In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic ...In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it a展开更多
The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joi...The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joint rock-l!ke specimens under uniaxial loading have been investigated by DIC （digital image correlation） and discrete element numerical method （PFC2D）. The results are obtained. Firstly, the UCSJ of spec- imens with γ= 15° or 30° shows similar tendency while α goes from 0° to 75°. With γ= 45° or 60°, the UCSJ of specimens increases when α goes from 0° to 30° and decreases after α goes beyond 30°. With γ=75°, the peak UCSJ value is reached when α=0°. The UCSJ value shows an increasing trend when α goes from 60° to 75°. Secondly, the ubiquitous-joint specimens present different failure modes for various levels of α and γ（β-α）. Based on the experimental results, the failure mode of ubiquitous-joint specimens can be classified into three categories： stepped path failure, failure through parallel plane, and failure through cross plane.展开更多
Background Inflammation is an important element of the pathophysiological process of heart failure (HF) and is correlated with subtypes of HF. The association between multiple biomarkers of inflammation and HF subtype...Background Inflammation is an important element of the pathophysiological process of heart failure (HF) and is correlated with subtypes of HF. The association between multiple biomarkers of inflammation and HF subtypes in Chinese subjects remains unclear. This study aimed to compare the differences in inflammation biomarkers among Chinese patients with different subtypes of HF who have been identified to date. Methods We included 413 consecutive patients with HF,including 262 with preserved ejection fraction (HFpEF),55 with middle-ranged ejection fraction (HFmrEF) and 96 with reduced ejection fraction (HFrEF). Ten inflammation biomarkers were analyzed and compared according to the HF subtypes. One hundred contemporary non-HF subjects were also recruited as the control group. Moreover,the correlations between the inflammatory biomarkers and left ventricular ejection fraction of the HF subtypes were assessed. Results The mean age of the HF patients was 65.0 ± 12.0 years,65.8% were male. Distinct subtypes of HF demonstrated different inflammation biomarker panels. IL-6,PTX-3,ANGPTL-4 and TNF-α were correlated with HFrEF;IL-1β and PTX-3 were correlated with HFmrEF;and IL-1β and IL-6 were correlated with HFpEF. The multivariable logistic regression showed that IL-1β[relative ratio (RR)= 1.08,95% CI: 1.02–1.15,P = 0.010],IL-6 (RR = 1.03,95% CI: 1.01–1.06,P = 0.016),PTX-3 (RR = 1.31,95% CI: 1.11–1.55,P = 0.001),and ANGPTL-4 (RR = 1.05,95% CI: 1.02–1.07,P < 0.001) were independently associated with HF,while IL-6 (RR = 1.03,95% CI: 1.01–1.04,P = 0.019),PTX-3 (RR = 1.23,95% CI: 1.06–1.43,P = 0.007),and ANGPTL-4 (RR = 1.03,95% CI: 1.01–1.06,P = 0.005) were independently associated with the HF subtype. Conclusions Diverse inflammation biomarkers have multifaceted presentations according to the subtype of HF,which may illustrate the diverse mechanisms of inflammation in Chinese HF patients. IL-6,PTX-3,and ANGPTL-4 were independent inflammation factors associated with HFrEF and HF.展开更多
Multi-failures are possible to appear in the process of using the structural system, such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact...Multi-failures are possible to appear in the process of using the structural system, such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation in- duced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reli- ability analysis considering static strength, fatigue and stiffness is given. A nu- merical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the pa- per, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.展开更多
Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of roc...Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.展开更多
Background Recently, increasing number of literature has identified the posterior tibial slope （PTS） as one of the risk factors of primary anterior cruciate ligament （ACL） injury. However, few studies concerning t...Background Recently, increasing number of literature has identified the posterior tibial slope （PTS） as one of the risk factors of primary anterior cruciate ligament （ACL） injury. However, few studies concerning the association between failure of ACL reconstruction （ACLR） and PTS have been published. The objective of this study was to explore the association between the failure of ACLR and PTS at a minimum of two years follow-up. Methods Two hundred and thirty eight eligible patients from June 2009 to October 2010 were identified from our database. A total of 20 failure cases of ACLR and 20 randomly selected controls were included in this retrospective study. The demographic data and the results of manual maximum side-to-side difference with KT-1000 arthrometer at 30°of knee flexion and pivot-shift test before the ACLR and at the final follow-up were collected. The medial and lateral PTSs were measured using the magnetic resonance imaging （MRI） scan, based on Hudek＇s measurement. A comparison of PTS between the two groups was performed. Results The overall failure rate of the present study was 8.4%. Of the 40 participants, the mean medial PTS was 4.1°±3.2°and the mean lateral PTS was 4.6°±2.6°. The medial PTS of the ACLR failure group was significantly steeper than the control group （3.5°±2.5° vs. 6.1°±2.1°, P=0.000）. Similarly, the lateral PTS of the ACLR failure group was significantly steeper than the control group （2.9°±2.1 °vs. 5.5°±3.0°, P=0.006）. For medial PTS ≥5°, the odds ratio of ACLR failure was 6.8 （P=0.007）; for lateral PTS ≥5°, the odds ratio of ACLR failure was 10.8 （P=0.000）. Conclusion Both medial and lateral PTS were significantly steeper in failures of ACLR than the control group. Medial or lateral PTS ≥5° was a new risk factor of ACLR failure.展开更多
基金supported by the National Basic Research 973 Program of China (Grant 2014CB046905)the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars (Grant BK20150005)+1 种基金the Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grant 2014XT03)the innovation research project for academic graduate of Jiangsu Province (Grant KYLX16_0536)
文摘In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it a
基金funding from Project (Nos.51474249 and 51404179) supported by National Natural Science Foundation of ChinaProject Supported by Innovation Driven Plan of Central South University of China (No.2016CX019)Project (No. SKLGDUEK1405) funded by the Open Projects of State Key Laboratory for Geo-mechanics and Deep Underground Engineering of China University of Mining and Technology,in China
文摘The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joint rock-l!ke specimens under uniaxial loading have been investigated by DIC （digital image correlation） and discrete element numerical method （PFC2D）. The results are obtained. Firstly, the UCSJ of spec- imens with γ= 15° or 30° shows similar tendency while α goes from 0° to 75°. With γ= 45° or 60°, the UCSJ of specimens increases when α goes from 0° to 30° and decreases after α goes beyond 30°. With γ=75°, the peak UCSJ value is reached when α=0°. The UCSJ value shows an increasing trend when α goes from 60° to 75°. Secondly, the ubiquitous-joint specimens present different failure modes for various levels of α and γ（β-α）. Based on the experimental results, the failure mode of ubiquitous-joint specimens can be classified into three categories： stepped path failure, failure through parallel plane, and failure through cross plane.
基金supported by the National Natural Science Foundation of China (No.31701155)the National Key Research and Development Program of China (2017YFC 0114001)Chinese PLA General Hospital Medical Big Data Research and Development Project (No.2017MBD-007)
文摘Background Inflammation is an important element of the pathophysiological process of heart failure (HF) and is correlated with subtypes of HF. The association between multiple biomarkers of inflammation and HF subtypes in Chinese subjects remains unclear. This study aimed to compare the differences in inflammation biomarkers among Chinese patients with different subtypes of HF who have been identified to date. Methods We included 413 consecutive patients with HF,including 262 with preserved ejection fraction (HFpEF),55 with middle-ranged ejection fraction (HFmrEF) and 96 with reduced ejection fraction (HFrEF). Ten inflammation biomarkers were analyzed and compared according to the HF subtypes. One hundred contemporary non-HF subjects were also recruited as the control group. Moreover,the correlations between the inflammatory biomarkers and left ventricular ejection fraction of the HF subtypes were assessed. Results The mean age of the HF patients was 65.0 ± 12.0 years,65.8% were male. Distinct subtypes of HF demonstrated different inflammation biomarker panels. IL-6,PTX-3,ANGPTL-4 and TNF-α were correlated with HFrEF;IL-1β and PTX-3 were correlated with HFmrEF;and IL-1β and IL-6 were correlated with HFpEF. The multivariable logistic regression showed that IL-1β[relative ratio (RR)= 1.08,95% CI: 1.02–1.15,P = 0.010],IL-6 (RR = 1.03,95% CI: 1.01–1.06,P = 0.016),PTX-3 (RR = 1.31,95% CI: 1.11–1.55,P = 0.001),and ANGPTL-4 (RR = 1.05,95% CI: 1.02–1.07,P < 0.001) were independently associated with HF,while IL-6 (RR = 1.03,95% CI: 1.01–1.04,P = 0.019),PTX-3 (RR = 1.23,95% CI: 1.06–1.43,P = 0.007),and ANGPTL-4 (RR = 1.03,95% CI: 1.01–1.06,P = 0.005) were independently associated with the HF subtype. Conclusions Diverse inflammation biomarkers have multifaceted presentations according to the subtype of HF,which may illustrate the diverse mechanisms of inflammation in Chinese HF patients. IL-6,PTX-3,and ANGPTL-4 were independent inflammation factors associated with HFrEF and HF.
基金Supported by the Basic Research Program of Military Industrial Technology of CSTIND (Grant No. Z192003A001)the Monograph Fund of CSTIND (Commission No. [2002]86)
文摘Multi-failures are possible to appear in the process of using the structural system, such as dead load failure, fatigue failure and stiffness failure. The expression of residual resistance is given based on the impact of random crack propagation in- duced by the fatigue load on the critical limit stress and section modulus in this paper. The failure modes of every element of the structural system are analyzed under dead and fatigue loads, and the influence of the correlation of failure modes on reliability of the element is considered. Failure mechanism and the correlation of failure modes under dead and fatigue loads are discussed, and the method of reli- ability analysis considering static strength, fatigue and stiffness is given. A nu- merical example is analyzed, which indicates that the failure probability is different for different use life and the influence of dead and fatigue loads on reliability of the structural system is different as well. This method of reliability analysis, in the pa- per, is better than the method only considering a single factor (or static strength, or fatigue, or stiffness, etc.) in the case of practical engineering.
基金supported by grants from the Research Grants Council of the Hong Kong,Special Administrative Region,China [Project No.9042172 (CityU11200115)and Project No.8779012(T22-603/15N)]
文摘Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.
文摘Background Recently, increasing number of literature has identified the posterior tibial slope （PTS） as one of the risk factors of primary anterior cruciate ligament （ACL） injury. However, few studies concerning the association between failure of ACL reconstruction （ACLR） and PTS have been published. The objective of this study was to explore the association between the failure of ACLR and PTS at a minimum of two years follow-up. Methods Two hundred and thirty eight eligible patients from June 2009 to October 2010 were identified from our database. A total of 20 failure cases of ACLR and 20 randomly selected controls were included in this retrospective study. The demographic data and the results of manual maximum side-to-side difference with KT-1000 arthrometer at 30°of knee flexion and pivot-shift test before the ACLR and at the final follow-up were collected. The medial and lateral PTSs were measured using the magnetic resonance imaging （MRI） scan, based on Hudek＇s measurement. A comparison of PTS between the two groups was performed. Results The overall failure rate of the present study was 8.4%. Of the 40 participants, the mean medial PTS was 4.1°±3.2°and the mean lateral PTS was 4.6°±2.6°. The medial PTS of the ACLR failure group was significantly steeper than the control group （3.5°±2.5° vs. 6.1°±2.1°, P=0.000）. Similarly, the lateral PTS of the ACLR failure group was significantly steeper than the control group （2.9°±2.1 °vs. 5.5°±3.0°, P=0.006）. For medial PTS ≥5°, the odds ratio of ACLR failure was 6.8 （P=0.007）; for lateral PTS ≥5°, the odds ratio of ACLR failure was 10.8 （P=0.000）. Conclusion Both medial and lateral PTS were significantly steeper in failures of ACLR than the control group. Medial or lateral PTS ≥5° was a new risk factor of ACLR failure.
