Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characte...Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ.展开更多
The center was first established in 2013 and affiliated to the Shanghai Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine.In 2015,the center was entitled as 3D Bioprinting Clinical Transformati...The center was first established in 2013 and affiliated to the Shanghai Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine.In 2015,the center was entitled as 3D Bioprinting Clinical Transformation Collaborative Innovation Center.In 2016,the center was renamed as Medical 3D Printing Innovation Research Center of Shanghai Jiao Tong University School of Medicine.Although the center was established in 2013,the clinical application of 3D printing in Shanghai Ninth People’s Hospital can be traced back to the 1990s.As early as 30 years ago,Prof.Kerong Dai had tried to rebuild patients pelvic by manually cutting the foam boards and layering them together based on the theory of 3D printing for preoperative planning model of abnormal skeleton structures and development of personalized prosthesis.That was the first application of 3D printing in the area of medicine in China.Now,The Research Center of 3D Bioprinting in Shanghai Ninth People’s Hospital comprised of subcenters including the outpatient department of 3D printing,medical 3D printing innovation research center and Shanghai key laboratory of orthopedic implant.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 52278420)the China Atomic Energy Authority (CAEA) for China’s URL Development Program and the Geological Disposal Program。
文摘Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ.
文摘The center was first established in 2013 and affiliated to the Shanghai Ninth People’s Hospital,Shanghai Jiao Tong University School of Medicine.In 2015,the center was entitled as 3D Bioprinting Clinical Transformation Collaborative Innovation Center.In 2016,the center was renamed as Medical 3D Printing Innovation Research Center of Shanghai Jiao Tong University School of Medicine.Although the center was established in 2013,the clinical application of 3D printing in Shanghai Ninth People’s Hospital can be traced back to the 1990s.As early as 30 years ago,Prof.Kerong Dai had tried to rebuild patients pelvic by manually cutting the foam boards and layering them together based on the theory of 3D printing for preoperative planning model of abnormal skeleton structures and development of personalized prosthesis.That was the first application of 3D printing in the area of medicine in China.Now,The Research Center of 3D Bioprinting in Shanghai Ninth People’s Hospital comprised of subcenters including the outpatient department of 3D printing,medical 3D printing innovation research center and Shanghai key laboratory of orthopedic implant.
