煤矿安全评价中评价指标安全度值的确定

煤矿安全评价是辨识和消除煤矿生产系统危险的重要方法，安全评价至为关键的因素之一是准确可靠的确定评价指标的安全度值．基于经典统计和模糊统计之上的集值统计，能有效的确定具有随机、模糊性质的煤矿安全评价指标的安全度值；并在确定过程中，给出评价指标安全度值的可靠性程度和各评价专家的偏离度．实例表明，此法弥补了目前煤矿安全评价中由经典统计法确定安全度值的不足，提高了煤矿安全评价的准确度和可靠性．

军机易损性评估体系安全度值的研究

军机易损性评估至为关键的因素之一是可靠的确定评估指标的安全度值。基于模糊统计基础上的集值统计 ,能有效地确定具有随机、模糊性质的军机易损性评估指标的安全度值 ;在确定过程中 ,可以给出易损性评估指标安全度值的可靠性程度和各评估专家的偏离度。实例表明 ,该法弥补了目前军机易损性评估中由经典统计法确定安全度值的不足 ,提高了军机易损性评估的准确度和可靠度。

安全定量检查表中安全度值确定方法的研究

安全定量检查表是一种赋予权值的安全检查表,它根据各个检查项目对安全影响程度的不同,采用科学方法赋予相应的权值——安全度值(分数值)。由于它具有定量化的特点,因此,根据检查结果可以进行安全定量评价。检查项目的设置及对应的安全度值是否合理、准确,直接关系到评价结果是否真实可靠,必须合理地确定各检查项目及其安全度值。

遗传神经网络在大坝安全评价中的应用

利用神经网络方法评价大坝安全具有一定的优势,但传统大坝安全评价方法不能为神经网络模型提供合适的学习样本。文中引入安全度值的概念,为神经网络提供可量化的学习样本,并针对BP神经网络收敛速度慢、稳定性差、易陷入局部极小等问题,利用遗传算法进行改进,提出基于遗传神经网络的大坝安全评价方法。工程实例表明,评价方法合理、可行。

Running safety and seismic optimization of a fault-crossing simply-supported girder bridge for high-speed railways based on a train-track-bridge coupling system

Bridges crossing active faults are more likely to suffer serious damage or even collapse due to the wreck capabilities of near-fault pulses and surface ruptures under earthquakes.Taking a high-speed railway simply-supported girder bridge with eight spans crossing an active strike-slip fault as the research object,a refined coupling dynamic model of the high-speed train-CRTS III slab ballastless track-bridge system was established based on ABAQUS.The rationality of the established model was thoroughly discussed.The horizontal ground motions in a fault rupture zone were simulated and transient dynamic analyses of the high-speed train-track-bridge coupling system under 3-dimensional seismic excitations were subsequently performed.The safe running speed limits of a high-speed train under different earthquake levels(frequent occurrence,design and rare occurrence)were assessed based on wheel-rail dynamic(lateral wheel-rail force,derailment coefficient and wheel-load reduction rate)and rail deformation(rail dislocation,parallel turning angle and turning angle)indicators.Parameter optimization was then investigated in terms of the rail fastener stiffness and isolation layer friction coefficient.Results of the wheel-rail dynamic indicators demonstrate the safe running speed limits for the high-speed train to be approximately 200 km/h and 80 km/h under frequent and design earthquakes,while the train is unable to run safely under rare earthquakes.In addition,the rail deformations under frequent,design and rare earthquakes meet the safe running requirements of the high-speed train for the speeds of 250,100 and 50 km/h,respectively.The speed limits determined for the wheel-rail dynamic indicators are lower due to the complex coupling effect of the train-track-bridge system under track irregularity.The running safety of the train was improved by increasing the fastener stiffness and isolation layer friction coefficient.At the rail fastener lateral stiffness of 60 kN/mm and isolation layer friction coefficients of 0.9 and 0.8,respectively,the safe running speed limits of the high-speed train increased to 250 km/h and 100 km/h under frequent and design earthquakes,respectively.

Influence of rainfall on skid resistance performance and driving safety conditions of asphalt pavements

To study the influence of rainfall on pavement skid-resistance performance and driving safety,the water film thickness(WFT)concept considering the longitudinal and transverse slopes of the pavement was utilized based on the total discharge formulation and turbulence theory of slope flow.Using experimental data measured using the British pendulum test under varying WFT levels,a model for calculating the skid resistance,namely the British pendulum number(BPN),was formulated and used to quantitatively evaluate the effects of rainfall intensity,transverse,and longitudinal slopes on the computed BPN.The study results reveal that skid resistance is linearly proportional to the pavement transverse slope and inversely proportional to the rainfall intensity and the pavement longitudinal slope.In particular,rainfall intensity,along with pavement texture depth,exhibited a significant impact on the tire-pavement friction and skid-resistance performance.The results further indicate that driving safety under wet weather is predominantly governed by skid resistance and visibility.The BPN and sideway force coefficient(SFC60)values for new asphalt pavements under different rainfall intensities are provided along with some modification to the stopping sight distance(SSD)criteria.Safe driving speed limits are also determined using a safe-driving model to develop the appropriate speed limit strategies.The overall study results provide some insights,methodology approach,and reference data for the evaluation of pavement skid-resistance performance and driving safety conditions under different pavement slopes and rainfall intensities.

Minimum secure speed of fully mechanized coal face based on critical temperature of coal spontaneous combustion

The critical temperature theory of spontaneous combustion of coal and the numerical simulation method are used to explore the minimum secure speed of fully mechanized coal face to prevent the spontaneous combustion in goaf. Combined with the actual situation of workface 31005 in a coal mine, the highest temperatures in goal at different advancing speeds were obtained by the numerical simulation of spontaneous combustion in goal, and then a power function equation between the highest temperature and the advancing speed was achieved by regression analysis. The advancing speed corresponding to the critical temperature value was taken as the minimum safe speed of workface based on the equation. Finally, the accuracy and reliability of the speed were verified by the actual advancing process of workface 31005. The results of this research show that the new judgment method of the minimum safety speed has a higher value to be applied in the field.

Improvement of Pseudo-static Method for Slope Stability Analysis

traditional In this paper, two drawbacks pseudo-static method （vertical of the slice method） in the slope stability evaluation have been studied. First, the sliding mass is divided into vertical slices according to this method, which is irrational to some extent in the seismic design of slope. Second, only peak ground acceleration （PGA） is considered, and the effects of shaking frequency and duration on slope stability are neglected. And then, based on the theory of elastic wave and the summarized geological model, this paper put forwards an improved method of pseudo-method by using the theory of elastic wave and Hilbert-Huang transform. The improved pseudostatic method gives reasonable considerations to the time-frequency effects of seismic wave and its rationality has been verified by the shaking table test. This method can evaluate the safety of a slope, the happening time and the scale of landslides. At the same time, this method also can improve the high accuracy of the evaluation of the safety of the slope.

Investigation on the threshold control of safety blasting vibration velocity for the extraction of complicated orebody under railway

The threshold control of safety blasting vibration velocity is a significant process for the underground mining of complicated ore deposit under construction,road,and water.According to the equivalent principle of displacement and velocity of mass point,differential evolution is put forward based on 3DEC dynamic analysis,making the calculation more efficient and accurate.The 3DEC model of the complicated orebody under railway is established according to the topographic maps and geological data of the eastern Pyrite Mine.The stimulus-response distribution of internal stress and displacement fields are demonstrated by analyzing the on-site monitoring vibration displacement and velocity data of the mass point.The reliability of parameter selection,such as blasting simulation waveforms,rock damping,is identified.The safety vibration velocity of railway is set to 4.5 cm/s in line with the requirement of safety blasting rules.Thus,the maximum amount of single-stage explosive in this region is 44.978 kg.The simulation result is in good agreement with the on-site monitoring datum.No displacement and settlement of the 701 railway special line was achieved by choosing the critical amount of the single-stage explosive.

A numerical simulation of the influence initial temperature has on the propagation characteristics of, and safe distance from, a gas explosion

A model roadway with a cross-sectional area of 80 mm 80 mm and a length of 100 m was used to estimate the overpressure, the temperature, the density, and the combustion rate during an explosion. Auto-ReaGas software was used for the calculations and the initial temperatures were 248, 268, 308, or 328 K. The methaneair mixture had a fuel concentration of 9.5% and the tunnel had a filling ratio of 10%. The results show that the safe distance necessary to avoid harm from the shock wave increases with increasing initial temperature. The distance where the peak overpressure begins to rise, and where the maximum value occurs, increases as the initial temperature increases. These are almost linear functions of the initial temperature. At locations before shock wave attenuation has occurred increasing the initial temperature linearly increases the maximum temperature at each point following along the tunnel. At the same time, the peak overpressure, the maximum density, and the maximum combustion rate decrease linearly. How-ever, after the shock wave has attenuated the attenuation extent of the peak overpressure decreases with an increase in initial temperature. The influence of the initial temperature on the explosion propagation depends on the combined effects of inhibiting and enhancing factors. The research results can provide a theoretical guidance for gas explosion disaster relief and treatment in underground coal mines.

Development of Design Response Spectra Based on Various Attenuation Relationships at Specific Location

Peninsular Malaysia is located and lies in a low seismic region. Although Malaysia is not located in the active fault seismic area, it is closed to the Sumatran active seismic zones. Tall building are fIequently felt the tremor generated fTom Sumatran subduction and fault zones especially in the west cost of Peninsular Malaysia such as Johor Bahru, Kuala Lumpur and Penang. Existing design response spectra was developed based on attenuation relationship for each subduction and fault zone. In this study, the design response spectra were developed based on various attenuation relationships for selected location in Kuala Lumpur area, namely, Mutiara Damansara, Bandar Petaling Jaya and Bandar Puteri Puchong. The development of design response spectra based on various attenuation relationships is more reliable in selecting the appropriate attenuation relationship for the study area. Seven attenuations have been chosen and results show that Megawati et al. are the most appropriate attenuation relation for fault zone, where the predicted PGA （peak ground acceleration） is 0.0187 g which is the proposed PGA value for this study area. This study also found that most of soil in the study area can be categorized into SD （stiff soil） according to site classification in the NEHRP 2000 Provision/UBC 97. Bandar petaling Jaya was found to be highest AF （amplification factor） of 3.74 for stiff soil and Mutiara Damansara with AF of 2.67 for very dense soil or soft rock. The proposed design response spectra for each location were developed based on UBC 1997 （Uniform Building Code 1997）. The peak RSA （response spectrum acceleration） of 0.30 g for soil type SD for Bandar Petaling Jaya is the maximum level of acceleration on the soil surface with a period range of 0.10 to 0.52 seconds. All these values can be used for the seismic safety evaluation of existing structures and as a guideline in designing new structures to resist future earthquake, within the study area.