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1
Kang, Kai, Andrey Ponomarev, Oleg Zerkal, Shiyuan Huang e Qigen Lin. "Shallow Landslide Susceptibility Mapping in Sochi Ski-Jump Area Using GIS and Numerical Modelling". ISPRS International Journal of Geo-Information 8, n. 3 (19 marzo 2019): 148. http://dx.doi.org/10.3390/ijgi8030148.
Testo completoAbstract (sommario):
The mountainous region of Greater Sochi, including the Olympic ski-jump complex area, located in the northern Caucasus, is always subjected to landslides. The weathered mudstone of low strength and potential high-intensity earthquakes are considered as the crucial factors causing slope instability in the ski-jump complex area. This study aims to conduct a seismic slope instability map of the area. A slope map was derived from a digital elevation model (DEM) and calculated using ArcGIS. The numerical modelling of slope stability with various slope angles was conducted using Geostudio. The Spencer method was applied to calculate the slope safety factors (Fs). The pseudostatic analysis was used to compute Fs considering seismic effect. A good correlation between Fs and slope angle was found. Combining these data, sets slope instability maps were achieved. Newmark displacement maps were also drawn according to empirical regression equations. The result shows that the static safety factor map corresponds to the existing slope instability locations in a shallow landslide inventory map. The seismic safety factor maps and Newmark displacement maps may be applied to predict potential landslides of the study area in the case of earthquake occurrence.
2
Montrasio, L., L. Schilirò e A. Terrone. "Physical and numerical modelling of shallow landslides". Landslides 13, n. 5 (2 ottobre 2015): 873–83. http://dx.doi.org/10.1007/s10346-015-0642-x.
Testo completo
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Schilirò, Luca, José Cepeda, Graziella Devoli e Luca Piciullo. "Regional Analyses of Rainfall-Induced Landslide Initiation in Upper Gudbrandsdalen (South-Eastern Norway) Using TRIGRS Model". Geosciences 11, n. 1 (11 gennaio 2021): 35. http://dx.doi.org/10.3390/geosciences11010035.
Testo completoAbstract (sommario):
In Norway, shallow landslides are generally triggered by intense rainfall and/or snowmelt events. However, the interaction of hydrometeorological processes (e.g., precipitation and snowmelt) acting at different time scales, and the local variations of the terrain conditions (e.g., thickness of the surficial cover) are complex and often unknown. With the aim of better defining the triggering conditions of shallow landslides at a regional scale we used the physically based model TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope stability) in an area located in upper Gudbrandsdalen valley in South-Eastern Norway. We performed numerical simulations to reconstruct two scenarios that triggered many landslides in the study area on 10 June 2011 and 22 May 2013. A large part of the work was dedicated to the parameterization of the numerical model. The initial soil-hydraulic conditions and the spatial variation of the surficial cover thickness have been evaluated applying different methods. To fully evaluate the accuracy of the model, ROC (Receiver Operating Characteristic) curves have been obtained comparing the safety factor maps with the source areas in the two periods of analysis. The results of the numerical simulations show the high susceptibility of the study area to the occurrence of shallow landslides and emphasize the importance of a proper model calibration for improving the reliability.
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Schilirò, Luca, José Cepeda, Graziella Devoli e Luca Piciullo. "Regional Analyses of Rainfall-Induced Landslide Initiation in Upper Gudbrandsdalen (South-Eastern Norway) Using TRIGRS Model". Geosciences 11, n. 1 (11 gennaio 2021): 35. http://dx.doi.org/10.3390/geosciences11010035.
Testo completoAbstract (sommario):
In Norway, shallow landslides are generally triggered by intense rainfall and/or snowmelt events. However, the interaction of hydrometeorological processes (e.g., precipitation and snowmelt) acting at different time scales, and the local variations of the terrain conditions (e.g., thickness of the surficial cover) are complex and often unknown. With the aim of better defining the triggering conditions of shallow landslides at a regional scale we used the physically based model TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope stability) in an area located in upper Gudbrandsdalen valley in South-Eastern Norway. We performed numerical simulations to reconstruct two scenarios that triggered many landslides in the study area on 10 June 2011 and 22 May 2013. A large part of the work was dedicated to the parameterization of the numerical model. The initial soil-hydraulic conditions and the spatial variation of the surficial cover thickness have been evaluated applying different methods. To fully evaluate the accuracy of the model, ROC (Receiver Operating Characteristic) curves have been obtained comparing the safety factor maps with the source areas in the two periods of analysis. The results of the numerical simulations show the high susceptibility of the study area to the occurrence of shallow landslides and emphasize the importance of a proper model calibration for improving the reliability.
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Zweifel, Lauren, Maxim Samarin, Katrin Meusburger e Christine Alewell. "Investigating causal factors of shallow landslides in grassland regions of Switzerland". Natural Hazards and Earth System Sciences 21, n. 11 (11 novembre 2021): 3421–37. http://dx.doi.org/10.5194/nhess-21-3421-2021.
Testo completoAbstract (sommario):
Abstract. Mountainous grassland slopes can be severely affected by soil erosion, among which shallow landslides are a crucial process, indicating instability of slopes. We determine the locations of shallow landslides across different sites to better understand regional differences and to identify their triggering causal factors. Ten sites across Switzerland located in the Alps (eight sites), in foothill regions (one site) and the Jura Mountains (one site) were selected for statistical evaluations. For the shallow-landslide inventory, we used aerial images (0.25 m) with a deep learning approach (U-Net) to map the locations of eroded sites. We used logistic regression with a group lasso variable selection method to identify important explanatory variables for predicting the mapped shallow landslides. The set of variables consists of traditional susceptibility modelling factors and climate-related factors to represent local as well as cross-regional conditions. This set of explanatory variables (predictors) are used to develop individual-site models (local evaluation) as well as an all-in-one model (cross-regional evaluation) using all shallow-landslide points simultaneously. While the local conditions of the 10 sites lead to different variable selections, consistently slope and aspect were selected as the essential explanatory variables of shallow-landslide susceptibility. Accuracy scores range between 70.2 % and 79.8 % for individual site models. The all-in-one model confirms these findings by selecting slope, aspect and roughness as the most important explanatory variables (accuracy = 72.3 %). Our findings suggest that traditional susceptibility variables describing geomorphological and geological conditions yield satisfactory results for all tested regions. However, for two sites with lower model accuracy, important processes may be under-represented with the available explanatory variables. The regression models for sites with an east–west-oriented valley axis performed slightly better than models for north–south-oriented valleys, which may be due to the influence of exposition-related processes. Additionally, model performance is higher for alpine sites, suggesting that core explanatory variables are understood for these areas.
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Urlaub, Morelia, Isabel Kratzke e Berit Oline Hjelstuen. "A numerical investigation of excess pore pressures and continental slope stability in response to ice-sheet dynamics". Geological Society, London, Special Publications 500, n. 1 (19 dicembre 2019): 255–66. http://dx.doi.org/10.1144/sp500-2019-185.
Testo completoAbstract (sommario):
AbstractSubmarine landslides are common at glaciated continental margins. The onset of large-scale landslides coincides with the initiation of Northern Hemisphere glaciations in the Quaternary. This implies that processes related to glacial cycling provide favourable conditions for submarine landslides at high-latitude margins. Potential processes include glacial deposition patterns and enhanced seismicity. It is also possible that advances and retreats of ice sheets, a highly dynamic process in geological terms, makes slopes discernible to failure by modifying the stress regime. Here, we quantify this effect using 2D finite element modelling of a glaciated continental margin. Different model runs investigate the pore-pressure development in homogeneous, as well as layered, slopes during glaciation when loaded by an ice stream with one or more ice advances. Ice streams cause significant variations in excess pore pressure in the very shallow sediment sequences at the continental shelf. However, lateral fluid flow is not efficient enough to increase pore pressures significantly at the slope, where large-scale submarine slides are observed. Hence, while ice-sheet dynamics appear to favour the occurrence of shallow slides close to the shelf edge, ice sheets seem to be irrelevant for the generation of large-scale submarine landslides at the continental slope.
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Lanni, C., M. Borga, R. Rigon e P. Tarolli. "Modelling shallow landslide susceptibility by means of a subsurface flow path connectivity index and estimates of soil depth spatial distribution". Hydrology and Earth System Sciences 16, n. 11 (2 novembre 2012): 3959–71. http://dx.doi.org/10.5194/hess-16-3959-2012.
Testo completoAbstract (sommario):
Abstract. Topographic index-based hydrological models have gained wide use to describe the hydrological control on the triggering of rainfall-induced shallow landslides at the catchment scale. A common assumption in these models is that a spatially continuous water table occurs simultaneously across the catchment. However, during a rainfall event isolated patches of subsurface saturation form above an impeding layer and their hydrological connectivity is a necessary condition for lateral flow initiation at a point on the hillslope. Here, a new hydrological model is presented, which allows us to account for the concept of hydrological connectivity while keeping the simplicity of the topographic index approach. A dynamic topographic index is used to describe the transient lateral flow that is established at a hillslope element when the rainfall amount exceeds a threshold value allowing for (a) development of a perched water table above an impeding layer, and (b) hydrological connectivity between the hillslope element and its own upslope contributing area. A spatially variable soil depth is the main control of hydrological connectivity in the model. The hydrological model is coupled with the infinite slope stability model and with a scaling model for the rainfall frequency–duration relationship to determine the return period of the critical rainfall needed to cause instability on three catchments located in the Italian Alps, where a survey of soil depth spatial distribution is available. The model is compared with a quasi-dynamic model in which the dynamic nature of the hydrological connectivity is neglected. The results show a better performance of the new model in predicting observed shallow landslides, implying that soil depth spatial variability and connectivity bear a significant control on shallow landsliding.
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Mergili, M., I. Marchesini, M. Alvioli, M. Metz, B. Schneider-Muntau, M. Rossi e F. Guzzetti. "A strategy for GIS-based 3-D slope stability modelling over large areas". Geoscientific Model Development 7, n. 6 (15 dicembre 2014): 2969–82. http://dx.doi.org/10.5194/gmd-7-2969-2014.
Testo completoAbstract (sommario):
Abstract. GIS-based deterministic models may be used for landslide susceptibility mapping over large areas. However, such efforts require specific strategies to (i) keep computing time at an acceptable level, and (ii) parameterize the geotechnical data. We test and optimize the performance of the GIS-based, 3-D slope stability model r.slope.stability in terms of computing time and model results. The model was developed as a C- and Python-based raster module of the open source software GRASS GIS and considers the 3-D geometry of the sliding surface. It calculates the factor of safety (FoS) and the probability of slope failure (Pf) for a number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Model input consists of a digital elevation model (DEM), ranges of geotechnical parameter values derived from laboratory tests, and a range of possible soil depths estimated in the field. Probability density functions are exploited to assign Pf to each ellipsoid. The model calculates for each pixel multiple values of FoS and Pf corresponding to different sliding surfaces. The minimum value of FoS and the maximum value of Pf for each pixel give an estimate of the landslide susceptibility in the study area. Optionally, r.slope.stability is able to split the study area into a defined number of tiles, allowing parallel processing of the model on the given area. Focusing on shallow landslides, we show how multi-core processing makes it possible to reduce computing times by a factor larger than 20 in the study area. We further demonstrate how the number of random slip surfaces and the sampling of parameters influence the average value of Pf and the capacity of r.slope.stability to predict the observed patterns of shallow landslides in the 89.5 km2 Collazzone area in Umbria, central Italy.
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Mergili, M., I. Marchesini, M. Alvioli, M. Metz, B. Schneider-Muntau, M. Rossi e F. Guzzetti. "A strategy for GIS-based 3-D slope stability modelling over large areas". Geoscientific Model Development Discussions 7, n. 4 (11 agosto 2014): 5407–45. http://dx.doi.org/10.5194/gmdd-7-5407-2014.
Testo completoAbstract (sommario):
Abstract. GIS-based deterministic models may be used for landslide susceptibility mapping over large areas. However, such efforts require specific strategies to (i) keep computing time at an acceptable level, and (ii) parameterize the geotechnical data. We test and optimize the performance of the GIS-based, 3-D slope stability model r.slope.stability in terms of computing time and model results. The model was developed as a C- and Python-based raster module of the open source software GRASS GIS and considers the 3-D geometry of the sliding surface. It calculates the factor of safety (FoS) and the probability of slope failure (Pf) for a number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Model input consists of a DEM, ranges of geotechnical parameter values derived from laboratory tests, and a range of possible soil depths estimated in the field. Probability density functions are exploited to assign Pf to each ellipsoid. The model calculates for each pixel multiple values of FoS and Pf corresponding to different sliding surfaces. The minimum value of FoS and the maximum value of Pf for each pixel give an estimate of the landslide susceptibility in the study area. Optionally, r.slope.stability is able to split the study area into a defined number of tiles, allowing parallel processing of the model on the given area. Focusing on shallow landslides, we show how multi-core processing allows to reduce computing times by a factor larger than 20 in the study area. We further demonstrate how the number of random slip surfaces and the sampling of parameters influence the average value of Pf and the capacity of r.slope.stability to predict the observed patterns of shallow landslides in the 89.5 km2 Collazzone area in Umbria, central Italy.
10
Kogut, Janusz P. "Landslide formation modelling and surveying of the slope in unsaturated and saturated ground conditions". E3S Web of Conferences 133 (2019): 01010. http://dx.doi.org/10.1051/e3sconf/201913301010.
Testo completoAbstract (sommario):
The terrestrial laser scanner enables site remote sensing of the slopes in a simple and automated manner. Regular measurements with multiple scanner positioning might be applied in long term landslide monitoring. A detailed geological structural model allows for hazard assessment, and then for a slope stability assessment. Numerical model, along with the subsoil parameters, introduced into the Finite Element Method (FEM) software enables an estimation of landslide susceptibility and the possible displacements of the terrain in longer period of time, as well as, due to different loading cases. In this paper the formation of landslides and stability of the slope after the retaining structure establishment is analysed. Two analysed landslides have different origin and may be a threat even after stabilization works already maintained.
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Jeong, S. S., J. H. Kim, Y. M. Kim e D. H. Bae. "Susceptibility assessment of landslides under extreme-rainfall events using hydro-geotechnical model; a case study of Umyeonsan (Mt.), Korea". Natural Hazards and Earth System Sciences Discussions 2, n. 8 (28 agosto 2014): 5575–601. http://dx.doi.org/10.5194/nhessd-2-5575-2014.
Testo completoAbstract (sommario):
Abstract. The influence of climate change on patterns has the potential to alter stability of partially saturated soil slopes. Changes in rainfall patterns have a strong influence on stability of partially saturated soil slopes, which recently have resulted in shallow landslides. In this paper, a comprehensive case study on the 2011 Umyeonsan (Mt.) landslides was highlighted. The incident involves the collapse of a soil slope and the debris flow under extreme-rainfall event, causing 16 fatalities and serious damaged to 146 housings. A fundamental study was carried out on the cause and mechanism of landslide/debris flow. An analytical method is developed for determining the failure mechanism of unsaturated soil slopes under extreme-rainfall, the effect of groundwater flow; the downward velocity of wetting front, and the upward velocity of groundwater level. Based on this, we propose the conceptual methodology of landslide design based on experimental tests and numerical analyses which consider the important mechanism of the combined effects of both groundwater flow and rainfall infiltration into the slope.
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Wang, Wencai, Yongfu Yan, Yue Qu e Pengfei Wang. "Shallow Failure of Weak Slopes in Bayan Obo West Mine". International Journal of Environmental Research and Public Health 19, n. 15 (8 agosto 2022): 9755. http://dx.doi.org/10.3390/ijerph19159755.
Testo completoAbstract (sommario):
The slope stability of large open-pit mines has always been a concern and the analysis of large-scale slope landslides is a focus. However, shallow failure in soft rock slopes also has a serious impact on safe production. The northern slope of Baiyunebo West Mine has many shallow landslides in the final slope, resulting in damage of the maintenance channel of the belt transportation system, which has a serious impact on the safety of production. In order to reduce the shallow failure in weak rock slope, it is necessary to analyze the behavior and characteristics of shallow failure in weak rock. Firstly, the mechanical parameters of the intact rock were obtained by using the exploration data; secondly, through the analysis of blasting-damage range, the distribution characteristics of fractures after the failure of weak rock were obtained. Finally, through theoretical analysis, numerical simulation, surface displacement monitoring and on-site shallow-failure case analysis, the deformation and characteristics of shallow failure of weak rock slope in West Mine were obtained. It was found that the mechanical parameters of rock mass strength on the surface of weak rock slope and the original rock were quite different after mining disturbance. The mode of failure of shallow weak rock slope in the West Mine was creep-cracking; the numerical modelling analysis was carried out by using the assignment method of shallow lithology weakening and gradual change, which is more in line with the deformation characteristics of weak rock slope in West Mine. The lower deformation of the soft rock slope in West Mine is 3–5 times that of the upper deformation. The research results are helpful to understand the influence of blasting on the stability of soft rock slope. At present, West Mine has started to adjust blasting parameters according to the research results, so as to reduce the excessive damage of blasting to rock mass, so the stability of the slope is improved.
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Chivatá Cárdenas, Ibsen. "Assessing landslide susceptibility by applying fuzzy sets, possibility evidence-based theories". Ingeniería e Investigación 28, n. 1 (1 gennaio 2008): 26–40. http://dx.doi.org/10.15446/ing.investig.v28n1.14865.
Testo completoAbstract (sommario):
A landslide susceptibility model was developed for the city of Manizales, Colombia; landslides have been the city’s main environmental problem. Fuzzy sets and possibility and evidence-based theories were used to construct the model due to the set of circumstances and uncertainty involved in the modelling; uncertainty particularly concerned the lack of representative data and the need for systematically coordinating subjective information. Susceptibility and the uncertainty were estimated via data processing; the model contained data concerning mass vulnerability and uncertainty. Output data was expressed on a map defined by linguistic categories or uncertain labels as having low, medium, high and very high susceptibility; this was considered appropriate for representing susceptibility. A fuzzy spectrum was developed for classifying susceptibility levels according to perception and expert opinion. The model showed levels of susceptibility in the study area, ranging from low to high susceptibility (medium susceptibility being more frequent). This article shows the details concerning systematic data processing by presenting theories and tools regarding uncertainty. The concept of fuzzy parameters is introduced; this is useful in modelling phenomena regarding uncertainty, complexity and nonlinear performance, showing that susceptibility modelling can be feasible. The paper also shows the great convenience of incorporating uncertainty into modelling and decision-making. However, quantifying susceptibility is not suitable when modelling identified uncertainty because incorporating model output information cannot be reduced into exact or real numerical quantities when the nature of the variables is particularly uncertain. The latter concept is applicable to risk assessment.
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Martino, Salvatore, Gian Marco Marmoni, Matteo Fiorucci, Antonio Francesco Ceci, Marco Emanuele Discenza, Javad Rouhi e Davit Tedoradze. "Role of Antecedent Rainfall in the Earthquake-Triggered Shallow Landslides Involving Unsaturated Slope Covers". Applied Sciences 12, n. 6 (12 marzo 2022): 2917. http://dx.doi.org/10.3390/app12062917.
Testo completoAbstract (sommario):
Different soil cover saturation has a significant effect in influencing slope stability conditions of weathered covers under earthquake-induced shaking. Here we analyze the Montecilfone, Italy (2018), case history, an Mw 5.1 earthquake that revealed an exceptionality in the spatial distribution of the surveyed earthquake-induced shallow landslides. This feature can be justified as intense rainfall occurred in the epicentral area before the seismic event, contributing to increasing the saturation and the weight of the soil covers. To verify the effective influence of antecedent rainfall as a preparatory factor in the earthquake triggering of soil covers, stability conditions for both static and dynamic scenarios were validated by reconstructing different saturation conditions related to a rainfall event that occurred before the earthquake. Soil cover surveying was performed within a 150 km2 area to output its spatial distribution in terms of their compositional features and thickness, whose variability was constrained through empirical models. Based on laboratory test results, 1D infiltration numerical models were performed through the Hydrus-1D free domain software to estimate the saturation degree of the soil cover and the water infiltration depth, taking as a reference the intensity of the rainfall event. Soil cover sequential charts of water content were obtained at different depths and times up to those recorded at the time of earthquake occurrence by the performed numerical modelling. Safety factors (SFs) of the slope covers were quantified assuming an unsaturated condition in the slope stability equation. The outputs reveal that pore pressure spatial distribution in the unsaturated medium infers on the earthquake-induced scenario of shallow landsliding, demonstrating its role as a preparatory factor for earthquake-induced shallow landslides.
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von Boetticher, Albrecht, e Axel Volkwein. "Numerical modelling of chain-link steel wire nets with discrete elements". Canadian Geotechnical Journal 56, n. 3 (marzo 2019): 398–419. http://dx.doi.org/10.1139/cgj-2017-0540.
Testo completoAbstract (sommario):
Chain-link mesh is one of several net types used as protection against rockfall, shallow landslides, and debris flows. The dynamic impact and the corresponding nonlinear barrier response require numerical models. Chain-link meshes show a nonlinear anisotropic behaviour caused by the geometry of the wire. Resolving this geometry and its deformation results in a bottleneck of numerical costs. We present a discrete element model that covers the nonlinear and anisotropic behaviour of the chain-link mesh, using results from either small-scale, quasi-static tension tests or from a detailed mechanical model as material-law input. The mesh stiffness, resistance, and failure depend on the inner mesh opening angle and thus on the direction of deformation. This information enters the model through the transformation of the nonlinear, three-dimensional deformation processes into a nonlinear material law, with an interpolated dependency on the inner mesh angle. The model maps the resistance of the mesh against impacting masses and covers the energy absorption and it is capable of predicting the dynamic behaviour of different protection barriers with high accuracy, optimized calculation time, and minimized calibration efforts. This is illustrated by high impact energy tests that follow the ETAG027 standard, and also with a rockfall attenuating system.
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Crosta, G. B., e P. Dal Negro. "Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event". Natural Hazards and Earth System Sciences 3, n. 1/2 (30 aprile 2003): 53–69. http://dx.doi.org/10.5194/nhess-3-53-2003.
Testo completoAbstract (sommario):
Abstract. Pyroclastic soils mantling a wide area of the Campanian Apennines are subjected to recurrent instability phenomena. This study analyses the 5 and 6 May 1998 event which affected the Pizzo d’Alvano (Campania, southern Italy). More than 400 slides affecting shallow pyroclastic deposits were triggered by intense and prolonged but not extreme rainfall. Landslides affected the pyroclastic deposits that cover the steep calcareous ridges and are soil slip-debris flows and rapid mudflows. About 30 main channels were deeply scoured by flows which reached the alluvial fans depositing up to 400 000 m3 of material in the piedmont areas. About 75% of the landslides are associated with morphological discontinuities such as limestone cliffs and roads. The sliding surface is located within the pyroclastic cover, generally at the base of a pumice layer. Geotechnical characterisation of pyroclastic deposits has been accomplished by laboratory and in situ tests. Numerical modelling of seepage processes and stability analyses have been run on four simplified models representing different settings observed at the source areas. Seepage modelling showed the formation of pore pressure pulses in pumice layers and the localised increase of pore pressure in correspondence of stratigraphic discontinuities as response to the rainfall event registered between 28 April and 5 May. Numerical modelling provided pore pressure values for stability analyses and pointed out critical conditions where stratigraphic or morphological discontinuities occur. This study excludes the need of a groundwater flow from the underlying bedrock toward the pyroclastic cover for instabilities to occur.
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Capecchi, V., M. Perna e A. Crisci. "Statistical modelling of rainfall-induced shallow landsliding using static predictors and numerical weather predictions: preliminary results". Natural Hazards and Earth System Sciences 15, n. 1 (13 gennaio 2015): 75–95. http://dx.doi.org/10.5194/nhess-15-75-2015.
Testo completoAbstract (sommario):
Abstract. Our study is aimed at estimating the added value provided by Numerical Weather Prediction (NWP) data for the modelling and prediction of rainfall-induced shallow landslides. We implemented a quantitative indirect statistical modelling of such phenomena by using, as input predictors, both geomorphological, geological, climatological information and numerical data obtained by running a limited-area weather model. Two standard statistical techniques are used to combine the predictor variables: a generalized linear model and Breiman's random forests. We tested these models for two rainfall events that occurred in 2011 and 2013 in Tuscany region (central Italy). Modelling results are compared with field data and the forecasting skill is evaluated by mean of sensitivity–specificity receiver operating characteristic (ROC) analysis. In the 2011 rainfall event, the random forests technique performs slightly better than generalized linear model with area under the ROC curve (AUC) values around 0.91 vs. 0.84. In the 2013 rainfall event, both models provide AUC values around 0.7. Using the variable importance output provided by the random forests algorithm, we assess the added value carried by numerical weather forecast. The main results are as follows: (i) for the rainfall event that occurred in 2011 most of the NWP data, and in particular hourly rainfall intensities, are classified as "important" and (ii) for the rainfall event that occurred in 2013 only NWP soil moisture data in the first centimetres below ground is found to be relevant for landslide assessment. In the discussions we argue how these results are connected to the type of precipitation observed in the two events.
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Schilirò, L., C. Esposito e G. Scarascia Mugnozza. "Evaluation of shallow landslide-triggering scenarios through a physically based approach: an example of application in the southern Messina area (northeastern Sicily, Italy)". Natural Hazards and Earth System Sciences 15, n. 9 (18 settembre 2015): 2091–109. http://dx.doi.org/10.5194/nhess-15-2091-2015.
Testo completoAbstract (sommario):
Abstract. Rainfall-induced shallow landslides are a widespread phenomenon that frequently causes substantial damage to property, as well as numerous casualties. In recent~years a wide range of physically based models have been developed to analyze the triggering process of these events. Specifically, in this paper we propose an approach for the evaluation of different shallow landslide-triggering scenarios by means of the TRIGRS (transient rainfall infiltration and grid-based slope stability) numerical model. For the validation of the model, a back analysis of the landslide event that occurred in the study area (located SW of Messina, northeastern Sicily, Italy) on 1 October 2009 was performed, by using different methods and techniques for the definition of the input parameters. After evaluating the reliability of the model through comparison with the 2009 landslide inventory, different triggering scenarios were defined using rainfall values derived from the rainfall probability curves, reconstructed on the basis of daily and hourly historical rainfall data. The results emphasize how these phenomena are likely to occur in the area, given that even short-duration (1–3 h) rainfall events with a relatively low return period (e.g., 10–20~years) can trigger numerous slope failures. Furthermore, for the same rainfall amount, the daily simulations underestimate the instability conditions. The high susceptibility of this area to shallow landslides is testified by the high number of landslide/flood events that have occurred in the past and are summarized in this paper by means of archival research. Considering the main features of the proposed approach, the authors suggest that this methodology could be applied to different areas, even for the development of landslide early warning systems.
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Cascini, L., S. Cuomo, M. Pastor e C. Sacco. "Modelling the post-failure stage of rainfall-induced landslides of the flow type". Canadian Geotechnical Journal 50, n. 9 (settembre 2013): 924–34. http://dx.doi.org/10.1139/cgj-2012-0375.
Testo completoAbstract (sommario):
The geomechanical modelling of failure and post-failure stages of rainfall-induced shallow landslides represents a fundamental issue to the proper assessment of failure conditions and recognizes the potential for long travel distances of the failed soil masses. Considering that these phenomena are among the most catastrophic natural hazards, as a contribution to the topic this paper discusses the potential of a hydromechanical coupled finite element model (FEM) to analyze the post-failure stage using an advanced constitutive model. In particular, simple undrained triaxial tests and experimental evidence of centrifuge tests are reproduced first, for both loose and dense soils. Then, two slope scale benchmarks are analyzed in the cases of vertical downward or horizontal water seepage and for both loose and dense soils. Compared with results obtained through standard limit equilibrium analyses, the coupled FEM provides a new comprehensive framework for failure and post-failure scenarios that includes a significant reduction of mean effective stresses, also in the case of a loose soil slope subjected to vertical downward water seepage. The obtained results are particularly encouraging because they outline the possibility to analyse both the failure and post-failure stages in a unique framework. Moreover, the numerical analyses indicate that the post-failure mechanisms are intimately tied to specific predisposing factors and boundary conditions, rather than to a single mechanical or state parameter of soil, such as, for instance, the soil relative density.
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Huntley, David, Peter Bobrowsky, James Goff, Catherine Chagué, Douglas Stead, Davide Donati e Danial Mariampillai. "Extending the terrestrial depositional record of marine geohazards in coastal NW British Columbia". Geological Society, London, Special Publications 477, n. 1 (27 aprile 2018): 277–92. http://dx.doi.org/10.1144/sp477.4.
Testo completoAbstract (sommario):
AbstractRecurrent storms, floods, landslides, earthquakes and tsunamis challenge the development of resilient infrastructure and communities in coastal northwestern British Columbia. Vulnerability assessment first requires extended and improved understanding of geohazards in the Pacific Basin to constrain modelling of future events. An investigation of soils and bedrock structures in the Douglas Channel provides insight into the distribution of deposits attributed to geohazards in the region. Newly discovered marine inundation deposits corroborate numerical models and suggest that Pacific-sourced storms and earthquake-triggered tsunamis expend much of their energy in the outer coast and rarely reach far up the mainland fjords. Small-volume Folisolic slides and rockfalls do not generate tsunamis of any consequence. In contrast, marine sediments deposited beyond storm berms at the fjord head are a record of local tsunamis generated by large-volume marine slumps. Deep-fractured bedrock mapped upslope from relict submarine features would trigger damaging tsunami waves if rapid failure into the fjord were to occur. The observations above suggest only great earthquakes, large landslides and seasonal storms above a certain threshold volume and impulse energy produce geomorphically significant inundation events. However, even small submarine landslides have tsunamigenic potential in Douglas Channel since they occur in shallow water.
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Cama, M., L. Lombardo, C. Conoscenti e R. Rotigliano. "Predicting storm triggered debris flow events: application to the 2009 Ionian-Peloritan disaster (Sicily, Italy)". Natural Hazards and Earth System Sciences Discussions 3, n. 3 (3 marzo 2015): 1731–74. http://dx.doi.org/10.5194/nhessd-3-1731-2015.
Testo completoAbstract (sommario):
Abstract. The main assumption on which landslide susceptibility assessment by means of stochastic modelling lays is that the past is the key to the future. As a consequence, a stochastic model able to classify a past known landslide scenario should be able to predict a future unknown one as well. However, storm triggered landslide events in the Mediterranean region could pose some limits on the operative validity of such expectation, as they typically result by a randomness in time recurrence and magnitude. This is the case of the 2007/09 couple of storm events, which recently hit north-eastern Sicily resulting in largely different disaster scenarios. The purpose of this study is to test whether a susceptibility model based on stepwise binary logistic regression is able to predict a storm triggered debris flow scenario. The study area is the small catchment of the Itala torrent (10 km2), which drains from the southern Peloritan Mountains eastward to the Ionian sea, in the province of the Messina territory (Sicily, Italy). The shallow landslides activated in the occasion of two close intense rainfall events have been mapped by integrating remote and field surveys, producing two event inventories which include 73 landslides, activated in 2007, and 616 landslides, triggered by the 2009 storm. The set of predictors were derived from a 2 m cell digital elevation model and a 1 : 50 000 scale geologic map. The topic of the research was explored by performing two types of validation procedures: self-validation, based on the random partition of each event inventory and chrono-validation, based on the time partition of the landslide inventory. It was therefore possible to analyse and compare the performances both of the 2007-calibrated model in predicting the 2009 landslides (forward chronovalidation) and vice versa of the 2009-calibrated model in predicting the 2007 landslides (backward chronovalidation). Both the two predictions resulted in largely acceptable performances, in terms of fitting, skill and reliability. However, a loss of performance and differences in the selected predictors between the self-validated and the chrono-validated models which are linked to the characteristics of the two triggering storms are highlighted.
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Sukatja, Cosmas Bambang, Banata W.R e Perdi Bahri. "MITIGASI DAN PENANGGULANGAN BENCANA BANJIR DEBRIS PASCA GEMPA PALU 2018". JURNAL TEKNIK HIDRAULIK 12, n. 1 (30 giugno 2021): 25–38. http://dx.doi.org/10.32679/jth.v12i1.648.
Testo completoAbstract (sommario):
The 7.4 SR earthquake which occurred in The Donggala Regency, Central Sulawesi on September 28th 2018 was a shallow earthquake due to the Palukoro fault activity. The impact of the quake’s shaking created pressure on the rock and soil masses of 77 hilly locations in the Palu, Sigi, and Donggala, causing several landslides and the increasing the potential of more. One of the slopes of at risk of landslides which can trigger debris flow is found on the hills of Poi Village, Dolo Selatan District, Sigi Regency. The estimated volume of lose material which could fall in a landslide is 4.8 million m3. Rainfall in the area is predicted to trigger debris flow with the potential to bury settlements and block the flow of the Palu tributary located downstream. For this reason, it is necessary to conduct a study of the lose material deposits in the Poi River channel which can trigger debris flows during the rainy season. The problem-solving method in this study used is a rationalistic and descriptive qualitative approach. In predicting the distribution direction, propagation and hydrograph of the debris flow ths study applies the numerical modelling SIMLAR 2.1. This debris disaster risk management effort uses Sabo technology physically and non-physically. Keywords: earthquakes, landslides, debris flow, debris disaster management, Sabo technology physically and non-physically.
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Baumann, Valérie, Costanza Bonadonna, Sabatino Cuomo, Mariagiovanna Moscariello, Sebastien Biass, Marco Pistolesi e Alessandro Gattuso. "Mapping the susceptibility of rain-triggered lahars at Vulcano island (Italy) combining field characterization, geotechnical analysis, and numerical modelling". Natural Hazards and Earth System Sciences 19, n. 11 (5 novembre 2019): 2421–49. http://dx.doi.org/10.5194/nhess-19-2421-2019.
Testo completoAbstract (sommario):
Abstract. The characterization of triggering dynamics and remobilized volumes is crucial to the assessment of associated lahar hazards. We propose an innovative treatment of the cascading effect between tephra fallout and lahar hazards based on probabilistic modelling that also accounts for a detailed description of source sediments. As an example, we have estimated the volumes of tephra fallout deposit that could be remobilized by rainfall-triggered lahars in association with two eruptive scenarios that have characterized the activity of the La Fossa cone (Vulcano, Italy) in the last 1000 years: a long-lasting Vulcanian cycle and a subplinian eruption. The spatial distribution and volume of deposits that could potentially trigger lahars were analysed based on a combination of tephra fallout probabilistic modelling (with TEPHRA2), slope-stability modelling (with TRIGRS), field observations, and geotechnical tests. Model input data were obtained from both geotechnical tests and field measurements (e.g. hydraulic conductivity, friction angle, cohesion, total unit weight of the soil, and saturated and residual water content). TRIGRS simulations show how shallow landsliding is an effective process for eroding pyroclastic deposits on Vulcano. Nonetheless, the remobilized volumes and the deposit thickness threshold for lahar initiation strongly depend on slope angle, rainfall intensity, grain size, friction angle, hydraulic conductivity, and the cohesion of the source deposit.
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Fusco, Francesco, Benjamin Mirus, Rex Baum, Domenico Calcaterra e Pantaleone De Vita. "Incorporating the Effects of Complex Soil Layering and Thickness Local Variability into Distributed Landslide Susceptibility Assessments". Water 13, n. 5 (5 marzo 2021): 713. http://dx.doi.org/10.3390/w13050713.
Testo completoAbstract (sommario):
Incorporating the influence of soil layering and local variability into the parameterizations of physics-based numerical models for distributed landslide susceptibility assessments remains a challenge. Typical applications employ substantial simplifications including homogeneous soil units and soil-hydraulic properties assigned based only on average textural classifications; the potential impact of these assumptions is usually disregarded. We present a multi-scale approach for parameterizing the distributed Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model that accounts for site-specific spatial variations in both soil thickness and complex layering properties by defining homogeneous soil properties that vary spatially for each model grid cell. These effective properties allow TRIGRS to accurately simulate the timing and distribution of slope failures without any modification of the model structure. We implemented this approach for the carbonate ridge of Sarno Mountains (southern Italy) whose slopes are mantled by complex layered soils of pyroclastic origin. The urbanized foot slopes enveloping these mountains are among the most landslide-prone areas of Italy and have been subjected to repeated occurrences of damaging and deadly rainfall-induced flow-type shallow landslides. At this scope, a primary local-scale application of TRIGRS was calibrated on physics-based rainfall thresholds, previously determined by a coupled VS2D (version 1.3) hydrological modeling and slope stability analysis. Subsequently, by taking into account the spatial distribution of soil thickness and vertical heterogeneity of soil hydrological and mechanical properties, a distributed assessment of landslide hazard was carried out by means of TRIGRS. The combination of these approaches led to the spatial assessment of landslide hazard under different hypothetical rainfall intensities and antecedent hydrological conditions. This approach to parameterizing TRIGRS can be adapted to other spatially variable soil layering and thickness to improve hazard assessments.
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Theron, C., S. A. Lorentz e Y. Xu. "Rainfall-induced groundwater ridging and the Lisse effect on tailings storage facilities: A literature review". Journal of the Southern African Institute of Mining and Metallurgy 122, n. 2 (28 febbraio 2022): 1–8. http://dx.doi.org/10.17159/2411-9717/1729/2022.
Testo completoAbstract (sommario):
The failure of tailings storage facilities (TSFs) results in the discharge of significant quantities of hazardous waste material into the natural environment. Research studies relating to slope instability have identified physical mechanisms such as rainfall-induced erosion, liquefaction, and shear failure as the main triggers. The generation of transient pressure waves and the mobilization of pre-event water in the unsaturated zone have been found to trigger shallow landslides in natural hillslopes. In this paper we review these physical mechanisms, known as groundwater ridging (GWR) and the Lisse effect (LE), from other studies. Previous researchers have explained both these phenomena through field and laboratory observations, numerical modelling, as well as conceptual discussions. These case studies demonstrate the impact of rainfall characteristics on the generation of transient pressure waves that rapidly increase the phreatic surface and change pore water suction. Reference is also made to the influence and behaviour of physical porous medium characteristics on the establishment of a continuous water phase that facilitates the transmission of an induced pressure head. However, previous studies fail to recognize the possibility that the pressure increase in pre-event water through pore air propagation could cause slope instability in tailings dams. The authors suggest that the physical properties and hydraulic behaviour of unsaturated porous tailings media make it susceptible to GWR and the LE, resulting in the creation of a potential failure plane.
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Hope, Jacqueline, e David Eaton. "Crustal structure beneath the Western Canada Sedimentary Basin: constraints from gravity and magnetic modelling". Canadian Journal of Earth Sciences 39, n. 3 (1 marzo 2002): 291–312. http://dx.doi.org/10.1139/e01-060.
Testo completoAbstract (sommario):
Regional gravity and magnetic anomalies that originate from crystalline basement rocks extend over many parts of the Western Canada Sedimentary Basin. Although these potential-field anomalies provide a basis for tectonic subdivisions of the basement crust, most previous interpretations of these features have been largely qualitative in nature. This study focuses on numerical simulation and quantitative interpretation of five regional potential-field anomalies in Alberta, Canada, for which independent constraints on crustal structure are available from Lithoprobe seismic and electromagnetic studies. The Kimiwan High (~55°N, 116°W) is a roughly 250 km long linear magnetic high. Seismic profiles across this anomaly provide evidence for a crustal-scale extensional fault system that offsets the Winagami reflection sequence, a series of mid-crustal sills. We find that the magnetic anomaly can be modelled as either a 1540 km wide zone of moderate positive susceptibility (4.5 × 103 SI units) in the hanging wall of the detachment (517 km depth), or as a narrower (510 km), steeply dipping zone of high susceptibility (2.5 × 102 SI units) in the footwall (1632 km depth). We interpret the former scenario as indicative of an extensive zone of alteration above the fault, whereas the latter could represent a decapitated granitic pluton that correlates with magmatic rocks farther north. To the southeast, the Thorsby Low (~53°N, 114°W) is a sinuous, 400 km long magnetic low and gravity gradient trend that appears to be a splay of the much more extensive Snowbird tectonic zone. Previous seismic interpretations across the Thorsby Low indicate that it coincides with a 10 km offset in the Moho. Our results show that this abrupt change in crustal thickness is consistent with, but not required by, the gravity signature of this feature. The northeast-striking Red Deer High (~53°N, 112°W) is a narrow magnetic anomaly in central Alberta with variable intensity along strike. Previous magnetotelluric studies suggest that the Red Deer anomaly is closely associated with a linear, highly conductive body in the upper basement. Our modelling results confirm the shallow depth of the causative body and suggest an eastward dip that is consistent with published seismic interpretations. Near the eastern border of Alberta, the 300 km long Eyehill High (~52°N, 110°W) is a prominent north-striking magnetic anomaly adjacent to the western hinterland of the Trans-Hudson Orogen. Combined gravity and magnetic modelling show that this feature occurs near the western boundary of a large block of dense material in the lower crust. The magnetic anomaly can be simulated by a near-vertical dyke-like body in the upper crust. Lastly, the Vulcan structure (~50.5°N, 112°W) forms the ~400 km long, northern boundary of the Archean Medicine Hat block. It is defined by a sinuous east-trending magnetic anomaly and gravity low. The wavelength and polarity of the magnetic anomaly (positive in the north), coupled with the coincident gravity low, are most simply explained by a mid-crustal low-density body with significant remanent magnetization oriented antiparallel to the present-day field.
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Khakimzyanov, Gayaz S., Oleg I. Gusev, Sofya A. Beizel, Leonid B. Chubarov e Nina Yu Shokina. "Simulation of tsunami waves generated by submarine landslides in the Black Sea". Russian Journal of Numerical Analysis and Mathematical Modelling 30, n. 4 (1 gennaio 2015). http://dx.doi.org/10.1515/rnam-2015-0020.
Testo completoAbstract (sommario):
AbstractNumerical technique for studying surface waves appearing under the motion of a submarine landslide is discussed. This technique is based on the application of the model of a quasi-deformable landslide and two shallow water models, namely, the classic (dispersion free) one and the completely nonlinear dispersive model of the second hydrodynamic approximation. Numerical simulation of surface waves generated by a large model landslide on the continental slope of the Black Sea near the Russian coast is performed. It is shown that the dispersion has a significant impact on the picture of propagation of tsunami waves on sufficiently long paths.
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Tufano, Rita, Giuseppe Formetta, Domenico Calcaterra e Pantaleone De Vita. "Hydrological control of soil thickness spatial variability on the initiation of rainfall-induced shallow landslides using a three-dimensional model". Landslides, 22 maggio 2021. http://dx.doi.org/10.1007/s10346-021-01681-x.
Testo completoAbstract (sommario):
AbstractThickness and stratigraphic settings of soils covering slopes potentially control susceptibility to initiation of rainfall-induced shallow landslides due to their local effect on slope hydrological response. Notwithstanding the relevance of the assessment of hazard to shallow landsliding at a distributed scale by approaches based on a coupled modelling of slope hydrological response and slope stability, the spatial variability of soil thickness and stratigraphic settings are factors poorly considered in the literature. Under these premises, this paper advances the well-known case study of rainfall-induced shallow landslides involving ash-fall pyroclastic soils covering the peri-Vesuvian mountains (Campania, southern Italy). In such a unique geomorphological setting, the soil covering is formed by alternating loose ash-fall pyroclastic deposits and paleosols, with high contrasts in hydraulic conductivity and total thickness decreasing as the slope angle increases, thus leading to the establishment of lateral flow and an increase of pore water pressure in localised sectors of the slope where soil horizon thickness is less. In particular, we investigate the effects, on hillslope hydrological regime and slope stability, of irregular bedrock topography, spatial variability of soil thickness and vertical hydraulic heterogeneity of soil horizons, by using a coupled three-dimensional hydrological and a probabilistic infinite slope stability model. The modelling is applied on a sample mountain catchment, located on Sarno Mountains (Campania, southern Italy), and calibrated using physics-based rainfall thresholds derived from the literature. The results obtained under five simulated constant rainfall intensities (2.5, 5, 10, 20 and 40 mm h−1) show an increase of soil pressure head and major failure probability corresponding to stratigraphic and morphological discontinuities, where a soil thickness reduction occurs. The outcomes obtained from modelling match the hypothesis of the formation of lateral throughflow due to the effect of intense rainfall, which leads to the increase of soil water pressure head and water content, up to values of near-saturation, in narrow zones of the slope, such as those of downslope reduction of total soil thickness and pinching out of soil horizons. The approach proposed can be conceived as a further advance in the comprehension of slope hydrological processes at a detailed scale and their effects on slope stability under given rainfall and antecedent soil hydrological conditions, therefore in predicting the most susceptible areas to initiation of rainfall-induced shallow landslides and the related I-D rainfall thresholds. Results obtained demonstrate the occurrence of a slope hydrological response depending on the spatial variability of soil thickness and leading to focus slope instability in specific slope sectors. The approach proposed is conceived to be potentially exportable to other slope environments for which a spatial modelling of soil thickness would be possible.
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Bryce, Erin, Luigi Lombardo, Cees van Westen, Hakan Tanyas e Daniela Castro-Camilo. "Unified landslide hazard assessment using hurdle models: a case study in the Island of Dominica". Stochastic Environmental Research and Risk Assessment, 2 giugno 2022. http://dx.doi.org/10.1007/s00477-022-02239-6.
Testo completoAbstract (sommario):
AbstractClimatically-induced natural hazards are a threat to communities. They can cause life losses and heavy damage to infrastructure, and due to climate change, they have become increasingly frequent. This is especially the case in tropical regions, where major hurricanes have consistently appeared in recent history. Such events induce damage due to the high wind speed they carry, and the high intensity/duration of rainfall they discharge can further induce a chain of hydro-morphological hazards in the form of widespread debris slides/flows. The way the scientific community has developed preparatory steps to mitigate the potential damage of these hydro-morphological threats includes assessing where they are likely to manifest across a given landscape. This concept is referred to as susceptibility, and it is commonly achieved by implementing binary classifiers to estimate probabilities of landslide occurrences. However, predicting where landslides can occur may not be sufficient information, for it fails to convey how large landslides may be. This work proposes using a flexible Bernoulli-log-Gaussian hurdle model to simultaneously model landslide occurrence and size per areal unit. Covariate and spatial information are introduced using a generalised additive modelling framework. To cope with the high spatial resolution of the data, our model uses a Markovian representation of the Matérn covariance function based on the stochastic partial differential equation approach. Assuming Gaussian priors, our model can be integrated into the class of latent Gaussian models, for which inference is conveniently performed based on the integrated nested Laplace approximation method. We use our modelling approach in Dominica, where hurricane Maria (September 2017) induced thousands of shallow flow-like landslides passing over the island. Our results show that we can not only estimate where landslides may occur and how large they may be, but we can also combine this information in a unified landslide hazard model, which is the first of its kind.
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M. Yahya, Sarder, Rini A. Abdullah, Mohd Ashraf Mohamad Ismail, Hisham Mohamad, Muhammad Azril Hezmi e Siti Norafida Jusoh. "3D NUMERICAL MODELLING OF SHALLOW TUNNEL IN WEATHERED GRANITE INCORPORATING MULTI-STAGE EXCAVATION AND PRE-SUPPORT". Jurnal Teknologi 78, n. 8-6 (30 agosto 2016). http://dx.doi.org/10.11113/jt.v78.9637.
Testo completoAbstract (sommario):
Generally tunnelling in urban ground condition is not always favourable due to the tunnels’ susceptibility to major displacement especially when excavated in the soft soil and/or weak weathered rock formation. Apart from conventional support systems, pre-support measure like forepoling umbrella arch is frequently used to reinforce the ground. Modern computational tools allows the inclusion of multi-stage excavations and pre-support which was not possible in two dimensional (2D) plane strain. This paper demonstrates the three dimensional (3D) finite element analysis of Pahang-Selangor raw water transfer tunnel, as a reference case, where multi-stage excavation and pre-support are incorporated as intrinsic part of the model. The New Austrian Tunnelling Method (NATM)-3 segments which encountered Grade III weathered granite, having shallow overburden cover, was selected for numerical analysis using RS3 software. Comparison between simulated and observed data has shown good agreement during verification
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Kameda, Jun. "Rheological properties of halloysite soil slurry: a case study of weathered tephra involved in a shallow landslide triggered by the 2018 Eastern Iburi earthquake in Hokkaido, Japan". Earth, Planets and Space 74, n. 1 (11 maggio 2022). http://dx.doi.org/10.1186/s40623-022-01623-4.
Testo completoAbstract (sommario):
AbstractThe 6.7 Mw Eastern Iburi earthquake of 6 September 2018 triggered destructive landslides in southern Hokkaido, Japan, many of which were characterized by the flow-like downslope movement of volcanic soils formed from weathered tephra containing halloysite. This study aims to elucidate the mechanism of landslide generation through rheological characterization of halloysite soil slurries. The examined slurries were prepared from either oven-dried or moist soil. Both slurries showed a power-law correlation between measured yield stress and moisture content. However, at a given water content, slurry made from dried soil showed stresses that are one-to-two orders of magnitude lower than those of slurry made from moist soil. Compared with the measurements for the slurry of dried soil, those for the slurry of moist soil are closer to prior numerical modeling of a specific landslide, indicating that the soils involved were moist. The yield stress also varied with slurry pH, generally increasing with decreasing pH, which is in part explained by the DLVO force model based on the electrical double layer and van der Waals forces between the colloidal particles. The pH dependence is more prominent in the slurry of moist soil, and thus the mechanical state of the slope appears to vary significantly with rainfall-induced changes in subsurface chemistry. Dynamic viscoelasticity measurement indicated that both initially solid-like slurries can become fluid under an applied oscillatory strain of 0.5 to 10 Hz: the susceptibility to fluidization depends greatly on water content and frequency. The ground motion during the earthquake easily fluidized the slurry, indicating this was a factor contributing to the observed flow-like landslides. Graphical Abstract
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Nazrien Ng, Jeffery, Aizat Mohd Taib, Irfan Haziq Razali, Norinah Abd Rahman, Wan Hanna Melini Wan Mohtar, Othman A. Karim, Safari Mat Desa, Suriyani Awang e Mohd Syazwan Faisal Mohd. "The Effect of Extreme Rainfall Events on Riverbank Slope Behaviour". Frontiers in Environmental Science 10 (2 marzo 2022). http://dx.doi.org/10.3389/fenvs.2022.859427.
Testo completoAbstract (sommario):
Many slope failures take place during or after rainfall events. Landslides are one of the tragedies associated with slope failures and often lead to fatal accidents. A study on the effects of extreme rainfall on slope stability considering the historical rainfall data, slope characteristics and properties, and flow boundary conditions was undertaken. This study investigated the behaviour of the Sg Langat slope under the influence of extreme rainfall gathered from historical data. Sg Langat was selected as the research area because of its high riverbank failures. The focus of this study are as follows: 1) to determine the effect of slope angles on slope stability, 2) to assess the development of pore-water pressure based on the changing groundwater levels, and 3) to analyse the influence of extreme rainfall events on the slope behaviour via numerical modelling. This study enhances the understanding of certain slope conditions and contributes to the analysis of slope stability through numerical modelling, making it relatively convenient to observe the soil conditions for determining the slope stability of the research area in regards to the effect of extreme rainfall. The results were obtained with respect to the changes in the pore-water pressure and the factor of safety. It was observed that the pressure changes were different for every channel, demonstrating that the generation of negative pore-water pressure was not directly affected by the type of analysis and the rainfall infiltration alone. Moreover, the slopes on all channels presented were considered unstable because of the considerable changes in the negative pore-water pressure at a relatively shallow depth, causing soil strength reduction. The factor of safety recorded for Channel 1 was the lowest at 0.18, whereas Channel 3 had the highest factor of safety of 1.11 but was still considered unsafe as it fell below the standard safety margin of 1.3. Apart from the different rainfall intensities applied, the geometry of the slopes also affected the slope stability.