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%。     

滑坡监测预警国内外研究现状及评述

本文从降雨临界值研究、监测技术方法、区域性监测预警系统三个方面对滑坡监测预警的国内外研究现状进行了回顾和总结。首先归纳了国内外28个国家或地区的滑坡降雨临界值及统计方法,三个模型——日降雨量模型、前期降雨量模型和前期土体含水状态模型,基本概括了当前降雨诱发滑坡临界值的确定方法;但由于降雨入渗触发滑坡的复杂性,不同机理的滑坡"需要"不同的降雨临界值;目前的研究趋势是对雨量雨强雨时—土体渗流场动态变化—土体抗剪强度变化的耦合关系进行研究。按监测对象的不同,滑坡监测可分为四大类,即位移监测、物理场监测、地下水监测和外部诱发因素监测;按监测手段的不同,则可分为人工监测、简易监测、专业监测三大类;目前国内外在滑坡监测技术、方法、手段上并无太大差距,专业仪器已成为常规设备,只是由于价格因素得不到普及;一些新技术如InSAR、三维激光扫描等能很快应用到滑坡监测领域;监测数据的采集和传输也都实现了自动化和远程化;监测和预警系统有向Web—GIS发展的趋势。利用一个地区的滑坡易发区划或危险区划,结合降雨临界值,可以设定不同的预警级别,在区内布设一定数量的雨量站,监测雨量加上预报雨量,就可进行滑坡预警预报,国内外的区域性降雨型滑坡监测预警大体都是这个思路和做法,该方法在对公众进行警示方面起到了良好效果,但由于预警的范围太大,在具体的单点防治上,难以做到有效。我国在近10年开展了大量的监测预警工作,并取得了丰硕的成果,但根据统计数据,其成功预警率却并不理想,这一方面表现在成功预警实例中专业预警所占比例过低,另一方面同时表现在发生的大量的地质灾害在已有的预警点之外。制约目前工作有效性的主要问题是滑坡隐患点的排查和识别问题,因为只有识别出了隐患点才能进行下一步的监测和预警,它是一切工作的基础。而解决这一问题的重要途径是分析区域上的滑坡发育规律,找到有效的隐患点识别技术方法,以及引进风险管理的概念,进行监测资源的合理分配和有效预警。     

Slope movements induced by rainfalls damaging an urban area: the Catanzaro case study (Calabria, southern Italy)

Calabria is one of the Italian regions mostly affected by mass movements. The case study of a densely populated neighborhood (Ianò) located in the central-western sector of Calabria is presented. The several landslides triggered in February 2010 caused heavy damages to the built area, infrastructures and productions of this neighborhood, and increased the risk for the inhabitants. The results obtained through field surveys, photo interpretation, analyses of rainfall data and of the urban fabric evolution, historical survey on the reports of the damages caused by landslides, have enabled to formulate hypotheses on the potential causes that triggered landslide events and produced severe consequences on the area. These results have revealed that almost all landslides of February 2010 are partial reactivations of pre-existing landslide deposits. Moreover, the analyses have indicated a critical role of cumulative rainfalls over an interval of 15 days. However, the severe damage framework is explained through an unplanned urbanization which took place across the years on an area characterized by a high level of instability per se. Some buildings have been erected in proximity of or within pre-existing landslide scarps; in other cases, buildings have been constructed even inside the landslide bodies.     

降雨诱发深层老滑坡复活变形的动态作用机制

强降雨易引发大型深层老滑坡的复活变形,研究其作用机制对建立滑坡变形破坏的降雨阈值,实现滑坡灾害的预警预报具有重要意义.以三峡库区秭归县谭家湾大型深层老滑坡为例,在地表宏观裂缝时空分布规律的精细描述基础上,结合15年的人工监测和2年的实时监测数据,分析了老滑坡的复活变形特征和发展过程.通过滑坡阶跃阶段的位移与降雨（当前降雨和前期降雨）的相关性分析,提出了降雨对深层滑坡复活变形演化过程的动态作用机制.谭家湾滑坡的7次“阶跃”变形与强降雨相关,但累积位移增量与累积降雨量无明显正相关关系,水平位移增量基本相同时,累积降雨量明显不同.引起第一次阶跃变形的累积降雨量和最大日降雨量均明显大于后续阶段,可能受控于强降雨的作用机制由“孔隙渗流”为主,逐渐转变为“渗透性增加的孔隙渗流+裂隙优势流”的综合渗流模式.这对进一步深入研究强降雨诱发深层老滑坡阶跃变形的内在机理与灾害预警具有一定的理论意义和参考价值.     

Landslide and debris flow initiated characteristics after typhoon Morakot in Taiwan

Typhoon Morakot brought extreme rainfall and initiated numerous landslides and debris flows in southern Taiwan in August of 2009. The purpose of this study is to identify the extreme rainfall-induced landslide frequency-area distribution in the Laonong River Basin in southern Taiwan and debris flow-initiated conditions under rainfall. Results of the analysis show that debris flows were initiated under high cumulative rainfall and long rainfall duration or high rainfall intensity. The relationship of mean rainfall intensity and duration threshold could reflect debris flow initiation characteristics under high rainfall intensity in short rainfall duration conditions. The relationship of cumulative rainfall and duration threshold could reflect debris flow initiation characteristics under high cumulative rainfall in long rainfall duration. Defining rainfall events by estimating rainfall parameters with different methodologies could reveal variations among intermittent rainfall events for the benefit of issuing debris flow warnings. The exponent of landslide frequency-area distribution induced by Typhoon Morakot is lower than that induced by the Chi-Chi earthquake. The lower exponent of landslide frequency-area distribution can be attributed to the transportation and deposition areas of debris flow that are included in the landslide area. Climate change induced high rainfall intensity and long duration of precipitation, for example, Typhoon Morakot brought increased frequency of debris flow and created difficulty in issuing warnings from rainfall monitoring.     

Analysis of Baishuihe landslide influenced by the effects of reservoir water and rainfall

Since the impoundment of the Three Gorges Reservoir in June 2003, a number of new landslides have occurred and existing landslides have been made worse. The 1,260 × 10⁴ m³ Baishuihe landslide, located at 56 km west of the Three Gorges Dam, began to deform more noticeably after the first impoundment in early July 2003. The sliding of the two blocks comprising the landslide, one an active block and the other a relatively stable block, became apparent after approximately 5 years of monitoring. Field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir. These effects have been investigated in the present paper, including the deformation characteristics (movement pattern, direction, displacement and velocity) earmarking the temporal evolution of the active block. Based on a practical creep model of a large rock slide, alert velocity thresholds for pre-alert, alert and emergency phases have been computed corresponding to the imminence of failure. The alert velocity thresholds are being proposed to be included as a part of an early-warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure. The emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the Three Gorges Reservoir in the near future.     

基于降雨响应的黄土丘陵区滑坡危险性预测研究——以宝鸡市麟游县为例

极端降雨易造成群发滑坡灾害,难以作为单体预测.为预测评估黄土丘陵区不同降雨强度诱发滑坡灾害危险性,论文在区域滑坡灾害特征研究的基础上,分析降雨强度特征及滑坡分布特征.以岭南滑坡为代表分析降雨诱发黄土-丘陵区滑坡的形成机制,介绍了无限斜坡模型原理、参数选取,利用GIS空间建模与分析功能,定量完成了无降雨、25 mm、50...     

Frequency–volume relation and prediction of rainfall-induced landslides

Rainfall-induced landslides constitute a major public concern in Hong Kong. This paper investigates two aspects of critical importance to landslide hazard and risk assessment and management: magnitude–cumulative frequency relationship for landslides, and relationship between rainfall and the occurrence of landslides. The results indicated that landslides with a failure volume of not less than 4 m³ have a cumulative frequency–size distribution with a power-law dependence on volume of failure. Analysis of rainfall/landslides showed that the 12-hour rolling rainfall is most important in predicting the number of landslides. Failure volume dependency in the relationships between rainfall and the number of landslides is also presented. However, with an increase in failure volume of landslides, the most important rainfall variable may vary from rainfall of short duration (12-h rolling rainfall) to that of relatively long duration (24-h rolling rainfall).     

Dendrogeomorphic reconstruction of past landslide reactivation with seasonal precision: the Bois Noir landslide, southeast French Alps

The purpose of this study was to reconstruct spatiotemporal patterns of past landslide reactivation in a forested area of the Barcelonnette Basin (Bois Noir landslide, Southern French Alps). Analysis of past events was based on tree ring series from 79 heavily affected Mountain pine (Pinus uncinata Mill. ex Mirb) trees growing near or next to the landslide body. Dendrogeomorphic analysis focused on the presence of compression wood and growth reductions, with the first reaction being used for a dating of past reactivations with seasonal precision. A total of 151 growth disturbances were identified in the samples representing eight different stages of reactivation of the landslide body between 1874 and 2008. The spatiotemporal accuracy of the reconstruction is confirmed by historical records from neighboring sites and by aerial photographs. The onset of compression wood formation allows identifying five stages of landslide reactivation during the dormant season or the very beginning of the growing season of trees, i.e., between early October and late May, and three stages toward the end of the growth period. Monthly rainfall data from the HISTALP database demonstrate that the rainfall during four out of the eight reactivations are characterized by summer rainfall totals (July?CAugust) exceeding 200?mm, pointing to the important role of summer rainstorms in the triggering of events at the Bois Noir landslide body.     

Rainfall-induced landslides in Hulu Kelang area, Malaysia

Hulu Kelang is known as one of the most landslide-prone areas in Malaysia. The area has been constantly hit by landslide hazards since 1990s. This paper provides an insight into the mechanism of rainfall-induced landslide in the Hulu Kelang area. Rainfall patterns prior to the occurrences of five selected case studies were first analyzed. The results showed that daily rainfall information is insufficient for predicting landslides in the area. Rainfalls of longer durations, i.e., 3–30 days prior to the landslides should be incorporated into the prediction model. Numerical simulations on a selected case study demonstrated that both matric suction and factor of safety decreased steadily over time until they reached the lowest values on the day of landslide occurrence. Redistribution of infiltrated rainwater in the soil mass could be a reason for the slow response of failure mechanism to rainfall. Based on 21 rainfall-induced landslides that had occurred in the area, three rainfall thresholds were developed as attempts to predict the occurrence of rainfall-induced landslide. The rainfall intensity–duration threshold developed based on the local rainfall conditions provided a reasonably good prediction to the landslide occurrence. The cumulative 3- versus 30-day antecedent precipitation index threshold chart was capable of giving the most reliable prediction with the limiting threshold line for major landslide yielded a reliability of 97.6 %.     

区域滑坡灾害预测预警与风险评价

区域滑坡灾害预测预警是滑坡灾害研究领域的难点和热点。过去10多年来在这方面的研究主要集中在区域降雨与地质环境的结合方面。文章总结了目前国内外滑坡灾害预测预报、预警和风险管理研究现状,认为把滑坡灾害预警预报与风险管理相结合是减灾防灾的需要,也是今后该领域研究的发展趋势。文章从区域滑坡灾害空间预测、时间预警预报的角度提出了滑坡灾害预测预报的分类和理论基础,并在此基础上,利用MapGIS软件平台进行二次开发,建立了基于WebGIS的滑坡灾害信息管理系统和实时预警发布系统。以2004年"云娜"台风期间浙江省永嘉县滑坡灾害预警预报为例,进行了滑坡危险性预测、人口易损性预测、经济易损性预测到风险预测的实例研究。     

郑家湾滑坡体蠕变对上跨桥梁的影响分析

当前滑坡蠕变对上跨桥梁影响研究甚少,实测数据更为匮乏。在对郑家湾滑坡体及上跨桥梁进行长期监测的基础上,根据深部位移监测数据推断出滑坡潜在滑面位置,分析了气象因素对滑坡及桥梁变形的影响,进而研究了滑坡蠕变与桥梁变形的相关性。研究表明:（1) 郑家湾滑坡深约3~19m,月位移0.64~5.16mm,累积位移20~62mm,处于间歇性蠕滑状态。（2) 降雨控制着郑家湾滑坡蠕变与桥梁变形,监测期间月最大降雨量390.2mm,此时滑坡与桥梁变形幅度最大,分别为2mm·月-1和7mm·月-1。（3) 桥梁变形与滑坡蠕变具有同步性,两者月位移相差0.24~2.13mm,累积位移相差6.3mm。本文数据和结论对郑家湾滑坡治理及今后类似上跨桥梁滑坡的分析具有很好的借鉴意义。     

地震与强降雨作用下堆积体滑坡变形破坏机理及防治方案分析

位于西南山地堆积体滑坡常受到地震和强降雨的双重作用,查明此类滑坡变形破坏机理是地质灾害防治和风险防控的基础。文章的研究对象是鲜水河断裂带附近的炉霍县马居滑坡。研究表明,地震作用对位于斜坡地带堆积体滑坡体结构损伤明显,不但使滑坡整体稳定性下降,还促使坡体内裂隙大量发育,利于降雨入渗,进一步恶化滑坡的水文地质条件。强降雨形成的大规模洪水和泥石流下切坡脚沟道,牵引滑坡体整体向下。长历时强降雨入渗影响坡体稳定性,且在降雨结束后较长时间持续影响坡体稳定性。因此,对此类滑坡防治的对策应考虑坡脚防护和抗滑支挡设置。在对防治方案的有效性分析后,表明防护方案在极端条件下仍然能保障安全性,达防治和风险管控的目的。     

Evolution Mechanism and Rainfall Warning Criteria for Maijianwo Slope in Henan Province,China

In this study, two different research methods are applied to investigate the evolution mechanism and rainfall warning criteria for Maijianwo slope located in Henan Province, China. On the one hand, an indoor-model test is performed under artificial rainfall and based on similarity theory. A set of monitoring system is utilized to track the moisture content, deformation and cracks of critical points of the model during the test. On the other hand, the numerical simulation is carried out to provide an insight into the variation of unstable zone and factor of safety for the landslide with the increasing cumulative rainfall. Results indicate that the evolution process of Maijianwo slope is composed of three stages of initiating, accelerating and failure respectively, and stability of slope decreases gradually as cumulative rainfall increases. Based on the evolution mechanism of retrogressive landslide verified by both model test and numerical simulation, cracking time of critical positions on the slope prior to each stage were set as the initiating time of each stage and the cumulative rainfall associated with each initiating time (E₁ = 75 mm, E₂ = 180 mm) has been defined as the warning criteria for the Maijianwo slope. As the cumulative rainfall in Maijianwo slope reaches 75 and 180 mm, the landslide orange and red warning codes are issued, respectively. Otherwise, the slope is in a safe condition when the cumulative rainfall is less than 75 mm.     

Regional prediction of landslide hazard using probability analysis of intense rainfall in the Hoa Binh province, Vietnam

The main objective of this study is to assess regional landslide hazards in the Hoa Binh province of Vietnam. A landslide inventory map was constructed from various sources with data mainly for a period of 21 years from 1990 to 2010. The historic inventory of these failures shows that rainfall is the main triggering factor in this region. The probability of the occurrence of episodes of rainfall and the rainfall threshold were deduced from records of rainfall for the aforementioned period. The rainfall threshold model was generated based on daily and cumulative values of antecedent rainfall of the landslide events. The result shows that 15-day antecedent rainfall gives the best fit for the existing landslides in the inventory. The rainfall threshold model was validated using the rainfall and landslide events that occurred in 2010 that were not considered in building the threshold model. The result was used for estimating temporal probability of a landslide to occur using a Poisson probability model. Prior to this work, five landslide susceptibility maps were constructed for the study area using support vector machines, logistic regression, evidential belief functions, Bayesian-regularized neural networks, and neuro-fuzzy models. These susceptibility maps provide information on the spatial prediction probability of landslide occurrence in the area. Finally, landslide hazard maps were generated by integrating the spatial and the temporal probability of landslide. A total of 15 specific landslide hazard maps were generated considering three time periods of 1, 3, and 5 years.     

The application of an innovative inverse model for understanding and predicting landslide movements (Salazie cirque landslides,Reunion Island)

The prediction of landslide movement acceleration is a complex problem, among others identified for deep-seated landslides, and represents a crucial step for risk assessment. Within the scope of this problem, the objective of this paper is to explore a modelling method that enables the study of landslide function and facilitates displacement predictions based on a limited data set. An inverse modelling approach is proposed for predicting the temporal evolution of landslide movement based on rainfall and displacement velocities. Initially, the hydrogeology of the studied landslides was conceptualised based on correlative analyses. Subsequently, we applied an inverse model with a Gaussian-exponential transfer function to reproduce the displacements. This method was tested on the Grand Ilet (GI) and Mare-à-Poule-d’Eau (HB) landslides on Reunion Island in the Indian Ocean. We show that the behaviour of landslides can be modelled by inverse models with a bimodal transfer function using a Gaussian-exponential impulse response. The cumulative displacements over 7 years of modelling (2 years of calibration period for GI, and 4 years for HB) were reproduced with an RMSE above 0.9. The characteristics of the bimodal transfer function are directly related to the hydrogeological functioning demonstrated by the correlative analyses: the rapid reaction of a landslide can be associated with the effect of a preferential flow path on groundwater level variations. Thus, this study shows that the inverse model using a Gaussian-exponential transfer function is a powerful tool for predicting deep-seated landslide movements and for studying how they function. Beyond modelling displacements, our approach effectively demonstrates its ability to contribute relevant data for conceptualising the sliding mechanisms and hydrogeology of landslides.     

滑坡风险评估的难点和进展

近年来,国内外滑坡研究日益重视滑坡风险评估和管理技术方法的研究,但滑坡风险评估依然是存在很多问题和难点,尤其是在中等—大比例尺区域滑坡风险定量评估方面,主要表现在滑坡编录数据库建设、滑坡影响因素的识别和建模、滑坡时间、空间预测的不确定性,滑坡诱发因素动态变化的定量刻画,承灾体识别和易损性定量评价等方面。在阐述滑坡风险评估流程的基础上,围绕滑坡风险评估与制图中滑坡编录和基础数据获取与更新,危险性分析中的滑坡空间、时间概率和滑坡特征预测、损失评估中的易损性分析与定量和承灾体定量化制图等技术方法中的难点和存在的问题,概述针对这些问题所取得的研究进展,并指出了滑坡风险研究的技术发展趋势。     

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。     

Spatio-temporal estimation of shallow landslide hazard triggered by rainfall using a three-dimensional model

A shallow landslide triggered by rainfall can be forecast in real-time by modeling the relationship between rainfall infiltration and decrease of slope stability. This paper describes a promising approach that combines an improved three-dimensional slope stability model with an approximate method based on the Green and Ampt model, to estimate the time–space distribution of shallow landslide hazards. Once a forecast of rainfall intensity and slope stability-related data, e.g., terrain and geology data, are acquired, this approach is shown to have the ability to estimate the variation of slope stability of a wide natural area during rainfall and to identify the location of potential failure surfaces. The effectiveness of the estimation procedures described has been tested by comparison with a one-dimensional method and by application to a landslide-prone area in Japan.