基于人工边坡稳定性的降雨型滑坡预警预报模型设计与应用

由削坡建房遗留的人工边坡存在大量滑坡隐患问题,在降雨引发土质边坡自身动力变化分析条件下,以稳定性评价建模为基础,提出降雨型滑坡动力学预警预报模型。文中以广东省梅州市花岗岩地区为例,使用GIS技术构建了1 727个预警分析单元,并进行关键地质环境因子赋值及与气象站点数据关联;按坡高、坡度等参数,分别构建16个边坡失稳动力学预警模块,并根据降雨量变化,计算边坡稳定性系数,最终按其阈值确定风险等级并予以预警。本研究对于推动人工边坡诱发的滑坡地质灾害预警预报与预防均具有重要意义。     

降雨型与地震型滑坡试验研究

为了研究和探索降雨和地震诱发滑坡灾害的成因机理,对降雨型滑坡和地震型滑坡进行了物理模拟试验,系统地研究了坡度、坡体结构、降雨量、振动强度等因素对斜坡破坏变形的影响规律,探讨了降雨和地震诱发斜坡失稳破坏的主要模式和过程.对于降雨型滑坡,通过实验确定不同坡度滑坡的临界降雨量,发现临界降雨量与滑坡坡度呈幂指数关系.对于地震型...     

降雨型滑坡时空预报新方法

地质条件和降雨是引起重庆地区山体滑坡的两个最主要条件. 文中在分析降雨型滑坡形成条件的基础上, 提出了将地质条件和降雨因素进行分级叠合的降雨型滑坡时空预报新方法. 首先, 利用多因素相互作用关系矩阵, 对某个地区或者某个边坡所在位置的地质条件进行半定量的评价和分级. 然后, 根据日最大降雨量和降雨过程的总降雨量, 对该地区降雨的严重程度进行分级. 最后将“地质条件影响因子”和“降雨影响因子”进行分级叠合, 得到了“滑坡易滑程度判别因子”, 并据此将滑坡按照其易滑度分为滑坡极易发生、滑坡易发生、滑坡不易发生和滑坡基本不发生4级. 通过对某个地区的一些危险边坡进行地质勘察, 结合比较准确的天气预报, 可以对该地区的降雨型滑坡进行较为准确的时空预测预报. 以鸡扒子滑坡为例, 验证了利用“双因素”分级叠合方法进行降雨型滑坡时空预报的可靠性和可行性.     

三峡库区卧沙溪次级滑体变形机理与阈值研究

在库水位升降及降雨作用下,三峡库区不少土质滑坡出现周期性阶跃变形,此类滑坡变形机理复杂,预警预报难。以典型涉水土质滑坡卧沙溪滑坡为例,通过10多年野外宏观巡查资料、13年的人工监测和4年的全自动监测数据,揭示卧沙溪滑坡次级滑体的变形机理,建立降雨及库水位相关阈值。结果表明：(1)次级滑体变形的主控因素由库水位下降和库水浸泡转变为持续性降雨。(2)持续性降雨导致坡体变形,监测点位移速率“峰值滞后”效应为1～2 d,位移速率衰减时间为5～9 d。(3)降雨及库水位阈值：30 d累积降雨量阈值150 mm,且变形前1 d降雨量40 mm;变形启动3 d内,累积降雨量超过50 mm会加速坡体变形,且变形时间延长。库水位下降至146 m前30 d累积降雨量115 mm,库水位下降速率阈值为0.8 m/d。研究成果可为类似滑坡的监测预警提供参考。     

白鹤坪边坡稳定性分析

边坡监测可为掌握边坡变形特征和规律提供依据,指导在边坡发生严重变形时的应急处理。白鹤坪边坡是三峡库区的典型边坡,依据边坡的变形特征定性地认为该边坡为潜在的推移式滑坡。1998年调查发现白鹤边坡存在一定的滑移,为了对其实施监测预报、预警,减轻因其滑动而引起的地质灾害,在该边坡上建立了由10个GPS观测点组成的边坡位移观测系统,以监测边坡的变形。本文以2014年5月至2016年4月近两年的白鹤坪边坡变形观测系统所获得的位移数据为基础,对边坡的位移变形进行了统计,并结合数值模拟分析了边坡的水平向相对位移。分析表明,在边坡由缓变陡处变形显著增加,边坡现处于基本稳定状态,其变形主要受降雨影响,每年汛期时（5-10月）边坡变形量偏高。其次为库水作用影响,江水对坡脚冲蚀,使边坡前缘局部产生了小规模崩滑现象。     

基于自然电位法的滑坡监测实验研究

降雨是诱发滑坡最主要的因素之一,认识雨水的渗流过程和地下水位的动态演化对滑坡的监测预警具有重要意义.基于动电机制,孔隙介质中的流体流动可产生自然电位,通过自然电位的观测可反演地下水动力过程,为滑坡稳定性分析及监测预警提供有效信息.本文基于室内小型滑坡控制实验平台,通过施加人工降雨模拟边坡雨水入渗过程,同步测量了在坡体内的自然电位、孔隙水压力和坡面变形数据.实验结果显示:(1)自然电位变化与孔隙水压力变化具有显著的相关性,自然电位的时移剖面可反映水在坡体内部的流动模式的演化;(2)表面变形发生在坡体下部饱和之后,即坡面变形滞后于自然电位与孔隙水压力变化.以上观测结果表明,自然电位在滑坡监测中具有潜在的应用价值.     

广东东源地震与震磁响应

采用地磁短周期日变之低点位移方法和加卸载响应比法,分析了广东东源县2012~2013年间三次MS4.0~4.8级地震的震磁响应,发现震前震中周边台站均存在有不同程度的低点位移异常和加卸载响应比异常情况。     

地震后降雨作用下堆积体滑坡模型试验研究

为研究震后降雨作用下堆积体滑坡的灾变机理、裂缝发展规律、滑坡启动时间等问题,以甘肃省舟曲县江顶崖滑坡为对象,采用振动台及人工降雨模型试验,开展4组相同地震烈度不同降雨强度的震后降雨试验。研究结果表明：(1)地震作用使坡体发生剪切破坏,震后降雨工况坡体呈现土体流失的浸蚀破坏,在坡脚处产生明显的剪出口,震后降雨作用诱发堆积体滑坡发生局部失稳。(2)地震作用使坡体中部产生剪切裂缝与错台,后缘处产生“圆弧状”张拉裂缝,在后期降雨中,裂缝变形随降雨强度增大而加剧,并在降雨中期发生突变变形。(3)地震烈度相同的情况下,滑坡启动时间与降雨强度呈指数函数关系,土体沉降变形与降雨强度呈对数函数关系。研究成果可为堆积体滑坡在震后降雨作用下的预警及防治提供参考。     

山西数字地下水位固体潮加卸载响应比与中强地震关系分析

运用加卸载响应比方法,计算和分析了山西省2008年以来数字化地下水位固体潮观测数据,并选取大于2倍加卸载响应比值作为异常判定指标,将山西及周边地区发生的ML≥4．0地震的参数与井水位固体潮响应比异常变化对比分析。结果表明,山西地区9口数字水位观测井的地下水位固体潮加卸载响应比异常变化与附近的地震活动存在不同程度的对应关系。从而说明,利用井水位固体潮观测的加卸载响应比是一种能有效识别和提取地震前兆的方法。     

五尺坝地区库岸蓄水诱发型滑坡稳定分析

库水位周期性变化将改变原有水—边坡作用条件。结合三峡五尺坝库岸型斜坡地质条件,探讨了五尺坝滑坡成因机制,基于滑坡地质调查及变形破坏特征分析,其失稳模式概化为蠕滑—拉裂破坏,采用数值分析有限元软件Geostudio2007,对降雨入渗和库水位变化进行了数值模拟,提出坡体稳定系数在受到降雨与库水位升降导致的滑体内孔隙水压力的影响下有所减小,正常工况下滑坡整体稳定,极端工况滑坡会失稳。     

A new method for spatio-temporal prediction of rainfall-induced landslide

1 Introduction The landslides influences on the human society have become an environment difficult problem not able to be neglected, and according to the priority of harms, harms of landslides are only smaller than those from earthquakes in all sorts of natural hazards[1]. Landslide is part of rock mass, soil mass or their compound mass slides downward along a certain slid- ing surface under the actions of inner and external dy- namics, and it is one severe instability phenomenon of rock and s…     

Testing a model for predicting the timing and location of shallow landslide initiation in soil‐mantled landscapes

The growing availability of digital topographic data and the increased reliability of precipitation forecasts invite modelling efforts to predict the timing and location of shallow landslides in hilly and mountainous areas in order to reduce risk to an ever‐expanding human population. Here, we exploit a rare data set to develop and test such a model. In a 1·7 km² catchment a near‐annual aerial photographic coverage records just three single storm events over a 45 year period that produced multiple landslides. Such data enable us to test model performance by running the entire rainfall time series and determine whether just those three storms are correctly detected. To do this, we link a dynamic and spatially distributed shallow subsurface runoff model (similar to TOPMODEL) to an in?nite slope model to predict the spatial distribution of shallow landsliding. The spatial distribution of soil depth, a strong control on local landsliding, is predicted from a process‐based model. Because of its common availability, daily rainfall data were used to drive the model. Topographic data were derived from digitized 1 : 24 000 US Geological Survey contour maps. Analysis of the landslides shows that 97 occurred in 1955, 37 in 1982 and ?ve in 1998, although the heaviest rainfall was in 1982. Furthermore, intensity–duration analysis of available daily and hourly rainfall from the closest raingauges does not discriminate those three storms from others that did not generate failures. We explore the question of whether a mechanistic modelling approach is better able to identify landslide‐producing storms. Landslide and soil production parameters were ?xed from studies elsewhere. Four hydrologic parameters characterizing the saturated hydraulic conductivity of the soil and underlying bedrock and its decline with depth were ?rst calibrated on the 1955 landslide record. Success was characterized as the most number of actual landslides predicted with the least amount of total area predicted to be unstable. Because landslide area was consistently overpredicted, a threshold catchment area of predicted slope instability was used to de?ne whether a rainstorm was a signi?cant landslide producer. Many combinations of the four hydrological parameters performed equally well for the 1955 event, but only one combination successfully identi?ed the 1982 storm as the only landslide‐producing storm during the period 1980–86. Application of this parameter combination to the entire 45 year record successfully identi?ed the three events, but also predicted that two other landslide‐producing events should have occurred. This performance is signi?cantly better than the empirical intensity–duration threshold approach, but requires considerable calibration effort. Overprediction of instability, both for storms that produced landslides and for non‐producing storms, appears to arise from at least four causes: (1) coarse rainfall data time scale and inability to document short rainfall bursts and predict pressure wave response; (2) absence of local rainfall data; (3) legacy effect of previous landslides; and (4) inaccurate topographic and soil property data. Greater resolution of spatial and rainfall data, as well as topographic data, coupled with systematic documentation of landslides to create time series to test models, should lead to signi?cant improvements in shallow landslides forecasting. Copyright © 2003 John Wiley & Sons, Ltd.     

Spatio-temporal analysis and simulation on shallow rainfall-induced landslides in China using landslide susceptibility dynamics and rainfall I-D thresholds

An empirical simulation method to simulate the possible position of shallow rainfall-induced landslides in China has been developed. This study shows that such a simulation may be operated in real-time to highlight those areas that are highly prone to rainfall-induced landslides on the basis of the landslide susceptibility index and the rainfall intensity-duration (I-D) thresholds. First, the study on landslide susceptibility in China is introduced. The entire territory has been classified into five categories, among which high-susceptibility regions (Zone 4- ‘High’ and 5-‘Very high’) account for 4.15% of the total extension of China. Second, rainfall is considered as an external triggering factor that may induce landslide initiation. Real-time satellite-based TMPA 3B42 products may provide real rainfall spatial and temporal patterns, which may be used to derive rainfall duration time and intensity. By using a historical record of 60 significant past landslides, the rainfall I-D equation has been calibrated. The rainfall duration time that may trigger a landslide has resulted between 3 hours and 45 hours. The combination of these two aspects can be exploited to simulate the spatiotemporal distribution of rainfall-induced landslide hazards when rainfall events exceed the rainfall I-D thresholds, where the susceptibility category is ‘high’ or ‘very high’. This study shows a useful tool to be part of a systematic landslide simulation methodology, potentially providing useful information for a theoretical basis and practical guide for landslide prediction and mitigation throughout China.     

地震作用下节理岩质边坡稳定性影响因素研究

汶川地震灾害调查表明,在基岩山区地震滑塌主要发育在局部强度相对较大、节理较发育的厚层或块状岩体中.以岩石中含两组节理的岩质边坡为例,输入实际的地震记录,采用离散单元法进行数值模拟,分别探讨坡高、地震烈度、坡角及节理倾角组合对节理岩质边坡稳定性的影响.结果表明:地震作用下坡体中质点的加速度、速度具有高程放大效应;节理岩质边坡稳定性随着坡高、坡角和地震烈度的增加而降低;两组节理不同组合的岩质边坡,其稳定性变化较为复杂,受节理倾角与坡角的关系、节理的倾向、两组节理之间夹角等因素的影响.节理岩质边坡在地震作用下是受拉区逐渐向受剪区扩展而最终导致边坡失稳破坏,是受拉和受剪的复合破坏.上述初步结论为评价山区节理较发育的岩质边坡在地震作用下的稳定性提供一定的依据.     

Relations between rainfall–runoff‐induced erosion and aeolian deposition at archaeological sites in a semi‐arid dam‐controlled river corridor

Process dynamics in fluvial‐based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam‐building affect fluvial processes, the complexity in local response can be further increased by flood‐ and sediment‐limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi‐temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446‐km‐long semi‐arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam‐controlled fluvial sand bar deposition, aeolian sand transport, and rainfall‐induced erosion. Empirical rainfall‐erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration‐excess overland flow and gullying govern large‐scale (centimeter‐ to decimeter‐scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic‐driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four‐minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short‐term, storm‐driven rainfall intensity rather than cumulative rainfall, and that erosion can occur outside of wet seasons and even wet years. These results can apply to other similar semi‐arid landscapes where process complexity may not be fully understood. Published 2015. This article is a U.S. Government work and is in the public domain in the USA     

Impact of the Rainfall Intensity and Seepage on Slope Stability in Loess Plateau

In recent years, with the increase of traffic construction in mountainous areas in China, road slope traffic accidents have become more and more common. In addition, natural disasters such as landslides, collapses and subgrade settlements caused by rainfall, driving load, seasonal variation and groundwater distribution are frequent. In particular, rainfall is one of the most common factors leading to slope instability (landslide). Therefore, this paper proposes the seep module based on the application software Geo-studio, and analyzes the slope soil parameters and slope stability under five types of rainfall conditions:light rain (10 mm/d), moderate rain (25 mm/d), heavy rain (50 mm/d), rainstorm(100 mm/d), and torrential rain (250 mm/d). The critical safety factor under rainfall intensity is fitted with nonlinear curve by sine function. The results show that the fitting curve of rainfall intensity and safety factor on the upper slope is excellent. The residual points are evenly distributed in the belt area of±0.1, and the data basically conform to the nonlinear sine model, indicating that the curve plays an essential role in slope health diagnosis.     

Internal soil moisture and piezometric responses to rainfall-induced shallow slope failures

Better knowledge regarding internal soil moisture and piezometric responses in the process of rainfall-induced shallow slope failures is the key to an effective prediction of the landslide and/or debris flow initiation. To this end, internal soil moisture and piezometric response of 0.7-m-deep, 1.5-m-wide, 1.7-m-high, and 3.94-m-long semi-infinite sandy slopes rested on a bi-linear impermeable bedrock were explored using a chute test facility with artificial rainfall applications. The internal response time defined by the inflection point of the soil moisture and piezometric response curves obtained along the soil–bedrock interface were closely related to some critical failure states, such as the slope toe failure and extensive slope failures. It was also found that the response times obtained at the point of abrupt bedrock slope decrease can be used as indicators for the initiation of rainfall-induced shallow slope failures. An investigation of spatial distributions of soil water content, ω (or degrees of saturation, S_r), in the slope at critical failure states shows that the 0.2 m – below – surface zone remains unsaturated with S_r 40–60%, regardless of their distances from the toe and the rainfall intensity. Non-uniform distributions of ω (or S_r) along the soil–bedrock interface at critical failure states were always associated with near-saturation states (S_r 80–100%) around the point of bedrock slope change or around the transient ‘toe’ upstream of the slumped mass induced by the retrogressive failure of the slope. These observations suggest the important role of the interflow along the soil–bedrock interface and the high soil water content (or high porewater pressure) around the point of bedrock slope deflection in the rainfall-induced failure of sandy slopes consisting of shallow impermeable bedrocks. The present study proposes an ‘internal response time’ criterion to substantiate the prediction of rainfall-induced shallow slope failures. It is believed that the ‘internal response time’ reflects the overall characteristics of a slope under rainfall infiltration and can be as useful as the conventional meteorology-based threshold times. The ‘internal response time’ theory can be generalized via numerical modeling of slope hydrology, slope geology and slope stability in the future.     

地震作用下反倾岩质斜坡动力响应规律及频谱特征研究

以四川昌都贡扎滑坡为原型,设计制作了1:1000的振动台试验模型,开展了包含软弱岩性组合和贯通性结构面的反倾岩质斜坡的振动台模型试验.考虑场地工程地质条件和场地特性,将富含多种频率的人工合成基岩地震波作为动力输入条件,探讨了不同概率水准人工合成地震波作用下反倾岩质斜坡的动力响应规律,并与输入正弦波的放大效应规律进行对比...     

Spatial analysis of the reliability of transport networks subject to rainfall‐induced landslides

A methodology is developed to examine the susceptibility of a transport system to rainfall‐induced landslides and is demonstrated for part of the UK rail network with regard to the potential changes that might occur with climate change. A mathematical model is given for the system failure and a statistical model is formulated for the joint distribution of rainfall at different points along the railway line. These are used to investigate the response of earth embankments along the railway line to current and future climate scenarios, including the effects of rainfall and evapotranspiration on slope hydrology and stability. It is shown that, for the system of clay embankments in question, the moisture profile through the embankment at the end of the summer months has a critical effect on system stability, both in terms of expected failure timing and probability of failure. Further, it is seen that, with changing climate, the system stability is likely to increase unless the degradation of embankment material properties, another potential effect of changed climate, is taken into account. The spatial distribution of failures is also likely to change. Copyright © 2008 John Wiley & Sons, Ltd.