Backfill is increasingly used in underground mines to reduce the surface impact from the wastes produced by the mining operations. But the main objectives of backfilling are to improve ground stability and reduce ore ...Backfill is increasingly used in underground mines to reduce the surface impact from the wastes produced by the mining operations. But the main objectives of backfilling are to improve ground stability and reduce ore dilution. To this end, the backfill in a stope must possess a minimum strength to remain self-standing during mining of an adjacent stope. This required strength is often estimated using a solution proposed by Mitchell and co-workers, which was based on a limit equilibrium analysis of a wedge exposed by the open face. In this paper, three dimensional numerical simulations have been performed to assess the behavior of the wedge model. A new limit equilibrium solution is proposed, based on the backfill displacements obtained from the simulations. Comparisons are made between the proposed solution and experimental and numerical modeling results. Compared with the previous solution, a better agreement is obtained between the new solution and experimental results for the required cohesion and factor of safety. For large scale(field) conditions, the results also show that the required strength obtained from the proposed solution corresponds quite well to the simulated backfill response.展开更多
In order to precisely predict the hazard degree of goaf(HDG), the RS-TOPSIS model was built based on the results of expert investigation. To evaluate the HDG in the underground mine, five structure size factors, i.e. ...In order to precisely predict the hazard degree of goaf(HDG), the RS-TOPSIS model was built based on the results of expert investigation. To evaluate the HDG in the underground mine, five structure size factors, i.e. goaf span, exposed area, goaf height, goaf depth, and pillar width, were selected as the evaluation indexes. And based on rough dependability in rough set(RS)theory, the weights of evaluation indexes were identified by calculating rough dependability between evaluation indexes and evaluation results. Fourty goafs in some mines of western China, whose indexes parameters were measured by cavity monitoring system(CMS), were taken as evaluation objects. In addition, the characteristic parameters of five grades' typical goafs were built according to the interval limits value of single index evaluation. Then, using the technique for order preference by similarity to ideal solution(TOPSIS), five-category classification of HDG was realized based on closeness degree, and the HDG was also identified.Results show that the five-category identification of mine goafs could be realized by RS-TOPSIS method, based on the structure-scale-effect. The classification results are consistent with those of numerical simulation based on stress and displacement,while the coincidence rate is up to 92.5%. Furthermore, the results are more conservative to safety evaluation than numerical simulation, thus demonstrating that the proposed method is more easier, reasonable and more definite for HDG identification.展开更多
To identify early predictive markers of poor outcomes in patients with acute liver injury from wild mushroom intoxication.METHODSThis observational, retrospective record review involved adults aged ≥ 18 years admitte...To identify early predictive markers of poor outcomes in patients with acute liver injury from wild mushroom intoxication.METHODSThis observational, retrospective record review involved adults aged ≥ 18 years admitted to emergency department with mushroom intoxication from January 2005 to December 2015. The diagnosis of mushroom intoxication was based on the following: (1) a positive history of recent wild mushroom intake (either raw or cooked); (2) the onset of gastrointestinal symptoms, such as watery diarrhea, vomiting, and/or abdominal pain, after ingestion; and (3) the exclusion of other possible causes of acute liver injury. Acute liver injury was defined by a > 5-fold elevation of liver enzymes or moderate coagulopathy [international normalized ratio (INR) > 2.0]. Clinical and laboratory findings were compared in survivors and non-survivors.RESULTSOf 93 patients with mushroom intoxication, 23, 11 men (47.8%) and 12 women (52.2%), of median age 61 years, developed acute liver injury. The overall in-hospital mortality rate was 43.5% (10/23). Among the laboratory variables, mean serum alkaline phosphatase (73.38 ± 10.89 mg/dL vs 180.40 ± 65.39 mg/dL, P < 0.01), total bilirubin (2.312 ± 1.16 mg/dL vs 7.16 ± 2.94 mg/dL, P < 0.01) concentrations and indirect/direct bilirubin (2.45 ± 1.39 mg/dL vs 0.99 ± 0.45 mg/dL, P < 0.01) ratio as well as prothrombin time (1.88 ± 0.83 mg/dL vs 10.43 ± 4.81 mg/dL, P < 0.01), and activated partial thromboplastin time (aPTT; 32.48 ± 7.64 s vs 72.58 ± 41.29 s, P = 0.01), were significantly higher in non-survivors than in survivors. Logistic regression analysis showed that total bilirubin concentration (OR = 3.58, 95%CI: 1.25-10.22), indirect/direct bilirubin ratio (OR = 0.14, 95%CI: 0.02-0.94) and aPTT (OR = 1.30, 95%CI: 1.04-1.63) were significantly associated with mortality. All patients with total bilirubin > 5 mg/dL or aPTT > 50 s on day 3 died.CONCLUSIONMonitoring of bilirubin concentrations and aPTT may help in predicting clinical outcomes in patients with acute liver injury from wild mushroom intoxication.展开更多
By field observation and simulating test in shallow seam longwall mining, the asymmetry breaking of main roof is discovered during the first weighting. Based on simulating model test and theoretical analysis, the mech...By field observation and simulating test in shallow seam longwall mining, the asymmetry breaking of main roof is discovered during the first weighting. Based on simulating model test and theoretical analysis, the mechanism of main roof first breaking is revealed, and the asymmetry breaking parameter is determined at all.展开更多
This paper provides an improved understanding of the movement mechanisms of both bed-rock gully and sandy soil gully when underground mining occurs underneath,followed by systematic analysis of the contributing factor...This paper provides an improved understanding of the movement mechanisms of both bed-rock gully and sandy soil gully when underground mining occurs underneath,followed by systematic analysis of the contributing factors such as mining advance direction,gully slope angle,gully erosion coefficient and mining height.This paper presents the results from monitoring,theoretical analyses and up to date modeling based on the geological features in the gully affected area,and the implications of these results to the success of roof support trial.It was observed that when mining occurred towards the gully,sliding of slope block along the fracture surface occurred,which resulted in unstable roof condition;when mining progressed away from the gully,polygon blocks developed in the gully slope and rotated in reversed direction forming hinged structure;within the bed-rock slope,the hinged structure was unstable due to shear failure of the polygon block;however,within the sandy soil slope,the structure was relatively stable due to the gradual rotating and subsiding of the polygon block.The increase of the value of slope angle and mining height lead to a faster and more intensive fracture development within the gully slope,which had a pronounced effect on gully slope stability and underground pressure.Various remediation approaches are hence proposed in this paper including introducing more powerful support and reasonable mining height,setting up working face along or away from gullies,using room and pillar,strip mining and backfill instead of longwall mining.展开更多
基金financial support of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the partners of Research Institute on Mines and the Environment (RIME UQAT-Polytechnique http://rime-irme.ca)
文摘Backfill is increasingly used in underground mines to reduce the surface impact from the wastes produced by the mining operations. But the main objectives of backfilling are to improve ground stability and reduce ore dilution. To this end, the backfill in a stope must possess a minimum strength to remain self-standing during mining of an adjacent stope. This required strength is often estimated using a solution proposed by Mitchell and co-workers, which was based on a limit equilibrium analysis of a wedge exposed by the open face. In this paper, three dimensional numerical simulations have been performed to assess the behavior of the wedge model. A new limit equilibrium solution is proposed, based on the backfill displacements obtained from the simulations. Comparisons are made between the proposed solution and experimental and numerical modeling results. Compared with the previous solution, a better agreement is obtained between the new solution and experimental results for the required cohesion and factor of safety. For large scale(field) conditions, the results also show that the required strength obtained from the proposed solution corresponds quite well to the simulated backfill response.
基金Project(51074178)supported by the National Natural Science Foundation of ChinaProject(2011ssxt274)supported by the Graduated Students’ Research and Innovation Foundation of Central South University of China+1 种基金Project(2011QNZT087)supported by the Graduated Students’ Free Exploration Foundation of Central South University of ChinaProject(1343-76140000011)supported by Scholarship Award for Excellent Doctoral Student granted by Ministry of Education,China
文摘In order to precisely predict the hazard degree of goaf(HDG), the RS-TOPSIS model was built based on the results of expert investigation. To evaluate the HDG in the underground mine, five structure size factors, i.e. goaf span, exposed area, goaf height, goaf depth, and pillar width, were selected as the evaluation indexes. And based on rough dependability in rough set(RS)theory, the weights of evaluation indexes were identified by calculating rough dependability between evaluation indexes and evaluation results. Fourty goafs in some mines of western China, whose indexes parameters were measured by cavity monitoring system(CMS), were taken as evaluation objects. In addition, the characteristic parameters of five grades' typical goafs were built according to the interval limits value of single index evaluation. Then, using the technique for order preference by similarity to ideal solution(TOPSIS), five-category classification of HDG was realized based on closeness degree, and the HDG was also identified.Results show that the five-category identification of mine goafs could be realized by RS-TOPSIS method, based on the structure-scale-effect. The classification results are consistent with those of numerical simulation based on stress and displacement,while the coincidence rate is up to 92.5%. Furthermore, the results are more conservative to safety evaluation than numerical simulation, thus demonstrating that the proposed method is more easier, reasonable and more definite for HDG identification.
文摘To identify early predictive markers of poor outcomes in patients with acute liver injury from wild mushroom intoxication.METHODSThis observational, retrospective record review involved adults aged ≥ 18 years admitted to emergency department with mushroom intoxication from January 2005 to December 2015. The diagnosis of mushroom intoxication was based on the following: (1) a positive history of recent wild mushroom intake (either raw or cooked); (2) the onset of gastrointestinal symptoms, such as watery diarrhea, vomiting, and/or abdominal pain, after ingestion; and (3) the exclusion of other possible causes of acute liver injury. Acute liver injury was defined by a > 5-fold elevation of liver enzymes or moderate coagulopathy [international normalized ratio (INR) > 2.0]. Clinical and laboratory findings were compared in survivors and non-survivors.RESULTSOf 93 patients with mushroom intoxication, 23, 11 men (47.8%) and 12 women (52.2%), of median age 61 years, developed acute liver injury. The overall in-hospital mortality rate was 43.5% (10/23). Among the laboratory variables, mean serum alkaline phosphatase (73.38 ± 10.89 mg/dL vs 180.40 ± 65.39 mg/dL, P < 0.01), total bilirubin (2.312 ± 1.16 mg/dL vs 7.16 ± 2.94 mg/dL, P < 0.01) concentrations and indirect/direct bilirubin (2.45 ± 1.39 mg/dL vs 0.99 ± 0.45 mg/dL, P < 0.01) ratio as well as prothrombin time (1.88 ± 0.83 mg/dL vs 10.43 ± 4.81 mg/dL, P < 0.01), and activated partial thromboplastin time (aPTT; 32.48 ± 7.64 s vs 72.58 ± 41.29 s, P = 0.01), were significantly higher in non-survivors than in survivors. Logistic regression analysis showed that total bilirubin concentration (OR = 3.58, 95%CI: 1.25-10.22), indirect/direct bilirubin ratio (OR = 0.14, 95%CI: 0.02-0.94) and aPTT (OR = 1.30, 95%CI: 1.04-1.63) were significantly associated with mortality. All patients with total bilirubin > 5 mg/dL or aPTT > 50 s on day 3 died.CONCLUSIONMonitoring of bilirubin concentrations and aPTT may help in predicting clinical outcomes in patients with acute liver injury from wild mushroom intoxication.
文摘By field observation and simulating test in shallow seam longwall mining, the asymmetry breaking of main roof is discovered during the first weighting. Based on simulating model test and theoretical analysis, the mechanism of main roof first breaking is revealed, and the asymmetry breaking parameter is determined at all.
基金provided by the National Natural Science Foundation of China (Grant No.51004101,No.51264035)the Science Foundation for Young Scholars of China University of Mining &Technology (Grant No.2009A001)+1 种基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)the Fundamental Research Funds for the Central Universities (2012QNA35)
文摘This paper provides an improved understanding of the movement mechanisms of both bed-rock gully and sandy soil gully when underground mining occurs underneath,followed by systematic analysis of the contributing factors such as mining advance direction,gully slope angle,gully erosion coefficient and mining height.This paper presents the results from monitoring,theoretical analyses and up to date modeling based on the geological features in the gully affected area,and the implications of these results to the success of roof support trial.It was observed that when mining occurred towards the gully,sliding of slope block along the fracture surface occurred,which resulted in unstable roof condition;when mining progressed away from the gully,polygon blocks developed in the gully slope and rotated in reversed direction forming hinged structure;within the bed-rock slope,the hinged structure was unstable due to shear failure of the polygon block;however,within the sandy soil slope,the structure was relatively stable due to the gradual rotating and subsiding of the polygon block.The increase of the value of slope angle and mining height lead to a faster and more intensive fracture development within the gully slope,which had a pronounced effect on gully slope stability and underground pressure.Various remediation approaches are hence proposed in this paper including introducing more powerful support and reasonable mining height,setting up working face along or away from gullies,using room and pillar,strip mining and backfill instead of longwall mining.
