某滑坡坝天然坝高评价及洪水漫坝可能性分析

滑坡坝及形成的堰塞湖在世界各国的山区广泛分布。它能够形成天然水库，在发生溃坝和洪水漫坝的情况下，造成的灾害损失很大。历史上产生过许多天然滑坡坝，有些很快发生溃坝，有些存在时间很长。存在时间较长的滑坡坝，它周围风景秀丽，成为旅游热点地区，同时也可开发其水资源。在开发和利用这种滑坡坝时，它的安全性需要分析评价。由于它的坝高是自然形成，不受人为控制，坝高的安全程度需要分析研究。在人工坝高超高设计方法中，库区风速、浪高等是影响坝高的因素。计算时考虑最危险的情况和风速、波浪等因素叠加，滑坡坝的坝高符合设计坝高，满足规范要求，在这种情况下不会发生洪水漫坝和溃坝，不会对下游造成危害。某滑坡坝位于拟建某水电站的上游，在国家级自然保护区内，是著名的旅游景点，其安全性对旅游开发、工程建设和下游居民生命财产安全影响很大。为了评价滑坡坝的稳定性，需要对其发生洪水漫坝和溃坝的可能性进行研究，论证其安全性。通过使用人工坝超高计算方法进行计算，结果表明：它的天然坝高超过同等规模人工坝的设计超高要求，不会发生洪水漫坝和溃坝，对电站建设和下游居民不会产生威胁。滑坡坝是稳定的，可以进行综合开发。这种计算方法对类似工程也有一定的借鉴意义。     

Case study of reservoir triggered seismicity, Latian Dam, Tehran, Iran

Latian dam is located in the North East of Tehran in Elburz Mountain. It falls in the category of large dams according to the International Committee on Large Dams (ICOLD). It was constructed in 1967 for agricultural purposes, drinking water, and power generation. Producing triggered earthquakes may be a consequent result of dam construction. In this paper, the complete seismic statistics of the region from 1996 onwards has been studied to understand the seismic condition of Latain region. For this purpose, frequency of earthquakes within a radius of 30/60 km around the dam is studied considering its relationship with the reservoir volume variation. Using Gutenberg-Richter rule, parameter b of the region was determined within the same region. The results of this study show the existence of triggered seismicity around the reservoir of Latian dam. Considering the tectonic-geological condition of the region, the existence of triggered earthquakes may create landslides in the reservoir and around it.     

一个由左右岸滑坡形成的滑坡坝成因机制分析

滑坡坝及形成的堰塞湖在世界各国特别是山区一带广泛分布。它能够形成天然水库 ,在发生溃坝和洪水漫坝的情况下 ,造成的灾害损失很大。历史上产生过许多天然滑坡坝 ,有些很快发生溃坝 ,有些存在时间很长。存在时间较长的滑坡坝 ,它周围风景秀丽 ,成为旅游热点地区 ,同时也可开发其水资源。滑坡坝的形成有滑坡堵江、崩塌堵江和泥石流堵江 3种形式 ,它的形成机制对于滑坡坝的存在时间起了重要的作用。在开发和利用滑坡坝时 ,它的成因机制需要分析评价。本文对某滑坡坝的形成机制进行了研究 ,在研究某滑坡坝时发现 ,它由左右两岸的滑坡共同作用形成 ,这种形成模式在国内外报道很少 ,对类似工程也有一定的借鉴意义     

长江三峡水电站坝址区断裂新活动年龄及地壳稳定性

长江三峡水电工程坝址区断裂新活动年龄分为两类:(1)>220×10⁴a BP.和(2)(131-54)×10⁴aBP.。坝区15公里范围内不存在近代活动断裂。地震基本烈度为Ⅵ度。地壳稳定性等级属稳定区。     

某地人工湖蓄水能力的论证研究

建造人工湖是城市生态建设的一个重要的组成部分,本文结合当地的水文地质条件和地形地貌对拟建人工湖的渗漏问题进行分析,确定了库底渗漏和绕坝渗是该人工湖渗漏的主要来源,并计算了相应的渗漏量,从而论证了该人工湖的蓄水能力完全能够维持其生态景观效应。     

Impact of rehabilitation of Assiut barrage, Nile River, on groundwater rise in urban areas

To make optimum use of the most vital natural resource of Egypt, the River Nile water, a number of regulating structures (in the form of dams and barrages) for control and diversion of the river flow have been constructed in this river since the start of the 20th century. One of these barrages is the Assiut barrage which will require considerable repairs in the near future. The design of the rehabilitation of the barrage includes a headpond with water levels maintained at a level approximately 0.60 m higher than the highest water level in the headpond of the present barrage. This development will cause an increase of the seepage flow from the river towards the adjacent agricultural lands, Assiut Town and villages. The increased head pond level might cause a rise of the groundwater levels and impedance of drainage outflows. The drainage conditions may therefore be adversely affected in the so-called impacted areas which comprise floodplains on both sides of the Nile for about 70 km upstream of the future barrage. A rise in the groundwater table, particularly when high river levels impede drainage, may result in waterlogging and secondary salinization of the soil profile in agricultural areas and increase of groundwater into cellars beneath buildings in the urban areas. In addition, a rise in the groundwater table could have negative impact on existing sanitation facilities, in particular in the areas which are served with septic tanks. The impacts of increasing the headpond level were assessed using a three-dimensional groundwater model. The mechanisms of interactions between the Nile River and the underlying Quaternary aquifer system as they affect the recharge/discharge processes are comprehensively outlined. The model has been calibrated for steady state and transient conditions against historical data from observation wells. The mitigation measures for the groundwater rise in the urban areas have been tested using the calibrated mode.     

混凝土面板堆石坝数值仿真分析

分析了面板堆石坝仿真计算中两种材料的本构模型的优缺点,根据混凝土面板堆石坝结构形式和坝体填筑材料物理性质复杂的特点,开发了FORTRAN语言编写的面板坝计算程序。该程序在面板分缝处理中采用分离缝模型的方法,符合实际面板之间的变形特性,并将该程序引进ANSYS商业软件中,充分利用商业软件的界面功能,提出了一种新的面板坝计算机数值模拟分析方法。该方法可以对混凝土面板堆石坝的整个施工过程和运行期进行二维和三维数值模拟计算和图形显示,结果形象、直观清楚。     

Simulation for the Spatial–Time Characteristics of High Arch Dam

As a kind of slim shell structure flexibly based on its deformable foundation, high concrete arch dam exhibits remarkable spatial–time characteristics. In this paper, the Xiaowan Hydropower Project accommodating 294.5 m high double curvature arch dam is taken as example, to which the factor of time is introduced in the whole numerical simulation procedure. The dynamic inputting of the parameters related to the structural geometry and material properties (e.g. thermal, permeability, deformation/stress) following the construction progress is realized in an intension to establish a four-dimensional (spatial–time) numerical simulation procedure. The Digitized System of Xiaowan Arch Dam (DSXAD) is further formulated by the combination of the instrumentation system, the spatial–time simulation procedure, and the engineering judgments. The DSXAD has been working well in tracing the real working status of the dam during its construction period as well as service period. A series of difficult technical issues in the construction of the Xiaowan Dam are successfully solved with the help of the DSXAD. Through this practices important theoretical insights are achieved, which founds a new landmark for the high arch dam construction in China.     

Environmental learning and the social construction of an exurban landscape in Fremont County, Colorado

Across the rural American West, the restructuring of rural capitalism has transformed production landscapes into those increasingly structured by the development and consumption of natural and cultural amenities. This project used principles from symbolic interactionism, ethnographic methods, and the analytical framework of regional political ecology to understand the role of environmental learning in negotiating the new management regime associated with amenity-based capitalism in rural Fremont County, Colorado. The study found that most amenity residents participate regularly in social learning about the environment through a variety of interpersonal and organizational behaviors. In addition, they are responding collectively to environmental risks and opportunities associated with wildfire, noxious weeds and invasive grass species, prospective uranium mining, and restoration of cultural-landscape features. Ultimately, the practices of environmental learning concern how private properties and assets will be managed relative to the social construction of the environment as an amenity for personal consumption. Conservation and management prospects in this and other rural areas in the postindustrial world can be enhanced by understanding the microsociology of exurban geographies and by engaging the social forms and processes related to this distinctive landscape construction.     

Combined numerical investigation of the Gangda paleolandslide runout and associated dam breach flood propagation in the upper Jinsha River,SE Tibetan Plateau

A large paleolandslide occurred opposite the Gangda village in the upper Jinsha River, SE Tibetan Plateau. Field geological investigations and remote sensing indicated that the Gangda paleolandslide once blocked the Jinsha River. Evidence of river blocking, including landslide dam relics, upstream lacustrine sediments, and downstream outburst sediments, has been well preserved. To understand the river-blocking event including landslide, dam breach, and associated outburst flooding, optically stimulated luminescence (OSL) dating and numerical simulations were performed in this study. OSL dating results showed that the paleolandslide dam was formed at 5.4?±?0.5 ka BP and breached at 3.4?±?0.3 ka BP, indicating that the dam lasted approximately 2000 years. The discrete element method was used to simulate the dynamics of the Gangda rock landslide based on the restored topography, while a fluid–solid coupling model was performed to simulate the landslide dam breaching and flooding. The fluid–solid coupling model can simultaneously reflect the process of landslide-dam collapse and the propagation of outburst flood. The simulated results indicate that the whole landslide process lasted about 60 s with a peak velocity of 38 m/s. It is significant that the simulated morphology of the residual landslide dam and downstream outburst sediments is consistent with the field observations. The combined numerical investigation in this paper provided new insights into the research of landscape evolution and helped to understand the chain disaster of landslide, dam breach, and flooding.

     

Recent paleolimnology of three lakes in Northwestern Minnesota

A paleolimnological study was undertaken to investigate changes in three Minnesota lakes over the last 100 years and to demonstrate the stratigraphic effects of cultural eutrophication in two of them. The study combined the analysis of the lake sediment from short cores with stratigraphic analyses of pollen, plant macrofossils, mollusks, diatoms and certain other algae, chydorid Cladocera, and Daphnia ephippia.The rise of Ambrosia type pollen (ragweed) marks the onset of interference with the landscape by European man, which can be closely dated. Calculations of sedimentation rates from this base gave reasonable correlations of other stratigraphic events with historical events.Elk Lake is considered “unpolluted” today and was chosen as a control. Man's effects are limited to logging some of the surrounding forest and to the construction of a dam. Small changes in the lake's fauna and flora are demonstrated, showing the sensitivity of the lake to changes in its catchment area.Lake Sallie and St. Clair Lake, in the same watershed as the city of Detroit Lakes, have been affected not only by logging but also by addition of nutrients from agricultural runoff and sewage effluent. Considerable responses by the lake organisms are apparent. In Lake Sallie the changes were gradual, but in St. Clair Lake they were very abrupt because the lake was partially drained at the same time and the water volume was thereby reduced.The merits of such an integrated study, the types of information gained from the analyses of the various fossils, and the wider application of the results are discussed.     

Lithospheric studies based on array analysis of P-coda and microseisms

A simple coherence measure—the semblance coefficient—has been used to sample the lithosphere beneath the NORSAR array in terms of its ability to produce coherent seismic energy. The data set is comprised of two samples of teleseismic P-coda waves (south of Honshu and Hindu-Kush events) and two samples of microseismic noise data with duration of about one hour each.Concerning the constitution of the earth structure there are two possibilities for coherent energy to be present in noise-like wavefields. The first is tied to scattering effects and the second may be brought about by seismic emission effects. The emissive component represents the seismic response of the medium to variations in the background stress field which may arise from various sources: passing seismic waves (body or surface), free oscillations of the Earth, tides, an abnormal level of heat flow, or geodynamic processes in general.The presence of a well known source of seismic signal—Hunderfossen dam—in the vicinity of NORSAR area provided an opportunity to test the data processing algorithm. Results obtained for two independent microseismic data samples point to the same location in close vicinity to the dam.For P-coda data the signal energy from the upper mantle areas, as indicated by the maximum of semblance measure values at the depth around 116 km, reaches about 3.8% and 5% of the total P-coda energy for Honshu and Hindu-Kush events, respectively. For microseismic noise data this value is about 1% at a depth around 100 km. Comparison with the results of holographic studies supports the assumption that, in the case of microseismic data, the detected signal energy is of emissive nature, while for P-coda data we need more coda samples to make a sound judgement about the nature (scattering or emission) of the detected signals.     

Making an impermeable clay core from a flysch mudrock

A flysch mudrock was used for the construction of the core of the Evinos embankment dam. The thinly bedded, slightly weathered and intensely folded mudrock was thoroughly investigated in order to prove its suitability to form an impermeable core. Proper winning and placing methods could produce an adequately impermeable homogeneous and plastic core material. The resulting material had a fines content (d < 0.076 mm) around 50%, low plasticity, high strength and small permeability. After a trial fill, placement procedures were finalised and the core was successfully built with small variations in its properties. A substantial increase in the depth of the borrow pit did not influence the core quality. The instrumentation results during construction and for the subsequent three years, showed that design assumptions were greatly validated and a clay material of low permeability was produced.     

Effect of Construction Material on Dam Type Selection of the Büyük Karaçay Dam (Hatay, Turkey)

This paper covers the investigation of construction materials and selection of the dam type for the Büyük Karaçay Dam, which was planned to be constructed on Büyük Karaçay River 20 km to the SW of Hatay (Southern Turkey). The purposes of the dam are irrigation, domestic water supply, and producing energy. Auxiliary structures locations have been determined during the study of detailed geological maps of the dam axis and reservoir area. Quality, quantity and hauling distance of natural construction materials were effective to select different dam types. For engineering geological studies exploration boreholes were drilled at the dam site; pressuremeter tests were performed in order to determine bearing capacity and elasticity properties of rocks; pressured water tests were also performed to determine permeability of the dam site. Moreover, physical and mechanical properties of rocks were determined by the laboratory test. In the feasibility stage, the dam type was chosen as the central core rock-fill dam, depending on state of natural construction materials. In design stage dam type was changed as faced symmetrical hardfill dam. Finally, the dam type was revised again during the design stage as concrete face rockfill dam.     

Landscape diagnosis as a geographical contribution to landscape management

Geographical analysis, diagnosis and prognosis of landscape centre on regional questions. Within this framework landscape diagnosis helps to evaluate capabilities of or hazards to landscape elements or landscape units, starting from an analysis of the equipment of the landscape and of land use patterns, taking into account tendencies of their development. Landscape diagnosis is connected with landscape prognosis, which characterizes conditions and processes of changes in the landscape and contributes to decision making with regard to landscape development. Examples from the densely populated areas round Halle and Karl-Marx-Stadt and the fruit-growing Havel region around Potsdam will serve to show that small-scaled and medium-scaled landscape diagnoses can be developed as secondary diagnoses mainly on the basis of thematic maps, which can then be used in the offices for regional planning in the GDR. Large-scaled landscape diagnoses, however, will be shown as directly derived from field data and as immediately applicable (as a working basis) to landscape management. The synthetic aspect, which takes into consideration the present state and the development of landscape as a whole, will apply to all scales.     

The Effect of Impervious Clay Core Shape on the Stability of Embankment Dams

One of the most important dangers that treat earth dams which can lead to interior failure over a prolonged period is the hydraulic fracturing factor. In the case of zoned dams, due to differences in stiffness of the core and its abutment zone, differential settlements occur between them. This factor is responsible for the arching phenomenon. Differential settlements between core and shell cause cracks within the core initially sub-surface, Those cracks may develop the first impounding causing internal erosion on the dam core. In this research, using a computer modeling of Ghavoshan rockfill dam (located the west part of Iran) as a case study computed by SIGMA/W program, the role of the dam core shape on those factors is demonstrated. It is found that an inclined core shape is preferred in a condition that is especially important settlements of construction during for dam body. The result of finite element analysis indicates desired conditions from the point of view of stress, deformation and resistance against hydraulic fracturing for the same width of dam designs. Moreover, this can be higher priority for embankment dam designs.     

典型岩溶湖泊湿地流域景观格局动态变化及趋势预测

岩溶湖泊湿地流域作为景观格局变化的热点研究区域,探讨景观格局动态变化及预测趋势,为岩溶流域生态安全研究提供科学依据。应用遥感与地理信息系统技术,结合普者黑岩溶湖泊湿地流域实际情况,分别对该地区1990、1995、2000、2005、2010、2015 年6 期遥感影像进行分类、解译,系统地获取地区景观格局状况,分析动态变化特征,并运用CA-Markov 模型对未来湿地景观格局进行模拟预测。结果表明：1990−2015年普者黑岩溶湿地流域景观格局随时间变化显著,景观破碎化程度总体呈现增加趋势,斑块数（NP）从861增加到889,景观类型的优势斑块面积在逐渐增加,而多样性指数从1.064下降到0.966;2020−2030年普者黑岩溶湿地流域建筑用地、农地和湿地景观类型面积在增加,农地和林地在减少,其中,较为突出的是建筑用地占有率由2.79%上升到2.97%,农地占有率60.12%增加到60.74%,湿地占有率6.67%上升7.02%,而林地占有率由26.70%下降到26.40%。景观格局进行预测可以发现湿地面积、建筑用地面积和农地变化幅度最大,本文相关研究和预测结果可为普者黑流域生态保护提供一定的建议和参考。     

土坡体系可靠度分析方法及在高土石坝工程中的应用

针对土坡稳定体系可靠度分析问题,提出了一种分析方法框架,包括采用缩减方差抽样技术生成随机变量样本值、采用全局优化算法搜索边坡最小安全系数、采用Monte-Carlo法计算边坡体系可靠度3个主要部分。在此框架下,建立了一种较为简便实用的高土石坝坝坡稳定体系可靠度分析方法。该方法采用拉丁超立方抽样技术生成随机变量的样本值,再用商业软件STAB搜索相应的坝坡最小安全系数,最后用可靠指标法或Monte-Carlo法计算坝坡体系可靠度。工程算例表明,筑坝材料强度参数的随机不确定性对坝坡临界滑弧的位置影响较大,坝坡稳定体系可靠度小于单一滑动面的坝坡稳定最小可靠度,提出的方法可用于实际工程坝坡稳定体系可靠度分析。     

Laboratory tests and numerical simulations on the impact of subsurface barriers to saltwater intrusion

The dams are built to supply water needs of people, to produce electricity and to supply irrigation water in agricultural activities since ancient times. They are very important because of their contribution to energy production. The construction of dams is very difficult and costly. It is vital that they are resistant to all kinds of effects, since they are built to prevent flooding in the region. The most important and dangerous of these effects are earthquake forces. It is very important that the dams are designed to be durable. In this study, the Darideresi-II Dam reservoir located in Isparta was examined in terms of the behavior under various earthquake loads. To reflect the behavior of the dam in a more realistic way, the finite element method is used. While developing this model, the material specifications and boundary conditions are taken into account. The dam reservoir was modeled using ANSYS program, and its behavior under different earthquake accelerations was investigated. The deformation and stress forces under earthquake accelerations are taken into account. By examining these results, it is interpreted how the Darideresi-II Dam reservoir will behave during earthquake.     

高堆石坝中期度汛挡水风险率估计

在考虑高堆石坝坝体中期临时挡水度汛不允许坝面过水条件下,综合考虑坝前洪水位与防洪度汛高程的随机性,构建高堆石坝工程中期度汛挡水风险数学模型.针对堆石坝施工系统的特点,考虑各月停工天数与日平均上升速度的随机性,建立了防洪度汛高程仿真计算模型.基于Monte-Carlo方法原理,耦合水文、水力和施工随机因素对风险模型进行求解,并研究了日均控制最低上升速度这一施工可控指标对风险率的影响.通过大渡河流域某大型工程实例分析表明,风险模型与计算方法可行、有效.