无人机航空摄影测量技术在崩塌灾害调查中的应用

无人机作为新兴的地理信息获取方法,其应用范围及数据精度受到广泛关注。相比于专业摄影测量的固定翼无人机及大型多旋翼无人机,小型四旋翼无人机对单体灾害或小区域进行地形测量,具有更灵活、可操作性更强、成本更低等优势。本文针对崩塌灾害调查工作环境的特殊性,研究了小型四旋翼无人机在无法布置控制点对数据进行优化的条件下,航拍高度和镜头方向对无人机数据的相对精度的影响。研究结果显示：（1）大疆精灵三系列无人机在缺少实地测量数据对无人机数据进行修正优化时,航高从150m下降到90m可使数据的水平精度提高63%,垂向精度提高7%;保持无人机的拍摄镜头垂直向下,在90～150m的航高范围内可以使数据的水平精度提高15%～69%,垂向精度提高6%～9%;（2）结合山东淄博的崩塌调查案例,利用无人机获取了崩塌地形数据,借助Rockyfor3D软件进行崩塌运动的三维数值模拟分析,得到崩塌将威胁电网线路及公路的安全,相关结论对于崩塌灾害的防治工作,有一定的指导意义。     

贵州上洋水河流域拉裂倾倒型崩塌机理研究

贵州上洋水河流域采矿工作引发了形式多样、成因复杂的崩塌地质灾害。以拉裂倾倒式崩塌失稳模式为例,在分析斜坡结构特征的基础上,运用岩体力学理论对崩塌形成岩体的受力演化过程以及中间出现的压缩、挤胀等现象进行了深入研究,并采用离散元数值模拟再现了崩塌形成的变形破坏过程。研究结果表明:磷矿开采产生采空区引起斜坡的应力应变调整,使得岩体产生变形,出现挤胀扩容现象导致岩体失稳倾倒,继而引发崩塌。岩体受力变形过程分为应力调整结构面张拉贯通-岩体变形受压-坡脚岩体挤胀扩容-岩体失稳破坏等4个阶段。在这整个过程中,应力应变的调整和岩体的变形形态以及裂隙的张拉形成相互作用,共同影响着崩塌的进行。     

高边坡滚石计算方法比较研究

作为一种地质灾害,虽然滚石的规模相对崩塌、滑坡等较小,但突发性极强、预测困难,会造成建筑物损坏、交通运输线路堵塞、人员伤亡等严重后果。汶川地震引发大量滚石,引起了工程界对其更多的重视。以岩质高边坡工程实践为背景,采用经验公式法以及运动学结合概率统计两种方法,分别计算了滚石沿高边坡运动至建筑物待建位置时的速度和动能。分析比较了两种方法的计算结果,经验公式法对边坡只能取得单一的计算值,而运动学结合概率统计方法的计算值可以分布图的形式给出。前者的速度计算值在后者的速度分布图中处于大值的区间,是偏于安全的; 而对于动能的计算,经验公式法对转动动能估计较小。认为运动学方法更为符合滚石灾害的特点。根据计算结果,该处滚石危险性较大,建议移动建筑物位置。     

滚石与滚石灾害

长期以来 ,滚石灾害是一种很少受到重视的地质灾害。本文从滚石的概念出发 ,对滚石的内涵、外延及特征进行了较为深入的论述。实际上 ,将各种动力地质现象涉及到的滚石问题提出来单独进行研究不仅有助于问题的简化 ,还有助于研究的深化。自然变异或人为扰动引发的滚石可能会给人类活动和社会造成一定的损失 ,而将滚石作为一类地质灾害并称之为滚石灾害是合理的 ,也是合适的。本文最后还给出了国际上滚石研究的主要方向与基本问题 ,为进一步研究提供参考     

四川高县芙蓉山白岩山崩的成因

根据芙蓉山白岩山崩区的环境地质特征、成因，得出白岩山崩是人类与环境没有协调好而酿成的地质灾害的结论。     

The characteristics and significance of some lateglacial protalus ramparts in upland Britain

Arcuate and linear protalus ramparts of inferred Loch Lomond Stadial age are widespread in upland Britain outside the limits of contemporaneous glaciers. Survey and analysis of the morphology of nine ramparts suggests that these may have formed at the foot of slowly thickening snowbeds, with rockfall debris accumulating against their distal slopes, and that snowbed melting at the end of the stadial was uninterrupted by prolonged periods of stability or renewed growth. Rampart sediments consist of poorly-sorted assemblages of clasts with a variable infill of fines. Clast size and shape are strongly influenced by lithology, but rampart clasts are characteristically more angular and ‘slabbier’ than those of similar lithology in ice-marginal moraines. Ramparts may also be distinguished from moraines by their location, morphology, lack of a true matrix of fines and absence of erratics, and from talus-foot rock glaciers in terms of their width and the absence of flow structures. The mapped distribution of rampart altitudes across the Scottish Highlands displays a marked regional trend, with the lowest features in the west and south and highest in the Cairngorms. This pattern mirrors that of reconstructed firn line altitudes of Loch Lomond Stadial glaciers, and is inferred to reflect a pronounced eastwards and northwards decline in snowfall during the stadial.     

Assessment of rockfall hazard around Afyon Castle,Turkey

The Afyon Castle is a tourist destination and a historical site in the City of Afyon in Turkey. The Castle is located on a steep hill, with a height of 226 m. In close proximity to the Castle there are settlements. The hill consists of trachitic andesite. The rock contains columnar joints and flow layering. Owing to these discontinuities, blocks of varying sizes had fallen down. The settlement areas near the Castle are now in danger because of the rockfall risk. In this study, rockfall analysis was carried out along nine profiles of the hill. Fall-out distance, bounce height, kinetic energy and velocity of the rocks along each profile were investigated. The results of the analyses were evaluated, and the areas delineated as susceptible to rockfall risk are highlighted. Remedial measures including rock bolts and protective fences were suggested on the basis of the field observations and the rockfall risk evaluation.     

Frost weathering and rockwall erosion in the southeastern Swiss Alps: Long-term (1994–2006) observations

Rates and processes of frost weathering in the Alps were investigated by visual observations of intensively shattered rocks, continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity. Rapid frost weathering of hard-intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock. Otherwise, rocks require pre-existing weakness or a long exposure period for intensively shattered. Automated monitoring shows that crack opening occurs at three scales, including small opening accompanying short-term frost cycles, slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow-melt water during seasonal thawing. The opening events require at least partial water saturation in the crack. The repetition of crack opening (frost wedging) results in permanent opening and finally debris dislocation. Debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0.1 mm a^− 1 with significant spatial and inter-annual variations. Occasional large boulder falls significantly raise the rockwall erosion rates, controlled by such factors as the joint distribution in the bedrock, repetition of annual freeze–thaw cycles and extraordinary summer thaw.     

Rockfall Hazard Analysis for Hong Kong Based on Rockfall Inventory

Summary ¶This paper compiles and analyzes the rockfall data in Hong Kong in the last fifty years. A simple rockfall hazard analysis is presented based on this rockfall inventory. A frequency-magnitude relation, which is analogous to the Gutenberg-Richter relation for earthquake occurrence, is proposed for rockfall, and direct correlation between rockfall frequency and the daily rainfall is observed. Data analysis shows that a threshold daily rainfall of about 150–200mm is expected in order to trigger rockfall events in Hong Kong. Among the 368 rockfall events in the 13 year period from 1984 to 1996 in Hong Kong, 35% of the incidents lead to blockage of or damage to roads, 22% lead to damages or evacuation of squatter huts, 21% lead to blockage of pedestrian pavement and footpath, and 15% affect buildings, such as housing apartments and schools. Only 15% of these rockfalls fell onto open space and caused negligible effects on human activities. Most of these rockfall events occurred during heavy rain and when landslide warning should has been issued by the Hong Kong Observatory, thus only 6% of these events led to injury or casualty, car damages, and damages to public utilities. Rockfall hazard zonation maps in terms of the spatial distribution of previous rockfalls are proposed for both Kowloon Peninsula and Hong Kong Island.     

Application of a long-range Terrestrial Laser Scanner to a detailed rockfall study at Vall de Núria (Eastern Pyrenees, Spain)

In this study we show the application of a long-range Terrestrial Laser Scanner (TLS) to a detailed rockfall study in a test zone at Vall de Núria, located in the Eastern Pyrenees. Data acquisition was carried out using TLS-Ilris3D, the new generation of reflector-less laser scanners with a high range, accuracy and velocity of measurements. Eight scans were performed at 3 stations to acquire coordinates of almost 4 million points. The results from the acquired data are a high accuracy Digital Elevation Model (DEM) and the reconstruction of the joint geometry. The former is used for inventory of rockfalls and for more accurate rockfall simulation (trajectories and velocities). The latter allows us to model the geometry and volume of the source area in recent rockfalls. Our findings suggest that TLS technology could be a tool of reference in rockfall studies in the near future.