In practical engineering applications,rock mass are often found to be subjected to a triaxial stress state.Concurrently,defects like joints and fractures have a notable impact on the mechanical behavior of rock mass.S...In practical engineering applications,rock mass are often found to be subjected to a triaxial stress state.Concurrently,defects like joints and fractures have a notable impact on the mechanical behavior of rock mass.Such defects are identified as crucial contributors to the failure and instability of the surrounding rock,subsequently impacting the engineering stability.The study aimed to investigate the impact of fracture geometry and confining pressure on the deformation,failure characteristics,and strength of specimens using sand powder 3D printing technology and conventional triaxial compression tests.The results indicate that the number of fractures present considerably influences the peak strength,axial peak strain and elastic modulus of the specimens.Confining pressure is an important factor affecting the failure pattern of the specimen,under which the specimen is more prone to shear failure,but the initiation,expansion and penetration processes of secondary cracks in different fracture specimens are different.This study confirmed the feasibility of using sand powder 3D printing specimens as soft rock analogs for triaxial compression research.The insights from this research are deemed essential for a deeper understanding of the mechanical behavior of fractured surrounding rocks when under triaxial stress state.展开更多
α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 ...α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 particles. Kinetic studies on the bismuth oxidation at low-temperatures were carried out by TGA method. The results show that bismuth beads should be reunited and oxidized to become irregular Bi2O3 powders. The bismuth oxidation follows shrinking core model, and its controlling mechanism varies at different reaction time. Within 0-10 min, the kinetics is controlled by chemical reaction, after that it is controlled by O2 diffusion in the solid α-Bi2O3 layer. The apparent activation energy is determined as 55.19 kJ/mol in liquid-phase oxidation.展开更多
基金Project(2021YFC2900600)supported by the Young Scientist Project of National Key Research and Development Program of ChinaProject(52074166)supported by the National Natural Science Foundation of China+1 种基金Projects(ZR2021YQ38,ZR2020QE121)supported by the Natural Science Foundation of Shandong Province,ChinaProject(2022KJ101)supported by the Science and Technology Support Plan for Youth Innovation of Colleges and Universities in Shandong Province,China。
文摘In practical engineering applications,rock mass are often found to be subjected to a triaxial stress state.Concurrently,defects like joints and fractures have a notable impact on the mechanical behavior of rock mass.Such defects are identified as crucial contributors to the failure and instability of the surrounding rock,subsequently impacting the engineering stability.The study aimed to investigate the impact of fracture geometry and confining pressure on the deformation,failure characteristics,and strength of specimens using sand powder 3D printing technology and conventional triaxial compression tests.The results indicate that the number of fractures present considerably influences the peak strength,axial peak strain and elastic modulus of the specimens.Confining pressure is an important factor affecting the failure pattern of the specimen,under which the specimen is more prone to shear failure,but the initiation,expansion and penetration processes of secondary cracks in different fracture specimens are different.This study confirmed the feasibility of using sand powder 3D printing specimens as soft rock analogs for triaxial compression research.The insights from this research are deemed essential for a deeper understanding of the mechanical behavior of fractured surrounding rocks when under triaxial stress state.
基金Project (2006BAB02B05-04- 01/02) supported by the National Key Technologies R&D Program of China
文摘α-Bi2O3 powders were prepared from nanometer Bi powders through low-temperature oxidation at less than 873.15 K. XRD, SEM, TEM and HRTEM were used to characterize the structure and morphology of Bi powders and Bi2O3 particles. Kinetic studies on the bismuth oxidation at low-temperatures were carried out by TGA method. The results show that bismuth beads should be reunited and oxidized to become irregular Bi2O3 powders. The bismuth oxidation follows shrinking core model, and its controlling mechanism varies at different reaction time. Within 0-10 min, the kinetics is controlled by chemical reaction, after that it is controlled by O2 diffusion in the solid α-Bi2O3 layer. The apparent activation energy is determined as 55.19 kJ/mol in liquid-phase oxidation.
