Urban soil characteristics and limitations for landscape planting in Hong Kong

Soils in urban areas have not received adequate attention in relation to landscape planting. Recent urban tree surveys in Hong Kong identified many arboricultural problems related to stressful habitat conditions including edaphic ones. Soil constraints in the crowded city are acute and yet relevant data are lacking. This project evaluated in the field and laboratory 100 soil samples obtained from sites of varied natural and disturbance history at difficult roadside tree-pit sites in urban Hong Kong. An extensive range of physical and chemical properties were assessed to establish baseline information on soil limitations to amenity-vegetation growth. Most soils have lost natural soil horizons with morphological features of fill materials such as poor structure and artificial layering. They are excessively stony and coarse-textured, with abundance of building rubble and other foreign substances. The extensive soil compaction, associated with structural degradation and loss of porosity, is inimical to aeration, drainage, storage of plant-available moisture, and root growth. Release of carbonate from the calcareous construction waste has induced alkaline pH, with consequences on micronutrient and phosphorus deficiency. Organic matter contents, and the related supply of essential nitrogen and phosphorus, are all meager. The capacity to hold nutrient bases and the amount held in available forms are both inadequate for vigorous plant performance. There are signs of pollution by heavy metals, especially lead, which are derived from air-borne sources related to vehicular traffic. The results help to ascertain the need for soil tests in landscaping endeavors, to reinforce a weak link in landscaping programs, to establish a package of recommendations to improve urban soil management, to enhance the cost-effectiveness of greening programs, and to augment urban-tree performance so as to reduce recurrent management liability and burden.     

Thermal sensation of Hong Kong people with increased air speed,temperature and humidity in air-conditioned environment

In the warm and humid climate zone, air-conditioning (AC) is usually provided at working places to enhance human thermal comfort and work productivity. From the building sustainability point of view, to achieve acceptable thermal sensation with the minimum use of energy can be desirable. A new AC design tactic is then to increase the air movement so that the summer temperature setting can be raised. A laboratory-based thermal comfort survey was conducted in Hong Kong with around 300 educated Chinese subjects. Their thermal sensation votes were gathered for a range of controlled thermal environment. The result analysis shows that, like in many other Asian cities, the thermal sensation of the Hong Kong people is sensitive to air temperature and speed, but not much to humidity. With bodily air speed at 0.1–0.2 m/s, clothing level 0.55 clo and metabolic rate 1 met, the neutral temperature was found around 25.4 °C for sedentary working environment. Then recommendations are given to the appropriate controlled AC environment in Hong Kong with higher airflow speeds.     

地源热泵土壤温度恢复特性研究

根据某实际工程的换热器管群的布置情况和地源热泵系统的运行情况,对典型区域典型年和运行5年的土壤温度变化情况进行了数值模拟,并对模拟结果进行了深入分析,所得结论可为地源热泵系统的优化设计提供参考.     

多年冻土地区路基温度场分布的探讨

基于多年冻土地区多边界条件瞬态路堤温度场的有限元计算,结合工程实际,从空间及时间的角度分析了沥青面层路堤温度场分布的非对称性,以及随着路堤高度和路堤走向变化的特点,并指出其分布特点对工程的影响,对工程具有重要的指导意义。     

高温差地区预应力混凝土箱形梁日照温度应力分析

阐述了预应力混凝土箱形桥梁温度应力产生的原因,依据箱型桥梁的温度边界特点,给出了高温差地区箱形桥梁日照温差分布形式,并将箱身温度应力按沿板厚非线性温差自约束应力和箱身横向约束应力来考虑。通过对奎北铁路线桥梁的计算表明：在高温差地区,温差变化作用下混凝土箱形桥梁桥身外表面将产生较大的横向温度应力,会导致桥身混凝土出现纵向裂缝,应通过施加横向干预,提高梁体的抗裂性能。     

土壤温度场对竖直U形地埋管换热性能的影响

对广州地区地下50 m以内土壤温度分布进行了模拟,研究了土壤温度的分布特性和变化规律,模拟了冬季工况下埋管区域土壤温度场的分布情况,分析了动态负荷分布对地埋管换热性能的影响.     

地源热泵系统运行中土壤温度场变化特性的实例分析

对某一地源热泵系统的实测土壤温度场数据进行了初步分析,总结了冬季、夏季及过渡季工况下土壤温度场的变化特点及其影响因素。指出地源热泵系统运行过程中的地下能量堆积问题是一个长期效应,记录分析土壤温度场的长期变化趋势对于调控地源热泵系统的运行状态具有积极的指导作用,有利于保证系统的长期可靠性和节能性。     

遥感数据的温度反演方法及其试验算例

我国是一个冻土分布较多的国家,以前利用遥感图像对冻土的研究与应用主要体现在冻土亚类划分等方面.红外遥感图像能够反演地表温度,而冻土区在不同亚类别地区,其地表温度也具有一定的差异性,因此本文在介绍了几种温度反演方法的基础上,利用Aster数据对冻土区地表温度进行了反演和分析.通过分析和研究,发现Aster数据能够反演冻土...     

Lowering the outdoor temperature in high-rise high-density residential developments of coastal Hong Kong: The vegetation influence

This paper investigates the impact of on-site variables on the influence of vegetation in lowering outdoor temperature. The study uses six critical on-site variables such as surface albedo, sky view factor, altitude, shrub cover, tree cover and average height to floor area ratio to carry out analysis in five data sets. The climatic parameters and physical characteristics were measured and surveyed, respectively in 216 stations in high-rise high-density residential developments of coastal Hong Kong. The data set is mainly categorised into peak summer clear sky days (PSCS-days), peak summer partially cloudy days (PSPC-days) and late summer days to address the issues related to cloudy sky conditions in Hong Kong. The trend analysis shows that at a lower sky view factor, ranging from 0.1 to 0.25, shrub cover as low as 10–15% in a 1000 m² open area is more effective in reducing outdoor temperature than the same level of tree cover in a location with a higher sky view factor (0.4 or above). The regression models used in this study were able to explain the influence of on-site variables on vegetation in lowering the outdoor temperature within the respective urban settings. In high-rise high-density environments, on-site variables such as sky view factor and altitude have a substantial impact on the influence of vegetation in lowering outdoor temperature. However, off-site variables such as high urban density and anthropogenic heat could negate the behaviour of sky view factor and altitude. The study suggests that increasing the tree cover from 25% to 40% in the pocket parks in coastal area residential developments of Hong Kong could reduce daytime urban heat island intensity (UHI) by further 0.5 °C.     

采用修正均摊恒定热流法对土壤温度场的分析

为了扩大均摊恒定热流法的适用范围,对其进行修正,提出完全法和分段法。结合实际工程,分别采用2种方法对土壤温度场进行模拟分析。结果显示,利用分段法可以准确得出任意时刻土壤温度场;采用2种方法得到的周期时间点上的土壤温度场非常近似;在分析周期时间点上的土壤温度场,或进行长时间模拟计算,或对数据精确度要求不高时,完全法是方便和简捷的。指出2种方法各自的适用范围。     

Effect of probabilistic variation in soil properties and profile of site response

Site response is a function of the soil profile, and the probable distribution of the soil profile has a significant effect on the seismic site response. In the present study, the influence of random variations in soil characterizations on the site response is investigated using different probabilistic distributions. The important characteristics of the local soil, corresponding to the layering, the shear wave velocity ($V_s$), the decrease in the nonlinear modulus, and the damping (MRD) curves, are considered when carrying out these random variations. Stochastic processes are generated by using different distribution models and keeping in mind the effect of the coefficients of the variations. In this research, a proposed procedure is developed and coded to perform the variations in soil characterizations. The coding of this new procedure is based on the original SHAKE91 framework. However, instead of using the fixed soil properties and profile, the uncertainties of the MRD curves, the layer thickness, and $V_s$ are generated as the input data. This analysis shows that the use of median $V_s$, obtained from all the possible inputs under the different stochastic processes, yields good agreements with the baseline profile. Modelling the variabilities in the layering and the $V_s$ profile is seen to have a slight effect on the performance of the site response. Additionally, the results of these analyses indicate that the variabilities in nonlinear soil properties have a significant impact on the median surface response spectrum and the amplification spectrum of the surface motions.     

Logistic regression modelling of storm-induced shallow landsliding in time and space on natural terrain of Lantau Island,Hong Kong

This study is aimed at developing a method for modelling the probability of landsliding using a geographical information system (GIS), rainstorm events and associated landslide distributions, with an attempt to assess where landslides are likely to occur when certain rainstorm events happen. This research focuses on the natural terrain of Lantau Island, Hong Kong. In order to derive a logistic regression model for statistical prediction of the probability of landsliding, topographic attributes derived from digital elevation model (DEM) data are combined with a variety of other digital datasets including 24 h rainfall, lithology and vegetation cover in a GIS. The model was then applied to given rainstorm events and rainfalls of a variety of periods of return time in order to predict the probability of landsliding on natural slopes in space and time. The modelling techniques described here can be used to develop effective mitigation strategies.     

Characteristics of emissions of air pollutants from burning of incense in temples, Hong Kong

Field investigations of target air pollutants at two of the most famous temples in Hong Kong were conducted. The air pollution problems in these two temples during peak and non-peak periods were characterized. The target air pollutants included particulate matters (PM(10), PM(2.5)), volatile organic compounds (VOCs), carbonyl compounds, carbon monoxide (CO), nitrogen oxides (NO(x)), methane (CH(4)), non-methane hydrocarbons (NMHC), organic carbon (OC), elemental carbon (EC), and inorganic ions (Cl(-), NO(3)(-), SO(4)(2-), Na(+), NH(4)(+), and K(+)). The pollutant levels of the two temples during peak period were shown to be significantly higher than those during non-peak period. The highest average CO level was obtained at Temple 1 during peak period, which exceeded IAQO 8-h Good Class criteria. In general, the average PM(2.5)/PM(10) ratios were approximately 82%. The results revealed that the fine particulates (PM(2.5)) constituted the majority of suspended particulates at both temples. It was noted that formaldehyde was the most abundant carbonyl compounds, followed by acetaldehyde. At Temple 1 during peak period, the average benzene concentration exceeded almost 8 times more than Indoor Air Quality Objectives for Office Buildings and Public Places (IAQO) [HKEPD, 2003. Guidance notes for the management of indoor air quality in offices and public places. Indoor air quality management group, The Government of the Hong Kong Special Administrative Region.] Good Class criteria. The average OC/EC ratios ranged from 2.6 to 17 in PM(10) and from 4.2 to 18 in PM(2.5) at two temples, which suggested that OC measured in these two temple areas may be due to both direct emission from incense burning and secondary formation by chemical reactions. The total mass of inorganic ions, organic carbon, and elemental carbon accounted for about 71% in PM(2.5) and 72% in PM(10).     

地埋管换热器形式、管径及岩土温度对其换热性能的影响

建立了单U形与双U形地埋管换热器的三维数学模型。对外径25mm与32mm的单U形与双U形地埋管换热器换热性能的模拟研究表明,相同管径双U形地埋管换热器比单U形地埋管换热器换热量提高20%左右,但外径25mm的单U形地埋管换热器可以获得更大的进出口温差;对于双U形地埋管换热器,外径32mm与25mm相比,换热性能无明显优势;工程应用中,在地埋管用地面积充足时,建议选用外径25mm的单U形地埋管换热器,否则应选用外径25mm的双U形地埋管换热器;岩土温度每升高1℃,出口水温升高0.23℃,换热量下降5%左右。     

基于Origin软件的土工试验数据处理

简要介绍Origin软件的基本功能及其应用，并结合岩土工程中的动三轴试验处理实例，利用Origin软件实现了对试验数据的绘图、更新、线性拟合等处理，获得可靠的试验参数及直观的图形，减少了数据处理过程中的误差。     

组合支护结构下土钉内力监测的回归分析

侨福花园广场深基坑工程基坑深达21.675m,采用上部复合土钉墙、下部地下连续墙的组合支护体系,按照信息化施工要求对土钉内力进行了长时间监测,根据监测曲线,运用回归分析方法建立了土钉内力非线性回归模型,得出了土钉内力与时间的相互关系,并得到了分别适合于中短期以及中长期土钉内力与时间相互关系的较为理想的回归函数。监测结果和数据分析表明,土钉内力监测中应用回归分析是完全可行的,有助于提高深基坑工程领域信息化施工的准确性和预见性。     

土工试验成果在岩土工程勘察中的应用

阐述了土工试验对于岩土工程的重要性,对土工试验成果表的组成及各组成部分在成果表中的作用进行了详细介绍,并结合实例论述了土工试验成果在岩土工程勘察中的具体应用,以指导今后工程实践。     

香港沙头角污水厂扩建工程的智慧管理及信息化建设

沙头角污水处理厂扩建工程是香港特别行政区政府渠务署首个推行"建造业2.0"的先导项目。重点探讨渠务署如何秉持"智慧及绿色工程管理"理念,通过工地管理数码化,应用建筑信息模拟、各种传感器、物联网、大数据、人工智能、虚拟现实等创新科技,再配合创新建筑技术,推行智能工地,实现信息化建设及智慧工程管理。     

合肥地区粘土地基承载力表建立方法的探讨

土的工程性质具有明显的区域性特点,如果简单地将来源于全国范围的地基承栽力经验表应用于某一特定地区,必然会带来地区适应性问题。根据合肥地区的地基场地分类,建立适用于该地区的地基承载力表,正是对全国规范的地基承载力表取消后的积极回应。本文以合肥地区33个工程场地的工程地质资料和地基承载力资料为依据,采用统计回归的方法,建立了地区性粘土地基的承载力表。     

由开放空间的公众选择解读香港房地产的环境经营理念

通过考察香港广场、公园、海滩、郊野公园4种开放空间类型的公众选择情况,了解香港市民的环境偏好,从而解读香港房地产独特的环境经营理念。