Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes ...Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes which are subjected to stress-induced failure.The probability of failure(POF)depends on many factors,of which the geometry of an open stope is especially important.In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF,using numerical modelling.Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines.A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D,to generate model realizations containing stopes with different geometrical features.The probability of failure(POF)for different categories of stope geometry,is calculated by considering two modes of failure;relaxation-related gravity driven(tensile)failure and rock mass brittle failure.The individual and interactive effects of stope geometrical parameters on the POF,are analyzed using a general multi-level factorial design.Finally,mathematical optimization techniques are employed to estimate the most stable stope conditions,by determining the optimal ranges for each stope’s geometrical parameter.展开更多
Abdominal compartment syndrome(ACS)develops when organ failure arises secondary to an increase in intraabdominal pressure.The abdominal pressure is determined by multiple factors such as blood pressure,abdominal compl...Abdominal compartment syndrome(ACS)develops when organ failure arises secondary to an increase in intraabdominal pressure.The abdominal pressure is determined by multiple factors such as blood pressure,abdominal compliance,and other factors that exert a constant pressure within the abdominal cavity.Several conditions in the critically ill may increase abdominal pressure compromising organ perfusion that may lead to renal and respiratory dysfunction.Among surgical and trauma patients,aggressive fluid resuscitation is the most commonly reported risk factor to develop ACS.Other conditions that have also been identified as risk factors are ascites,hemoperitoneum,bowel distention,and large tumors.All patients with abdominal trauma possess a higher risk of developing intra-abdominal hypertension(IAH).Certain surgical interventions are reported to have a higher risk to develop IAH such as damage control surgery,abdominal aortic aneurysm repair,and liver transplantation among others.Close monitoring of organ function and intra-abdominal pressure(IAP)allows clinicians to diagnose ACS rapidly and intervene with target-specific management to reduce IAP.Surgical decompression followed by temporary abdominal closure should be considered in all patients with signs of organ dysfunction.There is still a great need for more studies to determine the adequate timing for interventions to improve patient outcomes.展开更多
This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical slope.stability assessment m. ethodology （SSAM! is intended for use by geotechnical engineers at bo...This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical slope.stability assessment m. ethodology （SSAM! is intended for use by geotechnical engineers at both the design review and operational stages of a mine＇s life to categonse the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assess- ment methodology to assess the potential for, and consequence of, excavated coal mine slope failure. Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the exca- vated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope＇s propensity for failure. The SSAM is novel in that it considers the depo- sitional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope＇s likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools.展开更多
基金funded by a grant from Natural Sciences and Engineering Research Council of Canada (NSERC)the authors would like to acknowledge the Niobec mine (Saint-Honoré, QuébecQuébec)
文摘Stress-induced failure is among the most common causes of instability in Canadian deep underground mines.Open stoping is the most widely practiced underground excavation method in these mines,and creates large stopes which are subjected to stress-induced failure.The probability of failure(POF)depends on many factors,of which the geometry of an open stope is especially important.In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF,using numerical modelling.Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines.A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D,to generate model realizations containing stopes with different geometrical features.The probability of failure(POF)for different categories of stope geometry,is calculated by considering two modes of failure;relaxation-related gravity driven(tensile)failure and rock mass brittle failure.The individual and interactive effects of stope geometrical parameters on the POF,are analyzed using a general multi-level factorial design.Finally,mathematical optimization techniques are employed to estimate the most stable stope conditions,by determining the optimal ranges for each stope’s geometrical parameter.
文摘Abdominal compartment syndrome(ACS)develops when organ failure arises secondary to an increase in intraabdominal pressure.The abdominal pressure is determined by multiple factors such as blood pressure,abdominal compliance,and other factors that exert a constant pressure within the abdominal cavity.Several conditions in the critically ill may increase abdominal pressure compromising organ perfusion that may lead to renal and respiratory dysfunction.Among surgical and trauma patients,aggressive fluid resuscitation is the most commonly reported risk factor to develop ACS.Other conditions that have also been identified as risk factors are ascites,hemoperitoneum,bowel distention,and large tumors.All patients with abdominal trauma possess a higher risk of developing intra-abdominal hypertension(IAH).Certain surgical interventions are reported to have a higher risk to develop IAH such as damage control surgery,abdominal aortic aneurysm repair,and liver transplantation among others.Close monitoring of organ function and intra-abdominal pressure(IAP)allows clinicians to diagnose ACS rapidly and intervene with target-specific management to reduce IAP.Surgical decompression followed by temporary abdominal closure should be considered in all patients with signs of organ dysfunction.There is still a great need for more studies to determine the adequate timing for interventions to improve patient outcomes.
基金funded by the Australian Coal Association Research Program(ACARP)
文摘This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical slope.stability assessment m. ethodology （SSAM! is intended for use by geotechnical engineers at both the design review and operational stages of a mine＇s life to categonse the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assess- ment methodology to assess the potential for, and consequence of, excavated coal mine slope failure. Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the exca- vated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope＇s propensity for failure. The SSAM is novel in that it considers the depo- sitional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope＇s likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools.
