海滩养护工程质量评价研究进展          下载免费PDF全文

杨雯  王永红  杨燕雄 《海岸工程》2016,35(1):75-84

由于自然因素和人类活动的影响等原因,世界很多海滩经受着侵蚀和破坏。而利用人工养护工程来保护和恢复海滩具有养护效果较明显、干滩面积明显增加以及不破坏环境景观的优点,目前得到越来越多国家的认可。国外由于养滩历史较久,养滩工程后的监测和质量评价不仅开展得早,而且已经成为工程的一个重要部分。评价指标已经比较完善,甚至有些国家已经将养滩效果评价列入法规框架之中。我国的海滩养护工程在十几年前才开始,虽然工程量逐年增长,但是对海滩养护工程施工后的工程监测和工程评价却较少涉及。本文对美国、荷兰、英国、丹麦以及我国等国家的海滩养护工程的工程评价工作进行总结,从而提出适用于我国工程特点的养滩工程质量评价因子和方法。  相似文献   

210Pbex示踪法技术原理及其在土壤侵蚀中的应用          下载免费PDF全文

胡菊芳  沙占江  马玉军  翟于乐  王求贵 《盐湖研究》2016,24(1)

土壤侵蚀是全球性的环境问题之一,严重威胁到资源、环境和社会经济的可持续发展。应用核素示踪技术研究土壤侵蚀已成为当前该领域研究热点,它体现出了很多的优越性,并在今后研究中有着广阔的应用前景。本文介绍了210Pbex的示踪原理,概述了210Pbex在土壤侵蚀示踪研究中的存在的关键性问题及其应用,并对其研究进行了展望。  相似文献   

Cloud Forest Conservation in the Central Highlands of Guatemala Hinges on Soil Conservation and Intensifying Food Production     

Ian Pope  Jon Harbor  Laura Zanotti  Guofan Shao  Dawn Bowen  Gary R. Burniske 《The Professional geographer》2016,68(1):1-13

Soil erosion threatens long-term soil fertility and food production in Q’eqchi’ communities native to the Sierra Yalijux and Sierra Sacranix mountain ranges in the central highlands of Guatemala. Environmental factors such as steep topography, erodible soils, and intense precipitation events, combined with land subdivision and reduced fallow periods as a consequence of population growth, contribute to severe erosion and strain soil resources. The preservation of the region's cloud forests hinges on enhancing production of staple crops through agricultural intensification while maintaining soil fertility through implementation of soil conservation measures.  相似文献   

Effects of initial step height on the headcut erosion of bank gullies: a case study using a 3D photo-reconstruction method in the dry-hot valley region of southwest China   总被引：1，自引：0，他引：1  

Baojun Zhang  Zhengan Su  Dan Yang  Yifan Dong  Liang Xiao 《自然地理学》2016,37(6):409-429

Abstract

Headcut erosion has been recognized as one of the main processes involved in gully development in the dry-hot valley region of southwest China. To examine the effect of initial step height on headcut erosion processes, three headcuts were constructed ranging in height from 0.75 to 1.25 m on an active bank gully head, and a series of scouring experiments were conducted under a flow discharge of 120 L min^?1. The morphological evolutions of the plunge pools and soil loss volume were estimated by three-dimensional photo-reconstruction methods (3D-PR). As the step height increased, the experimental results showed that: (1) the transformed potential energy and shear stress would increase by approximately 4.89 J s^?1 and 26.4 Pa on average when the step height increased 0.25 m; (2) the mean depth and width of the plunge pool exhibited obvious growth, and the morphology of the cross-section developed from approximately V-shaped to U-shaped; and (3) soil loss volume increased logarithmically, with total soil loss volumes of 0.076, 0.105 and 0.116 m³, respectively. Although the significant effects of the initial step height on headcut erosion were verified, further quantitative studies are required to quantify the mechanism of headcut erosion, especially for plunge pool erosion.  相似文献   

Tectono–Thermal Evolution, Hydrocarbon Filling and Accumulation Phases of the Hari Sag, in the Yingen–Ejinaqi Basin, Inner Mongolia, Northern China     

YANG Peng  REN Zhanli  XIA Bin  TIAN Tao  ZHANG Yong  QI Kai  REN Wenbo 《《地质学报》英文版》2018,92(3):1157-1169

This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase,uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectonothermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY R_0% model, which is constrained by vitrinite reflectance(R_0) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a.105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43-45℃/km. The main hydrocarbon generation period ensued around 105.59-80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo-temperature was over 180℃.Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation(K_1 b) occurred primarily around 105.59-103.50 Ma with temperatures of 125-150℃. The second accumulation period observed in the Suhongtu Formation(K_1 s) occurred primarily around84.00-80.00 Ma with temperatures of 120-130℃. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono-thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation,which is the key reason for hydrocarbon filling and accumulation.  相似文献   

水射流破碎南海含水合物沉积物数值模拟研究          下载免费PDF全文

潘栋彬  陈晨  杨林  靳成才  李曦桐  刘书源  陈勇  朱江 《探矿工程》2018,45(10):27-31

为研究高压水射流切割、破碎南海天然气水合物储层的过程,采用著名的LS—DYNA显示动力分析有限元程序,对淹没状态下,水射流破碎海底含水合物沉积物过程进行数值模拟研究,研究了不同射流速度对高压水射流作用下含水合物沉积物破碎效果的影响规律。随着射流速度的增大,冲蚀深度逐渐增大,两者呈线性递增关系。含水合物沉积物冲蚀体积是轴向冲蚀与径向冲蚀共同作用的结果,射流速度越大,对含水合物沉积物的轴向与径向冲蚀作用增强,加大了含水合物沉积物冲蚀体积递增速率。  相似文献   

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS   总被引：1，自引：0，他引：1  

Jobin Thomas  Sabu Joseph  K.P.Thrivikramji 《地学前缘(英文版)》2018,9(3):893-906

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km~2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha~(-1) yr~(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha~(-1) yr~(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(5 t ha~(-1) yr~(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.  相似文献   

What is preserved in the aeolian rock record? A Jurassic Entrada Sandstone case study at the Utah–Arizona border     

《Sedimentology》2018,65(4):1301-1321

Aeolian dune fields evolve from protodunes and small dunes into a pattern of progressively fewer, larger and more widely spaced dunes within limits defined by boundary conditions. However, the allogenic boundary conditions that promote aeolian dune‐field development, accumulation of strata and preservation of accumulated strata are not the same. Autogenic processes, such as dune interactions, scour‐depth variation along migrating dunes and substrate cannibalization by growing dunes, result in removal of the stratigraphic record. Moreover, dune‐field events may be collapsed into major erosional bounding surfaces. The question is what stages of evolving dune fields are represented in the rock record? This case study of ca 60 m of Jurassic Entrada Sandstone on the Utah/Arizona border (USA) defines stratigraphic intervals by gross architecture of bounding surfaces and sets of cross‐strata. The interpreted intervals in stratigraphic order consist of: (i) a lower sabkha bed that transitions upward into erosional remnants of small sets representing an initial wet aeolian system; (ii) large, compound cross‐strata representing a mature dune field; (iii) isolated scour‐fill representing negatively climbing dunes that produced ca 25 m of palaeo‐topographic relief; (iv) downlapping sets that fill the landscape‐scale relief; (v) four intervals of stacked climbing sets that each represent short periods of time; and (vi) an upper sabkha bed that again transitions into small sets representing a wet system. Accumulations appear to be associated with sediment pulses, a rising water table, and filling of scoured troughs and landscape‐scale depressions. Preservation of the accumulations is selective and associated with a rising water table, burial and subsidence. The preserved record appears remarkably incomplete. Speculation about missing strata gravitates towards cannibalization of the record of early dune‐field construction, and strata removed during the formation of bounding surfaces. This local Entrada record is thought to represent a point in the spectrum of preservation styles in the rock record.  相似文献   

黄河口清水沟河道的冲淤过程与模拟          下载免费PDF全文

郑珊  吴保生  周云金  王开荣  韩沙沙 《水科学进展》2018,29(3):322-330

为揭示黄河口清水沟河道长时段的冲淤演变规律并建立其冲淤计算方法,分析了清水沟1976—2015年的时空冲淤演变过程,采用河床演变的滞后响应模型,考虑河口来水来沙及河道延伸与蚀退的影响,建立了清水沟累计冲淤量的计算方法。结果表明:1976—1980年改道初期清水沟改道点上游先冲后淤,改道点下游淤滩塑槽,淤积量随着下游河道展宽而增加,1980年后改道点上、下游河道冲淤过程趋于一致;受水沙条件等因素影响,1980—1986年清水沟主槽冲刷展宽,之后主槽淤积萎缩;1996年清八改汊和2002年小浪底水库"调水调沙"原型试验以来,河道转淤为冲,2002年后河道冲刷速率随时间指数衰减;河床演变的滞后响应模型可计算清水沟长时段的冲淤过程,该方法可为预测未来清水沟冲淤演变趋势提供科学参考。  相似文献   

对坡面径流挟沙力研究的几点认识   总被引：6，自引：0，他引：6       下载免费PDF全文

张光辉 《水科学进展》2018,29(2):151-158

坡面径流挟沙力是土壤侵蚀过程模型的核心输入参数。在系统界定坡面径流挟沙力概念的基础上,深入分析了坡面径流水动力学特性和泥沙特性对坡面径流挟沙力的影响及其机制,受降雨、地形、土壤、植被、土地利用、结皮形成、细沟发育和砾石出露等多种因素时空变异的综合影响,坡面径流挟沙力具有强烈的时空变化特征,导致坡面径流挟沙力的测定较为困难。将确定挟沙力常用的方法划分为河流挟沙力方程修正法、推理法、模型模拟法和测量法,比较分析了不同方法的优缺点。未来的研究应该重点关注挟沙力测定方法与技术、坡面径流输沙过程的动力机制、典型土壤的挟沙力、挟沙力方程构建与验证及变化条件下坡面径流挟沙力等方面。  相似文献