Fluoride distribution in the environment along the gradient of a phosphate-fertilizer production emission (southern Brazil)

Airborne fluoride was determined in the rainwater, surface soil and groundwater along a gradient of emission of a phosphate fertilizer factory in Rio Grande, southern Brazil. Concentrations of fluoride in rainwater and groundwater achieved 3 mg l⁻¹ and 5 mg l⁻¹, respectively, and were dependent on pH. The fluoride deposited from emissions accumulated in a superficial horizon of soil in quantities comparable to those in the manufactured end-products—up to 23,000 mg kg⁻¹. Fluoride distribution in the environment is controlled by physical–chemical parameters of emission, rain intensity and soil properties. The highest fluoride concentrations were registered at a close distance of up to 2 km from the factory. The distribution of fluoride in groundwater resembled the same distribution in rainwater due to the high permeability of the local soils. Fluoride penetration to the groundwater also depended on the type of vegetation cover. The groundwater in woodland areas was less affected by contamination of fluoride than in the grassland areas, most probably because of the influence of eucalyptus throughfall, which increases the pH of wet precipitates.     

基于HHT的煤岩破裂微震信号分析

微震信号处理是目前研究微震监测技术应用领域中的一个重要课题,应用ESG微震监测系统采集煤巷炮掘过程中产生的煤岩破裂微震信号,针对所采集微震信号具有明显的持续时间短、突变快等特点,选用希尔伯特黄变换(HHT)对其进行处理。HHT包括EMD分解和Hillert变换两部分,微震信号经过EMD自适应分解得出9个IMF分量和一个残余分量,对各IMF分量进行Hillert变换做出Hillert谱,从Hillert谱中得出煤岩破裂微震信号频率响应主要集中在500-800Hz,用边际能量谱加以验证得出Hillert谱在应用中的准确性,为进一步认识煤岩破裂的机理和预测煤岩动力灾害提供了有效的技术途径。     

A new shock tube configuration for studying dust-lifting during the initiation of a coal dust explosion

The traditional defence against propagating coal dust explosions is the application of dry stone dust. This proven and effective safety measure is strictly regulated based on extensive international experience. While new products, such as foamed stone dust, offer significant practical benefits, no benchmark tests currently exist to certify their dust lifting performance in comparison to dry stone dust. This paper reviews the coal dust explosion mechanism, and argues that benchmark testing should focus on dust lifting during the initial development of the explosion, prior to arrival of the flame. In a practical context, this requires the generation of shock waves with Mach numbers ranging from 1.05 to 1.4, and test times of the order of 10's to 100's of milliseconds. These proposed test times are significantly longer than previous laboratory studies, however, for certification purposes, it is argued that the dust lifting behaviour should be examined over the full timescales of an actual explosion scenario. These conditions can be accurately targeted using a shock tube at length scales of approximately 50 m. It is further proposed that useful test time can be maximised if an appropriately sized orifice plate is fitted to the tube exit, an arrangement which also offers practical advantages for testing. The paper demonstrates this operating capability with proof-of-concept experiments using The University of Queensland's X3 impulse facility.     

Environmental Pollution Due to Natural Factors: A Case Study in A Volcanic Area (Vulcano Island,Italy)

A major influence on the environment of active volcanic areas is expected from continuous input of chemical species pertaining to fumarolic activities occurring during inter-eruptive intervals.

The systematic investigations carried out during thirteen years in the island of Vulcano (Italy) showed also substantial contributions to phreatic waters and soils of minor constituents and trace metals from volcanic rocks with no negligible influence on growing crops.

Greater extents of these phenomena have been observed for products of hydromagmatic volcanic activity or of long-lasting weathering processes.     

基于细观尺度的岩体开挖渐进破坏模拟研究

岩土渐进式地质灾害是当前岩土工程领域的重要研究课题。基于颗粒离散元法导出颗粒连接损伤模型,建立岩石细观离散模型,进行不同颗粒参数条件下的岩石单轴受压数值模拟。结果表明,岩石细观颗粒间相互黏结力是影响颗粒黏结破坏的主要因素;颗粒间摩擦系数是影响宏观强度的敏感参数,单轴受压试验形成接近45°剪切带,数值模拟与试验结果较好吻合,验证了该模型的合理性。建立岩体开挖细观离散模型,模拟不同地层条件下的开挖过程,对比分析了开挖未支护和支护情况下检测点的沉降差异。研究发现,未支护支撑下,深层开挖时,检测点的位移沉降较浅层开挖时明显;支护可以有效降低围岩变形,防止拉应力产生。本文从细观上揭示岩体开挖条件下渐进式破坏过程形成机制,为更深入研究岩土力学特性和滑动断裂的形成与发展等渐进破坏过程提供了理论和技术支撑。     

钻机除尘设备的一种控制方法及其装置

针对工矿企业的除尘系统,提出了一种脉冲式除尘设备控制方法,将脉冲阀作为被控对象,并可任选同时工作的阀门,脉冲阀的工作时序为启动延时后,阀门按通电、断电时序反复进行,直到扩展时间到或停止信号到来,每个环节时间可调。基于单片机,研制了除尘设备控制装置。现场运行表明,该方法易于实现,其控制装置具有体积小、低功耗、可靠性高等优点。     

大变形巷道弹性锚喷混凝土耦合支护技术研究及应用

为提高层理地质条件下大变形巷道的稳定性,延长巷道使用寿命,采用具有较大变形承载能力的喷钢纤维混凝土与弹性锚杆耦合支护技术加固围岩。首先研究层理状地质条件下高应力软岩巷道的破坏特点及规律,确立支护结构和时效耦合的关系,并通过钢纤维混凝土试样的动静荷载试验,研究混凝土强度与钢纤维掺量的关系,得到喷钢纤维混凝土合理的钢纤维掺量。此外,针对大变形巷道开挖初期变形量大、破坏速度快的特点,设计具有让压吸能作用的新型弹性锚杆,并将此弹性锚杆结合喷钢纤维混凝土技术进行工业试验,试验的位移监测结果表明:该方案位移量比原方案减小约50%,且支护10个月后未出现裂缝。     

深部巷道围岩变形的数值模拟和模型试验

为研究煤柱宽度和煤层倾角对深部沿空巷道围岩的变形影响规律,采用数值模拟对沿空巷道煤柱宽度和煤层倾角的变化对围岩的变形影响规律进行分析,结果表明,煤柱宽度的变化对巷道围岩变形的影响十分明显。随着煤层倾角的增大,巷道围岩变形曲线呈现凹槽形状,表现出在煤层倾角中间值的巷道围岩变形值小于煤层小倾角和大倾角对应的巷道围岩变形值。然后,用模型试验验证数值模拟结果。验证结果表明,煤柱宽度和煤层倾角对应的巷道围岩变形较敏感期发生在开采深度600 m和900 m左右,开采深度在600～900 m之间时,巷道围岩变形与煤柱宽度和煤层倾角的大小基本上呈线性增长关系,而当开采深度超过900 m后,应适当加宽护巷煤柱宽度,以确保深部巷道围岩的稳定。     

石方爆破作业爆破冲击波事故分析

在进行工程爆破时,爆破所产生的飞石、振动、空气冲击波、噪音和毒气是公认的爆破公害,尤其是振动和飞石在爆破过程中是不可避免的危害.针对在实际工程中,由于爆破冲击波造成的人员伤害和设备的损害以及引起该事故发生的危险因素,采用事故树分析方法得到影响顶事件的最小割集,通过计算基本事件的结构重要度,确定了影响爆破冲击波事故的主要因素,并提出相应的安全措施,对降低爆破冲击波效应的影响以及降低露天爆破安全事故有重要意义.     

Spectrum characteristics analysis of microseismic signals transmitting between coal bedding

This study was performed to investigate the propagation law of microseismic signals transmitting along the direction parallel and vertical to the bedding in the process of coal rock rupture under uniaxial compression. Microseismic signals during the whole process of coal-rock deformation fracture until burst failure was tested by using the coal rock rupture microseismic experimental system. The empirical mode decomposition graphic, Hilbert spectrum and time-frequency spectrum were obtained by using Hilbert-Huang Transform or HHT. Also the microseismic signals transmitting along the direction parallel and vertical to the bedding in the process of coal rock rupture were spectrum comparative analyzed with EMD analysis method. Results show that amplitude and velocity of microseismic signals changed very small along the parallel direction to bedding in the process of propagation, but microseismic signals delayed and amplitude weakened obviously along the vertical direction to bedding. Signal delay and signal attenuation were confirmed that bedding impact on microseismic wave transmitting.