In current practice of bolt reaming and anchoring of roadways in soft coal and rock mass,resin cartridges bend easily under the strong pushing and stirring of bolts,and the resin accumulates in the bolt-reamed area an...In current practice of bolt reaming and anchoring of roadways in soft coal and rock mass,resin cartridges bend easily under the strong pushing and stirring of bolts,and the resin accumulates in the bolt-reamed area and does not participate in the stirring.As a result,bolts encounter high drilling resistance and cannot reach the bottom of drillholes.The effective anchorage length is far less than the actual anchorage length.Bolts are not centered,and the shear is misaligned at the joint surface in the reaming area,which leads to cracking of the whole anchoring solid and large shear deformation of bolts.This study systematically analyzes the characteristics of roadway bolt reaming and anchoring.The influences of resin stirring force,bolt pull-out force,and reamingeanchoring solid strength on reamingeanchoring performance were analyzed theoretically.The main purpose is to develop a device that enhances reaming and anchoring.The mechanism through which the device strengthens the reamingeanchoring solid was analyzed theoretically.Numerical simulation and experiments were carried out to verify the improved performance of the small-pore reaming and anchoring using the proposed technology.The results showed that the stirring migration rate of the resin cartridge is greatly improved by adding the device to bolts.The reaction rate of the anchoring mixture,stirring pressure,pull-out force of the reaming and anchoring system,bolt concentricity,and shear and compressive strengths of the anchoring solid are also enhanced in the reaming area.This ensures that the resin cartridge in the reaming area is completely stirred,which greatly improves the shear resistance of the reamingeanchoring solid.Meanwhile,the drilling performance,torsional force,and stirring efficiency of bolts are maximized and prevail over those of conventional bolts.展开更多
Through the analysis of the sliding failure form of soil mass under the bearing push-extend reamed of Push-extend Multi-under-reamed Pile, in the paper, the law of coulomb-Mohr is used to establish a stress function a...Through the analysis of the sliding failure form of soil mass under the bearing push-extend reamed of Push-extend Multi-under-reamed Pile, in the paper, the law of coulomb-Mohr is used to establish a stress function and the theory of the sliding line is used to establish Prandtl regional stress field, which determines the stress calculating mode of soil mass and provides a theoretical basis for a further study of this type of pile ultimate bearing capacity of soil mass.展开更多
Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the ...Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.展开更多
The hole reaming and side cutting characteristics of offset one-cone bit and conventional one- cone bit were investigated on simulated drilling experimental equipment. The borehole diameter was a little larger than th...The hole reaming and side cutting characteristics of offset one-cone bit and conventional one- cone bit were investigated on simulated drilling experimental equipment. The borehole diameter was a little larger than the bit diameter due to side force. However, the reaming effect was not very apparent, whether drilling with an offset or conventional one-cone bit. The side cutting displacement increased gradually with increasing depth of drilling and side force. The side cutting displacement of offset onecone bits was larger than that of conventional ones under the same conditions of weight-on-bit （WOB）, rotary speed, side force and borehole depth.展开更多
Electrochemical Discharge Machining(ECDM)is potentially applicable for the fabrication of film-cooling holes.However,It is extremely difficult for the holes to achieve higher precision and machining quality owing to t...Electrochemical Discharge Machining(ECDM)is potentially applicable for the fabrication of film-cooling holes.However,It is extremely difficult for the holes to achieve higher precision and machining quality owing to the working liquid diminish in the lateral machining gap.In this study,a non-metallic backing layer was proposed to overcome the diminish of working liquid,and the electrochemical reaming,as a post-processing method for ECDM,was used to further improve the machining accuracy and quality of the holes.First,the three-dimensional morphology of the melted pit of a paraffin backing layer was scanned to obtain the geometric parameters.Then,simulation analysis and experimental verification of auxiliary flushing by using the non-metallic backing layer were performed.The machining performance of the holes machined with electrochemical reaming based on non-metallic backing layer was confirmed by the observations of the surface topography of the hole wall and orifice,measurement of the orifice precision,and analysis of the element composition on the surface of the orifice wall.Finally,an optimum combination of machining parameters for electrochemical reaming is obtained through a process parameter optimization experiment.展开更多
<b><span>Background</span></b><b><span>: </span></b><span>Bisphosphonate abuse is associated with atypical femur fractures, which despite different fixation method...<b><span>Background</span></b><b><span>: </span></b><span>Bisphosphonate abuse is associated with atypical femur fractures, which despite different fixation methods have increased non-union, delayed union, and re-operation rates. Therefore, there is a need for a surgical technique that may enhance union in such cases. Herein we are introducing a novel technique of sequential multiple vigorous reaming across the fracture site to introduce reaming debris/endosteal bone graft around the fracture site.</span><span> </span><b><span>Materials and Methods</span></b><b><span>: </span></b><span>We present a retrospective analysis of five prospectively treated patients with atypical diaphyseal femur fracture who presented to us from January 2015 to August 2019.</span><span> </span><span>All the patients were followed up at regular intervals and assessed both clinically and radiologically.</span><span> </span><b><span>Results</span></b><b><span>: </span></b><span>All 5 cases operated with our technique showed union at a mean follow-up of 16 weeks (12</span><span> </span><span>-</span><span> </span><span>20 weeks). There were no complications reported in our study at the last mean follow-up of 25 months (12</span><span> </span><span>-</span><span> </span><span>51 months).</span><span> </span><b><span>Conclusion</span></b><b><span>: </span></b><span>This technique of multiple vigorous reaming at and around the fracture site provides a new paradigm in the management of AFF. The autograft around the outer cortex promotes the formation of bridging callus and results in the early union.</span>展开更多
利用扩孔实验机对合金成本优化前后1.2 mm CR820/1180DP扩孔性能进行了测定,并结合扩孔试验位移-载荷曲线、微观组织、力学性能拉伸曲线查找扩孔性能差异的原因。结果认为:优化后低合金成本CR820/1180DP微观组织状态大幅改善,表现为铁...利用扩孔实验机对合金成本优化前后1.2 mm CR820/1180DP扩孔性能进行了测定,并结合扩孔试验位移-载荷曲线、微观组织、力学性能拉伸曲线查找扩孔性能差异的原因。结果认为:优化后低合金成本CR820/1180DP微观组织状态大幅改善,表现为铁素体相形态由条带状变为球状或等轴状分布;马氏体则由条状聚集态变为团簇球状形态,且优化后马氏体相内发现大量(Fe,Mn)xCy粒状碳化物析出;扩孔性能较优化前提升1倍以上,平均极限扩孔率在25.2%,其主要是由于优化后CR820/1180DP铁-马双相弥散分布形态,相界面为球状,马氏体晶粒内部大量的第二相析出,大幅降低了扩孔实验过程中铁-马两相界面应力集中程度,且界面处发生应力集中也相对滞后,当应变发生在马氏体相时,由于其晶粒内部粒状第二相的存在,随塑性变形发生位错以绕过或切过第二相粒子的形式增强材料强度是扩孔性能大幅提升的根本原因。优化后低合金成本CR820/1180DP成功应用于前保险杠横梁的辊压成形制作,解决了CR820/1180DP辊压开裂的难题。展开更多
基金supported by the National Natural Science Foundation of China-Liaoning Joint Fund Key Project(Grant No.U1908222)the National Natural Science Foundation of China Youth Science Fund(Grant No.52104087).
文摘In current practice of bolt reaming and anchoring of roadways in soft coal and rock mass,resin cartridges bend easily under the strong pushing and stirring of bolts,and the resin accumulates in the bolt-reamed area and does not participate in the stirring.As a result,bolts encounter high drilling resistance and cannot reach the bottom of drillholes.The effective anchorage length is far less than the actual anchorage length.Bolts are not centered,and the shear is misaligned at the joint surface in the reaming area,which leads to cracking of the whole anchoring solid and large shear deformation of bolts.This study systematically analyzes the characteristics of roadway bolt reaming and anchoring.The influences of resin stirring force,bolt pull-out force,and reamingeanchoring solid strength on reamingeanchoring performance were analyzed theoretically.The main purpose is to develop a device that enhances reaming and anchoring.The mechanism through which the device strengthens the reamingeanchoring solid was analyzed theoretically.Numerical simulation and experiments were carried out to verify the improved performance of the small-pore reaming and anchoring using the proposed technology.The results showed that the stirring migration rate of the resin cartridge is greatly improved by adding the device to bolts.The reaction rate of the anchoring mixture,stirring pressure,pull-out force of the reaming and anchoring system,bolt concentricity,and shear and compressive strengths of the anchoring solid are also enhanced in the reaming area.This ensures that the resin cartridge in the reaming area is completely stirred,which greatly improves the shear resistance of the reamingeanchoring solid.Meanwhile,the drilling performance,torsional force,and stirring efficiency of bolts are maximized and prevail over those of conventional bolts.
文摘Through the analysis of the sliding failure form of soil mass under the bearing push-extend reamed of Push-extend Multi-under-reamed Pile, in the paper, the law of coulomb-Mohr is used to establish a stress function and the theory of the sliding line is used to establish Prandtl regional stress field, which determines the stress calculating mode of soil mass and provides a theoretical basis for a further study of this type of pile ultimate bearing capacity of soil mass.
基金support from the Natural Science Foundation of China(Grant Nos.52222401,52234002,51904317 and 52174012)Science Foundation of China University of Petroleum,Beijing(Grant No.ZXZX20230083)other projects(ZLZX2020-01-07-01).
文摘Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.
文摘The hole reaming and side cutting characteristics of offset one-cone bit and conventional one- cone bit were investigated on simulated drilling experimental equipment. The borehole diameter was a little larger than the bit diameter due to side force. However, the reaming effect was not very apparent, whether drilling with an offset or conventional one-cone bit. The side cutting displacement increased gradually with increasing depth of drilling and side force. The side cutting displacement of offset onecone bits was larger than that of conventional ones under the same conditions of weight-on-bit （WOB）, rotary speed, side force and borehole depth.
基金supported by the National Natural Science Foundation of China(No.51705239)。
文摘Electrochemical Discharge Machining(ECDM)is potentially applicable for the fabrication of film-cooling holes.However,It is extremely difficult for the holes to achieve higher precision and machining quality owing to the working liquid diminish in the lateral machining gap.In this study,a non-metallic backing layer was proposed to overcome the diminish of working liquid,and the electrochemical reaming,as a post-processing method for ECDM,was used to further improve the machining accuracy and quality of the holes.First,the three-dimensional morphology of the melted pit of a paraffin backing layer was scanned to obtain the geometric parameters.Then,simulation analysis and experimental verification of auxiliary flushing by using the non-metallic backing layer were performed.The machining performance of the holes machined with electrochemical reaming based on non-metallic backing layer was confirmed by the observations of the surface topography of the hole wall and orifice,measurement of the orifice precision,and analysis of the element composition on the surface of the orifice wall.Finally,an optimum combination of machining parameters for electrochemical reaming is obtained through a process parameter optimization experiment.
文摘<b><span>Background</span></b><b><span>: </span></b><span>Bisphosphonate abuse is associated with atypical femur fractures, which despite different fixation methods have increased non-union, delayed union, and re-operation rates. Therefore, there is a need for a surgical technique that may enhance union in such cases. Herein we are introducing a novel technique of sequential multiple vigorous reaming across the fracture site to introduce reaming debris/endosteal bone graft around the fracture site.</span><span> </span><b><span>Materials and Methods</span></b><b><span>: </span></b><span>We present a retrospective analysis of five prospectively treated patients with atypical diaphyseal femur fracture who presented to us from January 2015 to August 2019.</span><span> </span><span>All the patients were followed up at regular intervals and assessed both clinically and radiologically.</span><span> </span><b><span>Results</span></b><b><span>: </span></b><span>All 5 cases operated with our technique showed union at a mean follow-up of 16 weeks (12</span><span> </span><span>-</span><span> </span><span>20 weeks). There were no complications reported in our study at the last mean follow-up of 25 months (12</span><span> </span><span>-</span><span> </span><span>51 months).</span><span> </span><b><span>Conclusion</span></b><b><span>: </span></b><span>This technique of multiple vigorous reaming at and around the fracture site provides a new paradigm in the management of AFF. The autograft around the outer cortex promotes the formation of bridging callus and results in the early union.</span>
文摘利用扩孔实验机对合金成本优化前后1.2 mm CR820/1180DP扩孔性能进行了测定,并结合扩孔试验位移-载荷曲线、微观组织、力学性能拉伸曲线查找扩孔性能差异的原因。结果认为:优化后低合金成本CR820/1180DP微观组织状态大幅改善,表现为铁素体相形态由条带状变为球状或等轴状分布;马氏体则由条状聚集态变为团簇球状形态,且优化后马氏体相内发现大量(Fe,Mn)xCy粒状碳化物析出;扩孔性能较优化前提升1倍以上,平均极限扩孔率在25.2%,其主要是由于优化后CR820/1180DP铁-马双相弥散分布形态,相界面为球状,马氏体晶粒内部大量的第二相析出,大幅降低了扩孔实验过程中铁-马两相界面应力集中程度,且界面处发生应力集中也相对滞后,当应变发生在马氏体相时,由于其晶粒内部粒状第二相的存在,随塑性变形发生位错以绕过或切过第二相粒子的形式增强材料强度是扩孔性能大幅提升的根本原因。优化后低合金成本CR820/1180DP成功应用于前保险杠横梁的辊压成形制作,解决了CR820/1180DP辊压开裂的难题。
