The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engin...The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.展开更多
The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded c...The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded cast steel joint was analyzed to determine the optimal mesh size.Based on the stress field analysis of the finite element model of the welded cast steel joint at the weld toe and weld root,the sharp model of the extrapolation notch stress method was applied to derive the effective notch stress of the rounded model belonging to the effective notch stress method,in which the key problem is to calculate the extrapolation point C,and the extrapolation point C has an exponential function relationship with the geometric parameters of the welded cast steel joint.By setting different values of geometric parameters,the corresponding value of parameter C is calculated,and then the functional relationship between the extrapolation point C and the geometric parameters can be obtained by the multiple linear regression analysis.Meanwhile,the fatigue life evaluation of the girth butt weld within welded cast steel joints based on the effective notch stress was performed according to the guideline recommended by the IIW(International Institute of Welding).The results indicate that the extrapolation notch stress method can effectively simplify the process of calculating the effective notch stress and accurately evaluate the fatigue life of the girth butt weld within welded cast steel joints.展开更多
To investigate the effect of the radius of the spherical heads of the indenter on the results of a point load test,this study uses a discrete element model based on the flat joint contact for numerical simulation.Resu...To investigate the effect of the radius of the spherical heads of the indenter on the results of a point load test,this study uses a discrete element model based on the flat joint contact for numerical simulation.Results show that the discrete element model based on the flat joint model can accurately describe the damage process and size effects of rocks under point loads.Damage of rock samples under the loading of different radii of the indenter can be characterized as vertical splitting damage,and the larger the radius of the indenter is,the larger the damage area.Values of the point load strength of rock samples increase with increasing the radius of the indenter and obey a power function relationship.The results of this study provide a theoretical basis for the selection of the spherical heads of indenters in point load tests and tool design for mechanical rock breaking.展开更多
目的观察培元养心法(背俞穴温针灸)治疗肾阳不足型膝关节退行性病变疗效。方法纳入肾阳不足型膝关节退行性病变患者80例,采取随机数字表法分为对照组40例与观察组40例,对照组接受膝关节置换术治疗,观察组在对照组治疗基础上结合培元养心...目的观察培元养心法(背俞穴温针灸)治疗肾阳不足型膝关节退行性病变疗效。方法纳入肾阳不足型膝关节退行性病变患者80例,采取随机数字表法分为对照组40例与观察组40例,对照组接受膝关节置换术治疗,观察组在对照组治疗基础上结合培元养心法(背俞穴温针灸)治疗,观察各组数据情况:疗效优良率、治疗前后中医证候积分变化、术后3 d及术后6 d、术后9 d患者的疼痛评分[视觉模拟疼痛评分法(Visual analogue scale,VAS)],治疗前后患者C反应蛋白(C-reactive protein,CRP)及肿瘤坏死因子α(Tumor necrosis factor-α,TNF-α)和白介素-6(Interleukin-6,IL-6)指标变化、治疗前后患者Lysholm膝关节量表评分变化、并发症发生率、治疗前、治疗2周及治疗4周身体健康评分(the MOS item short from health survey,SF-36)。结果观察组患者治疗效果优良率(95.00%,38/40)高于对照组(80.00%,32/40),差异有统计学意义(P<0.05);各组患者治疗后中医证候积分下降,炎症因子(CRP、TNF-α、IL-6)均显著下降,Lysholm膝关节量表总评分显著上升,观察组治疗后中医证候积分及炎症因子(CRP、TNF-α、IL-6)均低于对照组,Lysholm膝关节量表总评分高于对照组,差异有统计学意义(P<0.05);观察组患者术后3、6、9 d的VAS评分均比对照组更低,差异有统计学意义(P<0.05);对照组并发症率为20.00%(8/40),比观察组的5.00%(2/40)更低,差异有统计学意义(P<0.05);治疗2周及治疗4周后观察组患者的SF-36评分均高于对照组患者,差异有统计学意义(P<0.05)。结论培元养心法(背俞穴温针灸)治疗肾阳不足型膝关节退行性病变疗效良好,患者症状改善,膝关节功能改善,并发症少,治疗安全可靠,且患者治疗后身体健康好转,值得应用。展开更多
Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineeri...Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineering, hydraulic and hydropower engineering caused by columnar jointed basaltic mass, Voronoi graph from geometry was introduced to simulate the irregular columnar jointed basaltic mass at Baihetan hydraulic station. Discrete element software UDEC was used to simulate the whole process of rigid bearing plate test. Anisotropic constitutive of columnar joints was adopted to analyze the stress diffusion of rock mass at dam base of Baihetan. The results show that, the compaction property and hysteresis effect are well simulated based on discrete element simulation of Voronoi joint structure by UDEC. Four stages of cyclic loading and unloading process are imaged clearly. The results from in situ rigid bearing plate tests are explicated and the stress diffusion rule of anisotropic body is affected by structure surface. The elements in the stress state of 4-5 MPa are the most, about more than 35% of the total. Appropriate constitutive must be proposed to columnar jointed rock mass with different styles. It has important significance to realize the nonlinear mechanical behavior of irregular columnar jointed basaltic mass.展开更多
基金supported by the National Natural Science Foundation of China(No.42207175)。
文摘The joint roughness coefficient(JRC) is one of the key parameters for evaluating the shear strength of rock joints.Because of the scale effect in the JRC,reliable JRC values are of great importance for most rock engineering projects.During the collection process of JRC samples,the redundancy or insufficiency of representative rock joint surface topography(RJST) information in serial length JRC samples is the essential reason that affects the reliability of the scale effect results.Therefore,this paper proposes an adaptive sampling method,in which we use the entropy consistency measure Q(a) to evaluate the consistency of the joint morphology information contained in adjacent JRC samples.Then the sampling interval is automatically adjusted according to the threshold Q(at) of the entropy consistency measure to ensure that the degree of change of RJST information between JRC samples is the same,and ultimately makes the representative RJST information in the collected JRC samples more balanced.The application results of actual cases show that the proposed method can obtain the scale effect in the JRC efficiently and reliably.
基金The National Key Research and Development Program of China(No.2017YFC0805100),the National Natural Science Foundation of China(No.51578137)the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Open Research Fund Program of Jiangsu Key Laboratory of Engineering Mechanics.
文摘The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded cast steel joint was analyzed to determine the optimal mesh size.Based on the stress field analysis of the finite element model of the welded cast steel joint at the weld toe and weld root,the sharp model of the extrapolation notch stress method was applied to derive the effective notch stress of the rounded model belonging to the effective notch stress method,in which the key problem is to calculate the extrapolation point C,and the extrapolation point C has an exponential function relationship with the geometric parameters of the welded cast steel joint.By setting different values of geometric parameters,the corresponding value of parameter C is calculated,and then the functional relationship between the extrapolation point C and the geometric parameters can be obtained by the multiple linear regression analysis.Meanwhile,the fatigue life evaluation of the girth butt weld within welded cast steel joints based on the effective notch stress was performed according to the guideline recommended by the IIW(International Institute of Welding).The results indicate that the extrapolation notch stress method can effectively simplify the process of calculating the effective notch stress and accurately evaluate the fatigue life of the girth butt weld within welded cast steel joints.
文摘To investigate the effect of the radius of the spherical heads of the indenter on the results of a point load test,this study uses a discrete element model based on the flat joint contact for numerical simulation.Results show that the discrete element model based on the flat joint model can accurately describe the damage process and size effects of rocks under point loads.Damage of rock samples under the loading of different radii of the indenter can be characterized as vertical splitting damage,and the larger the radius of the indenter is,the larger the damage area.Values of the point load strength of rock samples increase with increasing the radius of the indenter and obey a power function relationship.The results of this study provide a theoretical basis for the selection of the spherical heads of indenters in point load tests and tool design for mechanical rock breaking.
文摘目的观察培元养心法(背俞穴温针灸)治疗肾阳不足型膝关节退行性病变疗效。方法纳入肾阳不足型膝关节退行性病变患者80例,采取随机数字表法分为对照组40例与观察组40例,对照组接受膝关节置换术治疗,观察组在对照组治疗基础上结合培元养心法(背俞穴温针灸)治疗,观察各组数据情况:疗效优良率、治疗前后中医证候积分变化、术后3 d及术后6 d、术后9 d患者的疼痛评分[视觉模拟疼痛评分法(Visual analogue scale,VAS)],治疗前后患者C反应蛋白(C-reactive protein,CRP)及肿瘤坏死因子α(Tumor necrosis factor-α,TNF-α)和白介素-6(Interleukin-6,IL-6)指标变化、治疗前后患者Lysholm膝关节量表评分变化、并发症发生率、治疗前、治疗2周及治疗4周身体健康评分(the MOS item short from health survey,SF-36)。结果观察组患者治疗效果优良率(95.00%,38/40)高于对照组(80.00%,32/40),差异有统计学意义(P<0.05);各组患者治疗后中医证候积分下降,炎症因子(CRP、TNF-α、IL-6)均显著下降,Lysholm膝关节量表总评分显著上升,观察组治疗后中医证候积分及炎症因子(CRP、TNF-α、IL-6)均低于对照组,Lysholm膝关节量表总评分高于对照组,差异有统计学意义(P<0.05);观察组患者术后3、6、9 d的VAS评分均比对照组更低,差异有统计学意义(P<0.05);对照组并发症率为20.00%(8/40),比观察组的5.00%(2/40)更低,差异有统计学意义(P<0.05);治疗2周及治疗4周后观察组患者的SF-36评分均高于对照组患者,差异有统计学意义(P<0.05)。结论培元养心法(背俞穴温针灸)治疗肾阳不足型膝关节退行性病变疗效良好,患者症状改善,膝关节功能改善,并发症少,治疗安全可靠,且患者治疗后身体健康好转,值得应用。
基金Projects(50979030, 50911130366) supported by the National Natural Science Foundation of ChinaProject(2009B14014) supported by the Fundamental Research Funds for the Central Universities in China
文摘Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineering, hydraulic and hydropower engineering caused by columnar jointed basaltic mass, Voronoi graph from geometry was introduced to simulate the irregular columnar jointed basaltic mass at Baihetan hydraulic station. Discrete element software UDEC was used to simulate the whole process of rigid bearing plate test. Anisotropic constitutive of columnar joints was adopted to analyze the stress diffusion of rock mass at dam base of Baihetan. The results show that, the compaction property and hysteresis effect are well simulated based on discrete element simulation of Voronoi joint structure by UDEC. Four stages of cyclic loading and unloading process are imaged clearly. The results from in situ rigid bearing plate tests are explicated and the stress diffusion rule of anisotropic body is affected by structure surface. The elements in the stress state of 4-5 MPa are the most, about more than 35% of the total. Appropriate constitutive must be proposed to columnar jointed rock mass with different styles. It has important significance to realize the nonlinear mechanical behavior of irregular columnar jointed basaltic mass.
