Using GB-SAR technique to monitor slow moving landslide

A Ground-Based SAR (GB-SAR) interferometer was employed to measure the surface displacements of a landslide occurring in the Carnian Alps, north-eastern Italy, which has affected a national road and seriously damaged a road tunnel still under construction. Moreover, since the landslide is located on the left bank of the Tagliamento River Valley, it is feared that this mass movement might dam the river, creating a basin that would increase natural hazard for the valley inhabitants. The data collected from December 2002 to July 2005 by a conventional monitoring system, consisting of a GPS network and boreholes equipped with inclinometric tubes, showed that the landslide was moving at a quasi-constant rate of about 3 cm per year. Due to the slow deformation rate of the landslide, a recently developed GB-SAR technique based on the analysis of a restricted ensemble of coherent points was used. Two surveys, each lasting two days, were planned in December 2004 and July 2005, in order to map and measure the surface displacements that occurred over time. The results from the radar were compared with the ones derived from the GPS monitoring network. An agreement was achieved among the data collected, showing the capability of the GB-SAR technique to measure displacements even within a time span of several months between the surveys.     

河岸带土壤磷素空间分布及其对水文过程响应

野外观测太湖地区典型农业河岸带——浯溪荡河岸带土壤总磷（TP）和溶解性总磷（DTP）含量以及当地降雨量、河水水位和地下水水位,探讨了丰水年条件下该河岸带土壤TP和DTP的空间分布特征以及水文过程对其空间分布的影响。结果表明:①在水平方向上,土壤TP和DTP含量从远岸向近岸均呈现先减少后增加的变化趋势;在深度方向上,各断面TP和DTP含量随土层深度的增加均呈减少的变化趋势。②不同月份河水水位均低于地下水水位,地下水补给河水。河水水位和地下水水位随时间的变化规律与降雨量的相似,但具有一定的滞后性。③降雨是土壤水分运动的主要驱动力,降雨、河水水位以及地下水水位对河岸带土壤磷素空间分布的影响显著不同。     

堆积层滑坡地震动力响应的物理模型试验

以玉树7.1级地震诱发的玉树机场路堆积层滑坡为对象,该滑坡坡度约为10o,长×宽×厚为317 m×482 m×19.8 m,由以碎石土为主的上覆层、卵石土为主的滑动带及基岩3层组成,开展大型振动台模型试验,探究震后边坡再次承受振动荷载的能力以及地震垂直分量对坡体稳定性的贡献,分析其动力响应特征和失稳破坏机制。结果表明,强震作用下堆积层滑坡的永久变形是造成地震地质灾害的重要因素;随着输入地震荷载增大,坡脚率先破碎沉降,坡体中部产生弧形裂隙并产生沉降,坡顶出现贯穿张裂隙和剪切裂隙并向坡腰推进,表现出典型的牵引性滑坡特征;峰值加速度(PGA)、动土压力以及加速度频谱与输入地震波的强度、滑坡高程呈正相关;PGA放大系数呈现出明显的非线性特征,其变化趋势随地震荷载强度增大而减小,地震波垂直分量对滑坡PGA放大系数影响略大于水平分量。     

红岩煤矿岩溶水对暴雨响应特征研究

岩溶地下水系统由于管道流和扩散流同时存在而非常复杂。岩溶区暴雨过程中矿井突水造成了生命与财产的重大损失，因此在这些地区掌握矿井突水对暴雨响应特征是极其关键的。本文在大量监测资料基础上研究了红岩煤矿岩溶地下水系统，利用时间序列频谱分析建立了突水与暴雨之间的响应模型，并利用该模型预测了矿井突水趋势。     

某大型水电站水文站滑坡稳定性三维数值模拟分析

水文站滑坡位于某拟建的水电站坝址下游约300m的左岸。由于它距该坝址较近，若发生较大范围的变形或失稳，极有可能产生巨大的涌浪，并有可能导致大坝的损坏或完全破坏。所以，它的稳定性状况一直是各相关部门十分关心的重要问题。野外现场调研是判断滑坡体稳定性的行之有效的方法之一。在此基础上，对滑坡体模型做一较接近实际的概化，这是研究问题的关键之所在。采用三维有限元(FLAC-3D)对其进行数值模拟分析。当然，只有数值模拟手段这一种方法来判断滑坡体的稳定性还远不够的，必须与其它手段方法相结合，这样才使结论更可靠，更具有说服力。数值模拟结果表明：(1)水文站滑坡的潜在主滑动面为滑体与基岩的接触面。但其贯通性较差。因此，滑坡体的整体稳定性较好，不可能发生较大范围内的变形或失稳；(2)水文站滑坡的位移方向总体表现为向河谷方向运动。滑坡体前后缘的位移量较小，中间位移量相对较大(22．8cm)。总之，在天然情况下，水文站滑坡的整体稳定性较好，不可能发生较大范围的变形或破坏。这与野外现场调研的结果相一致。     

水库滑坡地下水动态响应规律及浸润线计算模型

库水和降雨直接导致水库滑坡地下水变动,是诱发滑坡的主要因素。已有研究大多是基于监测数据探讨库水与降雨对滑坡变形的影响,未能揭示水库滑坡地下水响应规律,地下水浸润线计算模型没有同时考虑降雨和库水的影响,且模型边界条件与水库滑坡实际情况差别较大。为了揭示大型水库滑坡地下水动态响应规律,需要构建更接近实际情况的地下水位浸润线计算模型。通过三峡水库石榴树包滑坡地下水动态监测,揭示了库水水位变化和降雨条件下滑坡地下水水位动态响应规律,其地下水渗流场近似层流,滑坡前缘和中部的地下水水位与库水位几乎同步,滑坡后部的地下水水位主要受降雨影响,日降雨30 mm会引发地下水水位明显变动。在周期性库水位变化和随机降雨耦合条件下,建立了滑坡地下水非稳定渗流微分方程,解算出水库滑坡地下水位浸润线计算模型,并采用实际监测结果进行了验证。应用计算模型分析了不同工况条件下的滑坡渗流场,并得出滑坡内距前缘水平距离145 m内,库水对地下水有影响;引发地下水变动的降雨和库水位变化阈值分别为0.03,0.1 m/d,且不同的条件组合下降雨和库水位对地下水水位影响存在一定差异。     

结构复杂滑坡活动对库水位变化的响应特征——以三峡库区柴湾滑坡为例

柴湾滑坡是三峡库区结构复杂的大型老滑坡之一,三峡水库蓄水后,该滑坡出现明显复活迹象。本文基于滑坡结构和2007-2015年监测数据,分析了该滑坡活动对库水位变化的响应特征;采用数值模拟手段分析了库水位变化时滑体内渗流场及孔隙水压力变化特征。研究发现,该滑坡在平、剖面上分别呈现牵引式分块与浅、中层分层的缓慢活动特征;当库水位降速>0 8 m/d时,滑坡活动呈现滞后的台阶式加剧趋势;越接近地表,滑坡活动对库水位变化愈敏感。柴湾滑坡活动特征受其复杂结构控制,滑坡中前部地下水与库水密切的水力联系以及中层、深层滑体良好的渗透性决定了滑坡的分块和分层活动特征。库水位上升时透水性较强滑体内的扬压力和库水位下降时透水性较弱滑体内的动水压力是造成滑坡分块分层活动的内在动力。     

Regional landslide risk to the Cairns community

A GIS-based regional reconnaissance-level assessment of landslide risk to the Cairns community has been carried out to provide information to the Cairns City Council for planning and emergency management purposes. Magnitude recurrence relations were tentatively established for the two main slope processes: landslides on the hill slopes; and large debris flows extending out from the gully systems on to the plains. From the recurrence relations, landslide hazard (H) was estimated as the annual probability of a point being impacted by a landslide. The nature, number (E) and geographic distribution of the elements at risk were obtained by interrogating the GIS, and their vulnerabilities (V) to destruction by the two main landslide slope processes were assessed. From this information, specific risk (= H × V) and total risk (= H × V× E) maps were produced.Although total landslide risk is relatively low at present, it will increase as development extends further into the hill slopes, unless adequate mitigation measures are taken. Large debris flows, while considerably less frequent than landslides on cut slopes, could impact on subdivisions at the base of the slopes. Blockage by landslides of roads and railways providing access to Cairns can cause isolation of the community. Flash flooding in Freshwater Creek, or debris flows, have the potential to disrupt the Cairns water supply by blocking the intake or destroying sections of the pipeline.     

Geo-diversity and its hydrological response in relation to landslide susceptibility in the Himalaya: a GIS-based case study

Assessment and inventory of landslide susceptibility are essential for the formulation of successful disaster mitigation plans. The objective of this study was to assess landslide susceptibility in relation to geo-diversity and its hydrological response in the Lesser Himalaya with a case study using Geographic Information System (GIS) technology. The Dabka watershed, which constitutes a part of the Kosi Basin in the Lesser Himalaya, India, in the district of Nainital, has been selected for the case illustration. The study constitutes three GIS modules: geo-diversity informatics, hydro informatics and landslide informatics. Through the integration and superimposing of spatial data and attribute data of all three GIS modules, Landslide Susceptibility Index (LSI) has been prepared to identify the level of susceptibility for landslide hazards. This resonance study, carried out over a period of five years (2007–2011), found that areas of most stressed geo-diversity (comprising very steep slopes above 30°, geology of Lower Krol and Lariakanta formation, geomorphology of moist areas and debris sites, land use of barren land with a very high drainage frequency and spring density) have a high landslide susceptibility because of high rate of average runoff (33 l/s/km²), flood magnitude (307.28 l/s/km²), erosion (398 tons/km²) and landslide density (5–10 landslides/km²). The areas of least stressed geo-diversity (comprising gentle slopes below 10°, geology of Kailakhan and Siwalik formation, geomorphology of depositional terraces, land use of dense forest with low drainage frequency and spring density) have the lowest landslide susceptibility because of the low rate of average runoff (6.27 l/s/km²), flood magnitude (20.49 l/s/km²), erosion (65.80 tons/km²) and landslide density (1–2 landslides/km²).     

Using multiple logistic regression and GIS technology to predict landslide hazard in northeast Kansas, USA

Landslides in the hilly terrain along the Kansas and Missouri rivers in northeastern Kansas have caused millions of dollars in property damage during the last decade. To address this problem, a statistical method called multiple logistic regression has been used to create a landslide-hazard map for Atchison, Kansas, and surrounding areas. Data included digitized geology, slopes, and landslides, manipulated using ArcView GIS. Logistic regression relates predictor variables to the occurrence or nonoccurrence of landslides within geographic cells and uses the relationship to produce a map showing the probability of future landslides, given local slopes and geologic units. Results indicated that slope is the most important variable for estimating landslide hazard in the study area. Geologic units consisting mostly of shale, siltstone, and sandstone were most susceptible to landslides. Soil type and aspect ratio were considered but excluded from the final analysis because these variables did not significantly add to the predictive power of the logistic regression. Soil types were highly correlated with the geologic units, and no significant relationships existed between landslides and slope aspect.     

Using wavelet tools to analyse seasonal variations from InSAR time-series data: a case study of the Huangtupo landslide

Synthetic aperture radar interferometry (InSAR) has proven to be a powerful tool for monitoring landslide movements with a wide spatial and temporal coverage. Interpreting landslide displacement time-series derived from InSAR techniques is a major challenge for understanding relationships between triggering factors and slope displacements. In this study, we propose the use of various wavelet tools, namely, continuous wavelet transform (CWT), cross wavelet transform (XWT) and wavelet coherence (WTC) for interpreting InSAR time-series information for a landslide. CWT enables time-series records to be analysed in time-frequency space, with the aim of identifying localized intermittent periodicities. Similarly, XWT and WTC help identify the common power and relative phase between two time-series records in time-frequency space, respectively. Statistically significant coherence and confidence levels against red noise (also known as brown noise or random walk noise) can be calculated. Taking the Huangtupo landslide (China) as an example, we demonstrate the capabilities of these tools for interpreting InSAR time-series information. The results show the Huangtupo slope is affected by an annual displacement periodicity controlled by rainfall and reservoir water level. Reservoir water level, which is completely regulated by the dam activity, is mainly in ‘anti-phase’ with natural rainfall, due to flood control in the Three Gorges Project. The seasonal displacements of the Huangtupo landslide is found to be ‘in-phase’ with respect to reservoir water level and the rainfall towards the front edge of the slope and to rainfall at the higher rear of the slope away from the reservoir.     

汾河上游土地利用变化及其水文响应研究

以河岔水文站以上的汾河流域为研究区,采用土地利用转移矩阵和SWAT模型模拟方法,就汾河上游土地利用变化对水文过程的影响进行研究. 流域从1995-2000年,以耕地向林地和草地转变为主;从2000-2010年,城市建设用地不断增加,主要是对耕地的占用. 结果显示,在相同气候背景、不同土地利用情景（1995、2000年2010年）下,流域1992-2000年多年平均产水量微弱增加（分别为85.69 mm、85.75 mm和85.82 mm）,主要因为耕地持续减少,草地和城市建设用地不断增加. 但是各年产水量的大小关系不完全一致,枯水年和平水年与丰水年存在差异,而土壤水分呈现一致的减少状况. 子流域水平上,降水条件同样影响水文过程对土地利用变化的响应程度. 以上结果表明,汾河流域在退耕还林还草政策等影响下,土地利用发生变化并且直接影响流域的水文过程,但是流域水文过程对土地利用变化的响应还受到降水的影响.     

SHALSTAB模型在浙南林溪流域滑坡预测中的应用

受台风暴雨影响,浙南林溪流域滑坡频发。针对该区域滑坡规模小、长度与厚度比值大的特点,采用浅层滑坡稳定性模型(SHALSTAB)对潜在滑坡进行了预测,以log(降雨量q/土壤的导水系数T)作为划分标准,结果显示随着log(q/T)值的提高,预测的滑坡区域逐渐扩大,预测捕获率升高的同时,误判率也随之上升。以log(q/T)≤-3.1作为预测滑坡的判别标准,模型效果较好,预测捕获率为62.50%,误判率(17.79%)较低。预测结果显示,滑坡潜在区域主要位于斜坡下部、土体厚度大和坡度陡峭的地区,山体顶部、土体厚度薄和地形平坦的区域斜坡稳定。     

麻疯树和枫杨幼苗对5种模拟喀斯特逆境的光合生理响应

通过测定麻疯树和枫杨幼苗在5种模拟喀斯特逆境下的光合以及δ13C值的变化,分析其光合响应特征.结果表明,第15天,麻疯树幼苗在偏碱性、干旱、低磷、高重碳酸盐和低营养下的净光合速率(Pn)分别为4.39、0.27、2.58、3.08和6.26 μmol·m-2·s-1,第25天则分别变为4.09、0.66、4.57、3.83和4.04μmol·m-2·s-1;枫杨幼苗的Pn和水分利用效率均低于麻疯树,枫杨幼苗在第25天的Pn有所升高.干旱下枫杨幼苗的初始荧光(Fo)显著升高,光系统Ⅱ原初光能转化效率(Fv/Fm)显著下降,与麻疯树幼苗相比,其光合结构受到更为严重的损害.第25天各逆境下麻疯树幼苗的δ13C值与对照相比显得更为偏正,其对胞内HCO3-的利用能力较强.因此,在山坡缺水环境适宜种植麻疯树,而在沿溪涧河滩阴湿环境则适宜种植枫杨.     

Using multiresolution and multitemporal satellite data for post-disaster landslide inventory in the Republic of Serbia

This paper focuses on a specific event-based landslide inventory compiled after the May 2014 heavy rainfall episode in Serbia as a part of the post-disaster recovery actions. The inventory was completed for a total of 23 affected municipalities, and the municipality of Krupanj was selected as the location for a more detailed study. Three sources of data collection and analysis were used: a visual analysis of the post-event very high and high (VHR-HR) resolution images (Pléiades, WorldView-2 and SPOT 6), semi-automatic landslide recognition in pre- and post-event coarse resolution images (Landsat 8) and a landslide mapping field campaign. The results suggest that the visual and semi-automated analyses significantly contributed to the quality of the final inventory, including the associated planning strategies for conducting future field campaigns (as a final stage of the inventorying process), all the more so because the field-based and image-based inventories were focused on different types of landslides. In the most affected municipalities that had very high resolution satellite image coverage (19.52% of the whole study area), the density of the recognized landslides was approximately three times higher than that in those municipalities without satellite image coverage (where only field data were available). The total number of field-mapped landslides for the 23 municipalities was 1785, while image-based inventories, which were available only for the municipalities with satellite image coverage (77.43% of the study area), showed 1298 landslide records. The semi-automated landslide inventory in the test area (Krupanj municipality), which was based on coarse resolution multitemporal images (Landsat 8), counted 490 landslide instances and was in agreement with the visual analysis of the higher resolution images, with an overlap of approximately 40%. These results justify the use of preliminary inventorying via satellite image analysis and suggest a considerable potential use for preliminary visual and semi-automated landslide inventorying as an important supplement to field mapping.     

Parametrical landslide modeling for the hydrogeological susceptibility assessment: from the Crati Valley to the Cavallerizzo landslide (Southern Italy)

The article deals with a tool for landslides susceptibility assessment as a function of the hydrogeological setting at different scales. The study has been applied to a test area located in Southern Italy. First, a 3D groundwater flow model was implemented for a large-scale area. The simulation of several groundwater conditions compared with the landslide activity map allows drawing a hydrogeological susceptibility map. Then, a slope scale analysis was carried out for the Cavallerizzo landslide. For this purpose, a 2D groundwater parametrical modeling was coupled with a slope stability analysis; the simulation was carried out by changing the values of the main hydrogeological parameters (recharge, groundwater supply level, etc.). The results enabled to connect the slope instability to some hydrogeological characteristics that are easy to survey and to monitor (e.g., rainfall, piezometrical level, and spring discharge), pointing out the hazard thresholds with regards to different triggering phenomena.     

Application of DDA to simulate characteristics of the Tsaoling landslide

This study simulates the kinematic behavior of sliding blocks of rock in the earthquake-induced Tsaoling landslide using seismic discontinuous deformation analysis (DDA). We assume sliding rocks are elastic blocks. Detailed joint shear strength parameters are set in DDA in a manner compatible with what is known about the Tsaoling landslide mechanisms. Landslide run-out distance, information from survivors, and the post-failure topography are used to constrain the computational results. Calculations demonstrate that sliding rocks from the ground surface decoupled from those near the basal shear surface during the landslide. Local residents survived because surficial rocks were never deeply buried during the landslide. Additionally, shear strength parameters of material in the deposition area strongly govern final deposit topography. Computational results correlate well with actual post-failure topography.     

YGM体系在滑坡治理工程中的应用

通过重庆丰都县楠竹滑坡群治理工程实例,对YGM体系在滑坡治理工程中的应用作出较为全面的阐述.采用锚拉抗滑桩治理该滑坡群,设置抗滑桩1排,共80根;每根抗滑桩桩顶下2m处设置1根预应力锚杆,采用3～4根φ32的高强精轧螺纹粗钢筋(40SiMnV)制作而成.文中详述了包括钻进成孔、锚杆的防护、锚杆组装和入孔、注浆、张拉锚固等施工方法,并在该治理工程中采用GMS钢弦式岩土锚测力计,对锚固预应力进行长期监测,从而实现对滑坡治理效果进行全过程的动态监测.