Geomechanics model test research on large deformation control mechanism of roadway disturbed by strong dynamic pressure

Comprehensive mechanized top-coal caving mining is one of the efficient mining methods in coal mines.However,the goaf formed by comprehensive mechanized top-coal caving mining is high,and the goaf roof collapse will cause strong dynamic pressure disturbance,especially the collapse of thick hard roof.Strong dynamic pressure disturbance has an influence on the stability of the roadway,which can lead to large deformation.In order to solve the above problem,a comprehensive pressure releasing and constant resistance energy absorbing control method is proposed.Comprehensive pressure releasing can change the roadway roof structure and cut off the stress transfer between goaf and roadway,which can improve the stress environment of the roadway.The constant resistance energy absorbing(CREA)anchor cable can absorb the energy of surrounding rock deformation and resist the impact load of gangue collapse,so as to ensure the stability of roadway disturbed by strong dynamic pressure.A three-dimensional geomechanics model test is carried out,based on the roadway disturbed by strong dynamic pressure of the extra-large coal mine in western China,to verify the control effect of the new control method.The stress and displacement evolution laws of the roadway with traditional control method and new control method are analyzed.The pressure releasing and energy absorbing control mechanism of the new control method is clarified.The geomechanics model test results show that the new control method can increase the range of low stress zone by 150%and reduce the average stress and the displacement by 34.7%and 67.8%respectively,compared with the traditional control method.The filed application results show that the new control method can reduce the roadway surrounding rock displacement by 67.4%compared with the traditional control method.It shows that the new control method can effectively control the displacement of the roadway disturbed by strong dynamic pressure and ensure that the roadway meets the safety requirements.On this basis,the engineering suggestions for large deformation control of this kind of roadway are put forward.The new control method can provide a control idea for the roadway disturbed by strong dynamic pressure.

Dating of the Dachang Superlarge Tin-polymetallic Deposit in Guangxi and Its Implication for the Genesis of the No. 100 Orebody

The Dachang superlarge Sn-polymetal deposit in Guangxi, China, is one of the largest tin deposit all over the world. However, this deposit has long been in debate as to its origin. One of the opinions is that the Dachang deposit was formed by replacement of hydrothermal solution originating from Yanshanian granites, and the other is that this deposit was formed by submarine exhalation in the Devonian. This paper presents some new isotopic geochronology data obtained with the 40Ar-39Ar method for quartz and sanidine from massive ore in the No. 91 and No. 100 orebodies. Analytic results show that the No. 91 orebody was formed at 94.52±0.33 Ma (the plateau age obtained with the 40Ar-39Ar method for quartz) or 91.4±2.9 Ma (the plateau age obtained with the 40Ar-39Ar method for feldspar), while the No. 100 orebody was formed at 94.56±0.45 Ma (the plateau age obtained with the 40Ar-39Ar method for quartz), suggesting that both the No. 91 and the No. 100 orebodies were formed at the Late Yanshanian instead of the Devonian. The No. 100 orebody might be formed by filling of ore materials into caves in Devonian reef limestone. Because the ore-bearing solution released its pressure and lowered its temperature suddenly in a cave environment, ore minerals were formed concentratedly while water and other materials such as CO2 evaporated quickly, resulting less alteration of host rocks.

Discovery of “Enveloping Surface of Oil and Gas Overpressure Migration” in the Songliao Basin and its bearings on hydrocarbon migration and accumulation mechanisms

The Fuyang oil layer of the Songliao Basin is a tight and low-permeability sandstone pay zone formed in the fluvial-shallow water delta environment.In the formation are mainly lithologic reservoir and tight reservoir.The lacustrine-mudstone of K2qn1 is a good source rock and also acts as a good regional cap rock.The Fuyang oil layer is a typical upper-source and lower-reservoir pattern distributed in a large area.Based on a large number of exploration and development data, a macroscopic enveloping surface is found developed in the Fuyang oil layer, which is below K2qn1.The effective reservoirs within the enveloping surface are commonly saturated with oil, and below the enveloping surface are mainly water layers.The distance from the enveloping surface to the bottom of the source rock is usually 100-350 m and at most 550 m.Through the research of the distribution patterns and the physical properties of the sandbodies above or beneath the source rock, it is concluded that: 1) the enveloping surface is the boundary of the overpressure hydrocarbon migration; 2) the spacial distribution of the pressure release beds controls the direction and the distance of the overpressure hydrocarbon migration; 3) tight oil reservoirs and lenticular oil reservoirs are mainly formed inside the envelope surface, whereas, conventional reservoirs are formed outside the envelope surface as a result of the buoyancy hydrocarbon migration.The discovery of the "overpressure hydrocarbon migration enveloping surface" and the concepts of overpressure hydrocarbon migration and buoyancy hydrocarbon migration not only challenge the old notion that "hydrocarbon migrates along the faults and is distributed along fault belts" in the Fuyang oil layer of the Songliao Basin, give a new explanation to the long-distance-oil-downwards migration (hundreds of meters) and expand the exploration potential of the Fuyang oil layer, and provide a rational guidance to the exploration of syncline plays, but also better categorize tight oil/gas and conventional reservoirs in all of the key elements related to hydrocarbon migration, accumulation, reservoir characteristics and oil and gas spatial distribution.

Does airway pressure release ventilation offer new hope for treating acute respiratory distress syndrome?

Mechanical ventilation(MV)is an essential life support method for patients with acute respiratory distress syn-drome(ARDS),which is one of the most common critical illnesses with high mortality in the intensive care unit(ICU).A lung-protective ventilation strategy based on low tidal volume(LTV)has been recommended since a few years;however,as this did not result in a significant decrease of ARDS-related mortality,a more optimal venti-lation mode was required.Airway pressure release ventilation(APRV)is an old method defined as a continuous positive airway pressure(CPAP)with a brief intermittent release phase based on the open lung concept;it also perfectly fits the ARDS treatment principle.Despite this,APRV has not been widely used in the past,rather only as a rescue measure for ARDS patients who are difficult to oxygenate.Over recent years,with an increased under-standing of the pathophysiology of ARDS,APRV has been reproposed to improve patient prognosis.Nevertheless,this mode is still not routinely used in ARDS patients given its vague definition and complexity.Consequently,in this paper,we summarize the studies that used APRV in ARDS,including adults,children,and animals,to illustrate the settings of parameters,effectiveness in the population,safety(especially in children),incidence,and mechanism of ventilator-induced lung injury(VILI)and effects on extrapulmonary organs.Finally,we found that APRV is likely associated with improvement in ARDS outcomes,and does not increase injury to the lungs and other organs,thereby indicating that personalized APRV settings may be the new hope for ARDS treatment.

Airway pressure release ventilation forin-vivodonor lung management and lung transplant outcomes

Background:Airway pressure release ventilation(APRV)can be used for cadaveric donor lung recruitment.APRV elevates PaO_(2)in donor lungs;however,reported outcomes in recipients with APRVmanaged donor lungs are limited.Methods:We retrospectively reviewed patients who underwent lung transplantation(LTx)from 2012 to 2013 and divided them into two groups based on mode of ventilation used during donor management and organ extraction(A:non-APRV;B:APRV).Kaplan-Meier method and multivariate Cox regression were used for analysis.Results:We found 126 LTx recipients(LTxRs);9 were excluded for use of portable ventilation perfusion systems.Of the remaining 117 patients,81(69%)were in Group A;36(31%)were in Group B.Preoperative LTxR characteristics(age,sex,lung allocation score,endstage lung disease type)were comparable between groups.Donors for Group B were older(P=0.03)and had higher body mass index(BMI)(P<0.001),higher incidence of death from chest trauma(P=0.008),longer ventilation duration after brain death(P<0.001),and higher pre-explant PaO_(2)/FiO_(2)ratios(P<0.001).Post-LTx duration of mechanical ventilation,hospital stay,and median survival were similar in both groups.Risk of death was comparable between the two groups at the end of follow-up(HR=1.42;95%CI:0.57-3.56;P=0.45).Conclusions:APRV is a safe and effective pre-LTx donor lung management strategy.Short-and long-term survival outcomes were comparable in LTx recipients,irrespective of donor ventilation mode.APRV may help recruit lungs from older donors with higher BMI who die from chest trauma and have anticipated longer ventilation duration.

A Systematic Study of Disaster Risk in Brunei Darussalam and Options for Vulnerability-Based Disaster Risk Reduction

This systematic study of disaster risk and disaster management efforts in Brunei Darussalam uncovers the reasons why floods and landslides in particular continue to inflict significant social,economic,and psychological toll.Vulnerability to the impacts of hydro-meteorological hazards continue to rise despite international awareness and improved disaster governance and information,and regardless of the vast financial and material resources spent on structural and nonstructural measures for disaster relief and community awareness.Our premise is that,a poor diagnosis of the disaster risk issue is at the root of the disaster risk dilemma in Brunei Darussalam.We conducted our vulnerability-centered disaster risk assessment based largely on the Pressure and Release(PAR) Model proposed by Wisner et al.Our research results reveal that:(1)Hazard-risk in Brunei is high due to the impact of global climate change,the country's local geography,and Brunei's relative location in the Asia–Pacific Region.Limited reporting of localized disasters to international databases however fuels the misperception of low disaster risk in Brunei;(2) High community vulnerability and disaster risk is due to limited knowledge,awareness,and motivation among the general population,which prevents effective mitigation and adaptation to low magnitude but recurrent hazardous events;and(3) Partial incorporation of disasterrisk reduction into governance structures and development plans contributes to heightened disaster risks.Integrated frameworks are proposed that can minimize social vulnerability,reduce disaster risk,and enhance community resilience and adaptive capacity as part of a strengthened governance mechanism.Coupled with improvements in preparedness,response,recovery,and reconstruction promoted by the National Disaster Management Centre(NDMC),vulnerability and disaster risk can be minimized,and a more inclusive and sustainable growth can be generated.