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1.
Veerle Vanacker Michiel Vanderschaeghe Gerard Govers Edith Willems Jean Poesen Jozef Deckers Bert De Bievre 《Geomorphology》2003,52(3-4):299-315
In the Ecuadorian Andes, episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common. Consequently, not only considerable financial costs are experienced, but also major ecological and environmental problems arise in a larger geographical area. Sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels. In developing countries world-wide, slope movement hazards are growing: increasing population pressure and economic development force more people to move to potentially hazardous areas, which are less suitable for agriculture and rangelands.This paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process-based slope stability model, which includes a dynamic soil wetness index using a simple subsurface flow model. The model provides a time-varying estimate of slope movement susceptibility, by linking land-use data with spatially varying hydrologic (soil conductivity, evapotranspiration, soil wetness) and soil strength properties. The slope stability model was applied to a high Andean watershed (Gordeleg Catchment, 250 ha, southern Ecuadorian Andes) and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements, as measured in the field with GPS. The proposed methodology allows assessment of the effects of past and future land-use change on slope stability. A realistic deforestation scenario was presented: past land-use change includes a gradual fragmentation and clear cut of the secondary forests, as observed over the last four decades (1963–2000), future land-use change is simulated based on a binary logistic deforestation model, whereby it was assumed that future land-use change would continue at the same rate and style as over the last 37 years (1963–2000). 相似文献
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Vertical trends in architecture and facies of delta systems are preserved in a clastic wedge of an expanding marine half-graben in which tectonics, eustatic sea-level change and climatic change are roughly known from independent evidence. The studied half-graben is situated on Crete (Greece) and part of a larger, E-W-trending extensional domain situated north of the Hellenic subduction zone. The extension seems to be related to the southward migration of the trench (roll-back) in early Late Miocene times. The infill pattern is discussed in the light of theoretical fault-growth models for expanding half-grabens. The geometry of the half-graben fill is typically wedge shaped, with a thickness of nearly 1000 m near the fault scarp thinning to c. 50 m about 20 km away from the scarp. The lower part of the wedge (Stratified Prina Series) contains coarsening-upward units representing progradational, shallow-marine deltas. At the base of the wedge these units are thin and retrogradationally stacked. Upwards in the succession, the units become composite (coarsening-upward subunits), thicker and finer grained. The composite structure, the thickening and the fining trend is related to progressive increase in accommodation space inherent in fault growth. Rapid deepening of the basin from the photic zone (evidenced by intercalated coral and stromatolite beds) up to a depth of 900 m started at the top of the Stratified Prina Series. The deepening continued over some tens of metres of marly sediments of the base of the Kalamavka Formation and may be related to structural collapse of the fault block. After the structural collapse, basin depth remained more or less constant and basin infilling occurred by progradation of deep-water delta systems. These systems are characterized by a muddy delta slope with channelized conglomerates, and by mainly aggradation of prodelta turbidites deposited in small lobes at the base of slope. 相似文献
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基于无人机倾斜摄影技术的崩岗动态变化监测 总被引：3，自引：0，他引：3
利用无人机倾斜摄影技术，对德庆县马圩镇典型崩岗区域进行2016和2017年连续2年的动态监测，结合ArcGIS软件对数据进行处理分析，分析了崩岗在空间上的变化特征。结果表明：1）研究区域2017年崩岗总面积比2016年增加16 401.2 m2，变化率为10.21%，说明研究区的崩岗仍处于发育状态；2）研究区西南偏南方向的崩岗面积减少最明显，总体侵蚀最严重的坡向集中在南向；3）崩岗侵蚀最为强烈的部位发生在海拔高程51~60 m和81~90 m处，整体侵蚀呈现出中下部位大于上部位的现象；4）研究区崩岗近2年的年侵蚀体积量为1 172.68×103 m3。无人机航测数据的质量能够满足无人机摄影测量的规范要求，与传统调查方法相比时效性更高、更方便和成本更低。 相似文献
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An integrated model for predicting rainfall-induced landslides 总被引：2，自引：0，他引：2
This study proposes a novel method that combines a deterministic slope stability model and a statistical model for predicting rainfall-induced landslides. The method first uses the deterministic model to derive the rainfall rate critical to induce slope failure for each land unit. Then it calculates the difference between the critical rainfall threshold and estimated rainfall intensity. Using the difference and estimated rainfall duration as explanatory variables, the method derives a logit (integrated) model to compute landslide occurrence probabilities. To demonstrate the effectiveness of this method, the study used radar rainfall estimates and landslides associated with a typhoon (tropical cyclone) to develop the integrated model and the same types of data associated with another typhoon to validate the model. The model had a modified success rate of 84.0% for predicting landslides and stable areas, and model validation yielded a modified success rate of 87.4%. Both rates were better than those from the critical rainfall model. The main advantage of the integrated model lies in its use of rainfall variables that are not included in calculating the critical rainfall. Also, as a probabilistic model, the integrated model is better suited for decision-making in watershed management. This study has advanced the method for predicting rainfall-triggered landslides. 相似文献
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多数岩质边坡稳定性分析已基本解决了常走向单坡面临空的边坡平面滑动问题。然而,在路堑边坡工程和自然边坡中有很多边坡坡面并不是平面,它包含多个坡面。多坡面边坡包含两个或多个不同走向的坡面。多坡面边坡几何特征不同于单坡面边坡,所以滑动条件也不一样。在赤平投影图上,多坡面的滑动包络线是组成边坡的每个坡面单独投影包络线的组合。为了探讨方便,只讨论了双坡面临空岩质边坡的滑动破坏模式,并将其分为双坡面临空下的平面破坏和楔形体破坏。在赤平投影图上,双坡面滑动区域定义为双坡面边坡滑动包络图中两侧坡面的真倾线之间的面积。如果有一两个节理面真倾向线落在滑动区内,滑动破坏才可能发生。 相似文献
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Experimental modelling of forearc basin development during accretionary wedge growth 总被引：1，自引：0，他引：1
CHRISTOPHE Larroque SYLVAIN Calassou† JACQUES Malavieille† FRANK Chanier‡ 《Basin Research》1995,7(3):255-268
We present results of three sand-box experiments that model the association between tectonic accretion and sedimentation in a forearc basin. Experimental sedimentation occurs step by step in the forearc basin during shortening of the sand wedge. In each experiment, the development of the accretionary wedge leads to the formation of a major backthrust zone. This major deformation zone accounts for the thickening in the rear part of the wedge. In natural settings this tectonic bulge dams sediments that are transported toward the trench from mountainous terrain behind the forearc. We test the variation of friction along the déollement and note the following: (1) shortening of a low-friction wedge involves a mechanical balance between forethrusts and backthrust propagation and this balance is recorded by the sedimentary sequence trapped in the forearc basin. Indeed, if most of the movement occurs along the backthrust, the deepening of the basin will be larger and consequently the thickness of the sedimentary sequence will be greater. (2) Such balance does not exist in the case of a high-friction wedge. (3) Variation of friction along the décollement during shortening of the sand wedge leads to modification in the forearc basin filling. Thus, for similar increments of convergence, the sequence deposited in the forearc basin shows relatively larger thickness when the wedge is shortened above a high-friction décollement. We suggest that contraction and thickening in the rear part of the wedge is an efficient mechanism to, initiate and develop a forearc basin. Thus, this kind of basin occurs in convergent settings, without collapse related to local extension or tectonic erosion. They represent a sedimentary trap on a passive basement, bounded by a tectonic bulge. The Quaternary Hikurangi forearc basin, southeast of the North Island of New Zealand, is bounded by two actively uplifting ridges. Thus, this basin is considered to be a possible example of the basins modelled in our experiments, and we suggest that the limit between the basin and the wedge could be a complex backthrust zone. 相似文献
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对国道321线七宝莲边坡的气候、地质、地貌、水文等条件进行了综合分析，认为该边坡是潜伏着危险的不稳定边坡，其中地质构造、岩体结构、地表水和地下水作用是边坡变表破坏的主要影响因素，建议采用预应力框架挡土墙对边坡进行加固的防护措施。 相似文献
9.
朱静 《云南地理环境研究》1995,7(1):48-57
本文划分出澜沧江中下游斜坡结构类型并分析了各斜坡类型的基本特征、变形机制和演化方式，阐述了斜坡变形破坏对该地区人类经济活动的影响，为评价预测澜沧江中下游斜坡稳定性奠定了基础。 相似文献
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The Molasse Basin of Switzerland evolved through a distinct late Neogene history with initial development as a classic foredeep or foreland basin in response to loading of the lithosphere by the Alpine orogen. In the central and western foreland, the foredeep behaviour was terminated by deformation and uplift of the Jura Mountains in the distal regions of the foredeep. Following the Jura deformation the Plateau Molasse remained largely undeformed as it rode ‘piggy‐back’ style above the decollement feeding displacement into the Jura. Sediment accumulation data for the Molasse suggests that sedimentation in the Plateau Molasse region continued until the basin was inverted at about 5 Ma. We present a mechanical model for this sequence of events in which deformation jumps across much of the basin to the distal Jura because of the dip on the weak evaporitic decollement and the wedge‐shape of the foredeep basin. Subsequently, the Plateau Molasse remained largely undeformed as a result of continued sedimentation in a wedgetop basin, where the physical properties and geometry of the orogenic wedge combine to produce a critical wedge whose critical surface slope would be less than zero and thus should dip towards the Alpine interior. Accommodation space is created over this negative surface–slope segment of the wedge and sedimentation maintains this slope near zero, stabilizing the wedge. We present a simple analytical theory for the necessary conditions for such a ‘negative‐alpha basin’ to develop and be maintained. We compare this theory to the late Neogene evolution of the Alps, Molasse Basin and Jura Mountains and infer physical properties for the decollement. 相似文献
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An investigation of periglacial slope stability in relation to soil properties based on physical modelling in the geotechnical centrifuge 总被引：3，自引：0，他引：3
Results are presented from eight scaled centrifuge modelling experiments designed to investigate mass movement processes on thawing ice-rich slopes. Four pairs of simple planar slope models were constructed, one in each pair being of sufficient gradient to promote slope failure during soil thaw and the second having a gradient below the threshold for instability. Four frost susceptible soils were used, three were normally consolidated and had different clay contents (2%, 12% and 20%) and the fourth comprised the 20% clay soil, but was over consolidated prior to model testing. Modelling protocols included freezing from the surface downwards under an open hydraulic system, and thawing from the surface downwards under an enhanced gravitational field within the geotechnical centrifuge, thereby utilising scaling laws to simulate correct prototype self weight stresses during thaw. Slopes below the stability threshold gradient were subjected to between 2 and 4 cycles of freezing and thawing, simulating annual cycles. Those above the stability threshold were subjected to only one cycle, since they failed during the first thaw phase. Thermal conditions, pore water pressures, surface movements, and profiles of displacement are reported. Measured pore pressures are used in slope stability analyses based on a simple planar infinite slope model. Profiles of solifluction shear strain and mechanisms of slope failure are both shown to be sensitive to small changes in soil properties, particularly clay content and stress history. In all cases, pore pressures rose rapidly immediately following thaw, remained below the threshold for failure in low gradient models, but exceeding the threshold to trigger landslides on steeper slopes. Upward seepage of melt water away from the thaw front contributed to loss of shear strength. Mechanisms of slope failure differed between test soils, ranging from mudflow in non-cohesive silt to active layer detachment sliding in over consolidated silt–clay. During solifluction, shear strain was greatest at the surface in non-cohesive silt and decreased rapidly with depth, but in test soils containing clay, the zone of maximum shear strain was located lower in the displacement profiles. 相似文献
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Rainfall thresholds for landsliding in the Himalayas of Nepal 总被引：5，自引：0，他引：5
Emmanuel J. Gabet Douglas W. Burbank Jaakko K. Putkonen Beth A. Pratt-Sitaula Tank Ojha 《Geomorphology》2004,63(3-4):131-143
Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to three orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 years of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure. 相似文献
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Recession rates for unconsolidated bluffs at 23 sites along Lake Michigan's southeast shore are compared with deep water wave energy probabilities to estimate the relative degradational importance of recurrent 5, 10, 20, 50, and 100-year storms. Recession rates are based on measured bluff crest retreat while wave energies are calculated using standard water wave theory and data interpolated from a meteorologically based hindcast model. Correlation and regression tests suggest the following: (1) although wave energy is certainly a destructive factor, it explains less than half of the variation in bluff crest recession, supporting the interpretation that shorezone erosion here results from the interaction of numerous factors; and (2) over long time periods the total effect of more frequent moderate intensity storms is greater than that from rare, especially high energy events. 相似文献
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《Basin Research》2018,30(4):688-707
Investigations of syn‐sedimentary growth faults in the Last Chance delta (Ferron Sandstone, Utah, USA) show that fault‐bounded half‐grabens arrested high amounts of sand in the mouth bar and/or distributary channel areas. Fault‐controlled morphology causes changes in routing of the delta top to delta front drainage towards the long axis of half‐grabens. Faulting was spatially and temporally non‐systematic, and polyphase, with 3D cusp/listric fault geometries instigated by linkage of variously oriented segments. Hanging wall rollover folds consisting of wedge‐shaped syn‐kinematic sand attest to rapid <1‐m slip increments on faults followed by mild erosion along crests of fault blocks and sedimentary infill of adjacent accommodation. Triangle‐zones in prodelta to delta front muds are located underneath steeper faults and interconnected rotated fault‐flats. Their geometry is that of antiformal stack duplexes, in an arrangement of low‐angle‐to‐bedding normal faults at the base, replaced by folded thrusts upwards. These faults show a brittle, frictional flow deformation mechanism ascribed to early compaction of mud. For syn‐kinematic sand, there is a change from general granular/hydroplastic flow in shear zones to later brittle failure and cataclasis, a transition instigated by precipitation of calcite cement. Extensional faulting in the Last Chance delta was likely controlled by gravity driven collapse towards the delta slope and prodelta, as is commonly observed in collapsing deltas. The trigger and driving mechanism is envisioned as localized loads from sand deposited within distributary channels/mouth bars and fault‐controlled basins along the delta top. A regional tilt and especially displacement of compacted mud below sand bodies towards less compacted muds also contributed to the faulting. 相似文献
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Ferricretes can be formed along some valley-side slopes in the southeastern United States coastal plain as a consequence of erosional exposure of zones of iron precipitation in areas of groundwater discharge. This mode of ferricrete formation was demonstrated due to the recession of estuarine shoreline bluffs after hurricanes in 1996. Iron-precipitation zones exposed by bluff retreat at Flanner Beach, North Carolina in 1996 had formed indurated ferricretes by 1998. This confirms the valley-side groundwater discharge model of ferricrete formation, and shows that, once the zone of iron precipitation is exposed, ferricrete can form in less than two years. The newly formed ferricretes also allow the identification of five distinct stages in their formation: (1) iron precipitation in the zone of water table fluctuation; (2) the formation of brittle iron-cemented layers; (3) exposure by erosion or mass wasting and the first stage of hardening; (4) further hardening into indurated ferricrete; and (5) formation of limonite ferricretes, and impregnation with manganese oxides. The results from Flanner Beach show that the process may proceed from stages two and three to four and five in less than two years, suggesting that only short periods of stability following erosion or mass wasting episodes are necessary to allow ferricrete formation. 相似文献
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Evolution stages of large deep-seated landslides at the front of a subalpine meridional chain (Maritime-Alps, France) 总被引：1，自引：0，他引：1
Studying long term-evolution of gravitational slope evolution is a key to understanding deep-seated landslide processes. This paper deals with three large Deep-Seated Landslides (DSLs) at a front of a subalpine meridional chain, on the “La Marbrière” slope near the town of Grasse (Alpes-Maritimes, France). The geological framework controlling the stability and morphology of the DSLs is associated with thick and tamped Triassic layers of mudstone with gypsum overlain by highly faulted Jurassic limestone. Gravitational deformation affects the entire slope, involving a movement of about 1.1 × 108 m3 of rock material. It creates large disturbances in landscape morphology, such as scarps, counter-slope scarps, trenches and other typical gravitational morpho-structures. Geomorphological mapping coupled with deep electrical resistivity tomography (ERT) reveals a strong correlation between these morpho-structures and inherited brittle tectonic features. This observation relies on spatial and geometrical relations (on the surface and at the depth of more than 150 m, checked by ERT) between the most persistent fault and the gravitational morpho-structures. The specific distribution of the morpho-structures on the basis of their morphological typologies and variations in the stage of evolution of three DSLs provides an interpretation of their kinematics during the last 400 ka. It appears that soft substratums combined with inherited persistent anisotropies are key factors in the development of the DSLs. Indeed, outflow of mudstone due to the lithostatic pressure imposed by individual limestone compartments has led to general slope subsidence. Then, a progressive toppling of a rock mass may have led to the catastrophic rock collapse along bedding planes.The evolution of the DSLs can be divided into three distinct stages represented by three zones: a young collapse stage (zone 1), a pre-collapse stage (zone 2) and an old mature stage (> 400 ka, zone 3). As the DSLs occur on the same slope and in the same geological context, this area offers interesting perspectives for understanding factors controlling the long-term gravitational evolution of slopes. 相似文献
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在应用有限差分FLAC3D软件对黄土高原小流域概化模型塑性屈服区分布规律进行数值模拟的基础上,采用基于FLAC3D的有限元强度折减法和简化一次二阶矩法相结合的方法研究了小流域概化模型重力侵蚀稳定可靠度和破坏概率。结果表明：小流域剪切塑性区域主要分布于坡面和沟坡大部分区域,张拉塑性区域主要分布于梁峁顶和梁峁坡上部;小流域边坡整体破坏概率达到28.6%,高于1%,表明流域重力侵蚀处于高破坏概率范畴之内,处于不可接受的风险水平,需采取适当的工程措施以提高其稳定性;采用安全系数法和可靠度相结合的二元指标评价体系分析和评价边坡稳定性,能获得更为合理、可靠的分析结果。相关数值模拟和稳定可靠度分析结果可应用于流域重力侵蚀研究中,为推动流域侵蚀产沙时空规律研究的深入发展和小流域水土流失综合治理提供科学依据。 相似文献
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新月形沙丘顶部稳定性是风沙地貌学尚未解决的科学问题。研究新月形沙丘的顶部稳定性,对于绿洲边缘风沙运动规律揭示、防沙工程建设和沙区生态环境保护等具有重要的现实意义。选择民勤沙区新月形沙丘,通过测定沙丘各部位风速、风蚀风积和粒度等,分析了新月形沙丘顶部稳定机理。主风向（NW）作用是新月形沙丘最高点与沙脊线重合、沙丘前移和高度降低的过程;反向风（SE）作用是沙丘最高点与沙脊线分离、沙丘背风坡风蚀与沙丘增高的过程。由于研究区以NW风为主,新月形沙丘沿NW-SE方向前移,SE风只能风蚀减缓沙丘背风坡的坡度。人为干预将会阻止或减少从迎风坡向沙丘顶部输送沙量,使得新月形沙丘背风坡尤其是背风坡上部风蚀过程增强,新月形沙丘逐渐过渡为抛物线形沙丘。 相似文献
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滑坡稳定性判别的非计算方法 总被引：2，自引：6，他引：2
用计算来确定滑坡的稳定性，由于参数选取存不确定因素，就必然导致了其计算结果的不确定性。而滑坡稳定性判别的非计算方法，是通过对滑坡发育程度、形成条件的综合分析来确定滑坡的稳定程度的方法。文中通过归纳分析波坡的形成条件，然后从滑坡地貌条件、动力作用、堆积物特征、诱发因素等方面详细阐述了滑坡稳定性判别的方法，最后，例举了川藏公路102滑坡实例对该方法进行了验证。实践证明该方法是滑坡稳定性中非常实用和有效的方法。 相似文献