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1.
Causes of large-scale landslides in the Lesser Himalaya of central Nepal   总被引：1，自引：0，他引：1  
Geologically and tectonically active Himalayan Range is characterized by highly elevated mountains and deep river valleys. Because of steep mountain slopes, and dynamic geological conditions, large-scale landslides are very common in Lesser and Higher Himalayan zones of Nepal Himalaya. Slopes along the major highways of central Nepal namely Prithvi Highway, Narayangadh-Mugling Road and Tribhuvan Highway are considered in this study of large-scale landslides. Geologically, the highways in consideration pass through crushed and jointed Kathmandu Nappe affected by numerous faults and folds. The relict large-scale landslides have been contributing to debris flows and slides along the highways. Most of the slope failures are mainly bechanced in geological formations consisting phyllite, schist and gneiss. Laboratory test on the soil samples collected from the failure zones and field investigation suggested significant hydrothermal alteration in the area. The substantial hydrothermal alteration in the Lesser Himalaya during advancement of the Main Central Thrust (MCT) and thereby clay mineralization in sliding zones of large-scale landslide are the main causes of large-scale landslides in the highways of central Nepal. This research also suggests that large-scale landslides are the major cause of slope failure during monsoon in the Lesser Himalaya of Nepal. Similarly, hydrothermal alteration is also significant in failure zone of the large-scale landslides. For the sustainable road maintenance in Nepal, it is of utmost importance to study the nature of sliding zones of large-scale landslides along the highways and their role to cause debris flows and slides during monsoon period.  相似文献   

2.
In late-June, 1998, a series of thunderstorms dropped 16.5 cm (6.5 in.) of rain in a 72-h period over southeastern Ohio, causing extensive flooding, six deaths, and 179 million dollars in property damage. The storms also triggered more than 60 shallow landslides along a 64 km (40-mi) stretch of Interstate 77 between Buffalo and Marietta, Ohio. Almost all of the landslides were translational, occurring along the contact between colluvial soils and the underlying bedrock (shales, claystones, mudstones). Six sites were selected in the affected area for a detailed study of the shallow landslides. At each site, a record was made of the stratigraphy, slope geometry, number of landslides, landslide dimensions, hydrologic conditions, and influence of vegetation on landslide distribution. Both colluvial soils and underlying bedrock were sampled for laboratory investigations, which included determination of natural water content, grain size distribution, Atterberg limits, permeability, slake durability, and shear-strength parameters. Data from laboratory tests were used to perform sensitivity and stability analyses with respect to varying slope angles, strength parameters, and thicknesses of saturated colluvial soil. The results of the study indicate that the shallow landslides along Interstate 77 occurred when the colluvial soils reached 90% to 100% saturation, depending upon the slope angles.  相似文献   

3.
滑坡体水-岩(土)作用是一种复杂的物理化学综合作用,影响坡体的稳定性,但关于目前水-岩(土)相互作用对地质灾害发生方面的影响研究仍较为薄弱。以贵州省鸡场滑坡为研究对象,分析滑坡区岩土体矿物组成和化学成分特征,结合区域内基岩裂隙水、大气降水的成分变化,利用主成分分析方法,研究鸡场滑坡水-岩(土)作用过程,并分析水岩演化作用对滑坡稳定性的影响。结果表明：(1)滑体内玄武岩的风化过程是一种机械破碎-矿物蚀变耦合的水-岩相互作用,发生在“微观-细观-宏观”3种尺度上;(2)选取前3个因子Z1、Z2、Z3(分别占总方差的49.365%、27.135%、15.092%)分析地下水的化学特征,主因子Z1反映了玄武岩原生矿物的溶蚀作用对地下水化学成分的控制作用,主因子Z2反映了地下水的蒸发作用与SiO2溶解度随pH变化的矿物沉淀作用,主因子Z3反映了地下水与岩(土)体间存在离子交换作用且主参与离子为Mg2+和K+  相似文献   

4.
岑巩县大榕滑坡发生于2012年6月29日, 属于大型平缓堆积层滑坡。其主体堆积区斜坡坡度8～20, 主滑区基覆界面倾角4～11; 下伏基岩中存在强风化层; 2009年以来, 有持续人工弃土堆积于左侧汇水区。结合滑坡特征及三维数值分析可见, 大榕滑坡是由持续人工弃土堆积和强降雨共同诱发产生, 弃土堆积区首先局部失稳, 导致坡脚破坏而逐步引发滑坡整体失稳; 滑面位于下伏强风化层中。结合典型案例, 总结了大型平缓堆积层滑坡结构特征, 强降雨是必要诱发因素; 失稳时, 局部往往带动下伏基岩失稳。  相似文献   

5.
2013年1月11日云南省镇雄县发生特大山体滑坡灾害,造成赵家沟村民小组46人遇难和严重经济损失。基于数次滑坡现场调查和勘查所获得的基础数据,本文对滑坡特征及变形失稳机理进行了较系统的研究。（1）滑坡发育在崩坡积体中,坡体自后缘向前缘具有黏粒含量、密实度增加而孔隙度、透水性减小的特点;（2）滑坡后缘为飞仙关组强风化粉砂岩与崩坡积体的接触界面,滑动带为崩坡积体内含砾粉质黏土坡积层;（3）滑坡发生前,坡体后缘已发育张拉裂缝,前缘已发生小型鼓胀破坏,属典型蠕滑-拉裂变形破坏模式;（4）滑坡具有分块先后滑动特点,左、右及后缘边界坡体在主滑体后发生滑动,滑移过程中也存在分区现象;（5）滑带土为低液限含砾黏性土,呈液化流塑状态,抗剪强度低;（6）启程高速是斜坡应变能长期积累、瞬间释放的结果,滑程高速与滑坡体冲击液化有关,部分滑体存在临空飞行现象。建议加强滑源区两侧裂缝的变形监测和乌蒙山区类似坡体的灾害预警。  相似文献   

6.
福建南安市地质灾害特征及防治对策   总被引：1，自引：0，他引：1  
根据福建省南安市地质灾害调查和区划工作成果，总结该区地质灾害类型主要有滑坡、崩塌和泥石流，尤以滑坡和崩塌的危害性最大。全市共发现地质灾害140处，其中滑坡72处(含土质滑坡67处)，崩塌65处(土质崩塌55处)，泥石流3处。南安市地质灾害具有分布广、规模小、突发性强、危害性大等特点，其控制因素：包括地形地貌、岩土体性质、降雨和人类工程活动等。南安市属于低山丘陵地貌，其中低山山地占全市面积的50％，丘陵、台地占25％；花岗岩、凝灰岩分布面积广，其残积层厚度较大，约5～17m，岩性为残积砾(砂)质粘性土，是致灾的主要土体。98％的地质灾害与降雨有直接的关系，当过程雨量达到100mm时，滑坡开始产生；过程雨量大于200mm时，滑坡普遍发生。直接与人类工程活动有关的地质灾害共134处，占地质灾害总数的95％，坡脚开挖是引发地质灾害的主要因素，占调查总数的84．4％。论文还提出了地质灾害防治的相应对策。  相似文献   

7.
Ashland  Francis X. 《Landslides》2021,18(6):2159-2174

The potential for widespread landslides is generally increased when extraordinary wet periods occur during times of elevated subsurface hydrologic conditions. A series of storms in early 2018 in Pittsburgh, Pennsylvania, overlapped with a period of increased shallow soil moisture and rising bedrock groundwater levels resulting from seasonally diminished evapotranspiration and induced widespread landslides in the region. Most of the landslides were shallow slope failures in colluvium, landslide deposits, and/or fill. However, deep-seated landslide activity also occurred and corresponded with record cumulative precipitation from late February to April and bedrock groundwater levels rising to an annual high. Landslides blocked or damaged roads, adversely affected multiple houses, disrupted electrical service, crushed vehicles, and resulted in considerable economic losses. The initial landslides occurred during or immediately after a rare period of three successive days of heavy rain that began on February 14. Subsequent landslides between late February and April were induced by multiday storms with smaller rainfall totals. As shallow soil moisture at a monitoring site rose above a volumetric water content of 32%, the mean rainfall intensities necessary to induce slope failure in colluvium and other surficial deposits decreased. Deep-seated landslide movement occurred in the region mostly when the groundwater level in a bedrock observation well was shallower than 1.7 m. The availability of hydrologic and landslide movement monitoring data during this extraordinary series of storms highlighted the evolution of the landslide hazard with changing moisture conditions and yielded insights into potential hydrologic criteria for anticipating future widespread landslides in the region.

  相似文献   

8.
Sangrumba landslide is one of the largest and the most active landslides in Nepal Himalaya. Geologically the landslide belongs to the Higher Himalaya and consists of Pre-Cambrian biotite–garnet and sillimanite gneiss with some quartzite. The present paper aims at describing various degrees of rock weathering and their effect in Sangrumba landslide. Field study followed by mineralogical, geochemical and geotechnical analyses of the collected rock and soil samples from the landslide zone were used in characterizing weathering degree. The gneisses are intensely weathered while quartzite is unweathered. Petrographical and X-ray diffraction analyses showed that the rocks in the landslide zone had undergone weathering process with the formation of different types of clay minerals as kaolinite, vermiculite, smectite and chlorite. This was further confirmed by the Scan Electron Microscope and Energy Dispersive X-ray analyses. These clay minerals drastically reduced the rock strength facilitating the extensive failure of the Sangrumba landslide. The major and trace element composition of the rock and soil samples was calculated from the XRF analyses. The geochemical analyses and weathering indexes of rocks showed that they are significantly weathered and had a major influence in the formation of the Sangrumba landslide. In addition, mechanical strength measurement of rock/soil showed that the strength drastically decreases as the weathering intensity increases. Rainfall followed by the rock type are the most dominant parameters influencing the weathering process which leads to the formation of large landslide as the present one. These findings can be used in other areas with similar geological and topographical conditions.  相似文献   

9.
为了研究堆积层-基岩接触面滑坡的形成机理,以陕西省岚皋县广泛分布的堆积层-基岩接触面滑坡为研究对象,采用野外调查和数理统计的方法,总结了该类型滑坡的基本特征,并以祖师庙滑坡为例,借助室内试验和数值模拟手段,研究了堆积层-基岩接触面滑坡的形成机理。结果表明:1)堆积层-基岩接触面滑坡主要发育在坡度为20°~40°、下伏基岩为碎裂状结构的斜坡,多为浅表层滑坡;2)碎石土和堆积层-基岩接触面的内摩擦角随含水量增大而降低,堆积层-基岩接触面是斜坡变形破坏的软弱结构面;3)细颗粒物质的增加降低了堆积层-基岩接触面的内摩擦角,且细颗粒粒径越小,内摩擦角也越小,在饱和状态下降幅度越大;4)因细颗粒物质在堆积层-基岩接触面处聚集造成的强度降低和因水文地质条件改变造成的滑带土饱和是祖师庙滑坡主要的诱发因素。研究结果对揭示堆积层-基岩接触面滑坡的形成机理和地质灾害防治具有一定的指导意义。  相似文献   

10.
This study aimed to identify displacement properties of landslide masses at the initiation of failure and factors that affect the landslides activities in areas where quick clay is found. We set up a research site in a quick clay deposit area in Norway and monitored the displacements of landslide masses and meteorological and hydrological factors for a long period of time using an automatic monitoring system. The system collected data for two landslides that occurred at the site from the start of their movement until their ultimate collapse.

The two landslides that were monitored showed definite secondary and tertiary creep stages before they collapsed. One of the landslides moved from the secondary stage to the tertiary creep stage when another landslide occurred nearby. The tertiary stage of this landslide showed reconstruction of short primary, secondary, and tertiary creep stages. These phenomena suggested that (1) the stress at the end of the landslide mass was released during the nearby landslide, and (2) a new stress distribution was formed in the landslide mass. The critical strain differed for 14 times between the two landslide masses we monitored. The difference was likely attributable to the difference in the contents of quick clay, which shows small critical stress against slope failure, as well as topological factors.

Our analyses of the effects of hydrological and meteorological factors on landslides showed that the precipitation of 3 and 10 days before six slope failures as the final stages of the landslides that had occurred in the research area was no different from the mean precipitation of periods that showed no slope failure, suggesting that precipitation had no direct effects on the collapse of the landslide masses. On the other hand, the traveling velocities of the landslide masses during the secondary creep stage, which was prior to their collapse, were affected by the water content of the soil and precipitation (and the amount of snowmelt water), but was little correlated with the pore-water pressure of the quick clay layer. We also found that the presence of snow cover scarcely affected landslide movements.  相似文献   


11.
Statistical and deterministic methods are widely used in geographic information system based landslide susceptibility mapping. This paper compares the predictive capability of three different models, namely the Weight of Evidence, the Fuzzy Logic and SHALSTAB, for producing shallow earth slide susceptibility maps, to be included as informative layers in land use planning at a local level. The test site is an area of about 450 km2 in the northern Apennines of Italy where, in April 2004, rainfall combined with snowmelt triggered hundreds of shallow earth slides that damaged roads and other infrastructure. An inventory of the landslides triggered by the event was obtained from interpretation of aerial photos dating back to May 2004. The pre-existence of mapped landslides was then checked using earlier aerial photo coverage. All the predictive models were run on the same set of geo-environmental causal factors: soil type, soil thickness, land cover, possibility of deep drainage through the bedrock, slope angle, and upslope contributing area. Model performance was assessed using a threshold-independent approach (the ROC plot). Results show that global accuracy is as high as 0.77 for both statistical models, while it is only 0.56 for SHALSTAB. Besides the limited quality of input data over large areas, the relatively poorer performance of the deterministic model maybe also due to the simplified assumptions behind the hydrological component (steady-state slope parallel flow), which can be considered unsuitable for describing the hydrologic behavior of clay slopes, that are widespread in the study area.  相似文献   

12.
In Nepal, people live in widely spread settlements in the fragile Himalayan terrains, and suffer more from landslides than from any other type of natural disaster. The small-scale rainfall-triggered landslides in the Lesser Himalaya of Nepal are generally shallow (about 0.5 to 2.5 m) and are triggered by changes in the physical property of soil layers during rainfall. The relation between landslides and slope hydrology has received little attention in Himalayan landslide research. Thus, this paper deals with the probability of slope failure during extreme rainfall events by considering a digital elevation model (DEM)-based hydrological model for soil saturation depth and an infinite slope stability model. Deterministic distributed analysis in a geographic information system (GIS) was carried out to calculate the probability of slope failure. A simple method of error propagation was used to calculate the variance of the safety factors and the probability of failure. When normally distributed failure probability values were checked against existing landslides, it was found that more than 50% of the pixels of existing landslides coincided with a high calculated probability of failure. Although the deterministic distributed analysis has certain drawbacks, as described by previous researchers, this study concluded that the calculated failure probability can be utilised to predict the probability of slope failure in Himalayan terrain during extreme rainfall events.  相似文献   

13.
岩溶山区浅层滑坡具有发育规律性差、前期变形迹象小、面小点多等特征,早期识别难度大,难以实现全面调查与监测,因此,对典型案例的成因机理进行研究具有重要意义。2016年7月1日贵州省大方县金星组发生滑坡,共造成23人死亡。金星组滑坡滑体厚度平均仅为4 m,总方量约9.5×104 m3,属于典型的岩溶山区浅层基岩滑坡。研究认为,坡角大于岩层倾角的顺层坡体结构是滑坡发生的主要内在因素,而滑坡发生前的降雨入渗且无有效的排泄途径,导致坡体中的薄层泥岩发生泥化是金星组滑坡发生的直接触发因素。  相似文献   

14.
Landslides are one of the most frequent and common natural hazards in many parts of Himalaya. To reduce the potential risk, the landslide susceptibility maps are one of the first and most important steps in the landslide hazard mitigation. Earth observation satellite and geographical information system-based techniques have been used to derive and analyse various geo-environmental parameters significant to landslide hazards. In this study, a bivariate statistics method was used for spatial modelling of landslide susceptibility zones. For this purpose, thematic layers including landslide inventory, geology, slope angle, slope aspect, geomorphology, slope morphology, drainage density, lineament and land use/land cover were used. A large number of landslide occurrences have been observed in the upper Tons river valley area of Western Himalaya. The result has been used to spatially classify the study area into zones of very high, high, moderate, low and very low landslide susceptibility zones. About 72% of active landslides have been observed to occur in very high and high hazard zones. The result of the analysis was verified using the landslide location data. The validation result shows significant agreement between the susceptibility map and landslide location. The result can be used to reduce landslide hazards by proper planning.  相似文献   

15.
三峡库区崩滑地质灾害频发,堆积层滑坡是最常见的滑坡类型。在分析三峡库区145处库岸堆积层滑坡资料基础上,选取地形地貌、地质岩性和斜坡构造作为控制因素、降水和库水波动作为主要诱发因素,探究堆积层滑坡在上述关键影响因子下的分布发育规律及变形破坏响应特征,阐明内在机理,结果表明:(1)受区域地质构造和基岩地层岩性显著控制,滑坡发育频次和规模沿长江存在显著空间差异性;(2)砂页岩夹煤层岩组(SC)和泥灰岩与砂泥岩互层岩组(MSM)对库区堆积层滑坡危害最大,软岩、“软-硬”互层二元结构和水-岩(土)相互作用是主导滑坡发育的主要影响因素;(3)大多数滑坡涉水,主要发育在10°~30°斜坡上,前缘高程集中在100~175 m,受库水波动影响严重,岸别和斜坡结构对堆积层滑坡发育没有明显控制作用;(4)库区滑坡主要由降雨-库水下降联合诱发滑体前缘滑移-拉裂,引发牵引式滑坡,降雨与库水波动各自对滑体的影响格局和程度存在明显差异。以期研究成果为有针对性的库区滑坡总体防治提供一定的科学指导。  相似文献   

16.
Chong Xu  Xiwei Xu  Guihua Yu 《Landslides》2013,10(4):421-431
On 14 April 2010 at 07:49 (Beijing time), a catastrophic earthquake with Ms 7.1 struck Yushu County, Qinghai Province, China. A total of 2,036 landslides were interpreted from aerial photographs and satellite images, verified by selected field checking. These landslides cover about a total area of 1.194 km2. The characteristics and failure mechanisms of these landslides are presented in this paper. The spatial distribution of the landslides is evidently strongly controlled by the locations of the main co-seismic surface fault ruptures. The landslides commonly occurred close together. Most of the landslides are small; there were only 275 individual landslide (13.5 % of the total number) surface areas larger than 1,000 m2. The landslides are of various types. They are mainly shallow, disrupted landslides, but also include rock falls, deep-seated landslides, liquefaction-induced landslides, and compound landslides. Four types of factors are identified as contributing to failure along with the strong ground shaking: natural excavation of the toes of slopes, which mean erosion of the base of the slope, surface water infiltration into slopes, co-seismic fault slipping at landslide sites, and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by the co-seismic ground shaking. To analyze the spatial distribution of the landslides, the landslide area percentage (LAP) and landslide number density (LND) were compared with peak ground acceleration (PGA), distance from co-seismic main surface fault ruptures, elevation, slope gradient, slope aspect, and lithology. The results show landslide occurrence is strongly controlled by proximity to the main surface fault ruptures, with most landslides occurring within 2.5 km of such ruptures. There is no evident correlation between landslide occurrences and PGA. Both LAP and LND have strongly positive correlations with slope gradient, and additionally, sites at elevations between 3,800 and 4,000 m are relatively susceptible to landslide occurrence; as are slopes with northeast, east, and southeast slope aspects. Q4 al-pl, N, and T3 kn 1 have more concentrated landslide activity than others. This paper provides a detailed inventory map of landslides triggered by the 2010 Yushu earthquake for future seismic landslide hazard analysis and also provides a study case of characteristics, failure mechanisms, and spatial distribution of landslides triggered by slipping-fault generated earthquake on a plateau.  相似文献   

17.
摘 要 竖井作为井下开采矿山的咽喉工程,在矿山的安全生产中起着举足轻重的作用。金川二矿区14行主力回风井位于矿体下盘,井深715.5m,穿过的工程围岩有超基性岩、花岗岩、大理岩、辉绿岩等以及F207断层。该风井于1999年10月开工下掘, 2002年投入使用,2005年3月突然跨塌。本文根据现场调查和数值模拟,分析了风井变形破坏的特征和机制。发现主要有井壁错动开裂、片冒、冒落物冲击井壁等几种破坏形式,并得出在采动影响下最易在以下几个位置发生破坏:①井筒上部（0～200m）,易出现拉裂破坏和围岩整体剪切滑动;②F207断层及其上下接触部位（200～220m）,井筒很有可能在此处发生上下错动,从而导致剪切破坏;③井筒中部（360～460m）,受采动影响较大,可能发生鼓肚子破坏;④井筒下部F16断层影响带（井底以上50m）,岩体在采动影响下将发生松动,从而导致在结构面穿插部位可能发生冒落。  相似文献   

18.
In the last 20 years, major efforts have been made to investigate shallow flow-type landslides. Such phenomena are usually rainfall-induced and in the geological context of Campania (Southern Italy) occur in pyroclastic soils resting on steep slopes mainly constituted by carbonate or volcanic bedrock and by flysch deposits. They are generally complex landslides with an early soil slide and a subsequent flow evolution. In this paper, a database of flowslides occurring in recent years within the flysch deposits of Avellino (Campanian Apennines) is first discussed and then the case study of Bosco de’ Preti landslide on March 4, 2005, is described. The geological and geotechnical characteristics of the soils involved are described and the monitoring of the groundwater heads collected over 1 year from June 2005 to June 2006 is also shown. The last part of the paper illustrates the results of numerical modelling of the landslide triggering to gain insights into such phenomena. Slope stability analyses are preceded by hydrological modelling of the slope based on the monitoring data. Numerical analysis demonstrated that the rainfall during the 2 months preceding the event was able to fully saturate the pyroclastic cover and to establish positive pore water pressure at the depth of the surface of rupture, a soil condition never witnessed in carbonatic contexts. Hence, a combination of antecedent (predisposing factors) and single rainfall events (triggering factors) led to slope failure, as usually happens in pyroclastic soils in carbonatic and volcanic contexts. Finally, analysis of the historical landslides together with detailed investigation of the Bosco de’ Preti case study permitted comparison between flow-type landslides in pyroclastic soils on carbonatic/volcanic bedrock and those on flysch.  相似文献   

19.
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。  相似文献   

20.
Damaging landslides in the Appalachian Plateau and scattered regions within the Midcontinent of North America highlight the need for landslide-hazard mapping and a better understanding of the geomorphic development of landslide terrains. The Plateau and Midcontinent have the necessary ingredients for landslides including sufficient relief, steep slope gradients, Pennsylvanian and Permian cyclothems that weather into fine-grained soils containing considerable clay, and adequate precipitation. One commonly used parameter in landslide-hazard analysis that is in need of further investigation is plan curvature. Plan curvature is the curvature of the hillside in a horizontal plane or the curvature of the contours on a topographic map. Hillsides can be subdivided into regions of concave outward plan curvature called hollows, convex outward plan curvature called noses, and straight contours called planar regions. Statistical analysis of plan-curvature and landslide datasets indicate that hillsides with planar plan curvature have the highest probability for landslides in regions dominated by earth flows and earth slides in clayey soils (CH and CL). The probability of landslides decreases as the hillsides become more concave or convex. Hollows have a slightly higher probability for landslides than noses. In hollows landslide material converges into the narrow region at the base of the slope. The convergence combined with the cohesive nature of fine-grained soils creates a buttressing effect that slows soil movement and increases the stability of the hillside within the hollow. Statistical approaches that attempt to determine landslide hazard need to account for the complex relationship between plan curvature, type of landslide, and landslide susceptibility.  相似文献   

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