increase the concentration.Higher underflow concentration improves the waste recycling and water recovery rate,especially for arid areas.
基金the National Natural Science Foundation of China(No.11827803)China Space Station Engineering Experiment Project(No.HYZHXM01016)111 Project(B13003).
文摘Cortical bone is the main mechanical bearing structure of bone,and the mechanical properties of materials are not only related to bone mineral density,but also largely depend on its pores microstructure which affected by blood vessels.However,the change of pores structure in cortical bone under microgravity was still unclear.In this study,in order to clear the changes of pore structure with cortical vascular pores and its effect on bone mechanical properties,rat tail-suspension was used to simulate microgravity and the changes of the microstructure in rat tibia cortices were investigated by high-resolution micro-CT(3μm)while the bone mechanical properties were measured via three point bending test.The results showed the bone mineral density of cortical bone didn't change in tail-suspended rats.However,the pore structure of cortical bone in tail-suspended rats changed significantly,the proportion of pores greater than 15μm(cortical vascular pores)increased while that less than 15μm decreased.The mechanical properties of bone(such as maximum load and maximum stress)in tail-suspended rats deteriorated.And the volume ratio of pore vessels(vessel volume/tissue volume)was negatively correlated with the mechanical properties.In conclusion,the increase of cortical vascular pores in rats caused by the simulated microgravity contributes to the decrease of mechanical properties.
