流域尺度土地利用调蓄视角的雨洪管理探析     

苏伟忠  汝静静  杨桂山 《地理学报》2019,74(5):948-961

发达国家雨洪管理焦点历经管网设计、不透水面阈值控制、低影响开发及土地利用管理等过程,呈现“多尺度多视角衔接”趋势。本文聚焦太湖流域土地利用调蓄功能变化机制及管理应用,揭示了1985-2015年来建设占用耕地是调蓄功能降低的主要原因;发现基于小流域的调蓄功能变化与建设用地强度整体低关联,但局部高相关,高相关的地区位于大城市或某些乡镇周边的建设增长热区,而这些热区的建设用地与调蓄空间规模较大且接触机会更多,是开发之前调蓄空间保护、开发控制以及开发之后综合管理等3个土地利用调蓄目标因子协调不当的结果;最后提出流域尺度土地利用调蓄视角的雨洪管理“345”模式,即以3个目标因子和5类控制要素为基础,实施土地利用调蓄创建、防御、拓展与保护等4类差别化战略模式,从更大尺度认识老城区和新区的雨洪关联,拓展海绵城市建设的本土认知和视野。  相似文献   

海上风机吸力式桶形基础承载特性研究综述     

毋晓妮  廖倩  李晔 《海洋技术学报》2020,39(1):91-106

风机基础作为海上风机整体结构的重要组成部分,承受着上部风机所受到的风浪流荷载,并且对风机的安全性及可靠性至关重要。吸力式桶形基础由于其安装简单和可重复利用等优点,在海洋平台基础中得到了广泛应用,并逐步应用于海上风机基础中。但由于海上风机与海洋平台在海洋环境中的荷载工况有一定的差别,仍需要通过对其承载特性研究现状进行全面认识,以实现吸力式桶形基础在海上风机基础中的可靠应用。文中通过总结和评价现有研究对桶形基础在不同土体条件以及荷载条件下进行试验及数值模拟分析得到的研究结果,综述了静荷载和循环荷载作用下砂土和黏土中的吸力式桶形基础的承载特性研究现状,以及海上风机吸力式桶形基础的相关研究。文章展望了目前应用于海上风机基础的桶形基础仍缺乏的研究,为海上风机吸力式桶形基础的可靠应用及后续研究提供重要参考。  相似文献   

海南岛海岸带土地利用强度与生态承载力分析     

李通  闫敏  陈博伟  张丽  宋茜茜 《测绘通报》2020,(9):54-59

随着海南省进一步开放发展，海岸带区域的土地利用强度逐渐加强，生态保护需求日益增强。利用4期（1990、2000、2009、2015年）海岸带土地利用分类数据，研究海岸带土地开发利用强度，并分析了其生态承载力。结果表明：①耕地和林地是海南岛海岸带地区的主要土地类型。②25年间，海南岛海岸带土地利用强度整体较高且逐年上升，2000—2009年土地利用强度增速最高，达2.03%；海口市和澄迈县土地利用强度4期均值最大，分别为300.5和286.1。③25年来海南岛海岸带生态状况呈下降趋势，57%的海岸带市县实际生态承载压力增长了1倍以上。  相似文献   

Why asymptotic limit of the acid dissolution capacity can lead to a sharp dissolution front in chemical dissolution of porous rocks?          下载免费PDF全文

Chongbin Zhao  B.E. Hobbs  A. Ord 《国际地质力学数值与分析法杂志》2017,41(15):1590-1602

The use of the asymptotic limit can greatly simplify the theoretical analysis of chemical dissolution front instabilities in fluid‐saturated rocks and therefore make it possible to obtain mathematical solutions, which often play a crucial role in understanding the propagation behavior of chemical dissolution fronts in chemical dissolution systems. However, there has been a debate in recent years that the asymptotic limit of the acid dissolution capacity (i.e., the acid dissolution capacity number approaching zero) alone cannot lead to a sharp dissolution front of the Stefan type in the acidization dissolution system, in which the dissolvable minerals of carbonate rocks are chemically dissolved by the injected acid flow. The acid dissolution capacity number is commonly defined as the ratio of the volume of the carbonate rock dissolved by an acid to that of the acid. In this paper, we use four different proof methods, including (i) direct use of the fundamental concepts; (ii) use of the mathematical governing equations of an acidization dissolution system; (iii) use of the different time scaling approach; and (iv) use of a moving coordinate system approach, to demonstrate that the asymptotic limit of the acid dissolution capacity can indeed lead to sharp dissolution fronts of the Stefan type in acidization dissolution systems on a much larger time scale (than the dissolution time scale). Our new finding is that on the reaction time scale, the condition of the conventional time derivative of porosity approaching zero alone can ensure that the acidization dissolution front has a sharp shape of the Stefan type. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Analysis of Water Resources Carrying Capacity of the “Belt and Road” Initiative Countries based on Virtual Water Theory     

ZHENG Xin  XU Zengrang 《资源与生态学报(英文版)》2019,10(6):574-583

Most countries along the route of the “Belt and Road” initiative are faced with a shortage of water resources. However, successful implementation of the initiative depends on water availability to support economic and social development. We designed a water resources carrying capacity evaluation index system, assigned grades and weights to each evaluation index and calculated a water resources carrying index for the 65 countries along the route. We used virtual water theory to analyze China’s net virtual water import from key bulk agricultural products through international trade. For more than half of the countries along the route, their water resources will be unable to support the economic development that will be necessary for fulfilling the goals of the Initiative. As a country with insufficient water resources carrying capacity, China is a net virtual water importer in the virtual water trade. This virtual water trade can improve China’s water resources support capacity, and ensure China’s water and food security for the future.  相似文献   

A new approach to estimate canopy evaporation and canopy interception capacity from evapotranspiration and sap flow measurements during and following wetting          下载免费PDF全文

J. Uddin  J. P. Foley  R. J. Smith  N. H. Hancock 《水文研究》2016,30(11):1757-1767

Canopy interception and its evaporation into the atmosphere during irrigation or a rainfall event are important in irrigation scheduling, but are challenging to estimate using conventional methods. This study introduces a new approach to estimate the canopy interception from measurements of actual total evapotranspiration (ET) using eddy covariance and estimation of the transpiration from measurements of sap flow. The measurements were conducted over a small‐scale sprinkler‐irrigated cotton field before, during and after sprinkler irrigation. Evaporation and sap flow dynamics during irrigation show that the total ET during irrigation increased significantly because of the evaporation of free intercepted water while transpiration was suppressed almost completely. The difference between actual ET and transpiration (sap flow) during and immediately following irrigation (post irrigation) represents the total canopy evaporation while the canopy interception capacity was calculated as the difference between actual ET and transpiration (sap flow) during drying (post irrigation) following cessation of the irrigation. The canopy evaporation of cotton canopy was calculated as 0.8 mm, and the interception capacity was estimated to be 0.31 mm of water. The measurement uncertainty in both the non‐dimensional ET and non‐dimensional sap flow was shown to be very low. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

基于GIS的资源环境承载力评价与空间布局优化—以荣成市为例          下载免费PDF全文

邵艳坡  郭志勇  白书建 《山东国土资源》2019,35(1)

随着工业化、城镇化、农业现代化和信息化的进程加快,我国面临的资源环境承载规模将进一步扩大,经济社会活动强度也将更高,人口、资源、环境之间的矛盾与冲突将不可避免地日趋激烈,因此开展资源环境承载力评估研究十分必要。以荣成市为研究对象,建立了资源环境承载力评价指标体系,基于GIS技术实现了属性数据的空间化,完成了各项指数的计算,分析了荣成市资源环境承载力状况。在资源环境承载力评价的基础上,分乡镇对荣成市土地空间布局进行优化,并形成综合分区引导。研究结论显示,荣成市资源环境基础性评价为可载,基于水资源系统的综合承载状态判定为临界,基于生态条件与环境质量系统的综合承载状态判定为可载。基于评价结果结合区位特点,荣成市各乡镇可按新兴产业、制造业、服务业,生态旅游业,生态农业,生态林业4个方向引导开发。  相似文献   

Unified numerical study of shallow foundation on structured soft clay under unconsolidated and consolidated-undrained loadings     

Santosh Kumar Yadav  Guan-lin Ye  Usama Khalid 《Marine Georesources & Geotechnology》2020,38(4):400-416

Abstract

Based on a new elasto-plastic constitutive model, this paper presents a soil–water coupled numerical prediction of the bearing capacity for shallow foundation constructed on Ballina soft clay for unconsolidated undrained (UU) and consolidated undrained (CU) conditions. This elasto-plastic constitutive Shanghai model has an advantage of describing the mechanical behaviour of over-consolidated and structured soil under different loading and drainage conditions, by using one set of material parameter. In this paper, the Shanghai model used for both UU and CU conditions has the same initial parameters obtained from laboratory test results. The loading conditions and consolidation stages vary based on construction details. The predicted bearing pressure-settlement responses for UU and CU, approves the field observation. The phenomenon of gaining the bearing capacity due to consolidation is captured and explained by the use of soil–water coupled numerical analysis with a new elasto-plastic model. The stress strain behaviour, stress paths and the decay of the structure of elements at different depths presented in this study, reveal the mechanism for the difference between UU and CU conditions to understand the foundation behaviour. Effect of the initial degree of soil structure on the bearing capacity is also addressed. Overall, this approach provides the integrated solution for the shallow foundation design problems under short and long-term loadings.  相似文献   

Analysis of shaft resistance of jacked piles in sands     

Rodrigo Salgado 《国际地质力学数值与分析法杂志》2011,35(15):1605-1635

In recent years, pile jacking has become a viable alternative installation method for displacement piles. Pile jacking produces minimal noise, vibration and air pollution during installation. In addition, it is possible, at the end of jacking, to have a good estimate of the ultimate static capacity of the pile. In this paper, the shaft resistance of piles jacked into sand is studied using one‐dimensional finite element analysis. The finite element simulations, using a two‐surface plasticity model, demonstrate the effects of relative density and confinement on the unit shaft resistance of piles jacked in sand. The impact of the number of jacking strokes on the unit shaft capacity is also assessed. Based on the numerical results, we developed equations for shaft resistance quantifying the effects of relative density, initial confinement and number of jacking strokes. Predictions using these equations are compared with data obtained from centrifuge tests and field tests. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

附有物理量和气象条件约束的光学卫星国土观测有效覆盖率评估     

巫兆聪  巫远  张熠  杨帆 《测绘学报》2016,45(7):841-849

传统光学卫星国土观测覆盖评估建立在卫星对地理想覆盖的基础上,并未考虑卫星存储、星地数据传输、观测时长等物理量及观测区域气象因素对于覆盖性能的影响。本文针对光学遥感卫星的国土观测需求.建立国土观测有效覆盖能力评估指标体系,根据卫星数据存储能力、星地数据传输能力、卫星单圈最大观测时长、卫星观测太阳高度角等性能参数,提出了基于物理性能约束下的有效覆盖计算方法。根据气象台站历年气象数据,提出了气象约束因子的计算方法。综合考虑卫星物理性能约束与观测区域气象约束,计算光学遥感卫星对地观测有效覆盖能力。最后根据专家设计的光学遥感卫星国土观测有效覆盖能力评估指标权重,利用层次分析法(AHP)评估光学遥感卫星系统对于国土观测的需求满足程度。试验结果表明,本文方法对于国土观测有效覆盖的估算和评价结果更加精确,更接近于国土观测的实际应用需求,为对地观测有效覆盖能力评估提供了一种更为精确的可行方案。  相似文献