Geomechanics in deep mines becomes more complex and structural support in soft rock can be very difficult.Highly stressed soft rock subject to expansion deformation is particularly difficult to control.The Tiefa Coal ...Geomechanics in deep mines becomes more complex and structural support in soft rock can be very difficult.Highly stressed soft rock subject to expansion deformation is particularly difficult to control.The Tiefa Coal Industry Group Daqiang Coal Mine is used as an example.A ventilation shaft,à550 horsehead,is located in tertiary soft rock.Analysis of the reasons for deformation shows an intumescent rock,which is easily damaged.Field observations and theoretical analysis led to a design capable of stabilizing the rock.A combination of spray,anchors,anchor bolts,and soft corner coupled truss supports allowed the deformation to be controlled.This provides a model for similar designs when support of a horsehead roadway is required.展开更多
A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large d...A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation（CRLD） bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt（rebar） using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson＇s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson＇s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.展开更多
目的探讨有创机械通气患者在通过自主呼吸试验后拔管失败的危险因素。方法对2006年5月～2007年10月入住中山医院急诊ICU并接受有创机械通气48 h以上的患者进行前瞻性调查,采用7 cm H2O的压力支持模式持续30 min进行自主呼吸试验,记录自...目的探讨有创机械通气患者在通过自主呼吸试验后拔管失败的危险因素。方法对2006年5月～2007年10月入住中山医院急诊ICU并接受有创机械通气48 h以上的患者进行前瞻性调查,采用7 cm H2O的压力支持模式持续30 min进行自主呼吸试验,记录自主呼吸试验前后的临床资料,按照拔管结局将患者分为拔管成功组和拔管失败组。结果58例患者通过自主呼吸试验后拔管,其中47例(81%)拔管成功,11例(19%)拔管失败进行再插管。单因素分析显示:老年人[拔管失败组年龄(78.1±7.9)岁,拔管成功组年龄(67.4±15.1)岁,P<0.05]、较高的浅快呼吸指数[拔管失败组(83±12)次.min-1.L-1,拔管成功组(68±19)次.min-1.L-1,P<0.05]以及较多的气道分泌物(拔管失败组54.5%,拔管成功组21.3%,P<0.05)与拔管失败有关。结论有创机械通气患者在通过自主呼吸试验后,年龄、浅快呼吸指数及气道分泌物量是预测拔管失败的有效指标。展开更多
基金supported by the National Basic Research Program of China (No.2006CB202200)the Ministry of Education Innovation Team Project (No. IRT0656)+2 种基金the Central University Basic Research Special Fund Operating Expense (No.2009QL06)the New Century Excellent Talents Support Projects of Ministry of Education (No.NCET-08-0833)the National Natural Science Foundation of China (No.41040027)
文摘Geomechanics in deep mines becomes more complex and structural support in soft rock can be very difficult.Highly stressed soft rock subject to expansion deformation is particularly difficult to control.The Tiefa Coal Industry Group Daqiang Coal Mine is used as an example.A ventilation shaft,à550 horsehead,is located in tertiary soft rock.Analysis of the reasons for deformation shows an intumescent rock,which is easily damaged.Field observations and theoretical analysis led to a design capable of stabilizing the rock.A combination of spray,anchors,anchor bolts,and soft corner coupled truss supports allowed the deformation to be controlled.This provides a model for similar designs when support of a horsehead roadway is required.
基金supported by National Key Research and Development Program(2016YFC0600901)the National Natural Science Foundation of China(Grant Nos.51374214,51134005 and 51574248)+1 种基金the Special Fund of Basic Research and Operating of China University of Mining&Technology,Beijing(Grant Nos.2009QL03)the State Scholarship Fund of China
文摘A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation（CRLD） bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt（rebar） using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson＇s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson＇s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.
文摘目的探讨有创机械通气患者在通过自主呼吸试验后拔管失败的危险因素。方法对2006年5月～2007年10月入住中山医院急诊ICU并接受有创机械通气48 h以上的患者进行前瞻性调查,采用7 cm H2O的压力支持模式持续30 min进行自主呼吸试验,记录自主呼吸试验前后的临床资料,按照拔管结局将患者分为拔管成功组和拔管失败组。结果58例患者通过自主呼吸试验后拔管,其中47例(81%)拔管成功,11例(19%)拔管失败进行再插管。单因素分析显示:老年人[拔管失败组年龄(78.1±7.9)岁,拔管成功组年龄(67.4±15.1)岁,P<0.05]、较高的浅快呼吸指数[拔管失败组(83±12)次.min-1.L-1,拔管成功组(68±19)次.min-1.L-1,P<0.05]以及较多的气道分泌物(拔管失败组54.5%,拔管成功组21.3%,P<0.05)与拔管失败有关。结论有创机械通气患者在通过自主呼吸试验后,年龄、浅快呼吸指数及气道分泌物量是预测拔管失败的有效指标。
