Prediction of rainfall-triggered landslides: a test of the Antecedent Water Status Model

A rainfall-based landslide-triggering model, developed from previous landslide episodes in Wellington City, New Zealand, is tested for its ability to provide a 24-hour forecast of landslide occurrence. The model, referred to as the Antecedent Water Status Model, calculates an index of soil water, by running a daily water balance and applying a soil drainage factor to excess precipitation, over the preceding ten days. Together with the daily rainfall input, the soil water status has been used empirically to identify a threshold condition for landslide triggering. The prediction process provides a daily update of the soil water status and thereby the amount of rainfall required on the following day to equal or exceed the triggering threshold. The probability that this triggering rainfall will occur is then determined from the frequency/magnitude distribution of the local rainfall record. The model produces a satisfactory level of prediction, particularly for periods of concentrated landslide activity. Copyright © 1999 John Wiley & Sons, Ltd.     

Slopewash,surface runoff and fine-litter transport in forest and landslide scars in humid-tropical steeplands,luquillo experimental forest,Puerto Rico

Rainfall, slopewash (the erosion of soil particles), surface runoff and fine-litter transport steepland sites in the Luquillo Experimental Forest, Puerto Rico (18° 20’ N, 65° 45’ W) were measured from 1991 to 1995. Hillslopes underlain by (1) Cretaceous tuffaceous sandstone and silstone in subtropical rain (tanonuco) forest with vegetation recovering from Hurricane Hugo (1989), and (2) Tertiary quartz diorite in subtropical lower mantone wet (colorado and dwarf) forest with undisturbed forest canopy were compared to recent landslide scars. Monthly surface runoff on these very steep hillslopes (24° to 43°) was only 0·2 to 0·5 per cent of monthly rainfall. Slopewash was higher in sandy loam soils whose parent material is quartz diorite (averaging 46 g m⁻² a⁻¹) than in silty clay loam soils derived from tuffaceous sandstone and siltstone where the average was 9 g m⁻² a⁻¹. Annual slopewash of 100 to 349 g m⁻² on the surfaces of two recent, small landslide scars was measured initially but slopewash decreased to only 3 to 4 g m⁻² a⁻¹ by the end of the study. The mean annual mass of fine litter (mainly leaves and twigs) transported downslope at the forested sites ranged from 5 to 8 g m⁻² and was lower at the tabonuco forest site, where post-Hurricane Hugo recovery is still in progress. Mean annual fine-litter transport was 2·5 g m⁻² on the two landslide scars. Copyright © 1999 John Wiley & Sons, Ltd.     

芦山地震崩滑灾害空间分布及相关问题探讨

由于逆断层作用,2013年芦山M_S 7.0地震诱发的崩滑地质灾害分布表现出了明显的上盘效应与方向效应。在震后应急科考中未发现发震断层的地表破裂带,然而灾区大量出现的地震诱发滑坡、崩塌,加之密集的余震分布、地震烈度调查结果等,提供了确定芦山地震宏观震中、地震动错动方向以及研究地震发震构造等的诸多线索。 统计结果表明,芦山地震诱发的滑坡、崩塌具有明显的优势滑动方向（135°～144°）,该方向揭示了地震断层的错动方向,与震源机制解反映的一致,大体垂直于发震断层的走向;从地震诱发崩塌、滑坡灾害点的分布与密度判断,宏观震中位于宝盛乡北,在仪器记录震中东北约3.6km处;从余震群分布、地震诱发滑坡分布特点及地震等烈度线等,结合以往强震如汶川地震等的调查经验,推测当震级足够大时,发震断层地表破裂带可能通过地质灾害、余震密集区东侧的边缘地带,总体平行于双石-大川断裂。另外,通过分析地层岩性与崩滑地形条件之间的关联性,发现崩滑灾害在某些地层岩性中易发,灾害点呈线性排列的原因是不同地层岩性之间抗风化能力的差异性,造成在地层分界线上形成线性陡崖或高坡度地带,使之在强震作用下容易发生崩塌、滑坡。     

鄂西清江流域滑坡崩塌致灾背景及成灾模式

鄂西清江流域是我国滑坡崩塌地质灾害易发区。在该区域11个县市地质灾害详细调查成果基础上,运用归纳和类比等方法,对区内2 276个滑坡和567个崩塌(危岩)的要素数据进行统计分析;归纳总结了区域滑坡崩塌的基本发育特征和分布规律,并从构造作用、岩性组合、河流地貌演化、人类活动、降雨等几个方面,分析多种致灾背景对滑坡崩塌的不同影响和控制作用;继而根据主控因素归纳分析了区内滑坡具有的降雨型、箱形(紧窄)背斜型、宽缓向斜型和水库型等4类主要成灾模式,以及崩塌(危岩)具有的宽缓向斜型和岩溶石柱型两类主要成灾模式;指出了今后需要重点防控的三种类型滑坡崩塌风险。     

典型滑坡监测点优化布置

利用数值模拟技术与模糊模式识别算法提出了滑坡监测点优化布置的基本方法。以链子崖危岩体为例,以Ⅳ-Ⅳ′剖面作为滑坡监测点优化布置的典型剖面,根据监测变量（位移）对外界干扰因素作用下的灵敏度大小与监测信息量获取大小之间的关系,对该危岩体的监测变量（位移）进行了灵敏度分区研究,进而对该典型剖面的监测点进行了优化设计。研究结果表明,链子崖危岩体地表位移监测点宜布置在位移量明显和状态变化灵敏度较高的部位,深部位移监测钻孔宜穿越所有水平位移变化的灵敏区域。     

Erosional power in the Swiss Alps: characterization of slope failure in the Illgraben

Landslides and rockfalls are key geomorphic processes in mountain basins. Their quantification and characterization are critical for understanding the processes of slope failure and their contributions to erosion and landscape evolution. We used digital photogrammetry to produce a multi‐temporal record of erosion (1963–2005) of a rock slope at the head of the Illgraben, a very active catchment prone to debris flows in Switzerland. Slope failures affect 70% of the study slope and erode the slope at an average rate of 0.39 ± 0.03 m yr¯¹. The analysis of individual slope failures yielded an inventory of ~2500 failures ranging over 6 orders of magnitude in volume, despite the small slope area and short study period. The slope failures form a characteristic magnitude–frequency distribution with a rollover and a power‐law tail between ~200 m³ and 1.6 × 10⁶ m³ with an exponent of 1.65. Slope failure volume scales with area as a power law with an exponent of 1.1. Both values are low for studies of bedrock landslides and rockfall and result from the highly fractured and weathered state of the quartzitic bedrock. Our data suggest that the magnitude–frequency distribution is the result of two separate slope failure processes. Type (1) failures are frequent, small slides and slumps within the weathered layer of highly fractured rock and loose sediment, and make up the rollover. Type (2) failures are less frequent and larger rockslides and rockfalls within the internal bedded and fractured slope along pre‐determined potential failure surfaces, and make up the power‐law tail. Rockslides and rockfalls of high magnitude and relatively low frequency make up 99% of the total failure volume and are thus responsible for the high erosion rate. They are also significant in the context of landscape evolution as they occur on slopes above 45° and limit the relief of the slope. Copyright © 2012 John Wiley & Sons, Ltd.     

基于加卸载响应比理论的降雨型滑坡预警研究

在建立边坡远程实时监测系统并获得变形与降雨量连续监测数据的基础上,运用加卸载响应比理论的基本原理,提出以一用为加卸载周期、将日降雨量及其变化作为边坡的加卸载参数、相应的日平均变形速率及其变化值为加卸载响应参数,建立了基于加卸栽响应比的降雨型滑坡短周期预警模型。以某公路边坡为例,运用加卸载响应比预测模型对边坡的2个监测点进行了加卸载响应比计算,发现2个点的加卸载响应比时序曲线与其稳定性动态演化规律相吻合。研究结果表明,可以运用该模型进行降雨型滑坡短周期预测预警。     

金沙江水电站工程区典型单体滑坡风险评价探讨

在对金沙江流域内的部分大型水电站工程区内的滑坡分析基础上,以两个滑坡为例,针对水电站工程区讨论了单体滑坡的风险评价方法。选取滑坡稳定性,规模和可能造成的涌浪高度3个指标进行危险性评价;并且定性地将大坝的易损性确定为高、中、低三个等级。在此基础上,对研究区的牛滚函滑坡和东岳庙滑坡进行了危险性分析和易损性评价,得出这两个单体滑坡的风险分析结果：牛滚函滑坡为低度风险,东岳庙滑坡为中度风险。研究成果为水电站工程区滑坡减灾防灾与风险管理提供了科学依据。     

基于数值模拟的三峡库区典型堆积层滑坡变形预测方法

目前对堆积层滑坡的变形预测大多基于数学模型或方法,忽略了引起滑坡位移显著变化的动力外因及滑坡自身的地质特征,因此,预报准确度和可信度较低。以三峡库区典型堆积层滑坡--鹤峰场镇滑坡为例,通过4组主要控制因素科学组合构建了滑坡的基本地质模型;以此为基础,重点考虑引起滑坡发生变形的库水作用动力因素,建立滑坡的数值-力学模型。通过实际监测点的变形监测结果与数值-力学模型中模型监测点的变形进行拟合分析,获取了实际时间与数值-力学模型中时步的等效关系;基于时间-时步等效关系及三峡水库设计水位调度曲线,得到了不同时步水位的波动特征;通过时步的外延,并在相应的时步段对数值-力学模型施加等效时间的库水作用,预测了滑坡在未来库水位变动条件下的变形。该预测方法既考虑了滑坡的工程地质模型又考虑了地下水作用效应,克服了纯数学方法预测的不足。     

滑坡降雨阈值模型的应用

在数字高程模型（DEM）的基础上,运用滑坡降雨阈值模型,以楚雄丁家坟一斜坡作为试验研究工点,结合现场勘察、监测数据以及斜坡岩土体主要特性、地形地貌、降雨强度与降雨持续时间、地下水位等因素,模拟斜坡单元产生潜在滑动时的临界降雨量,研究降雨对滑坡发生、分布的影响。研究结果表明：各斜坡单元产生潜在滑动时的临界降雨量各不相同,在不同的降雨量及地下水位条件下滑坡降雨阈值模型模拟的潜在滑坡位置主要位于楚勐公路下边坡处,与实际发生滑坡的位置吻合率达80%以上,滑坡降雨阈值模型可实现对斜坡稳定性进行可视化分析与预测,为降雨型滑坡提供一种有效的预测与分析方法。