Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings ...Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings of true triaxial hydraulic fracturing experiments and field pilot under this technology and the cohesive element method,a 3D numerical model of indirect fracturing in the roof of broken soft coal seams was established,the fracture morphology propagation and evolution law under different conditions was investigated,and analysis of main controlling factors of fracture parameters was conducted with the combination weight method,which was based on grey incidence,analytic hierarchy process and entropy weight method.The results show that“士”-shaped fractures,T-shaped fractures,cross fractures,H-shaped fractures,and“干”-shaped fractures dominated by horizontal fractures were formed.Different parameter combinations can form different fracture morphologies.When the coal seam permeability is lower and the minimum horizontal principal stress difference between layers and fracturing fluid injection rate are both larger,it tends to form“士”-shaped fractures.When the coal seam permeability and minimum horizontal principal stress between layers and perforation position are moderate,cross fractures are easily generated.Different fracture parameters have different main controlling factors.Engineering factors of perforation location,fracturing fluid injection rate and viscosity are the dominant factors of hydraulic fracture shape parameters.This study can provide a reference for the design of indirect fracturing in the roof of broken soft coal seams.展开更多
Purpose： To describe an indirect reduction technique during minimally invasive percutaneous plate osteosynthesis （MIPPO） of tibial shaft fractures with the use of a distraction support. Methods： Between March 2011...Purpose： To describe an indirect reduction technique during minimally invasive percutaneous plate osteosynthesis （MIPPO） of tibial shaft fractures with the use of a distraction support. Methods： Between March 2011 and October 2014, 52 patients with a mean age of 48 years （16-72 years） sustaining tibial shaft fractures were included. All the patients underwent MIPPO for the fractures using a distraction support prior to insertion of the plate. Fracture angular deformity was assessed by goniometer measurement on preoperative and postoperative images. Results： Preoperative radiographs revealed a mean of 7.6°（1.2°-28°） angulation in coronal plane and a mean of 6.8°（0.5°-19°） angulation in sagittal plane. Postoperative anteroposterior and lateral radio graphs showed a mean of 0.8°（0°-4.0°） and 0.6°00-3.6°） of varusvalgus and apex anterior/posterior angulation, respectively. No intraoperative or postoperative complications were noted. Conclusions： This study suggests that the distraction support during MIPPO of tibial shaft fractures is an effective and safe method with no associated complications.展开更多
基金National Natural Science Foundation of China(11672333).
文摘Indirect fracturing in the roof of broken soft coal seams has been demonstrated to be a feasible technology.In this work,the No.5 coal seam in the Hancheng block was taken as the research object.Based on the findings of true triaxial hydraulic fracturing experiments and field pilot under this technology and the cohesive element method,a 3D numerical model of indirect fracturing in the roof of broken soft coal seams was established,the fracture morphology propagation and evolution law under different conditions was investigated,and analysis of main controlling factors of fracture parameters was conducted with the combination weight method,which was based on grey incidence,analytic hierarchy process and entropy weight method.The results show that“士”-shaped fractures,T-shaped fractures,cross fractures,H-shaped fractures,and“干”-shaped fractures dominated by horizontal fractures were formed.Different parameter combinations can form different fracture morphologies.When the coal seam permeability is lower and the minimum horizontal principal stress difference between layers and fracturing fluid injection rate are both larger,it tends to form“士”-shaped fractures.When the coal seam permeability and minimum horizontal principal stress between layers and perforation position are moderate,cross fractures are easily generated.Different fracture parameters have different main controlling factors.Engineering factors of perforation location,fracturing fluid injection rate and viscosity are the dominant factors of hydraulic fracture shape parameters.This study can provide a reference for the design of indirect fracturing in the roof of broken soft coal seams.
文摘Purpose： To describe an indirect reduction technique during minimally invasive percutaneous plate osteosynthesis （MIPPO） of tibial shaft fractures with the use of a distraction support. Methods： Between March 2011 and October 2014, 52 patients with a mean age of 48 years （16-72 years） sustaining tibial shaft fractures were included. All the patients underwent MIPPO for the fractures using a distraction support prior to insertion of the plate. Fracture angular deformity was assessed by goniometer measurement on preoperative and postoperative images. Results： Preoperative radiographs revealed a mean of 7.6°（1.2°-28°） angulation in coronal plane and a mean of 6.8°（0.5°-19°） angulation in sagittal plane. Postoperative anteroposterior and lateral radio graphs showed a mean of 0.8°（0°-4.0°） and 0.6°00-3.6°） of varusvalgus and apex anterior/posterior angulation, respectively. No intraoperative or postoperative complications were noted. Conclusions： This study suggests that the distraction support during MIPPO of tibial shaft fractures is an effective and safe method with no associated complications.
