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1.
Three active earth-slide slopes of Tertiary mudstone were investigated: Slope 1 has an angle of 17 ?4°, Slope 2 of 12.9°, and Slope 3 of 11.6°. Infinite slope analysis indicated that the instability of these three slopes can be well explained by using the residual strength parameters of earth-slide soils near the sliding surface in conjunction with the highest ground water table. The residual angle of shearing resistance, ø'r, plays an important role in the determination of slope angle because it differs greatly among slopes. Mineralogical studies and X-ray diffraction analyses were performed for the clay minerals included in the slope material. The results showed that illite and chlorite were found in Slope 1, and also in Slopes 2 and 3 together with interstratified illite/montmorillonite and montmorillonite. The degree of weathering is progressive in order of Slopes 1, 2 and 3. The alteration of clay minerals by weathering causes the reduction in ø'r -values, i.e., 19.4° in Slope 1 (steep, less weathered) and 12.1-9.2° in Slopes 2 and 3 (gentle, much more weathered). This result indicates that the degree of weathering has a great influence on the value of ø'r, which in turn determines the slope angle.  相似文献   

2.
利用高分辨率无人机航拍影像,结合基本地质资料,分析了影响2014年8月3日鲁甸M_S6.5地震震后崩塌滑坡分布的主要因素,使用M5'模型树算法建立了崩塌滑坡密度与其影响因子间的分段线性模型,并检验了该模型的预测性能。结果表明,地震诱发的崩塌滑坡分布受断层距、岩土体结构强度、坡度、植被条件等的影响,其中,断层距、岩土体结构强度及坡度等为主要影响因素;崩塌滑坡易发生在结构破裂区及坡度为38°~50°的区域,其分布密度随断层距的增加而减小;利用M5'模型树算法建立的模型体现出崩塌滑坡分布与其影响因子间复杂的非线性关系,模型检验结果显示,理论模型与实际关联函数间的相关系数达到0.88,因此,可利用该模型预测地震诱发的崩塌滑坡的分布。  相似文献   

3.
Slope frequency distributions are computed from Digital Elevation Models (DEMs) of 18 areas from five different geographic and physiographic regions. Over 160,000 slope estimates are used in the definition of the slope frequency distribution for each area. Analysis of several transformations of the slope data indicates that no single transformation is capable of normalizing all slope distributions. This is, in part, due to the arbitrary placement of the boundaries of the map sheets used in the data collection. The square root of sine, however, provides better results than sine, log-tangent, or several other transformations. The degree of (positive) skewness of gradients in degrees correlates with the proportion of slopes below 2° or 5° (rs = + 0·93), as does the kurtosis (rs = + 0·91).  相似文献   

4.
Landsliding induced by earthquakes and rainstorms in montane regions is not only a sculptor for shaping the landscape, but also a driver for delivering sediments and above‐ground biomass downstream. However, the terrain attributes of earthquake‐ and rainstorm‐induced landslides are less discussed comprehensively in Taiwan. As part of an island‐wide inventory, we here compare and contrast the landslide terrain attributes resulting from two catastrophic events: the Chi‐Chi earthquake (M w = 7.6, September 1999) and typhoon Morakot (rainfall >2500 mm, August 2009). Results show that the earthquake‐induced landslides are relatively small, round‐shaped and prone to occur primarily in middle and toe of slopes. In contrast, the rainstorm‐induced landslides are larger, horseshoe‐shaped and preferentially occurring in slope toes. Also, earthquake‐induced landslides, particularly large landslides, are usually found at steeper gradients, whereas rainstorm‐induced landslides aggregate at gradients between 25° and 40°. Lithologic control plays a secondary role in landsliding. From an island‐wide perspective, high landslide density locates in the region of earthquake intensity ≥ VI or one‐day rainfall ≥600 mm day?1. Through the landslide patterns and their terrain attributes, our retrospective approach sheds light on accessing the historical and remote events for close geophysical investigations. Finally, we should bear in mind that the landslide location, size, and terrain attributes varying with triggers may affect the landscape evaluation or biogeochemical processes in landslide‐dominated regions. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

5.
Knowledge of the mechanisms of rain‐induced shallow landslides can improve the prediction of their occurrence and mitigate subsequent sediment disasters. Here, we examine an artificial slope's subsurface hydrology and propose a new slope stability analysis that includes seepage force and the down‐slope transfer of excess shear forces. We measured pore water pressure and volumetric water content immediately prior to a shallow landslide on an artificial sandy slope of 32°: The direction of the subsurface flow shifted from downward to parallel to the slope in the deepest part of the landslide mass, and this shift coincided with the start of soil displacement. A slope stability analysis that was restricted to individual segments of the landslide mass could not explain the initiation of the landslide; however, inclusion of the transfer of excess shear forces from up‐slope to down‐slope segments improved drastically the predictability. The improved stability analysis revealed that an unstable zone expanded down‐slope with an increase in soil water content, showing that the down‐slope soil initially supported the unstable up‐slope soil; destabilization of this down‐slope soil was the eventual trigger of total slope collapse. Initially, the effect of apparent soil cohesion was the most important factor promoting slope stability, but seepage force became the most important factor promoting slope instability closer to the landslide occurrence. These findings indicate that seepage forces, controlled by changes in direction and magnitude of saturated and unsaturated subsurface flows, may be the main cause of shallow landslides in sandy slopes. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

6.
Better knowledge regarding internal soil moisture and piezometric responses in the process of rainfall-induced shallow slope failures is the key to an effective prediction of the landslide and/or debris flow initiation. To this end, internal soil moisture and piezometric response of 0.7-m-deep, 1.5-m-wide, 1.7-m-high, and 3.94-m-long semi-infinite sandy slopes rested on a bi-linear impermeable bedrock were explored using a chute test facility with artificial rainfall applications. The internal response time defined by the inflection point of the soil moisture and piezometric response curves obtained along the soil–bedrock interface were closely related to some critical failure states, such as the slope toe failure and extensive slope failures. It was also found that the response times obtained at the point of abrupt bedrock slope decrease can be used as indicators for the initiation of rainfall-induced shallow slope failures. An investigation of spatial distributions of soil water content, ω (or degrees of saturation, Sr), in the slope at critical failure states shows that the 0.2 m – below – surface zone remains unsaturated with Sr 40–60%, regardless of their distances from the toe and the rainfall intensity. Non-uniform distributions of ω (or Sr) along the soil–bedrock interface at critical failure states were always associated with near-saturation states (Sr 80–100%) around the point of bedrock slope change or around the transient ‘toe’ upstream of the slumped mass induced by the retrogressive failure of the slope. These observations suggest the important role of the interflow along the soil–bedrock interface and the high soil water content (or high porewater pressure) around the point of bedrock slope deflection in the rainfall-induced failure of sandy slopes consisting of shallow impermeable bedrocks. The present study proposes an ‘internal response time’ criterion to substantiate the prediction of rainfall-induced shallow slope failures. It is believed that the ‘internal response time’ reflects the overall characteristics of a slope under rainfall infiltration and can be as useful as the conventional meteorology-based threshold times. The ‘internal response time’ theory can be generalized via numerical modeling of slope hydrology, slope geology and slope stability in the future.  相似文献   

7.
In undisturbed tropical montane rainforests massive organic layers accommodate the majority of roots and only a small fraction of roots penetrate the mineral soil. We investigated the contribution of vegetation to slope stability in such environments by modifying a standard model for slope stability to include an organic layer with distinct mechanical properties. The importance of individual model parameters was evaluated using detailed measurements of soil and vegetation properties to reproduce the observed depth of 11 shallow landslides in the Andes of southern Ecuador. By distinguishing mineral soil, organic layer and above‐ground biomass, it is shown that in this environment vegetation provides a destabilizing effect mainly due to its contribution to the mass of the organic layer (up to 973 t ha? 1 under wet conditions). Sensitivity analysis shows that the destabilizing effect of the mass of soil and vegetation can only be effective on slopes steeper than 37.9°. This situation applies to 36% of the study area. Thus, on the steep slopes of this megadiverse ecosystem, the mass of the growing forest promotes landsliding, which in turn promotes a new cycle of succession. This feedback mechanism is worth consideration in further investigations of the impact of landslides on plant diversity in similar environments. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

8.
The infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models. Its assumption that shallow landslides are infinitely long (in a downslope direction) is usually considered valid for natural landslides on the basis that they are generally long relative to their depth. However, this is rarely justified, because the critical length/depth (L/H) ratio below which edge effects become important is unknown. We establish this critical L/H ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two‐dimensional slopes, assuming that the difference between the predictions is due to error in the infinite slope method. We test the infinite slope method for six different L/H ratios to find the critical ratio at which its predictions fall within 5% of those from the finite element method. We repeat these tests for 5000 synthetic slopes with a range of failure plane depths, pore water pressures, friction angles, soil cohesions, soil unit weights and slope angles characteristic of natural slopes. We find that: (1) infinite slope stability predictions are consistently too conservative for small L/H ratios; (2) the predictions always converge to within 5% of the finite element benchmarks by a L/H ratio of 25 (i.e. the infinite slope assumption is reasonable for landslides 25 times longer than they are deep); but (3) they can converge at much lower ratios depending on slope properties, particularly for low cohesion soils. The implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse (e.g. >25 m). However, it may also be valid even at much finer grid resolutions (e.g. 1 m), because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have L/H ratios less than 25. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

9.
A catalogue of historical landslides, 1951–2002, for three provinces in the Emilia‐Romagna region of northern Italy is presented and its statistical properties studied. The catalogue consists of 2255 reported landslides and is based on historical archives and chronicles. We use two measures for the intensity of landsliding over time: (i) the number of reported landslides in a day (DL) and (ii) the number of reported landslides in an event (Sevent), where an event is one or more consecutive days with landsliding. From 1951–2002 in our study area there were 1057 days with 1 ≤ DL ≤?45 landslides per day, and 596 events with 1 ≤ Sevent ≤ 129 landslides per event. In the first set of analyses, we find that the probability density of landslide intensities in the time series are power‐law distributed over at least two‐orders of magnitude, with exponent of about ?2·0. Although our data is a proxy for landsliding built from newspaper reports, it is the first tentative evidence that the frequency‐size of triggered landslide events over time (not just the landslides in a given triggered event), like earthquakes, scale as a power‐law or other heavy‐tailed distributions. If confirmed, this could have important implications for risk assessment and erosion modelling in a given area. In our second set of analyses, we find that for short antecedent rainfall periods, the minimum amount of rainfall necessary to trigger landslides varies considerably with the intensity of the landsliding (DL and Sevent); whereas for long antecedent periods the magnitude is largely independent of the cumulative amount of rainfall, and the largest values of landslide intensity are always preceded by abundant rainfall. Further, the analysis of the rainfall trend suggests that the trigger of landslides in the study area is related to seasonal rainfall. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
The extrapolation of results from field trials to larger areas of land for purposes of regional impact assessment is an important issue in geomorphology, particularly for landform properties that show high stochastic variability in space and time, such as shallow landslide erosion. It is shown in this study, that by identifying the main driver for spatial variability in shallow landslide erosion at field scales, namely slope angle, it is possible to develop a set of generic functions for assessing the impact of landslides on selected soil properties at larger spatial scales and over longer time periods. Research was conducted within an area of pastoral soft‐rock Tertiary hill country in the North Island of New Zealand that is subject to infrequent high intensity rainfall events, producing numerous landslides, most of which are smaller than several hundred square metres in size and remove soil to shallow depths. All landslides were mapped within a 0·6 km2 area and registered to a high resolution (2 m) slope map to show that few landslides occur on slopes < 20° and 95% were on slopes > 24°. The areal density of landslides from all historical events showed an approximately linear increase with slope above 24°. Integrating landslide densities with soil recovery data demonstrates that the average value of a soil property fluctuates in a ‘saw‐tooth’ fashion through time with the overall shape of the curve controlled by the frequency of landslide inducing storm events and recovery rate of the soil property between events. Despite such fluctuations, there are gradual declines of 7·5% in average total carbon content of topsoil and 9·5% in average soil depth to bedrock, since the time of forest clearance. Results have application to large‐scale sediment budget and water quality models and to the New Zealand Soil Carbon Monitoring System (CMS). Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

11.
We examined the characteristics of landslides triggered by the 2016 Kumamoto earthquake (Mw = 7.0: focal depth=10.0 km) in forests and grasslands within two affected watersheds (Tokosegawa: 6.9 km2 and Nigorigawa: 6.1 km2) in southwestern Japan. We identified 190 landslides using aerial photographs and analyzed their sizes by geographic information system (GIS). Field investigations were conducted to obtain landslide depth, volume and residual sediment for 38 selected landslides (21 in forests and 17 in grasslands). The minimum area of detected landslides in grasslands (400 m2) was smaller than in forests (1000 m2), probably because of reduced detectability of landslides under tree cover. The ratio of total area occupied by landslides for a given range of slope gradient in the watersheds increased from 3.2% on gentle grassland slopes (10–15°) to 15.5% on steep (>45°) slopes, whereas the maximum landslide-area ratio in forest sites (7.4%) occurred on relatively gentle slopes (25–30°). Estimated landslide volume ranged from 27 to 9622 m3, based on mean depth of each landslide measured around individual landslide scars. Moreover, the volumetric ratio of landslide deposit volume to total landslide volume exceeded 100% for 48% of the landslides within forests and 35% of the landslides within grasslands. Our findings show that land cover had extensive and recognizable effects on the characteristics of landslides and resulting in-channel sediment accumulations. Resetting sediment dynamics after earthquakes associated with different land cover distributions needs to be considered within watersheds. © 2019 John Wiley & Sons, Ltd.  相似文献   

12.
Understanding water infiltration and transfer in soft‐clay shales slopes is an important scientific issue, especially for landsliding. Geochemical investigations are carried out at the Super‐Sauze and Draix‐Laval landslides, both developed in the Callovo‐Oxfordian black marls, with the objective to define the origin of the groundwater. In situ investigations, soil leaching experiments and geochemical modeling are combined to identify the boundaries of the hydrological systems. At Super‐Sauze, the observations indicate that an external water flow occurs in the upper part of the landslide at the contact between the weathered black marls and the overlying formations, or at the landslide basement through a fault network. Such external origin of water is not observed at the local scale of the Draix‐Laval landslide but is detected at the catchment scale with the influence of deep waters in the streamwater quality of low river flows. Hydrogeological conceptual models are proposed emphasizing the role of the interactions between local (slope) and regional (catchment) flow systems. The observations suggest that this situation is a common case in the Alpine area. Expected consequences of the regional flows on slope stability are discussed in term of rise of pore water pressures and physicochemical weathering of the clay shales.  相似文献   

13.
The morphological consequences of paraglacial modification of valley-side drift slopes are investigated at six sites in Norway. Here, paraglacial slope adjustment operates primarily through the development of gully systems, whereby glacigenic sediment is stripped from the upper drift slope and redeposited in debris cones downslope. This results in an overall lowering of average gradient by up to 4·5° along gully axes. In general, slope profile adjustment appears to be characterized by a convergence of slope profiles towards an ‘equilibrium form’ with an upper rectilinear slope gradient at 29°± 4° and a range of concavities of approximately 0·0 to 0·4. After initial rapid incision, further gully deepening is limited, but gullies become progressively wider as sidewall gradients decline to c. 25°, after which parallel retreat appears to predominate. The final form of mature paraglacial gully systems consists of an upper bedrock-floored source area, a mid-slope area of broad gullies whose sidewalls rest at stable, moderate gradients, and a lower slope zone where gullies discharge onto the surfaces of debris cones and fans. Some gullies appear to have attained this final form and have stabilized following exhaustion of readily entrainable sediment within decades of gully initiation. At most sites, paraglacial activity has transformed steep drift-mantled valley sides into gullied slopes where an average of c. 2–3 m of surface lowering has taken place. At the most active sites, these average amounts imply minimum erosion rates averaging c. 90 mm a−1 since gully initiation, which highlights the extreme rapidity of paraglacial erosion of deglaciated drift-mantled slopes. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

14.
In this work, a transient rainfall infiltration and grid‐based regional slope‐stability model (TRIGRS) was implemented in a case study of Yan'an City, Northwest China. In this area, widespread shallow landslides were triggered by the 12 July 2013 exceptional rainstorm event. A high‐resolution DEM, soil parameters from in‐situ and laboratory measurements, water table depths, the maximum depth of precipitation infiltration and rain‐gauge‐corrected precipitation of the event, were used as inputs in the TRIGRS model. Shallow landslides triggered on the same day were used to evaluate the modeling results. The summarized results are as follows: (i) The characteristics and distribution of thirty‐five shallow landslides triggered by the 12 July 2013 rainfall event were identified in the study area and all were classified as shallow landslides with the maximum depth, area and volume less than 3 m, 200 m2 and 1000 m3, respectively, (ii) Four intermediate factor of safety (FS) maps were generated using the TRIGRS model to represent the scenarios 6, 12, 18 and 24 hours after the storm event. The area with FS < 1 increased with the rainfall duration. The percentage of the area with FS < 1 was 0.2%, 3.3%, 3.8% and 5.1% for the four stages, respectively. Twenty‐four hours after the rainstorm, TRIGRS predicted that 1255 grid cells failed, which is consistent with the field data. (iii) TRIGRS generated more satisfactory results at a given precipitation threshold than SINMAP, which is ideal for landslide hazard zoning for land‐use planning at the regional scale. Comparison results showed that TRIGRS is more useful for landslide prediction for a certain precipitation threshold, also in the regional scale. (iv) Analysis of the responses of loess slope prone to slope failure after different precipitation scenarios revealed that loess slopes are particularly sensitive to extended periods of heavy precipitation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
On many more or less loamy soils, rill erosion is reported to start on slopes that are equal to or steeper than 2–3°; critical Froude numbers for the start of rill wash on these slopes vary between 2·0 and 3·0. This explains why colluvial deposition often occurs on slopes below 2–3°, when water spreads out at the downslope extremities of the rills. The critical hydraulic conditions for loess loam deposition were tested in the laboratory for slopes of 0·5° and 2°, applying unit-discharges (q) up to 10 cm2/s. It appeared from these experiments that for afterflow, without raindrop impact, deposition starts for critical load concentrations (ccr) varying between several g/1 and about 60 g/l. Under rain ccr amounts to a minimum value of 100–125 g/l and it increases when the runoff film becomes thinner. Nevertheless, deposition in pluvial runoff is also possible, as was the case during the Weichselian, according to data from quarries in Belgium and in The Netherlands. A modified Kalinske equation is proposed for ccr prediction, with the introduction of a typical empirical coefficient Cr and considering such factors as shear stress and mean particle size. Massive sedimentation may occur when it stops raining and afterflow starts, since ccr values are then much lower. It is shown from the Shields' diagram that loamy suspensions are more sensitive to sedimentation than sands in clear water.  相似文献   

16.
A database of seismically-induced landslides in the Betic Cordillera is presented. Data included were classified according to landslide typology. Most of them (≈80%) correspond to small size, disrupted landslides (including rock/earth falls and earth slides that disorganize as mass-movement progresses) and the remaining consist mainly of coherent landslides (slumps in soils and rock-slides). Deep seated induced landslides are uncommon in the study zone and have occurred only after the few events of large magnitude reported in the Cordillera. Data available show that events of small magnitude (Mw<5.0) can induce instabilities in the study zone for comparatively large distances (>10 km) when compared with available upper bound curves for maximum epicentral distances for seismic induced landslides, that concentrate along areas prone to landsliding, like river banks or slopes on soft materials, which points out the importance of the role of slope susceptibility on the occurrence of instabilities during earthquakes. Landslides in the database are then analyzed and a power-law relationship that relates earthquake size, measured as epicentral intensity (Io), to maximum distance of induced landslide valid for the study zone is proposed. Although included data represent a clear partial and incomplete dataset, they show the landslide state of knowledge for this region.  相似文献   

17.
The analysis of the positive feedback between landslides and erosion requires determination of the precise temporal and spatial relations between events of colluvium delivery and fluvial erosion. In our study we use decennial datasets on the occurrence of landsliding and erosion achieved through dendrochronological methods. Four sites covering areas of landslide slopes and adjacent valley floors with stream channels were studied. Landsliding on slopes was dated from the tree‐ring eccentricity developed in stems tilted due to bedrock instability. Erosion in channels was dated using the wood anatomy of roots exposed by erosion of the soil cover. Analysis of the temporal relations between dated landsliding, erosion and precipitation record has revealed that two types of repeating sequences can be observed: (1) rainfall → landsliding → erosion; (2) rainfall → erosion → landsliding. These sequences are an indication of the occurrence of slope‐channel positive feedback in the sites studied. In the first type, landsliding triggered by rainfall delivers colluvia into the valley floor and causes its narrowing, which in turn causes increased erosion. In the second type erosion triggered by rainfall disturbs the slope equilibrium and causes landsliding. Landsliding and erosion, once triggered by precipitation, can occur alternately in years with average precipitation and reinforce one another. Bidirectional coupling between landsliding and channel erosion was shown notably through the effects of channel shifting and forced sinuosity and by increased erosion of the slopes opposite the active landslides. Observations also suggest that the repetition of sequences described over longer periods of time can lead to a general widening of the valley floor at the expense of slopes and to a gradual change of the valley cross‐profile from narrow, V‐shaped into a wide flat‐bottomed. Thus landsliding–erosion coupling/positive feedback was recognized as an important factor shaping hillslope–valley topography of the mid‐mountain areas studied. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

18.
Different mountain shapes in sedimentary sequences in the Canadian Rockies were enhanced by glacial erosion and have been modified postglacially by gravity-driven slope processes. Slope modification by both glacial erosion and postglaciation landslides is related to rock structure, particularly bedding dip, rock mass strength and slope geometry. Five mountain peak shapes in monoclinal sequences each fall into different ranges of bedding dips. Castellate (1) and matterhorn (2) mountains occur in sub-horizontal beds and their slopes on all sides follow combinations of bedding planes and joints. The overall slopes are generally 37 to 65° and oblique to both bedding and joints. Slopes in sub-horizontal beds may be controlled by their rock mass strength. Cuestas (3) develop in gently to moderately dipping beds. Dip slopes and steeper, normal escarpments form their cataclinal and anaclinal sides respectively, with the dihedral angle between them about 90°. Hogbacks (4) in moderately to steeply dipping beds have similar slope angles on both cataclinal and anaclinal slopes. Cataclinal slopes are either dip slopes or underdip slopes but anaclinal slopes are often steepened escarpments; the dihedral angle between the slopes is usually less than 90°. Dogtooth (5) mountains occur in steeply dipping to sub-vertical beds and the dihedral angle can be as low as 60°. Slope gradients in inclined beds are closely related to landslides, whose modes are controlled by bedding dips. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

19.
Transfer of atmospheric N deposition on shallow‐soil forested basins on the Canadian Shield to receiving water bodies may be enhanced by rapid preferential flow along the soil–bedrock interface (BR runoff) on basin slopes. Controls on BR runoff, partitioning of event and pre‐event water contributions to this flow, and implications of this partitioning for N fluxes in BR runoff were studied under natural and artificial inputs to an instrumented slope. BR runoff as a fraction of water inputs to the slope increased with antecedent soil wetness and input depth. Event water contributions to BR runoff initially increased with antecedent soil wetness, but then declined at large antecedent soil wetness. Export of applied NH4+ from the slope was maximized when event water contributions containing large NH4+ concentrations dominated BR runoff; however, there was no relationship between the fraction of NO3? application transported in BR runoff and either application input or the event water fraction of that runoff. The applicability of our results to other shallow‐soil areas of the Canadian Shield is limited by artificial N inputs to the slope in excess of natural loads and by low rates of N mineralization and negligible nitrification in the slope's soils. Nevertheless, the study reinforces the need to consider how the hydrologic, geometric and pedologic properties of forest slopes interact with biotic and abiotic soil processes to control N transport and transformation. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

20.
This paper uses the catastrophic landslide that occurred in Zhongxing Town, Dujiangyan City, as an example to study the formation mechanism of landslides induced by heavy rainfall in the post-Wenchuan earthquake area. The deformation characteristics of a slope under seismic loading were investigated via a shaking table test. The results show that a large number of cracks formed in the slope due to the tensile and shear forces of the vibrations, and most of the cracks had angles of approximately 45° with respect to the horizontal. A series of flume tests were performed to show how the duration and intensity of rainfall influence the responses of the shaken and non-shaken slopes. Wetting fronts were recorded under different rainfall intensities, and the depth of rainfall infiltration was greater in the shaken slope than in the non-shaken slope because the former experienced a greater extreme rainfall intensity under the same early rainfall and rainfall duration conditions. At the beginning of the rainfall infiltration experiment, the pore water pressure in the slope was negative, and settling occurred at the top of the slope. With increasing rainfall, the pore water pressure changed from negative to positive, and cracks were observed on the back surface of the slope and the shear outlet of the landslide on the front of the slope. The shaken slope was more susceptible to crack formation than the non-shaken slope under the same rainfall conditions. A comparison of the responses of the shaken and non-shaken slopes under heavy rainfall revealed that cracks formed by earthquakes provided channels for infiltration. Soil particles in the cracks of slopes were washed away, and the pore water pressure increased rapidly, especially the transient pore water pressure in the slope caused by short-term concentrated rainfall which decreased rock strength and slope stability.  相似文献   

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