Geotechnical methods of reinforcement of slopes near railroads

In order to generate well-based design decisions on reinforcement of landslide slopes and road embankment slopes, a system of combined geotechnical analysis of geological conditions is suggested which includes topographic and geophysical survey, and laboratory studies of soils using infra-red spectroscopy methods. Calculations of slopes' deflected modes are carried out with taking into account elastic and elasto-plastic behavior of soil, and the presence of supporting man-made constructions. Results of the application of the system suggested may be used as criteria for the classification of landslide slopes along permanent ways according to the degree of danger when used for transportation.     

Case studies: Frozen ground design and construction in Kotzebue, Alaska

Alaska has many construction design challenges due to permafrost. Due to either climate changes or human activities and development, permafrost often becomes unstable. Unstable soils can cause thaw settlement, frost jacking, or heaving. These can cause damage to infrastructure, increase maintenance costs, and decrease the life of construction projects. Kotzebue, Alaska, a remote village in the northwest arctic part of Alaska, is ideal for observing such permafrost effects on infrastructure. Three case studies of Kotzebue construction projects are reviewed here： the Front Loop Water Main Extension, which shows the importance of both passive and active freeze thaw protection for water service pipes and how to minimize differential movement between pipes and buildings; the Wastewater Lift Station Replacement, which describes methods for reducing thaw settlement in buildings over time when it is not feasible to prevent thaw settlement, and compares the benefits of frozen ground excavation over traditional excavation practices; and the Ted Stevens Way Rehabilitation, which discusses the effectiveness of 2001 best design practices for gravel road construction over tundra and permafrost, identifies their design and construction failures, and proposes future solutions.     

中国公路交通的重金属排放及其对土地污染的初步估算

本文研究了全国各省市机动车Pb、Cu、Zn、Cd排放总量和公路两侧土壤中Pb含量的分布及其面积。结果表明,东部发达省份机动车的重金属排放量较西部地区大。使用含铅汽油的1990~1996年期间,北京市公路两侧土壤中Pb的年输入量为2.48~3.17 mg/ (kg · a)、累积量为11.4 mg/kg;1997~2003年使用无铅汽油后,两者分别下降到0.26~0.29 mg/(kg · a)和1.30 mg/kg。公路两侧的土壤中Pb含量随垂直距离的外延呈指数形式下降。公路交通对道路两侧土壤产生严重和轻度Pb污染的范围分别为距公路0~10 m和10~65 m。2003年北京市和全国受公路交通Pb污染的土地面积为2310 km²和28900 km²。公路交通的重金属排放是导致我国土地污染的重要原因之一。     

Quality issues in harvested rainwater in arid and semi-arid Loess Plateau of northern China

Loess soils cover vast areas in the arid and semi-arid regions of northern China. Due to the lack of reliable surface water and ground-water, rainwater harvesting has played a prominent role in farmers’ domestic usage and agricultural irrigation. An economical and valid type of water storage cistern with optimum design of components has been introduced to rural areas in the Loess Plateau. Different collection alternatives showed apparent variations in rainwater quality. By using different catchments, such as mortar roofs and cement-paved courtyards, compacted land or road surfaces, rainwater can be effectively collected for storage in cisterns. This study focused mainly on the quality of rainwater harvested from the different catchment systems and stored for different periods of time. By analysis of the water samples stored in these cisterns, it was evident that rainwater quality could be improved significantly by self-purification during the storage. With emphasis on rainwater quality affected by the different catchment systems, it was found that the measured inorganic compounds in the rainwater harvested from roof-yard catchment systems generally matched the WHO standards for drinking water, while the concentrations of some inorganic compounds in the rainwater collected from land and road surfaces appeared to be higher than the guideline values for drinking water, but generally not beyond the maximum permissible concentrations. However, Fecal Coliform, which is an important bacteriological parameter for the three catchment systems, exceeded the limits of drinking water to a greater extend. Trace amounts of 55 organic pollutants were identified, including aliphatic hydrocarbons, aromatic compounds and phthalate esters, etc. The analytical results indicated that roof-yard catchments that included the “first flush” usually provided safe drinking water with low organic contents, even for rainwater collected immediately after rainfall. In contrast, rainwater harvested from road surfaces had poor quality with respect to the organic constituents, regardless of stored time.     

Predicting pore-water pressures in road cut slopes in the West Indies

Pore-water conditions are not well known in road cut slopes in the tropics, despite the particularly acute stability problems in many areas in that climatic zone. Two prediction models are formulated from a study of conditions in road cut slopes in the Caribbean island of St Lucia. These are shown to be capable of predicting pore-water pressures to an acceptable level of accuracy from knowledge of only storm precipitation, material permeability and topography. More generally, such procedures are seen as potentially helpful in the context of cut slope design in tropical areas.     

西溪湿地土壤重金属分布特征及其生态风险评价

测试和研究了杭州西溪湿地土壤中铜(Cu)、锌(Zn)、铅(Pb)、镉(Cd)、汞(Hg)、砷(As)和铬(Cr)的含量与分布特征,采用内梅罗综合污染指数和Hakanson潜在生态危害指数法对湿地土壤重金属污染环境质量和潜在生态风险进行了评价。结果表明,西溪湿地土壤表层7种重金属平均含量的质量比分别为36.8 mg/kg(Cu)、91.5 mg/kg(Zn)、39.2 mg/kg(Pb)、0.23 mg/kg(Cd)、0.19 mg/kg(Hg)、6.3 mg/kg(As)和64.9 mg/kg(Cr)。由于受各种人为作用的影响,与浙江省土壤背景值相比,Cu、Pb、Cd和Zn在湿地土壤中的积累较大,有3个采样点[菜地、芦苇(Phram ites austrlis)滩地和靠马路的居民区]土壤中的Cd含量超过《土壤环境质量标准》(GB15618-1995)标准值的二级标准(pH<6.5)。湿地土壤重金属污染环境质量和生态风险评价结果显示,内梅罗综合污染指数平均值为1.73,多种重金属潜在生态风险指数平均值为114.6,说明总体上西溪湿地土壤重金属污染及其潜在生态风险为轻微级。最后,讨论了西溪湿地公园土壤重金属的可能来源,对比了重金属污染评价中不同评价标准和评价方法的差异性。     

Qinghai-Tibet Expressway experimental research

As one part of the National Highway Network Planning in China, the Qinghai-Tibet Expressway （QTE） from Golmud to Lhasa will be built in the interior of the Qinghai-Tibet Plateau （QTP） across about 630 km of permafrost lands. Due to the problematic interactions between the engineering foundations and permafrost, the frozen-soil roadbed of the QTE will be subjected to the more intense thermal disturbances due to the wider black surface. The design and construction for long-term thermal and mechanical stability will face more severe challenges than those in ordinary highways and railways in the same region. In order to provide scientific support for cold regions engineering practices, the QTE Experimental Demonstration Project （EDP） was constructed in situ in the vicinity of the Beilu＇he Permafrost Station in the interior of the QTP. In this paper, the anticipated problems of the proposed QTE project are enumerated, and the structures of the test sections for QTE EDP are described. Through numerical simulations, it was found that the heat transfer processes occurring in each specific road structure are significantly different. The heat accumulation in the highway embankment is mainly due to the black bituminous pavement, but in the railway embankment with its gravel surfaces, it mainly comes from the side slopes. As a result, the net heat accumulation of the highway embankment is three times higher than that in the railway. In expressway, the heat accumulation is further increased because of the wider pavement so that significantly more heat will be accumulated in the roadbed beneath the centerline area. Thus, the thermal stability of the fro- zen-soil roadbed and the underlying permafrost of the QTE can be seriously threatened without proper engineering measures protection against thawing. Based on research and practical experiences from the operating Qinghai-Tibet Railway （QTR） and the Qinghai-Tibet Highway （QTH）, combined with the predicted characteristics of heat transfer in an expressway embankment, nine kinds of engineering measures for mitigating the thaw settlement of foundation soils through the cooling the roadbed soils were built and are being tested in the EDP. The design of the monitoring system for the EDP and the observed parameters were also described.     

Evaluating the Characteristics of the Meander Belt Soils of the Niger Delta, Southeastern Nigeria

The morphological, physical, chemical and pedological properties of eight pedons representative of the four physiographic units in the Meander Belt of the Niger Delta were studied. The soils were classified and the constraints to their agricultural and engineering uses evaluated. The soils were generally poorly drained, having an Aquic moisture regime, mottles and Fe and Mn concretions. They belong to the Entisol and Inceptisol USDA soil taxonomy orders. Soil textures were generally clayey, except for the pedons of the levee crest with sandy loam textures. Bulk density, particle density and total porosity were generally low. Total nitrogen and available phosphorus were also low. The cation exchange capacity (CEC) and base saturation were high. Organic matter was low to moderate. Total elements of the clay were generally high. The soils have poor physical conditions. The high clay content, and the presence of 2:1 lattice clay minerals could account for the deterioration of the major east-west interstate road linking southeast and southwest Nigeria that passes through the area. Optimum use of the soils for agriculture would depend on good land evaluation and efficient soil water management.     

Human impacts on headwater fluvial systems in the northern and central Andes

South America delivers more freshwater runoff to the ocean per km² land area than any other continent, and much of that water enters the fluvial system from headwaters in the Andes Mountains. This paper reviews ways in which human occupation of high mountain landscapes in the Andes have affected the delivery of water and sediment to headwater river channels at local to regional scales for millennia, and provides special focus on the vulnerability of páramo soils to human impact. People have intentionally altered the fluvial system by damming rivers at a few strategic locations, and more widely by withdrawing surface water, primarily for irrigation. Unintended changes brought about by human activities are even more widespread and include forest clearance, agriculture, grazing, road construction, and urbanization, which increase rates of rainfall runoff and accelerate processes of water erosion. Some excavations deliver more sediment to river channels by destabilizing slopes and triggering processes of mass-movement.The northern and central Andes are more affected by human activity than most high mountain regions. The wetter northern Andes are also unusual for the very high water retention characteristics of páramo (high elevation grass and shrub) soils, which cover most of the land above 3000 m. Páramo soils are important regulators of headwater hydrology, but human activities that promote vegetation loss and drying cause them to lose water storage capacity. New data from a case study in southern Ecuador show very low bulk densities (median 0.26 g cm^− 3), high organic matter contents (median 43%), and high water-holding capacities (12% to 86% volumetrically). These data document wetter soils under grass than under tree cover. Effects of human activity on the fluvial system are evident at local scales, but difficult to discern at broader scales in the regional context of geomorphic adjustment to tectonic and volcanic processes.     

浅析北美湿地林道规划及设计

通过分析北美湿地林地规划及设计的理念,特别推出了美国联邦政府对湿地林地规划及设计具体的法规及列举美国主要湿地林道路基类型。通过美国国际重要湿地和地方湿地公园湿地林道的几个具体实例,阐明北美遵循最优管理实践原则及联邦政府湿地林道规划设计法规,促进湿地生态系统可持续发展。     

基于分形维数测算的西安古城道路网研究

基于人类尺度营建的古城道路网经过历史演化具有分形结构.在汽车成为道路设计导向的背景下,立足于分形连接的古城道路网应回归人性化出行的视角,应用Hausdorff维数简化分析法,长度--半径维数分析法及分枝数目--半径维数分析法,对1735年,1893年,1949年及2014年四个时期西安古城道路网进行了分形维数的测算,揭示了道路网分形演化趋势和不同时期的分形特征,探讨了演化原因并确定了分形演化过程中的三个阶段(不断向更高层次演化阶段;演化到较高等级,但外部因素对道路网产生逆向扰动;处于较高层级,但交通方式变革使基于人类尺度的道路网在结构和功能上发生局部蜕变),指出目前西安古城道路网在结构和功能上的局部蜕化趋势不容忽视,并针对问题提出应推崇适宜步行和自行车出行的模式典范,对古城道路网保护乃至整个古城的可持续发展具有重要意义.     

基于路网形态的上海住宿业空间布局特征

采用中心性模型、空间自相关理论、核密度法等,从城市路网形态角度分析上海市住宿业的空间格局特征及其与路网结构的空间响应关系。结果发现,上海市住宿业分布具有空间集聚性、类型分异性和距离衰减性,集聚核心与路网节点密度核心一致,主要围绕中心城区形成一级集聚核,星级酒店集聚分布在中心城区,经济型酒店和旅馆在一级集聚核外形成多个散状集聚核心,旅馆集聚依附性较为明显,民宿集聚度最高。不同类型的住宿设施分布存在较显著的空间相关性,对路网依赖性具有多元性,受路网影响的程度不同,道路连接值较高的区域交通可达性较好,住宿设施密度也相应较高。经济型酒店受到城市路网相对可达性和直线型交通效率的依赖最大,旅馆和民宿对于路网节点间通达性的依赖相对较大。住宿业发展要在产品偏好设计的前提下兼顾城市路网结构和消费需求进行合理选址,以实现综合效益最大化。     

Re-placing soil and its mattering in more-than-human cities

ABSTRACT

What role does soil play in sustainable design interventions and can it help to reconfigure human place experiences and human-nature relations in cities? Cities are home to a host of nonhuman actors that are overlooked or under-acknowledged in design and planning practices and in everyday dwelling. Soil is one such under-acknowledged urban inhabitant. In a period where cities and their inhabitants must adapt to the challenges of a changing climate, the paper draws together theory in design, planning and geography and empirical research with designers and residents in Australian cities to re-place soil as mattering in place(making) practices, everyday urban dwelling and urban sustainability transitions. The research contributes to recent work in (post)human geography to discuss ‘soil-planty mattering’, or the active role of soils and their intra-actions with other urban matter in shaping place. Soil-planty mattering is shown to disrupt human place(making), extending cities in material, temporal and spatial ways. In these extensions, the research suggests that soils have particular potential to re-orient human relationships with nonhumans in urban realms.     

Integrated geophysical surveys on railroads in permafrost areas

The zones of thawed ground in the permafrost area are most dangerous from engineer-geologist effect point of view. Detection of such zones, as making forecast of their movement is the main task of engi...     

广州市中山大道BRT主干道的联动分析

为探索BRT方案在高密度开发地区实施的可行性及其运行效益,采用实地调查与案例分析的方法,以广州中山大道BRT干道的设计为例,结合中山大道现有交通组织特点,指出BRT建设可能对其交叉路口交通组织、周边线路的联动和车辆过量占道等方面造成影响,认为实现"人地车"的协调才是城市交通规划的关键;提出促成交叉口BRT优先通行技术和ITS(智能交通系统)技术的应用、进一步优化运营模式、适当限制私人交通、合理规划公交地铁的驳接和大力发展快速公交并构建快速公交网络系统等措施。     

Geomorphological characteristics of slope failures in northeast Viti Levu island,Fiji, triggered by Tropical Cyclone Winston in February 2016

The highways circumnavigating Viti Levu play a pivotal role in Fiji's socioeconomic development, and are a crucial link to transport aid during disasters. Slope failures triggered by heavy rainfall and tropical cyclones have led to considerable damage and fatalities along Viti Levu's main roads in the past. Knowledge of slope instability mechanisms is key for the successful identification and management of slope failure hazards, however, there is a paucity of such information for Fiji's main roads. Severe Tropical Cyclone (STC) Winston was the strongest cyclone on record to make landfall in Fiji and affected the Fiji Islands from the early hours of 20 February until 3 am, 21 February, 2016. We present a field reconnaissance examining the characteristics and mechanisms of slope failures induced by STC Winston along a 35 km stretch of the northern part of the Viti Levu's ring road, “Kings Road”. Approximately 61 distinct shallow, small‐scale slope failures were identified most of which were of a complex type and included earth and debris slides (planar and rotational) with a minor flow component. The trigger for the slope failures was the ~258 mm of rainfall in 24 hours after 30‐days of antecedent rainfall totalling 482 mm. This caused rapid increases in porewater pressures, especially at the contact of residual soils and the underlying weathered basement rock. Evidence of recurring slips along Kings Road indicates that contemporary slope instability is likely caused by elevated porewater pressure during high intensity rainfall events in clay‐dominated soils.     

Freeze-thaw performance of chemically stabilized natural and recycled highway materials

This article provides an overview of several previous studies that investigated the stiffness and strength performance of chemically stabilized roadway materials under winter conditions (freeze-thaw cycling). The objective of this research was to understand the behavior of different materials stabilized with different type of binders when they were subjected to freeze-thaw cycling. Nine different materials including natural soils (organic soil, clay, silt, sand, and road surface gravel), reclaimed pavement material, and recycled asphalt pavement stabilized with nine different binders (five different fly ashes, lime, cement, lime kiln dust, cement kiln dust) were discussed. This article investigated how the volume, resilient modulus and unconfined compressive strength of soils/materials stabilized with different binders change in response to freeze-thaw cycling. Overall, the review results indicate that the stiffness and strength of all stabilized materials decrease somewhat with freeze-thaw cycling. However, the reduced strength and stiffness of stabilized materials after freeze-thaw cycling was still higher than that of unstabilized-unfrozen original soils and materials. In addition, materials stabilized with cement kiln dust provided the best performance against freeze-thaw cycling.     

Automatic change detection in lane-level road networks using GPS trajectories

Lane-level road network updating is crucial for urban traffic applications that use geographic information systems contributing to, for example, intelligent driving, route planning and traffic control. Researchers have developed various algorithms to update road networks using sensor data, such as high-definition images or GPS data; however, approaches that involve change detection for road networks at lane level using GPS data are less common. This paper presents a novel method for automatic change detection of lane-level road networks based on GPS trajectories of vehicles. The proposed method includes two steps: map matching at lane level and lane-level change recognition. To integrate the most up-to-date GPS data with a lane-level road network, this research uses a fuzzy logic road network matching method. The proposed map-matching method starts with a confirmation of candidate lane-level road segments that use error ellipses derived from the GPS data, and then computes the membership degree between GPS data and candidate lane-level segments. The GPS trajectory data is classified into successful or unsuccessful matches using a set of defuzzification rules. Any topological and geometrical changes to road networks are detected by analysing the two kinds of matching results and comparing their relationships with the original road network. Change detection results for road networks in Wuhan, China using collected GPS trajectories show that these methods can be successfully applied to detect lane-level road changes including added lanes, closed lanes and lane-changing and turning rules, while achieving a robust detection precision of above 80%.     

武汉城市圈城乡道路网的空间结构复杂性

以武汉城市圈为研究区,借助ArcGIS9.3、Pajek2.7和SPSS16.0等软件,从节点重要性、可达性、集聚性3个方面定量揭示了复杂城乡道路网的空间异质性:①高度节点重要性呈幂律分布,表现出无标度性,低度节点重要性则基本呈钟型泊松分布,呈现一定的随机性,导致整个圈域节点的重要性分布曲线既不遵循钟型泊松分布也不遵循幂律分布,出现"涌现"性;节点度值空间分布较均匀,呈现点状特征和弱集聚性,具有明显间断性和跳跃性,表现出一定的"中心-边缘"和"等级圈层"的复合结构;②节点的可达性主要由网络平均路径长度、紧密度和介数指标表达,其中道路网平均路径长度较大,节点交通联系呈线状组织,遵循距离衰减律,成等级圈层分异,但受快速干道影响明显,空间收敛减慢,发生"摄动"变形,形成两条以南北京珠高速和东西宜黄高速为轴的城市交通走廊;节点的紧密度系数较随机网络小,但高紧密度节点在空间分布上较为集中,呈现出一定的"中心-边缘"空间格局;节点的介数指标相对较高,呈现指数分布,空间分布较均匀,但仍呈现出一定的"等级圈层"分异;③网络的集聚性空间差异显著,形成多个大型网络社团,网络的聚类系数近似为零,局部呈现耦合性质,高聚类系数节点集聚成"半月形"展布,低聚类系数节点分布较为离散。     

武汉都市圈路网空间通达性分析

以武汉都市圈为例.通过距离算法、拓扑算法和空间句法模型,构建系列通达性数理模型.定量分析武汉都市圈路网发育的空间结构性规律:武汉都市圈路网整体发育水平和通达性格局保持高度相关性和一致性.空间差异显著;通达性遵循距离衰减律,空间收敛整体效应明显.呈现三大等级圈层和"中心-外围"结构:高等级路网发育不均衡.引起时空距离通达性圈发生"摄动"变形,呈西北-东南向倾斜的"Y"字形结构:拓扑连接等通达性圈更是出现"破碎化",交通轴线网络呈"轴一辐"式和"鱼骨刺"状空间伸展序:同时,路网发育的等级差异性也导致整个网络伺服效率和应对"拥堵"能力的低下,并形成沿长江东西向、沿京广南北向两条带状集成核.成为整个路网的第一等级交通轴线,控制整个都市圈网络连接性,强化交通轴线交汇处-武汉市的中心性优势:路网通达性这种等级空间格局与圈域城镇体系、交通设施和社会经济发展状况密切相关.尤其是与高速公路为代表的高等级路网发育水平,表现出复杂的共轭协调关系.