【目的】揭示三峡库区库水位周期性变动下库岸边坡土体力学性能及微观结构的劣化机制,为库岸边坡灾害防治提供理论依据。【方法】选取库岸边坡不同高程(145、155、165、175、180 m)的土体进行宏观力学测试及微观矿物分析,划分消落带劣...【目的】揭示三峡库区库水位周期性变动下库岸边坡土体力学性能及微观结构的劣化机制,为库岸边坡灾害防治提供理论依据。【方法】选取库岸边坡不同高程(145、155、165、175、180 m)的土体进行宏观力学测试及微观矿物分析,划分消落带劣化区域;并以劣化程度最严重区域土体为研究对象,设计“干燥-饱水”干湿交替不同次数(1、2、3、5、8次)的周期性试验模拟库水位升降的干湿交替环境,最后采用宏-细-微观多尺度结合的分析方法来开展本次研究。【结果】该滑坡消落带土体劣化呈现显著高程分异:[145,155)m区间分形维数增加3.6%,黏聚力下降16.7%,为劣化增强区;[155,175]m区间分形维数减少5.7%,黏聚力提升50.0%,属劣化减弱区;175 m以上无劣化。在干湿循环作用下,155 m高程的土体在前5次循环内抗剪强度衰减28.18%,水土流失度为4.88%,后续趋于稳定。扫描电子显微镜(scanning electron microscope,SEM)与核磁共振(nuclear magnetic resonance,NMR)测试表明,水分侵入引发土体细颗粒含量增加,大孔隙占比提升。【结论】消落带土体劣化受库水位变动影响:在蓄水初期,冲刷作用导致土体内部出现“裂隙萌生-贯通-崩解”三阶段损伤演化,促使土体由密实向松散多裂隙转化;在蓄水后期,不同高程土体与库水有不同程度接触,使得土体内部发生不同程度的水化学反应,造成土体骨架矿物溶解及黏结物破碎-胶结。细观孔隙网络重构与颗粒侵蚀破碎协同作用是土体劣化的本质原因。展开更多
In order to study the effect of electromagnetic compound treatment on the mechanical property, cutting performance and microstructure of cemented carbide, the samples were treated by a self-made electromagnetic compou...In order to study the effect of electromagnetic compound treatment on the mechanical property, cutting performance and microstructure of cemented carbide, the samples were treated by a self-made electromagnetic compound treatment device with different magnetic field strength(H=1, 1.25 and 1.5 T). The electromagnetic compound treatment method was proposed to couple pulsed magnetic field and pulsed current. The results show that after the pulsed magnetic field treatment, the values of the transverse rupture strength of the samples were respectively reduced by 21%, 20.6% and 20.1%;the cutting performance was decreased by about 4.5%, which means the tool life was decreased. After the electromagnetic compound treatment, the values of the transverse rupture strength of the rectangular samples were respectively increased by 8%, 8.6% and 9.5%, and the tool life was increased by 4.2%, 7% and 10.3%. After the electromagnetic compound treatment, the pulse current provided the driving force for dislocation motion. A strong pulse current driving force is more likely to make the dislocation multiply and slip. A high density dislocation cell is formed within the material, so the mechanical properties were significantly increased.展开更多
文摘【目的】揭示三峡库区库水位周期性变动下库岸边坡土体力学性能及微观结构的劣化机制,为库岸边坡灾害防治提供理论依据。【方法】选取库岸边坡不同高程(145、155、165、175、180 m)的土体进行宏观力学测试及微观矿物分析,划分消落带劣化区域;并以劣化程度最严重区域土体为研究对象,设计“干燥-饱水”干湿交替不同次数(1、2、3、5、8次)的周期性试验模拟库水位升降的干湿交替环境,最后采用宏-细-微观多尺度结合的分析方法来开展本次研究。【结果】该滑坡消落带土体劣化呈现显著高程分异:[145,155)m区间分形维数增加3.6%,黏聚力下降16.7%,为劣化增强区;[155,175]m区间分形维数减少5.7%,黏聚力提升50.0%,属劣化减弱区;175 m以上无劣化。在干湿循环作用下,155 m高程的土体在前5次循环内抗剪强度衰减28.18%,水土流失度为4.88%,后续趋于稳定。扫描电子显微镜(scanning electron microscope,SEM)与核磁共振(nuclear magnetic resonance,NMR)测试表明,水分侵入引发土体细颗粒含量增加,大孔隙占比提升。【结论】消落带土体劣化受库水位变动影响:在蓄水初期,冲刷作用导致土体内部出现“裂隙萌生-贯通-崩解”三阶段损伤演化,促使土体由密实向松散多裂隙转化;在蓄水后期,不同高程土体与库水有不同程度接触,使得土体内部发生不同程度的水化学反应,造成土体骨架矿物溶解及黏结物破碎-胶结。细观孔隙网络重构与颗粒侵蚀破碎协同作用是土体劣化的本质原因。
基金Funded by the National Natural Science Foundation of China(Nos.51575369&51675357)
文摘In order to study the effect of electromagnetic compound treatment on the mechanical property, cutting performance and microstructure of cemented carbide, the samples were treated by a self-made electromagnetic compound treatment device with different magnetic field strength(H=1, 1.25 and 1.5 T). The electromagnetic compound treatment method was proposed to couple pulsed magnetic field and pulsed current. The results show that after the pulsed magnetic field treatment, the values of the transverse rupture strength of the samples were respectively reduced by 21%, 20.6% and 20.1%;the cutting performance was decreased by about 4.5%, which means the tool life was decreased. After the electromagnetic compound treatment, the values of the transverse rupture strength of the rectangular samples were respectively increased by 8%, 8.6% and 9.5%, and the tool life was increased by 4.2%, 7% and 10.3%. After the electromagnetic compound treatment, the pulse current provided the driving force for dislocation motion. A strong pulse current driving force is more likely to make the dislocation multiply and slip. A high density dislocation cell is formed within the material, so the mechanical properties were significantly increased.
