1、Central South UniversitySchool of Civil Engineering2011-7-1滑坡灾害评估滑坡灾害评估Landslide hazard evaluation主要内容主要内容1 地质灾害简介地质灾害简介3 滑坡概述滑坡概述4 滑坡易发性区划滑坡易发性区划5 工作小结及计划工作小结及计划2 我国我国2010年地质灾害灾情概况年地质灾害灾情概况1 地质灾害简介地质灾害简介 自然的变异和人为的作用都可能导致地质环境或地质体发生变化，当这种变化达到一定程度、其产生的后果便给人类和社会造成危害，称为地质灾害。地质灾害可划分为30多种类型，常见的地质灾害包括：地震、火
2、山喷发、地裂缝、地面沉降、地面塌陷、沙漠化、水土流失、土地盐渍化、沼泽化、滑坡、崩塌、泥石流、煤与瓦斯突出、矿坑突水、岩（煤）爆、顶板冒落、地下热害、煤田燃烧、地下水污染、诱发地（矿）震、边岸再造、泥沙淤积、库区侵没、洪涝、海岸侵蚀、黄土湿陷、膨胀土胀缩、冻土冻融等等。由降雨、融雪、地震等因素诱发的称为自然地质灾害，由工程开挖、堆载、爆破、弃土等引发的称为人为地质灾害。根据2004年国务院颁发的地质灾害防治条例规定，常见的地质灾害主要指危害人民生命和财产安全的崩塌、滑坡、泥石流、地面塌陷、地裂缝、地面沉降等六种与地质作用有关的灾害。(1)什么是地质灾害？什么是地质灾害？在一定的自然条件与地质条
3、件下，斜坡上的土体或岩体，受河流冲刷、地下水活动、地震及人工切坡等因素的影响，在重力作用下，沿斜坡内部一定的软弱面或软弱带，整体地或分散地顺坡向下滑动的自然现象与过程。1 地质灾害简介地质灾害简介(2)什么是滑坡？什么是滑坡？崩塌是较陡斜坡上的岩土体在重力作用下突然脱离母体崩落、滚动、堆积在坡脚（或沟谷）的地质现象。1 地质灾害简介地质灾害简介(3)什么是崩塌？什么是崩塌？泥石流是指在山区或者其他沟谷深壑，地形险峻的地区，因为暴雨暴雪或其他自然灾害引发的山体滑坡并携带有大量泥沙以及石块的特殊洪流。(4)什么是泥石流？什么是泥石流？1 地质灾害简介地质灾害简介 地面塌陷是指地表岩、土体在自然或人
4、为因素作用下向下塌落，并在地表形成塌陷坑（洞）的一种动力地质现象。地面塌陷包括采空塌陷、岩溶塌陷。(5)什么是地面塌陷？什么是地面塌陷？1 地质灾害简介地质灾害简介 地裂缝是地表岩、土体在自然或人为因素作用下，产生开裂，并在地面形成一定长度和宽度的裂缝的一种地质现象，当这种现象发生在有人类活动的地区时，便可成为一种地质灾害。地裂缝的形成原因复杂多样。地壳活动、水的作用和部分人类活动是导致地面开裂的主要原因。地裂缝分为：构造地裂缝(地震地裂缝、构造蠕变地裂缝）和非构造地裂缝(岩土体变形地裂缝、采矿地裂缝)。(5)什么是地裂缝？什么是地裂缝？1 地质灾害简介地质灾害简介 地面沉降是在人类工程经济活
5、动影响下，由于地下松散地层固结压缩，导致地壳表面标高降低的一种局部的下降运动（或工程地质现象）。地面沉降分构造沉降、抽水沉降和采空沉降三种类型。(5)什么是地面沉降？什么是地面沉降？1 地质灾害简介地质灾害简介地面沉降地面沉降地面下沉最大沉降量达1.04米 广东省江门市江海区礼乐镇自2000年全镇不同程度发生地面沉降。在枯水期大量抽取地下水，使松散土层被压缩，是发生地面沉降的主要原因。因地面下沉而垫高的楼梯return2 灾情概况灾情概况 2010年全国共发生地质灾害30670起，其中滑坡22329起、崩塌5575起、泥石流988起、地面塌陷499起、地裂缝238起、地面沉降41起；造成人员伤
6、亡的地质灾害382起，2246人死亡、669人失踪、534人受伤；直接经济损失63.9亿元。与去年同期相比，发生数量、造成的死亡失踪人数和直接经济损失均有较大幅度增加。References：全国地质灾害通报2010中华人民共和国国土资源部(The Ministry of Land and Resources P.R.C)http:/ 灾害类型构成灾害类型构成2010年与年与2009年全国地质灾害基本情况对比表年全国地质灾害基本情况对比表2.2 灾害损失灾害损失 2010年地质灾害发生在我国28个省(区、市)境内。以华东、中南、西南以及西北的部分地区最为集中。发生数量居于前三位的依次是江西、湖南
7、和福建；因灾死亡失踪人数居于前三位的依次是甘肃、陕西和云南；因灾直接经济损失居于前三位的依次是陕西、四川和吉林。2.3 区域分布区域分布重大灾害事件多重大灾害事件多西北、西南地区人员伤亡突出西北、西南地区人员伤亡突出强降雨引发的地质灾害多，灾情严重强降雨引发的地质灾害多，灾情严重2.4 灾害特点灾害特点return 在一定的自然条件与地质条件下，斜坡上的土体或岩体，受河流冲刷、地下水活动、地震及人工切坡等因素的影响，在重力作用下，沿斜坡内部一定的软弱面或软弱带，整体地或分散地顺坡向下滑动的自然现象与过程。3 滑坡滑坡Landslide is a general term for a wide
8、variety of downslope movements of earth materials that result in the perceptible downward and outward movement of soil,rock,and vegetation under the influence of gravity.The materials may move by falling,toppling,sliding,spreading,or flowing.Some landslides are rapid,occurring in seconds,whereas oth
9、ers may take hours,weeks,or even longer to develop.2.1 滑坡类型滑坡类型The used classification factors:A1)Type of movementA2)Involved materialA3)ActivityA4)Movement velocityB1)The age of the movementB3)Morphological characteristicsB4)Geographical locationB5)Topographical criteriaB6)Type of climateB7)Causes
10、of the movements 对滑坡进行分类的目的在于对各种地质环境下所产生的各种滑坡现象进行概括，以便正确反映滑坡作用的某些规律。因此，滑坡分类可根据不同的目的，有多种多样的分类法。2.1 滑坡类型滑坡类型In the following table shows a schematic landslide classification adopting the classification of Varnes 1978 and taking into account the modifications made by Cruden and Varnes,in 1996.Some inte
11、gration have been made by using the definitions of Hutchinson(1988)and Hungr et al.2001.The causes of landslides are usually related to instabilities in slopes.It is usually possible to identify one or more landslide causes and one landslide trigger.The difference between these two concepts is subtl
12、e but important.Causes may be considered to be factors that made the slope vulnerable to failure,that predispose the slope to becoming unstable.The trigger is the single event that finally initiated the landslide.Thus,causes combine to make a slope vulnerable to failure,and the trigger finally initi
13、ates the movement.Usually,it is relatively easy to determine the trigger after the landslide has occurred(although it is generally very difficult to determine the exact nature of landslide triggers ahead of a movement event).2.2 滑坡产生的原因滑坡产生的原因a.Weak or sensitive materials 软弱岩体b.Weathered materials 风
14、化岩体c.Sheared,jointed,or fissured materials 剪切、节理、裂隙岩体d.Adversely oriented discontinuity(bedding,schistosity,fault,unconformity,contact,and so forth)逆向不连续(层面、片理、断层、不整合面、接触面等）e.Contrast in permeability and/or stiffness of materials 渗透率差异和刚度差异2.2.1 Geological causes2.2 滑坡产生的原因滑坡产生的原因a.Tectonic or volca
15、nic uplift 构造隆起或火山隆起b.Glacial rebound 冰川回弹c.Fluvial,wave,or glacial erosion of slope toe or lateral margins 河流、海浪、冰河对坡脚和坡体侧缘的侵蚀d.Subterranean erosion(solution,piping)地下侵蚀（溶液侵蚀，管涌）e.Deposition loading slope or its crest 边坡或坡顶加载f.Vegetation removal(by fire,drought)植被破坏g.Thawing 冰雪融化h.Freeze-and-thaw w
16、eathering 冻融风化i.Shrink-and-swell weathering 收缩膨胀风化2.2.2 Morphological causes2.2 滑坡产生的原因滑坡产生的原因滑坡产生的原因滑坡产生的原因a.Intense rainfall or prolonged precipitation 强降雨或长期降雨b.Rapid snow melt 冰雪骤融c.Rapid drawdown 水位骤降d.Earthquake 地震e.Volcanic eruption 火山喷发f.Thawing 融化g.Freeze-thaw 冻融h.Ground water changes 地下水变化
17、i.Soil pore water pressure 孔隙水压力j.Surface runoff 地表径流k.Seismic activity 地震活动2.2.3 Physical causes滑坡产生的原因滑坡产生的原因a.Excavation of slope or its toe 开挖坡体或坡脚b.Loading of slope or its crest 坡体或坡顶堆载c.Drawdown(of reservoirs or aquifers)水库或蓄水层水位降低d.Deforestation 采伐森林e.Irrigation 灌溉f.Mining 采矿g.Artificial vibr
18、ation 人工震动h.Water leakage from utilities 公共设施漏水2.2.4 Human causesreturn滑坡灾害性评估滑坡灾害性评估单体滑坡危险性评估单体滑坡危险性评估区域滑坡易发性评估区域滑坡易发性评估评估对象评估对象评估方面评估方面空间预测空间预测时间预测时间预测4.1 滑坡灾害性评估滑坡灾害性评估规模预测规模预测 滑坡灾害性评估可以为土地可持续利用规划和重点工程项目的建滑坡灾害性评估可以为土地可持续利用规划和重点工程项目的建设及维护提供有用的信息和辅助决策指南，减少灾难损失。设及维护提供有用的信息和辅助决策指南，减少灾难损失。滑坡易发性区划滑坡易发性
19、区划(Landslide susceptibility mapping)滑坡易发性区划滑坡易发性区划(Landslide susceptibility mapping)4.2 滑坡易发性区划滑坡易发性区划关键点及步骤：关键点及步骤：(1)提出假设提出假设(Basic assumptions)；(2)建立评价指标体系建立评价指标体系(Instability factors)；(3)选择区划单元选择区划单元(The mapping unit)；(4)选择模型方法选择模型方法(Modelling);(5)检验检验(Verification)。(1)Slope failures leave disce
20、rnible morphological features;most of them can be recognized,classified and mapped both in the field or through remote sensing,chiefly aerial photographs.Despite the conflicting views among geomorphologists and engineers,all the proposed methods are based upon a few,widely accepted principles or ass
21、umptions(Varnes et al.,1984;Carrara et al.,1991;Hutchinson and Chandler,1991;Hutchinson,1995;Turner and Schuster,1995),namely,the following:4.3 基本假设基本假设(2)Landsliding is controlled by mechanical laws that can be determined empirically,statistically or in deterministic fashion.Conditions that cause l
22、andslides(instability factors)directly or indirectly linked to slope failure,can be collected and used to build predictive models of landslide occurrence.(3)The past and present are keys to the future,which follows from uniformitarianism,implies that slope failures in the future will be more likely
23、to occur under the conditions which led to past and present instability.Hence,the understanding of past failures is essential in the assessment of landslide hazard.4.3 基本假设基本假设Ideally,evaluation of landslide hazard and its mapping should derive from all of these assumptions.Failure to comply to them
24、 will limit the applicability of any hazard assessment,regardless of the methodology used or the goal of the investigation.Unfortunately,satisfactory application of all of these principles proves difficult,both operationally and onceptually.(4)Landslide occurrence,in space or time,can be inferred fr
25、om heuristic investigations,computed through the analysis of environmental information,or inferred from physical models.Therefore,a territory can be zoned into hazard classes ranked according to different probabilities.4.4 评价指标体系评价指标体系 根据前述滑坡产生的原因，常用的评价指标主要有地貌指标、地志指标、根据前述滑坡产生的原因，常用的评价指标主要有地貌指标、地志指标、
26、物理指标、人类活动指标等。物理指标、人类活动指标等。滑坡易发性评价指滑坡易发性评价指标体系标体系地质指标地质指标：人类活动指标：人类活动指标：地貌指标：地貌指标：主要包括坡度、高程、坡向、地面起伏主要包括坡度、高程、坡向、地面起伏度度(地面曲率地面曲率)等。等。主要包括岩性、水系、地质构造线主要包括岩性、水系、地质构造线(如断如断层层)等的影响。等的影响。主要包括人类工程项目的影响。主要包括人类工程项目的影响。物理指标：物理指标：主要包括降雨量、地震活动影响等。主要包括降雨量、地震活动影响等。4.4 评价指标体系评价指标体系数据来源：需要的数据主要包括历史滑坡数据、地貌指标、地质指标、物数据来
27、源：需要的数据主要包括历史滑坡数据、地貌指标、地质指标、物理指标、人类活动指标等，主要从相关部门购买，小比例尺的数据可以从理指标、人类活动指标等，主要从相关部门购买，小比例尺的数据可以从网上下载。网上下载。数据格式：数据格式：ArcGIS软件兼容的各类数据格式，经常使用的是软件兼容的各类数据格式，经常使用的是GDB数据库格数据库格式、式、shp格式、栅格格式格式、栅格格式(grid、img等，主要是等，主要是DEM数据数据)。纸质文件可以。纸质文件可以通过扫描成栅格图片，通过通过扫描成栅格图片，通过ArcGIS软件矢量化工具进行编辑，得到我们需软件矢量化工具进行编辑，得到我们需要的数据格式。要
28、的数据格式。实现工具：实现工具：ArcMap软件。软件。4.5 区划单元区划单元Evaluation of landslide hazard requires the preliminary selection of a suitable mapping unit.The term refers to a portion of the land surface which contains a set of ground conditions which differ from the adjacent units across efinable boundaries.At the scale
29、 of the analysis,a mapping unit represents domain that maximises internal homogeneity and between-units heterogeneity.Arious methods have been proposed to partition the landscape for landslide hazard assessment and mapping.All methods fall into one of the following five roups:grid-cells;terrain unit
30、s;unique-condition units;slope-units;topographic units.4.6 建模方法建模方法建模方法建模方法定性方法定性方法(qualitative methods)确定性方法确定性方法(determinate methods)定量方法定量方法(qualitative methods)(1)定性方法定性方法(qualitative methods)Qualitative methods are subjective and portray the hazard zoning in descriptive terms.专家打分法专家打分法(层次分析法、模
31、糊数法等层次分析法、模糊数法等)4.6 建模方法建模方法(2)定量方法定量方法(qualitative methods)Quantitative methods produce numerical estimates of the occurrence of landslide phenomena in any hazard zone.判别分析法、逻辑回归模型、人工神经网络模型等判别分析法、逻辑回归模型、人工神经网络模型等 (3)确定性方法确定性方法(determinate methods)Process-based(geotechnical)models rely upon the unde
32、rstanding of few physical laws controlling slope instability.无限边坡模型等无限边坡模型等4.7 计算结果聚类计算结果聚类(1)ArcMap自带重分类工具自带重分类工具(2)聚类方法聚类方法Equal intern(3)建模方法包含聚类建模方法包含聚类4.8 模型检验模型检验(1)统计分布图法统计分布图法统计区划图统计区划图(3)AUC受试者工作曲线受试者工作曲线4.6.1 WLC方法举例方法举例WLC模型模型(Weighted Linear Combination Model)即权重线性组合模型即权重线性组合模型，属于半定性半定量方
33、法，属于半定性半定量方法关键点：关键点：(1)计算客观权重；计算客观权重；(2)计算主观权重；计算主观权重；(3)主客观权重线性叠加。主客观权重线性叠加。首先需要说明的是，首先需要说明的是，WLC模型中，客观权重的计算一般都是基于各指标模型中，客观权重的计算一般都是基于各指标子类的滑坡密度，主观权重的计算是专家打分法，然而权重的具体计算子类的滑坡密度，主观权重的计算是专家打分法，然而权重的具体计算方法可能不同，而且既可以对一级因子权重进行主观赋权，二级因子权方法可能不同，而且既可以对一级因子权重进行主观赋权，二级因子权重客观赋权，亦可反之。重客观赋权，亦可反之。评价指标体系评价指标体系步骤步骤
34、2：计算客观权重：计算客观权重计算方法：(1)首先计算各指标子类所对应的滑坡密度dij。(2)将滑坡密度dij 归一化，得pij。njijijijddp1(3)采用熵值法计算客观权重 。miiiiHmH11nppHniijijiln)ln(1步骤步骤3：计算主观权重：计算主观权重计算方法：(1)首先请决策组成员应用表中的模糊词汇对各个指标的相对重要性 进行评价，并计算决策组综合权重。(2)将滑坡密度dij 归一化，得pij。模糊词汇模糊数很低（0，0，0，3）低（0，3，3，5）中等（3，5，5，7）高（5，7，7，10）很高（7，10，10，10）全国地质灾害通报全国地质灾害通报Add Yo
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