降雨型滑坡失稳概率计算方法

为了解决滑坡风险评价中的滑坡失稳概率计算问题,利用前人在降雨阈值的研究成果,结合气象学中降雨概率分布理论,以云南省盐津县庙坝滑坡为例进行计算,建立降雨型滑坡失稳概率计算模型。结果表明,盐津县降雨型滑坡的降雨阈值类型为累积降雨量-历时关系阈值,即为单日降雨阈值,降雨阈值为29.7 mm;盐津县在当日降雨量达到或超过阈值水平时可能诱发滑坡,对滑坡影响的滞后天数最大为5天;庙坝滑坡在8月20—25日6天内单日降雨达到或超过29.7 mm的降雨概率为46.49%;庙坝滑坡在8月25日因前5天或当天单日降雨量超过29.7 mm而失稳的概率为0.2853%。     

基于有效降雨强度的滑坡灾害危险性预警

选取湖北省恩施地区1 000 km2区域作为典型研究区, 在全面分析该区域历史滑坡资料的基础上, 根据该区滑坡生成与地层岩性之间的关系, 将研究区地层划分为高、中、低3类易发性岩组.分岩组统计降雨监测数据与历史滑坡信息, 得出有效降雨强度与关键降雨持续时间的散点图, 由此确定不同滑坡发生概率的有效降雨强度阈值, 提出该区的滑坡灾害危险性预警判别模型.基于样本区统计数据建立滑坡预测指标体系, 运用GIS得出研究区域的滑坡空间易发性区划结果, 并根据不同易发岩组-有效降雨强度模型, 叠加滑坡灾害易发性分区结果与降雨危险性预警等级分级结果, 对研究区的滑坡灾害危险性进行了预测预警.结果表明: 不同易发岩组-有效降雨强度模型所得预警结果与实际情况吻合, 预警模型具有考虑全面和预警精度高的特点, 在实际预警中切实可用.      

基于易发性分区的区域滑坡降雨预警阈值确定——以云南龙陵县为例

滑坡所处不同易发等级的区域,降雨预警阈值差别较大。为提高滑坡降雨预警的针对性和准确率,文章以野外地质调查和滑坡易发条件分析为基础,结合信息量模型和层次分析法开展滑坡易发性评价,再通过滑坡发生概率与前期累计降雨量的相关性分析,分区进行滑坡降雨预警阈值模型研究。结果表明：坡度、高程、距断层距离、工程地质岩组、水系是龙陵县滑坡的主要孕灾地质条件;龙陵县滑坡非易发区面积为14.33 km²,低易发区面积为1 053.87 km²,中易发区面积为1 471.65 km²,高易发区面积为254.73 km²;确定单日和前3日为降雨预警时间,分区分时细化了降雨预警阈值模型;对比降雨预警阈值模型应用于龙陵县滑坡监测预警中的前后,预警信息减少了70条,预警准确率提高了14.4%,并实现了镇安镇户帕村施家寨组滑坡的有效预警。文章为区域滑坡降雨预警阈值确定提供了一种较好的参考方法。     

降雨型浅层滑坡危险性预测模型

通过分析SHALSTAB和TRIGRS等浅层滑坡物理确定性模型存在的问题,提出了基于降雨入渗动态守恒的瞬态降雨入渗模型,该模型考虑了初期降雨过程、降雨历程以及饱和非饱和入渗过程,证明了SHALSTAB模型是该模型的特殊形式,并克服了TRIGRS模型参数繁多及一维入渗路径的问题.将无限边坡模型、瞬态降雨入渗模型和GIS进行耦合,研发了可用于大范围降雨型浅层滑坡危险性预测的集成系统,根据边坡的地质条件、地形参数和降雨特征即可对降雨条件下浅层滑坡的危险性进行评估.     

降雨型滑坡危险性区划方法

降雨诱发的滑坡等地质灾害分布广、危害大,开展地质灾害危险性区划是减轻地质灾害损失的有效途径之一。以湖南省为例,根据地质灾害调查成果,选取3 412处滑坡,分析了区域降雨型滑坡的发育特点和分布规律,建立了危险性区划指标体系,利用不确定性推理中的确定性系数法,对滑坡与工程地质岩组、坡度、坡向、植被和年均降水量5个评价因子进行了相关性分析,建立了Logistic多元回归模型;采用不规则网格单元划分方法,形成了湖南省滑坡灾害危险性区划图。     

基于有效降雨强度和逻辑回归的降雨型 滑坡预测模型

以湖南省张家界市桑植县为研究区,在全面分析近30年降雨及滑坡数据的基础上,对滑坡及滑坡数量与降雨因子的关系开展了统计分析研究。首先确定了区域最佳有效降雨衰减系数,同时分别按滑坡规模、坡度、厚度大小统计了降雨与历史滑坡信息,得出有效降雨强度（I）与持续时间（D）散点图,由此确定各不同概率下诱发滑坡的区域有效降雨强度阈值,并进行了滑坡灾害危险性等级划分。进而,利用部分样本数据进行逻辑回归分析,得到了该研究区的滑坡发生概率预测方程,并给出了降雨强度临界值定量表达式,最后选用实际降雨诱发滑坡事件与未诱发滑坡事件进行对比验证。结果表明,文章所建立的滑坡预测模型准确性较高,预测情况与实际情况比较吻合。     

三峡库区降雨型滑坡预警雨量阈值研究

三峡库区是滑坡灾害高发地区,降雨是诱发滑坡的主要因素之一。本文以三峡库区101例降雨型滑坡为研究对象,结合1980—2019年降雨监测数据,采用滑坡发生前10 d的日降雨量数据,拟合出三峡库区降雨强度-降雨历时（I-D）关系阈值曲线表达式,进一步拟合出不同规模、地层岩性、坡度、坡向、高程等因素下,不同发生概率的降雨型滑坡I-D阈值曲线表达式,并计算滑坡不同发生概率的临界降雨阈值。研究表明：滑坡易发地层区的降雨阈值相对小。三叠纪巴东组岩层发生滑坡的降雨阈值最小,其次为侏罗系;阳坡为滑坡的易发坡向,且阳坡滑坡的降雨阈值小于阴坡;滑坡规模和高程与降雨阈值呈正相关性;坡度小于25°时滑坡发生的概率最大,对应的降雨阈值最小。本文研究成果可为三峡库区降雨型滑坡预警预报提供支持。     

重庆地区降雨型滑坡相关性分析及预报模型

整理大量重庆地区降雨诱发滑坡资料,对降雨因子、累积降雨因子、前期降雨衰减系数与滑坡发生与否及滑坡发生数量之间进行系统的相关分析。结果表明:(1)当日降雨量对滑坡的诱发作用最显著,当日最大小时降雨与当日降雨量高度相关;(2)据滑坡发生前日期增加,降雨因子与滑坡相关及偏相关系数随之降低,在据滑坡发生前3d之后已变得很小;(3)大范围滑坡一般在暴雨当日或滞后一天产生,仅有短时强降雨很难诱发大范围滑坡,还需要一定前期降雨量为基础;(4)累积降雨因子与滑坡因子间都显著相关,且随着累积降雨日数的增加,其相关系数先上升后下降;(5)重庆地区适宜的前期降雨衰减系数在0.6左右。在此基础上拟合出了有效累积降雨量-滑坡发生概率预报模型,并使用当日最大小时降雨量-滑坡发生概率模型对其进行修正。最后使用降雨诱发滑坡实例检验该修正模型,结果可为重庆地区降雨型滑坡的预测预报提供科学依据。     

Validation of Spatial Prediction Models for Landslide Hazard Mapping

This contribution discusses the problemof providing measures of significance ofprediction results when the predictionswere generated from spatial databases forlandslide hazard mapping. The spatialdatabases usually contain map informationon lithologic units, land-cover units,topographic elevation and derived attributes(slope, aspect, etc.) and the distributionin space and in time of clearly identifiedmass movements. In prediction modelling wetransform the multi-layered databaseinto an aggregation of functional values toobtain an index of propensity of the landto failure. Assuming then that the informationin the database is sufficiently representativeof the typical conditions in which the massmovements originated in space and in time,the problem then, is to confirm the validity ofthe results of some models over otherones, or of particular experiments that seem touse more significant data. A core pointof measuring the significance of a prediction isthat it allows interpreting the results.Without a validation no interpretation is possible,no support of the method or of theinput information can be provided. In particularwith validation, the added value canbe assessed of a prediction either in a fixedtime interval, or in an open-ended time orwithin the confined space of a study area.Validation must be of guidance in datacollection and field practice for landslidehazard mapping.     

Use of GIS Technology in the Prediction and Monitoring of Landslide Hazard

Technologies such as Geographical Information Systems (GIS) have raised great expectations as potential means of coping with natural disasters, including landslides. However, several misconceptions on the potential of GIS are widespread. Prominent among these is the belief that a landslide hazard map obtained by systematic data manipulation within a GIS is assumed to be more objective than a comparable hand-made product derived from the same input data and founded on the same conceptual model. Geographical data can now be handled in a GIS environment by users who are not experts in either GIS or natural hazard process fields. The reality of the successful application of GIS within the landslide hazard domain seems to be somewhat less attractive than current optimistic expectations.In spite of recent achievements, the use of GIS in the domain of prevention and mitigation of natural catastrophes remains a pioneering activity. Diffusion of the technology is still hampered by factors such as the difficulty in acquiring appropriate raw data, the intrinsic complexity of predictive models, the lack of efficient graphical user interfaces, the high cost of digitisation, and the persistence of bottlenecks in hardware capabilities.In addition, researchers are investing more in tuning-up hazard models founded upon existing, often unreliable data than in attempting to initiate long-term projects for the acquisition of new data on the causes of catastrophic events. Governmental institutions are frequently involved in risk reduction projects whose design and implementation appear to be governed more by political issues than by technical ones. There is an unfortunate general tendency to search for data which can be collected at low cost rather than attempting to capture the information which most readily explains the causes of a disaster.If the technical, cultural, economic and political reasons for this unhealthy state cannot be adequately tackled, the International Decade for Natural Disaster Reduction will probably come to an end without achieving significant advances in the prediction and control of natural disasters.     

基于信息量与Logistic模型的矿区滑坡灾害易发性评价

针对矿区长期煤矿开采引起的滑坡灾害频发问题,快速高效地模拟和评价矿致滑坡灾害易发性是实现采矿地区科学防灾减灾的关键。基于此,本文应用信息量与Logistic回归模型结合多源高分辨率光学遥感数据等,选取相对高差、坡度、坡向、距断层距离、NDVI、距采空区距离6个滑坡影响因子来评价采煤矿区滑坡灾害易发性。结果表明:(1)信息量与Logistic回归模型耦合的综合预测准确率为96%,信息量模型滑坡预测准确率为95%,实验结果表明耦合模型的预测精度优于单一信息量评价模型,评价模型的合理性和预测精度皆符合检验要求;(2)研究结果也表明了采用信息量+Logistic回归模型耦合能较为客观准确、快速高效地评价地下采矿引起的滑坡灾害易发范围,评价结果可为类似地区高效快速划定滑坡灾害易发区间提供技术支撑。     

逻辑回归和信息量模型在山区滑坡易发性评价中适宜性的分析

以万山区为例,在区域滑坡孕灾条件的基础上,筛选工程地质岩组、斜坡结构、平均坡度、地貌、距构造距离及距河流距离共6个易发条件因子,选取逻辑回归模型和信息量模型对山区滑坡进行易发性评价。结果显示逻辑回归模型中中高易发区面积占比分别为1578%和1970%,82%的地质灾害点落在该区域内;信息量模型中中高易发区面积占比为1241%、2519%,包含了区域88%的滑坡灾害点。最后通过实际发生的灾害点在各易发区的分布情况进行检验,逻辑回归模型中灾害点落在高易发区的比例远小于信息量模型,且高易发等级中灾害点实际发生的比值较小,说明针对山区区域滑坡地质灾害易发性评价结果预测上,信息量模型的评价结果更为客观准确。     

Overview Landslide Hazard Assessment of China

In recent years, China has suffered serious geological disasters, most of slope movements due to complex geology, geomorphology, unusual weather conditions, and large-scale land explorations during high speed economic development. According to geological hazard investigations organized by the Ministry of Land and Resources of China, there are 400 towns and more than 10000 villages under the threatening of those landslide hazards. This paper presents the overview landslide hazard assessment in terms of GIS, which aims to evaluate the overview geohazard potentials, vulnerabilities of lives and land resources, and risks in conterminous China on the scale of 1 : 6 000 000. This is the first overview landslide hazard potential map of China.     

Regional Assessment of the Effects of Land-Use Change on Landslide Hazard By Means of Physically Based Modelling

Physically based models are capable of evaluating the effects of environmental changes through adaptations in their parameters. For landslide hazard zonation, this gives them an edge over traditional, statistically based techniques that require large datasets and often lack the objectivity to achieve the same purpose. Therefore, physical models can be valuable tools for hazard assessment and planning purposes.The usefulness of the model prognosis depends largely on the ability of the physical model to mimic the landscape system. This implies that the model should be calibrated and validated and that the imposed changes do not lead to a radical departure from the present situation.Under the recognition of these constraints, a physically based model has been applied to a 1.5 km² catchment in the Alcoy region (SE Spain) to evaluate the effects of land use change on landslide activity. The model couples a transient, distributed hydrological model with a probabilistic assessment of the slope stability. Thus, it is able to assess the spatial and temporal activity of slope instability. For the present situation, validation demonstrates that the probability of failure returns a conservative estimate of the spatial frequency of landsliding. The model has subsequently been applied to two hypothetical land use change scenarios that extrapolate present and likely trends. For these scenarios, the model results indicate a marginal decrease in the spatial frequency of landsliding (aerial extent of instability). However, the decrease in the temporal activity (is total duration of instability over a given period) is substantial under the altered land use conditions. The forecasted change in landslide activity not only affects the relative weight of slope processes in the region. It also has implications for the perceived hazard levels and the landslide hazard zonation of the area.     

基于变系数回归模型的三峡库区滑坡位移预测

降雨-库水联合作用影响着三峡库区滑坡,而降雨、库水分别对滑坡演化的贡献及作用规律迄今尚不明确.以库区树坪滑坡和八字门滑坡为例,通过分析降雨和库水位资料,采用变系数回归模型,对滑坡位移进行预测.实验结果表明:经过改进的变系数回归模型方法不仅比传统的线性回归模型、自回归积分滑动平均模型、支持向量机模型方法具有更高的预测精度,而且能定量地给出各影响因素对滑坡位移的贡献.      

A Simplified Numerical Approach for the Prediction of Rainfall-Induced Retrogressive Landslides

Retrogressive landslides are common geological phenomena in mountainous areas and on onshore and offshore slopes. The impact of retrogressive landslides is different from that of other landslide types due to the phenomenon of retrogression. The hazards caused by retrogressive landslides may be increased because retrogressive landslides usually affect housing, facilities, and infrastructure located far from the original slopes. Additionally, substantial geomorphic evidence shows that the abundant supply of loose sediment in the source area of a debris flow is usually provided by retrogressive landslides that are triggered by the undercutting of water. Moreover, according to historic case studies, some large landslides are the evolution result of retrogressive landslides. Hence the ability to understand and predict the evolution of retrogressive landslides is crucial for the purpose of hazard mitigation. This paper discusses the phenomenon of a retrogressive landslide by using a model experiment and suggests a reasonably simplified numerical approach for the prediction of rainfall-induced retrogressive landslides. The simplified numerical approach, which combines the finite element method for seepage analysis, the shear strength reduction finite element method, and the analysis criterion for the retrogression and accumulation effect, is presented and used to predict the characteristics of a retrogressive landslide. The results show that this numerical approach is capable of reasonably predicting the characteristics of retrogressive landslides under rainfall infiltration, particularly the magnitude of each landslide, the position of the slip surface, and the development processes of the retrogressive landslide. Therefore, this approach is expected to be a practical method for the mitigation of damage caused by rainfall-induced retrogressive landslides.     

基于GIS的兰州滑坡与泥石流灾害危险性分析

频繁发生的灾害愈来愈对人类社会造成巨大影响, 遥感、地理信息系统、全球定位系统和网络技术日益在减灾行动中发挥重要的作用. 兰州区域地质岩性、构造断裂、地震活动带、地表侵蚀强烈和地形起伏破碎等因素造成了兰州滑坡与泥石流灾害的发育, 夏季暴雨、人类工程活动等诱发下灾害频繁, 风险加剧. 针对兰州地区滑坡与泥石流等山地灾害对区域社会经济的影响, 通过建立区域滑坡与泥石流灾害的空间数据库, 在GIS技术辅助下实现了专家经验模型和Logistic模型对滑坡与泥石流灾害危险性的预测, 其中滑坡Logistic模型准确性达到85.3%, 专家经验模型准确性达到74.2%; 泥石流Logistic危险性预模型准确性达到80.5%, 专家经验模型准确性达到90.5%. 随着研究的深入, 综合遥感、地理信息系统、全球定位系统和网络技术的灾害研究与应用将在灾害防治中发挥重要的作用.