Hydraulic conductivity of fly ash-sewage sludge mixes for use in landfill cover liners

Secondary materials could help meeting the increasing demand of landfill cover liner materials. In this study, the effect of compaction energy, water content, ash ratio, freezing, drying and biological activity on the hydraulic conductivity of two fly ash-sewage sludge mixes was investigated using a 2^7-1 fractional factorial design. The aim was to identify the factors that influence hydraulic conductivity, to quantify their effects and to assess how a sufficiently low hydraulic conductivity can be achieved. The factors compaction energy and drying, as well as the factor interactions material × ash ratio and ash ratio × compaction energy affected hydraulic conductivity significantly (α = 0.05). Freezing on five freeze-thaw cycles did not affect hydraulic conductivity. Water content affected hydraulic conductivity only initially. The hydraulic conductivity data were modelled using multiple linear regression. The derived models were reliable as indicated by R_adjusted² values between 0.75 and 0.86. Independent on the ash ratio and the material, hydraulic conductivity was predicted to be between 1.7 × 10⁻¹¹ m s⁻¹ and 8.9 × 10⁻¹⁰ m s⁻¹ if the compaction energy was 2.4 J cm⁻³, the ash ratio between 20% and 75% and drying did not occur. Thus, the investigated materials met the limit value for non-hazardous waste landfills of 10⁻⁹ m s⁻¹.     

Hydraulic conductivity changes and influencing factors in longwall overburden determined by slug tests in gob gas ventholes

This study presents the results of core-log analyses from the exploration boreholes, the analyses of face advance rates, and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern (SW) Pennsylvania section of Northern Appalachian Basin. In the first part of the study, coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated. In the second part, the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached. Hydraulic conductivities were analyzed with respect to the changes in overburden depth, the locations of the borehole, and mine face advance rates. These data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities.The general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces. Also, the probability of bedding plane separations increases as the interface is close to the extracted coal seam. Evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials. In situations where the roof material is stiff and thick, the development of high permeability fractures around the borehole will be less. Results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well. Greater overburden depths generally cause earlier fracturing as longwall face approaches, but eventually result in lower hydraulic conductivities and potentially less effective boreholes. Increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden. The results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes.     

补给区温度季节性周期波动对承压含水层温度影响的解析研究

本文介绍了补给区温度季节性周期波动对承压含水层温度的影响,建立了相应的数学模型,并导出了其解析解。通过对该解析解的分析表明:补给区温度的季节性波动会导致含水层中温度的周期性波动,其波动幅度随与补给区距离的增加而减小,并具有一定的时间滞后性,且含水层中温度的波动情况与含水层的热容量和地下水的流速有关。还发现当含水层自身的热容量发生改变时,含水层中温度波动始终围绕着同一个均值进行波动,只有振幅和相位上发生相应变化,而当含水层中地下水的流速发生改变时,含水层中温度波动的均值也发生相应改变。对于含水层中没有温度波动的区域,温度随距补给区水平距离的变化率与含水层的热容量和地下水流速无关。     

地下岩体温度变化影响区域探测方法的实验研究

在室内对沉积岩的砂岩和泥岩进行了多组岩样加热实验,给出了室内实验泥岩和砂岩温度上升与电阻率变化关系的回归方程。在东京郊区某野外地下实验场内进行了泥岩岩体的原位加热实验,使用特制的物探设备取得了温度变化各个阶段对应的岩体电阻率数据,通过处理解析取得的数据,了解了温度上升时原位岩体电阻率变化的实际情况。室内岩样实验与室外原位岩体实验研究结果表明:通过使用电法物探设备监测岩体的电阻率变化情况,可以及时了解地下高温源对围岩体的温度影响场范围。该实验研究为目前核废料储存及处理时,探测围岩体受高温影响的范围提供了一种可视化的监测方法,并研究了该方法在野外原位使用的可行性。     

Energy savings due to changes in design of ventilation and air flow systems

Procedures for the design of ventilation and air flow systems are shown to be energy wasteful. The cause lies both in the methodologies and their technical bases, and in the influence of other factors that enter into a final systems choice for a building (particularly economics).The issue of general outside air requirements is discussed. It is found that any system in which outside air supply is sufficient to control body odor necessarily meets oxygen requirements many times over, and that the ventilation rate can be reduced by about 45% to 60% if higher humidities are used. The long-standing belief that required ventilation flow rate for odor control must increase as air space per occupant decreases has previously been proven untrue, yet a survey of the ASHRAE recommendations and various building codes shows that present standards are based on this inaccurate and energy-wasteful principle. New standards, including a rate of 7.5 cmf/person of outdoor air (not conditioned) during the heating season, are proposed based on the result that the ventilation rate is independent of air space per person.Air distribution systems and sub-systems are analyzed in terms of minimum energy requirements. Energy saving by velocity reduction is discussed. Fan power requirements for a high velocity air distribution system are increased by 2500% over that for a low velocity system in commercial buildings.A comparison of the “old” ASHRAE definition of Effective Temperature, which serves as a thermal comfort criterion in AC systems design, is made with the “new” definition, and the consequent energy savings that should result when the “new” definition is accepted in practice is demonstrated.     

Long-term immersion corrosion of steel subject to large annual variations in seawater temperature and nutrient concentration

The corrosion of steel in open seawater is influenced mainly by water temperature. If nutrients critical for bacterial activity are available, it also may be influenced by microbiological activity. The combined effect is investigated here for the case of large variations both in the seawater temperature and in concentration of dissolved nutrients. A theoretical analysis is given for these effects acting in conjunction, with or without time-dependent differences. Field observations of corrosion losses for steel sheet piling exposed at three different locations at sea sites near Vladivostok, Russia, are used in conjunction with local temperature and nutrient concentration data to obtain trends for longer term corrosion. The main objective of the paper is to build a new long-term predictive model of corrosion which may be effectively used in conditions with large variable seasonal in water temperature and in nutrient availability.     

Inward vapor diffusion due to high temperature gradients in experimentally tested large-scale wall assemblies

Inward vapor flow due to high temperature gradients as a moisture source in building envelope has been documented, specifically when the exterior cladding is wetted by rain and then exposed to solar radiation. This phenomenon can bring large amount of undue moisture across the envelope assembly with a risk of damage of the wall elements. In this paper, inward vapor flow is applied to five large-scale monitored wall assemblies using a large-scale experimental facility consisting of a spraying array, a radiation array, and a test hut to provide controlled interior conditions. The variables studied include type of cladding (brick and cement stucco), presence and ventilation of air space, type of exterior sheathing (oriented strand board and extruded polystyrene) and type of interior finish (vinyl wall covering and paint). The results show that the presence of vapor tight interior finishes leads to the accumulation of moisture in the interior gypsum board, even in the presence of a vapor tight exterior sheathing. The presence of an air space reduces, but does not prevent moisture accumulation, while connecting the air space to the outdoor seems sufficient to short-circuit the inward vapor flow and prevent moisture accumulation.     

Regulation of sensory nerve conduction velocity of human bodies responding to annual temperature variations in natural environments

The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being.     

Some effects due to variations in turbulence integral length scales on the pressure distribution on wind-tunnel models of low-rise buildings

The work described here consists of results from wind-tunnel tests on models of the Building Research Establishment's experimental building at Aylesbury. The use of several scale models of this building in uniform and in simulated atmospheric boundary-layer flows together with the results from the full-scale experiments allowed an assessment of the effect of variations in the ratio of the longitudinal-turbulence integral length scale to body dimension (L_x/D). This confirmed that the values of L_x/D have to be modelled correctly even in a non-homogeneous, non-isotropic turbulent flow in order to obtain model results that are representative of the full-scale situation. The present results also appear to confirm explanations given for similar results for homogeneous, isotropic turbulent flows.     

地铁隧道列车火灾的火焰顶棚射流温度特性研究

以地铁隧道火灾为研究对象,通过1∶8缩尺模型试验和数值模拟分析夹带火焰的烟气顶棚射流的温度特性,为地铁隧道火灾的防灾减灾提供参考。假定火源位于列车中部,燃烧强度是经过相似变换的等量荷载。火焰直接撞击顶棚并向上、下游扩展。考虑隧道内热辐射效应,得到在不同燃料用量下火焰顶棚射流温度的时变规律与空间分布特征。结果表明:燃料的多少对火焰顶棚射流在燃烧时间内的温度时变曲线的变化趋势影响不大,燃烧达到稳定的时间非常接近,但稳定状态的温度明显不同;火焰区上方顶棚射流烟气的最高温度与燃料液面的高度有关,试验中出现在距隧道顶0.18H处,而不是纯烟气顶棚射流给出的0.01H的区域内;列车上方及列车首尾附近的火焰顶棚射流温度沿隧道纵向呈线性衰减,且衰减速率不随时间变化,而不是纯烟气顶棚射流的指数衰减形式。在一定的高度以下,火焰顶棚射流的温度迅速降低,存在温度较低的安全区域适合于人员疏散。