Objective To evaluate the clinical effect of the free-hand cervical pedicle screw fixation in treatment of the upper cervical fracture and instability. Methods A retrospective review was performed on 15 patients
Objective To explore the clinical effect of the trans-atlantoaxial pedicle screw-rod internal fixation and fusion in treatment of old odontoid fracture combined with atlantoaxial instability. Methods The study involve...Objective To explore the clinical effect of the trans-atlantoaxial pedicle screw-rod internal fixation and fusion in treatment of old odontoid fracture combined with atlantoaxial instability. Methods The study involved 48 patients with展开更多
According to the requirement of the project 'Establishment of the Physical Model of Earthquake PrecursorFields',this paper elucidates the train of thinking for research on the project and some scientific probl...According to the requirement of the project 'Establishment of the Physical Model of Earthquake PrecursorFields',this paper elucidates the train of thinking for research on the project and some scientific problems whichmust be studied i, the elucidation emphasizes that the core of this project is to study the conditions and processesof the generation of strong earthquakes. The paper first outlines the origin and development of the'strong-bodyearthquake-generating model' proposed by the author in the 1980;and then proves the reasonableness of themodel from three aspects, namely: deep structures, mechanical analysis and rock fracture experiments. Bystudying the tomographic image for the northern part of North China, it can be seen that the sources of strongearthquakes are all distributed in high-velocity bodies,or in the contact zone between high-velocity and lowvelocity bodies but nearer to the high-velocity body. It has been affirmed through studies of the mechanical modelsof hard and soft inclusions that the existence of a hard inclusion is an imPOrtant condition for the high concentration of large amounts of strain energy. A lot of theoretical and experimental studies have been made to investigate the conditions for rock instability; the results have consistently indicated that rock instability,sudden fracture and stress drop would be possible only if the stiffness of the source body is greater than the environmentalstiffness.展开更多
A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional(1-D) entities.The model overcomes the weakness of complex...A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional(1-D) entities.The model overcomes the weakness of complex meshing,a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method.Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single vertical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures,fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripefracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh generation, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10 % less than stripefracture model, and computational efficiency increases by about 50 %. The more fractures there are, the more the computational efficiency increases.展开更多
The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable fai...The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable failure of surrounding rock induced by fault activation under the influence of adoption,which was studied utilizing field case and numerical analysis for the deformation and failure process of surrounding rock near the fault-affected zone.Combined with field cases,this paper analyzes disturbance stress and roof abscission layer monitoring in effecting zones of fault activation.Using the discrete element 3DEC numerical analysis method,the model of surrounding rock unstable fracture induced by fault activation under adoption is established.The unstable fracture and stress variation characteristics of surrounding rock induced by fault activation during the excavation of the upper side wall and lower side wall of the faults are simulated and analyzed.Field analysis shows that as the coal working face continues to advance,the mining stress gradually increases.There is a zigzag wave on the relationship curve between coal mining and roof displacement near the fault,which reveals that the surrounding rock of the fault activation affected zone is in the superposition state of static load and dynamic load.Furthermore,the simulation results show that the stress and displacement of surrounding rock near the fault increase with the advance of coal mining face.The closer to the fault plane,the displacement gradually returns to zero,and the stress is also in a lower state.展开更多
文摘Objective To evaluate the clinical effect of the free-hand cervical pedicle screw fixation in treatment of the upper cervical fracture and instability. Methods A retrospective review was performed on 15 patients
文摘Objective To explore the clinical effect of the trans-atlantoaxial pedicle screw-rod internal fixation and fusion in treatment of old odontoid fracture combined with atlantoaxial instability. Methods The study involved 48 patients with
文摘According to the requirement of the project 'Establishment of the Physical Model of Earthquake PrecursorFields',this paper elucidates the train of thinking for research on the project and some scientific problems whichmust be studied i, the elucidation emphasizes that the core of this project is to study the conditions and processesof the generation of strong earthquakes. The paper first outlines the origin and development of the'strong-bodyearthquake-generating model' proposed by the author in the 1980;and then proves the reasonableness of themodel from three aspects, namely: deep structures, mechanical analysis and rock fracture experiments. Bystudying the tomographic image for the northern part of North China, it can be seen that the sources of strongearthquakes are all distributed in high-velocity bodies,or in the contact zone between high-velocity and lowvelocity bodies but nearer to the high-velocity body. It has been affirmed through studies of the mechanical modelsof hard and soft inclusions that the existence of a hard inclusion is an imPOrtant condition for the high concentration of large amounts of strain energy. A lot of theoretical and experimental studies have been made to investigate the conditions for rock instability; the results have consistently indicated that rock instability,sudden fracture and stress drop would be possible only if the stiffness of the source body is greater than the environmentalstiffness.
基金supported by the National Natural Science Foundation of China(Grant 51404232)the National Science and Technology Major Project(Grant 2011ZX05038003)the China Postdoctoral Science Foundation(Grant 2014M561074)
文摘A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional(1-D) entities.The model overcomes the weakness of complex meshing,a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method.Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single vertical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures,fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripefracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh generation, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10 % less than stripefracture model, and computational efficiency increases by about 50 %. The more fractures there are, the more the computational efficiency increases.
基金supported by the National key Research and development program for young scientists(2021YF2900400)Supported by Youth Foundation of National Natural Science Foundation of China(52104077)Major collaborative innovation project of Guizhou's mineral prospecting breakthrough strategic action[2022]ZD001-02-02,which are all gratefully appreciated.
文摘The fault is potentially vulnerability's geological structure in the working face and its vicinity,and it is also a crucial geological factor affecting coal mine safety exploitation.To investigate the unstable failure of surrounding rock induced by fault activation under the influence of adoption,which was studied utilizing field case and numerical analysis for the deformation and failure process of surrounding rock near the fault-affected zone.Combined with field cases,this paper analyzes disturbance stress and roof abscission layer monitoring in effecting zones of fault activation.Using the discrete element 3DEC numerical analysis method,the model of surrounding rock unstable fracture induced by fault activation under adoption is established.The unstable fracture and stress variation characteristics of surrounding rock induced by fault activation during the excavation of the upper side wall and lower side wall of the faults are simulated and analyzed.Field analysis shows that as the coal working face continues to advance,the mining stress gradually increases.There is a zigzag wave on the relationship curve between coal mining and roof displacement near the fault,which reveals that the surrounding rock of the fault activation affected zone is in the superposition state of static load and dynamic load.Furthermore,the simulation results show that the stress and displacement of surrounding rock near the fault increase with the advance of coal mining face.The closer to the fault plane,the displacement gradually returns to zero,and the stress is also in a lower state.