共查询到20条相似文献，搜索用时 15 毫秒
1.
The response of box culverts to static loads is controlled by soil arching. Soil arching is a result of a complex soil culvert interaction (SCI) due to the relative stiffness between the culvert and the surrounding soil, and is a critical consideration in culvert design. The factors that affect soil arching on box culverts include the soil height above the culvert, the geometrical configuration of the box culvert and the properties of the soil around it. Box culverts are typically designed using formulae that assume simplified behaviors and in some cases rely on considerable empiricism. In the present study, small scale centrifuge physical model tests were conducted to investigate SCI considering the height and density of soil above the culvert and the geometry of the culvert. The results of these centrifuge tests were used to calibrate and verify a numerical model that was used to further investigate the response of box culverts to static loads. The results have been evaluated for bending moment and soil culvert interaction factors. The results demonstrated that the soil culvert interaction factors are not only a function of the height of soil column above the culvert, but also a function of the culvert thickness, soil elastic modulus and Poisson’s ratio. Therefore, the results were used to establish charts and equations that can be employed to assess the design values of the static soil pressure and static bending moment for box culverts. 相似文献
2.
顶进箱涵全断面置换管幕工法中钢管幕内力研究及实例分析 总被引：1，自引：0，他引：1
顶进箱涵全断面置换管幕工法是在出发井和接收井之间,利用顶管法在箱涵所在位置顶推钢管,置换出土体,形成全断面管撑,再顶推箱涵,同步置换出已顶进的钢管。针对该工法中的钢管幕,建立其内力和变形计算简化模型,将钢管视为在附加荷载作用下的置于Winkler地基上的弹性地基梁,推导出全断面管幕形式顶进箱涵置换管幕工法的钢管幕内力和变形计算公式,以此分析钢管幕的竖向变形。并采用弹性地基梁法和模拟试验比拟法,发现二者在规律及大小上都较为接近,说明所推导出的内力和变形计算公式具有一定的合理性,为实际工程的设计提供了理论依据 相似文献
3.
郑州市下穿北京―珠海高速公路立交工程是目前亚洲在软土地层中施工的横截面最大的管棚内箱涵顶进工程,如何控制地层位移以及保证公路的安全,是设计和施工中必须考虑的主要问题。对现场的实测数据进行了分析,并应用FLAC数值方法对顶进过程中引起的地层位移进行模拟计算。现场监测和数值模拟结果对比表明,两者基本接近。总结出的地层移动规律如下：①路面发生最大沉降的位置不在轴线处,而是在箱涵跨度的一半处;②最大的水平位移出现在与箱涵中心同一标高掌子面正前方的土体中。管棚复合体的水平位移与路面大致相当,基底的水平位移略小。③孔隙水压力对箱涵顶进引起的周围土层的扰动更为灵敏。 相似文献
4.
5.
Mohsen Safari Reza Kakaei Mohammad Ataei Mohammad Karamoozian 《Arabian Journal of Geosciences》2011,5(5):1011-1019
Site selection for the mineral processing is the most important decision made by owner that has a significant impact on the efficiency of the whole process. This is a critical decision which involves considering a number of criteria and finding the best location among feasible alternatives. Therefore, a multicriteria decision-making method is necessary to apply site-selection process to find the best location that meet desired conditions set by the selection criteria. This paper presents an application of TOPSIS method based on fuzzy sets (fuzzy TOPSIS), which is one of the broader multicriteria decision making means, used to select an appropriate site for mineral processing plant for Sangan iron ore mine (phase 2). For this purpose, at first considering the geological, technical, economical, and environmental factors, three feasible alternatives were selected for the processing plant using Geographical Information System. Then, based on the technical and experimental experiences and through judgment of the decision makers and experts, 14 criteria were established and these alternatives were evaluated. Finally, the alternatives were ranked and the best location was recommended. 相似文献
6.
This study evaluated the use by fish of restored tidal wetlands and identified links between fish species composition and habitat characteristics. We compared the attributes of natural and constructed channel habitats in Sweetwater Marsh National Wildlife Refuge, San Diego Bay, California, by using fish monitoring data to explore the relationships between channel environmental characteristics and fish species composition. Fishes were sampled annually for 8 yr (1989–1996) at eight sampling sites, four in constructed marshes and four in natural marshes, using beach seines and blocking nets. We also measured channel habitat characteristics, including channel hydrology (stream order), width and maximum depth, bank slope, water quality (DO, temperature, salinity), and sediment composition. Fish colonization was rapid in constructed channels, and there was no obvious relationship between channel age and species richness or density. Total richness and total density did not differ significantly between constructed and natural channels, although California killifish (Fundulus parvipinnis) were found in significantly higher densities in constructed channels. Multivariate analyses showed fish assemblage composition was related to channel habitat characteristics, suggesting a channel’s physical properties were more important in determining fish use than its restoration status. This relationship highlights the importance of designing restoration projects with natural hydrologic features and choosing proper assessment criteria in order to avoid misleading interpretations of constructed channel success. We recommend that future projects be designed to mimic natural marsh hydrogeomorphology and diversity more closely, the assessment process utilize better estimates of fish habitat function (e.g., individual and community-based species trends, residence time, feeding, growth) and reference site choice, and experimental research be further incorporated into the restoration process. 相似文献
7.
A. Afsordegan M. Sánchez N. Agell S. Zahedi L. V. Cremades 《International Journal of Environmental Science and Technology》2016,13(6):1419-1432
Multi-criteria decision-making methods support decision makers in all stages of the decision-making process by providing useful data. However, criteria are not always certain as uncertainty is a feature of the real world. MCDM methods under uncertainty and fuzzy systems are accepted as suitable techniques in conflicting problems that cannot be represented by numerical values, in particular in energy analysis and planning. In this paper, a modified TOPSIS method for multi-criteria group decision-making with qualitative linguistic labels is proposed. This method addresses uncertainty considering different levels of precision. Each decision maker’s judgment on the performance of alternatives with respect to each criterion is expressed by qualitative linguistic labels. The new method takes into account linguistic data provided by the decision makers without any previous aggregation. Decision maker judgments are incorporated into the proposed method to generate a complete ranking of alternatives. An application in energy planning is presented as an illustrative case example in which energy policy alternatives are ranked. Seven energy alternatives under nine criteria were evaluated according to the opinion of three environmental and energy experts. The weights of the criteria are determined by fuzzy AHP, and the alternatives are ranked using qualitative TOPSIS. The proposed approach is compared with a modified fuzzy TOPSIS method, showing the advantages of the proposed approach when dealing with linguistic assessments to model uncertainty and imprecision. Although the new approach requires less cognitive effort to decision makers, it yields similar results. 相似文献
8.
9.
Landfill site selection by decision-making tools based on fuzzy multi-attribute decision-making method 总被引：2，自引：2，他引：0
Abdolhadi Nazari Mohammad Mehdi Salarirad Abbas Aghajani Bazzazi 《Environmental Earth Sciences》2012,65(6):1631-1642
Landfill site selection is a complex and time-consuming process, which requires evaluation of several factors where many different
attributes are taken into account. Decision makers always have some difficulties in making the right decision in the multiple
attribute environments. After identifying candidate sites, these sites should be ranked using decision-making methods. This
study applies Chang’s fuzzy AHP-based multiple attribute decision-making (MADM) method for selection of the best site of landfills
based on a set of decision criteria. The Fuzzy Analytic Hierarchy Process (FAHP) was designed to make pairwise comparisons
of selected criteria by domain experts for assigning weights to the decision criteria. Analytic Hierarchy Process (AHP) is
used to make pairwise comparisons and assign weights to the decision criteria. It is easier for a decision maker to describe
a value for an alternative by using linguistic terms and fuzzy numbers. In the fuzzy-based AHP method, the rating of each
alternative was described using the expression of triangular fuzzy membership functions. Once the global weights of the criteria
is calculated by AHP, they are incorporated into the decision matrices composed by decision maker and passed to fuzzy-AHP
method which is used to determine preference order of siting alternatives. In this study, a computer program based on the
Chang’s fuzzy method was also developed in MATLAB environment for ranking and selecting the landfill site. As an example of
the proposed methodology, four different hypothetical areas were chosen and implemented to demonstrate the effectiveness of
the program. By using this program, the precision was improved in comparison with traditional methods and computational time
required for ranking and selecting the suitable landfill site was significantly reduced. 相似文献
10.
11.
12.
Flood risk perceptions and spatial multi-criteria analysis: an exploratory research for hazard mitigation 总被引：7，自引：7，他引：0
The conventional method of risk analysis (with risk as a product of probability and consequences) does not allow for a pluralistic approach that includes the various risk perceptions of stakeholders or lay people within a given social system. This article introduces a methodology that combines the virtues of three different methods: the quantifiable conventional approach to risk; the taxonomic analysis of perceived risk; and the analytical framework of a spatial multi-criteria analysis. This combination of methods is applied to the case study ‘Ebro Delta’ in Spain as part of the European sixth framework project ‘Floodsite’. First, a typology for flood hazards is developed based on individual and/or stakeholders’ judgements. Awareness, worry and preparedness are the three characteristics that typify a community to reflect various levels of ignorance, perceived security, perceived control or desired risk reduction. Applying ‘worry’ as the central characteristic, a trade-off is hypothesized between Worry and the benefits groups in society receive from a risky situation. Second, this trade-off is applied in Spatial Multi-Criteria Analysis (SMCA). MCA is the vehicle that often accompanies participatory processes, where governmental bodies have to decide on issues in which local stakeholders have a say. By using risk perception-scores as weights in a standard MCA procedure a new decision framework for risk assessment is developed. Finally, the case of sea-level rise in the Ebro Delta in Spain serves as an illustration of the applied methodology. Risk perception information has been collected with help of an on-site survey. Risk perception enters the multi-criteria analysis as complementary weights for the criteria risk and benefit. The results of the survey are applied to a set of scenarios representing both sea-level rise and land subsidence for a time span of 50 years. Land use alternatives have been presented to stakeholders in order to provide the regional decision maker with societal preferences for handling risk. Even with limited resources a characteristic ‘risk profile’ could be drawn that enables the decision maker to develop a suitable land use policy. 相似文献
13.
钢筋混凝土箱涵竖向土压力理论研究 ——梯形沟谷设涵 总被引：2，自引：0，他引：2
梯形沟谷设涵在山区公路和铁路建设中的应用非常广泛。然而,目前规范中尚无梯形沟谷设涵的设计方法。现有的研究主要针对上埋式和沟埋式涵洞,对天然梯形沟谷埋设涵洞时的涵洞受力性状的研究甚少。通过数值模拟得出梯形沟谷设涵时,钢筋混凝土箱型涵洞顶部填土内的应力状态和土拱的分布规律。在此基础上建立理论模型,推导涵洞土压力理论计算式,并验证理论方法的正确性。此外,对涵顶土压力的影响因素进行了参数研究。结果表明,梯形沟谷设涵时涵洞的受力状态不同于上埋式和沟埋式两种情况。当涵顶填土高度到达临界高度时,填土中会形成上、下两层土拱。下层土拱效应使涵顶产生土压力集中,上层土拱效应会减小涵顶的土压力集中。涵顶土压力的大小取决于涵顶的填土高度、沟谷坡角、沟谷宽度、涵洞的几何尺寸及填土的性质。 相似文献
14.
R. Nabizadeh A. Mahvi G. Mardani M. Yunesian 《International Journal of Environmental Science and Technology》2005,1(4):325-333
A cross-sectional survey was conducted through Tehran city and a field study was conducted to prepare main and accessory drainage channels map. Three main drainage channels were identified for this research and some sampling stations were chosen. Three stations selected in south of Tehran. The reason for selecting these stations is that all urban surface runoff completelypass through these points and samples taken from these points are representative of all kinds of pollutants that transit from city surface. Another Three stations were selected in center and further three stations were selected at north of Tehran. Surface runoff flow in three main channels, from north to south of Tehran, converge at south of Rey city and finally end up to Ghom Salt lake. The stations were chosen at three trajectories, Sorkhe Hesar, Emad Avard, Kan. At each month two samples were prepared from nine different stations. After collection of samples with respect to standard methods, they were dissolved in nitric acid and then analyzed by atomic absorption device. The results show that the concentrations of pollutants increased from north to south. For instance, Zinc had most concentration with monthly average of 0.98 mg/l and Nickel had the lowest amount with 0.02 mg/l in southern stations. Average concentration of Zn, Pb, Cd, Cu and Ni were: 0.638, 0.097, 0.04 and 0.035 mg/l respectively. Total average concentrations of heavy metals at three main channels were of 0.177, 0.176 and 0.145 mg/l. Emad Avard was the most polluted channel. 相似文献
15.
Sedimentology and morphology of a low-sinuosity river: Calamus River, Nebraska Sand Hills 总被引：2，自引：0，他引：2
A study reach of the Calamus River, Nebraska Sand Hills, has a low sinuosity (less than 1.3) and braiding parameter (less than 1). Depending on sinuosity, the channel is occupied by alternate bars and point bars, the emergent parts of which form nuclei for midstream bars (islands). Channel migration occurs by bend expansion and translation, downstream and lateral growth of islands, and by chute cutoff. Channel-bed sediment is mainly medium-grained sand, but gravel and coarser sand sizes occur in thalweg areas adjacent to cutbanks and upstream parts of bars and islands, and finer sands occur on the downstream parts of bars and filling channels. Curved-crested dunes cover most of the channel bed at most flow stages, with ripples restricted to shallow areas near banks. Bed material is mostly large-scale cross-stratified, with small-scale cross-strata interbedded with plant debris occurring in topographically high areas near banks. Vibracores through channel bars show a basal erosion surface overlain by large-scale cross-stratified sands, in turn overlain by small-scale cross-stratified sand interbedded with plant debris. The overall sequence generally fines upwards, but the large-scale cross-stratified portion either fines upwards, coarsens upwards, or shows little grain size variation. Lithofacies distributions vary spatially within and between bars depending on position in the bar and local channel curvature/width, in a similar way to unbraided rivers elsewhere. Lithofacies of bar deposits are similar to those in the active channel, and the elevations of the basal erosion surface and adjacent channel thalweg correspond closely. Channels abandoned by chute cutoff are filled progressively from the upstream end, and comprise deposits similar to the downstream parts of bars (i.e. fining upwards). The downstream extremities of channel fills may contain large proportions of peat relative to sand, but little mud due to the paucity of such fine suspended load in the Calamus. 相似文献
16.
Stace E. Beaulieu Peter A. Fox Massimo Di Stefano Andrew Maffei Patrick West Jonathan A. Hare Michael Fogarty 《Earth Science Informatics》2017,10(1):85-97
There is a growing need for cyberinfrastructure to support science-based decision making in management of natural resources. In particular, our motivation was to aid the development of cyberinfrastructure for Integrated Ecosystem Assessments (IEAs) for marine ecosystems. The IEA process involves analysis of natural and socio-economic information based on diverse and disparate sources of data, requiring collaboration among scientists of many disciplines and communication with other stakeholders. Here we describe our bottom-up approach to developing cyberinfrastructure through a collaborative process engaging a small group of domain and computer scientists and software engineers. We report on a use case evaluated for an Ecosystem Status Report, a multi-disciplinary report inclusive of Earth, life, and social sciences, for the Northeast U.S. Continental Shelf Large Marine Ecosystem. Ultimately, we focused on sharing workflows as a component of the cyberinfrastructure to facilitate collaboration and reproducibility. We developed and deployed a software environment to generate a portion of the Report, retaining traceability of derived datasets including indicators of climate forcing, physical pressures, and ecosystem states. Our solution for sharing workflows and delivering reproducible documents includes IPython (now Jupyter) Notebooks. We describe technical and social challenges that we encountered in the use case and the importance of training to aid the adoption of best practices and new technologies by domain scientists. We consider the larger challenges for developing end-to-end cyberinfrastructure that engages other participants and stakeholders in the IEA process. 相似文献
17.
The effects of frictional forces acting on the sidewalls of buried box culverts are presented as determined with finite element method (FEM) and detailed soil modelling. The possibility of reducing earth pressure on deeply buried concrete box culverts by the imperfect trench installation (ITI) method has been contemplated during the last several decades. There have been limited research results published primarily regarding the qualitative aspect of load reduction in ITIs. It was found during the course of this study that significant frictional forces develop along the sidewalls of box culverts and adjacent sidefills in ITIs. Current American Association of State Highway and Transportation Officials provisions do not consider these frictional forces, but they cannot be neglected in ITIs, as their effect is dominant. An optimum geometry for the soft zone in ITIs is presented to maximize earth load reductions. The soil–structure interaction at the box culvert–soil interface was found to have a significant effect on total earth pressure acting on the bottom slab. Predictor equations for earth load reduction rates were formulated for ITIs incorporating the optimum soft zone geometry based on the FEM. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
18.
N. Van Cauwenbergh D. Pinte A. Tilmant I. Frances A. Pulido-Bosch M. Vanclooster 《Environmental Geology》2008,54(3):479-489
Water management in the Andarax river basin (Almeria, Spain) is a multi-objective, multi-participant, long-term decision-making
problem that faces several challenges. Adequate water allocation needs informed decisions to meet increasing socio-economic
demands while respecting the environmental integrity of this basin. Key players in the Andarax water sector include the municipality
of Almeria, the irrigators involved in the intensive greenhouse agricultural sector, and booming second residences. A decision
support system (DSS) is developed to rank different sustainable planning and management alternatives according to their socio-economic
and environmental performance. The DSS is intimately linked to sustainability indicators and is designed through a public
participation process. Indicators are linked to criteria reflecting stakeholders concerns in the 2005 field survey, such as
fulfilling water demand, water price, technical and economical efficiency, social and environmental impacts. Indicators can
be partly quantified after simulating the operation of the groundwater reservoir over a 20-year planning period and partly
through a parallel expert evaluation process. To predict the impact of future water demand in the catchment, several development
scenarios are designed to be evaluated in the DSS. The successive multi-criteria analysis of the performance indicators permits
the ranking of the different management alternatives according to the multiple objectives formulated by the different sectors/participants.
This allows more informed and transparent decision-making processes for the Andarax river basin, recognizing both the socio-economic
and environmental dimensions of water resources management. 相似文献
19.
G. Tuzkaya 《International Journal of Environmental Science and Technology》2013,10(3):423-432
Supplier evaluation problems deal with selecting appropriate suppliers considering multiple criteria, which may be related with qualitative and quantitative aspects. Traditional supplier selection criteria contain criteria such as cost, capacity, delivery reliability, flexibility, and responsiveness, etc. However, due to the increasing level of environmental problems, it is a necessity to take environmental criteria into account together with the traditional decision criteria in the supplier evaluation processes of companies. Considering this necessity, this paper proposes a decision making methodology for environmental criteria integrated supplier evaluation processes. A methodology based on intuitionistic fuzzy Choquet integral operator is utilized to take into account vagueness of the decision environment and the interactions among the criteria. This methodology also provides the consideration of the satisfaction and dissatisfaction degrees of alternatives for each criterion with the help of intuitionistic fuzzy values. In addition, the effects of the criteria weights to the final ranking of suppliers are analyzed via sensitivity analyses. 相似文献
20.
Selection of wastewater treatment process based on the analytical hierarchy process and fuzzy analytical hierarchy process methods 总被引：2，自引：1，他引：1
A. R. Karimi N. Mehrdadi Ph.D. S. J. Hashemian G. R. Nabi Bidhendi R. Tavakkoli Moghaddam 《International Journal of Environmental Science and Technology》2011,8(2):267-280
This paper presents an application of the analytical hierarchy process and fuzzy analytical hierarchy process methods for selecting the best wastewater treatment process. The analytical hierarchy process is one of the best ways for deciding among the complex criteria structure in different levels, and the fuzzy analytical hierarchy process is a synthetic extension of the classical method when the fuzziness of the decision makers are considered. After reviewing aerobic treatment processes operated in Iran’s industrial estates and determining the main criteria used for treatment process evaluation, they are arranged in a hierarchy structure. Selection of the best wastewater treatment process is a multi-criteria decision making problem. Conventional methods are inadequate for dealing with the imprecise or vague nature of linguistic assessment. To overcome this difficulty, the fuzzy analytical hierarchy process is proposed for dealing with the vagueness of decision makers’ judgments. The alternatives consist of extended aeration, absorption bio-oxidation, integrated fixed-film activated sludge, sequencing batch reactor, aerated lagoon. Based on the general condition of industrial estate’s wastewater treatment plants, technical/administrative, economic and environmental criteria and their sub-criteria are weighted and then criteria evaluated and priorities of alternatives have been done by analytical hierarchy process and fuzzy analytical hierarchy process methods by the use of triangular fuzzy numbers. Finally, selection of the best process and ranking of these five processes are carried out by these foregoing methods, and some sensitivity analyses are conducted to show the results’ sensitiveness to the changes of the weights of the evaluation criteria. 相似文献