scholarly journals Characterisation of weathered clayey soils responsible for shallow landslides

2006 ◽  
Vol 6 (5) ◽  
pp. 825-838 ◽  
Author(s):  
C. Meisina
Keyword(s):  
Slope Angle ◽  
Test Site ◽  
Linear Shrinkage ◽  
Strain Engineering ◽  
Shallow Landslides ◽  
Point Of View ◽  
Slope Instability ◽  
Clayey Soils ◽  
Landslide Occurrence ◽  
Geotechnical Characteristics

Abstract. Shallow earth translational slides and earth flows, affecting colluvial soils derived by the weathering of the clayey bedrock, are a recurrent problem causing damage to buildings and roads in many areas of Apennines. The susceptibility assessment, e.g. slope stability models, requires the preliminary characterization of these superficial covers (lithology, geotechnical and hydraulic parameters). The aim of the work is to develop and test a methodology for the identification and mapping of weathered clayey soils responsible for shallow landslides. A test site in Northern Apennines (Province of Pavia) was selected. Argillaceous and marly successions characterize the area. Shallow landslides occurred periodically due to high intensity rainfalls. Trench pits were used for the soil profile description (lithology, structure, grade of weathering, thickness) and sampling. The main geological, topographic and geomorphologic parameters of shallow landslides were analysed. Field surveys were integrated with some geotechnical laboratory tests (index properties, suction and volumetric characteristic determination, methylene blue adsorption test, linear shrinkage, swell strain). Engineering geological zoning was carried out by grouping the superficial soils on the basis of the following attributes: topographic conditions (slope angle), landslide occurrence, lithology (grain size), geometry (thickness), lithology of the bedrock, hydrogeological and geotechnical characteristics. The resulting engineering-geological units (areas that may be regarded as homogeneous from the geomorphologic and engineering – geological point of view) were analysed in terms of shallow slope instability.

scholarly journals Application of a probabilistic model of rainfall-induced shallow landslides to complex hollows

2008 ◽  
Vol 8 (4) ◽  
pp. 733-744 ◽  
Author(s):  
A. Talebi ◽  
R. Uijlenhoet ◽  
P. A. Troch
Keyword(s):  
Probabilistic Model ◽  
Slope Angle ◽  
Building Blocks ◽  
Shallow Landslides ◽  
Probability Models ◽  
Soil Thickness ◽  
Landslide Occurrence ◽  
Realistic Description ◽  
The Stability

Abstract. Recently, D'Odorico and Fagherazzi (2003) proposed "A probabilistic model of rainfall-triggered shallow landslides in hollows" (Water Resour. Res., 39, 2003). Their model describes the long-term evolution of colluvial deposits through a probabilistic soil mass balance at a point. Further building blocks of the model are: an infinite-slope stability analysis; a steady-state kinematic wave model (KW) of hollow groundwater hydrology; and a statistical model relating intensity, duration, and frequency of extreme precipitation. Here we extend the work of D'Odorico and Fagherazzi (2003) by incorporating a more realistic description of hollow hydrology (hillslope storage Boussinesq model, HSB) such that this model can also be applied to more gentle slopes and hollows with different plan shapes. We show that results obtained using the KW and HSB models are significantly different as in the KW model the diffusion term is ignored. We generalize our results by examining the stability of several hollow types with different plan shapes (different convergence degree). For each hollow type, the minimum value of the landslide-triggering saturated depth corresponding to the triggering precipitation (critical recharge rate) is computed for steep and gentle hollows. Long term analysis of shallow landslides by the presented model illustrates that all hollows show a quite different behavior from the stability view point. In hollows with more convergence, landslide occurrence is limited by the supply of deposits (supply limited regime) or rainfall events (event limited regime) while hollows with low convergence degree are unconditionally stable regardless of the soil thickness or rainfall intensity. Overall, our results show that in addition to the effect of slope angle, plan shape (convergence degree) also controls the subsurface flow and this process affects the probability distribution of landslide occurrence in different hollows. Finally, we conclude that incorporating a more realistic description of hollow hydrology (instead of the KW model) in landslide probability models is necessary, especially for hollows with high convergence degree which are more susceptible to landsliding.

Geophysical measurements in an abandoned old railway tunnel located in a karst area

2021 ◽  
Author(s):  
Enzo Rizzo ◽  
Luigi Capozzoli ◽  
Gregory De Martino ◽  
Giacomo Fornasari ◽  
Valeria Giampaolo
Keyword(s):  
Karst Aquifer ◽  
Geophysical Methods ◽  
Water Reservoir ◽  
Test Site ◽  
Point Of View ◽  
Karst Area ◽  
Fluid Circulation ◽  
Railway Tunnel ◽  
Interdisciplinary Field ◽  
Karst Systems

<p>Carbonate aquifers in karst systems are very important water reservoir and are recognized as the most difficult to characterize. The purpose of this article is to present a project aimed to understand the circulation of fluids in carbonate reservoirs through innovative hydrogeophysical methodologies both in the laboratory and in the field. The test site is located in the Castel di Lepre karst system, which is disposed in the Mezo-Cenozoic carbonate substratum of the Monti della Maddalena ridge (Southern Appenines). In the karst area are located several caves, but the presence of an artificial tunnel (disused railway tunnel) could give the opportunity to characterize the whole area and the fluid circulation by multisensors geophysical sensors installed inside the karst aquifer. This natural laboratory permits to define an Applied Geophysics strategy developing several main topics from an engineering to hydrogeological point of view. Firstly, the geophysical investigations conducted, without altering the structure and in a fast manner, obtains important information concerning the construction of the tunnel, and the interaction between the infrastructure and surrounding rock, in that area that we define infrastructural critical zone. The study conducted aims to highlight the potential and any limitations of the use of geophysical techniques applied to infrastructures, emphasizing the emerging role of urban geophysics for the importance and topicality of its contents as well as the important innovations that the use of these techniques they can contribute to the hazardous processes. Secondly, the geophysical methods are used as a tool to characterize the fluid circulation by hydrogeophysal sensors installed inside the karst aquifer. The hydrogeophysics arose as an interdisciplinary field that focuses on the improved understanding of hydrological processes through geophysical observation. These approaches aimed at mitigating the detrimental effects of environmental problems.</p>

scholarly journals Landslides susceptibility modelling using Multivariate Logistic Regression Model in the Sahla Watershed in Northern Morocco

2021 ◽  
Vol 33 ◽  
Author(s):  
Mohammed El-Fengour ◽  
Hanifa El Motaki ◽  
Aissa El Bouzidi
Keyword(s):  
Logistic Regression ◽  
Landslide Susceptibility ◽  
Slope Angle ◽  
Google Earth ◽  
Slope Aspect ◽  
Multivariate Logistic Regression Model ◽  
Susceptibility Map ◽  
Potential Hazard ◽  
Topographic Wetness Index ◽  
Landslide Occurrence

This study aimed to assess landslide susceptibility in the Sahla watershed in northern Morocco. Landslides hazard is the most frequent phenomenon in this part of the state due to its mountainous precarious environment. The abundance of rainfall makes this area suffer mass movements led to a notable adverse impact on the nearby settlements and infrastructures. There were 93 identified landslide scars. Landslide inventories were collected from Google Earth image interpretations. They were prepared out of landslide events in the past, and future landslide occurrence was predicted by correlating landslide predisposing factors. In this paper, landslide inventories are divided into two groups, one for landslide training and the other for validation. The Landslide Susceptibility Map (LSM) is prepared by Logistic Regression (LR) Statistical Method. Lithology, stream density, land use, slope curvature, elevation, topographic wetness index, slope aspect, and slope angle were used as conditioning factors. The Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) was employed to examine the performance of the model. In the analysis, the LR model results in 96% accuracy in the AUC. The LSM consists of the predicted landslide area. Hence it can be used to reduce the potential hazard linked with the landslides in the Sahla watershed area in Rif Mountains in northern Morocco.

scholarly journals Aveiro Canyon Head (Portugal) Submarine Slope Instability Assessment

2020 ◽  
Vol 10 (24) ◽  
pp. 9038
Author(s):  
Nuno Lapa ◽  
Fernando M. F. S. Marques ◽  
Aurora Rodrigues
Keyword(s):  
Marine Environment ◽  
Regional Scale ◽  
Slope Angle ◽  
Area Under The Curve ◽  
Roc Curves ◽  
Information Value ◽  
Slope Instability ◽  
Landslide Inventory ◽  
Spatial And Temporal Variability ◽  
Sedimentary Dynamics

Mass wasting events are the main processes of sedimentary dynamics that affect the marine environment and which, due to their spatial and temporal variability, are difficult to study and evaluate. Affecting the marine floor, between the coastline and the abyssal plain, these processes are triggered by multiple causes, having different magnitudes and causing drastic changes and impacts on the marine environment and human activities. In this paper, the submarine landslide susceptibility affecting the upper course of the Aveiro canyon (West Iberian Margin) is addressed using statistical models which are based on the statistical relations between a landslide inventory and the landslide predisposing factors bathymetry, sediment cover, slope angle, aspect and curvature. The statistical methods were the widely proven bivariate information value (IV) and the multivariate logistic regression (LR). The model results were validated against the landslide inventory using receiver operating characteristic (ROC) curves and the corresponding area under the curve (AUC), which provided satisfactory results, with IV AUC = 0.79 and LR AUC = 0.83, in spite of the limitations of the databases used in this study. The results obtained suggest that these methods may be useful for the preliminary assessment of sea floor slope instability at a regional scale of analysis, enabling the selection of sites to be studied with much more detailed and expensive methods.

scholarly journals Optimized Design of Earth Dams: Analysis of Zoning and Heterogeneous Material in Its Core

2020 ◽  
Vol 12 (16) ◽  
pp. 6667 ◽  
Author(s):  
José Sánchez-Martín ◽  
Rubén Galindo ◽  
Carlos Arévalo ◽  
Ignacio Menéndez-Pidal ◽  
Liliya Kazanskaya ◽  
...  
Keyword(s):  
Heterogeneous Material ◽  
Seepage Flow ◽  
Point Of View ◽  
Earth Dam ◽  
Optimized Design ◽  
Flow Rates ◽  
Geotechnical Characteristics ◽  
Large Dispersion ◽  
Hydraulic Gradients ◽  
Dam Core

To control the seepage in the design of an earth dam, guidelines prescribe a high proportion of fines and high homogeneity of geotechnical characteristics in the material used for the dam core. However, on many occasions there is no material of this nature near the dam placement and, from an economic or environmental point of view, it is not possible to locate and transport material with good geotechnical characteristics close to the dam. This research demonstrated the possibility of using impermeable materials in earth dam cores, as well as soils considered unsuitable according to the classic recommendations and guidelines. For an optimized design, two situations are analyzed here. First, we examined the possibility of using soil with a marked difference in grain size as the core of the dam, each with homogeneous geotechnical properties. In this case, the optimal zoning of up to three types of materials was studied to ensure adequate seepage control. Second, we examined the use of soil with great geotechnical heterogeneity, which presents high permeability dispersion. In such a case, the conditions that would allow its use were studied via the of Montecarlo analysis. By maintaining the soil’s global heterogeneity, it was possible to study an unlimited disposition of layers of different permeability. In the first situation, the results showed that the most effective zoning for decreasing seepage flow corresponded with three vertically set materials. In this design, the most optimized zoning (minimal seepage flow rates) corresponded to the most impermeable soil situated downstream when water heights were under 90% of the height of the dam core. However, for maximum water height, more optimized cases corresponded to the intermediate permeability material located downstream. In the second situation, when heterogeneous materials were used to construct the impervious element of the dams, the Montecarlo analysis indicated that the seepage flow rates were limited to sufficiently low values despite the large dispersion of material permeability. In addition, the highest maximum hydraulic gradients were observed in the lowest lifts of the dam core and for situations in which the seepage flow rates were moderate and low.

scholarly journals Application of Limit Equilibrium Analysis and Numerical Modeling in a Case of Slope Instability

2020 ◽  
Vol 12 (21) ◽  
pp. 8870
Author(s):  
Fhatuwani Sengani ◽  
François Mulenga
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Limit Equilibrium ◽  
Slope Angle ◽  
Road Construction ◽  
Soil Mass ◽  
Slope Instability ◽  
Equilibrium Analysis ◽  
Limit Equilibrium Analysis ◽  
The Common

The application of limit equilibrium analysis and numerical simulation in case of slope instability is described. The purpose of the study was to use both limit equilibrium methods (LEMs) and numerical simulations (finite element method (FEM)) to understanding the common factor imposing the selected slope into slope instabilities. Field observations, toppling analysis, rotational analysis, and numerical simulations were performed. The results of the study showed that the selected unstable slopes were associated with the sliding types of toppling; it was observed that the slopes were governed by tension cracks and layered soil mass and dominated with approximately two joints sets throughout. The simulated factor of safety (FoS) of the slopes composed of clay soil was denoted to be prone to slope instability while others were categorized as moderately stable. The simulated FoS of the slopes correlated very well with the visual observations; however, it is anticipated that properties of soil mass and other characteristics of the slopes contributed largely to the simulated FoS. The sensitivity of the model was further tested by looking into the effect of the slope angle on the stability of the slope. The results of the simulations showed that the steeper the slope, the more they become prone to instability. Lastly, Phase 2 numerical simulation (FEM) showed that volumetric strain, shear stress, shear strain, total displacement, and σ1 and σ3 components of the slope increase with the stages of the road construction. It was concluded improper road construction, steepness of the slope, slope properties (soil types), and multiple geological features cutting across are the common mechanisms behind the slope instability.

Pierre3D: a 3D stochastic rockfall simulator based on random ground roughness and hyperbolic restitution factors

2015 ◽  
Vol 52 (9) ◽  
pp. 1360-1373 ◽  
Author(s):  
Valentin S. Gischig ◽  
Oldrich Hungr ◽  
Andrew Mitchell ◽  
Franck Bourrier
Keyword(s):  
Stochastic Process ◽  
Slope Angle ◽  
Test Site ◽  
Fine Tuning ◽  
Model Parameters ◽  
Observation Data ◽  
Lumped Mass ◽  
Forest Road ◽  
Rockfall Hazard ◽  
The Impact

The use of dynamic computational methods has become indispensable for addressing problems related to rockfall hazard. Although a number of models with various degrees of complexity are available, model parameters are rarely calibrated against observations from rockfall experiments. A major difficulty lies in reproducing the apparent randomness of the impact process related to both ground and block irregularities. Calibration of rigorous methods capable of explicitly modeling trajectories and impact physics of irregular blocks is difficult, as parameter spaces become too vast and the quality of model input and observation data are insufficient. The model presented here returns to the simple “lumped-mass” approach and simulates the characteristic randomness of rockfall impact as a stochastic process. Despite similarities to existing approaches, the model presented here incorporates several novel concepts: (i) ground roughness and particle roughness are represented as a random change of slope angle at impact; (ii) lateral deviations of rebound direction from the trajectory plane at impact are similarly accounted for by perturbing the ground orientation laterally, thus inducing scatter of run-out directions; and (iii) a hyperbolic relationship connects restitution factors to impact deformation energy. With these features, the model is capable of realistically accounting for the influence of particle mass on dynamic behaviour. The model only requires four input parameters, rendering it flexible for calibration against observed datasets. In this study, we calibrate the model against observations from the rockfall test site at Vaujany in France. The model is able to reproduce observed distributions of velocity, jump heights, and runout at observation points. In addition, the spatial distribution of the trajectories and landing points has been successfully simulated. Different parameter sets have been used for different ground materials such as an avalanche channel, a forest road, and a talus cone. Further calibration of the new model against a range of field datasets is essential. This study is part of an extensive calibration program that is still in progress at this first presentation of the method, and focuses on fine-tuning the details of the stochastic process implemented both in two-dimensional (2D) and three-dimensional (3D) versions of the model.

Potential of dNDVI-method for landslide detection in Norway

2020 ◽  
Author(s):  
Erin Lindsay ◽  
Christy Rouault ◽  
Mads Fjeld ◽  
Steinar Nordal
Keyword(s):  
Vegetation Index ◽  
Slope Angle ◽  
Transport Systems ◽  
National Database ◽  
Acquisition Window ◽  
Alternative Source ◽  
Landslide Occurrence ◽  
Good Potential ◽  
Definition Of ◽  
Sentinel 2

<p>The Norwegian mass movements database contains over 33,000 registered snow avalanche and landslide events from the past 500 years and is used as an input for The Norwegian Landslide Early Warning System (LEWS). However, the usability of the database is limited by factors including a spatial bias towards transport systems and incomplete or missing information on landslide characteristics (including precise date, time or location). This has serious consequences for the definition of triggering thresholds. Sentinel-2 optical satellite data, with its frequent return period in Norway (up to three days) and relatively high resolution (10 m), could provide an alternative source of data on landslide occurrence to supplement ground-based observations and improve the information in the database.</p><p>This study examined the potential for using Sentinel-2 data to detect landslides with two approaches, using (i) a national-, and (ii) a local-survey. Both used the change in the vegetation index (denoted dNDVI) between pre- and post-event images, to identify a loss of vegetation as an indicator of landslide occurrence. Firstly, 30 well-documented landslides with a minimum volume of 1000m<sup>3</sup> were extracted from the national database. The selected landslides occurred across all Norway between 2015 to 2017. They were searched for in Sentinel 2 images to give insight into how factors including season, slope angle, aspect ratio, land cover, landslide size influenced landslide detection using the dNDVI-method. Secondly, the same approach was applied to the Jølster area in Western Norway, where an extreme short intense rainfall event in the summer of 2019 (30 July 2019) triggered multiple landslides. For Jølster, landslides were mapped and then verified by field and helicopter observations.</p><p>For the national survey, the season was found to have the greatest effect on detectability. For spring and summer events the percentage of landslides detected was 70-75%, while for winter and autumn this dropped to 14-20%. The main reasons for non-detection were clouds, shadows, snow, and lack of green vegetation. The average acquisition window for detected events was 43.3 days. The Jølster case study represented ideal conditions for using the dNDVI-method, with a five-day acquisition window (almost cloud-free images available from two days pre-, three days post-event), low shadow, and green summer vegetation. The mapping process produced an inventory of 99 events, giving a significant increase from the 14 events registered in the database.</p><p>The results indicate that the dNDVI-method has good potential for landslide detection in late-spring and summer in Norway, however, it is not recommended later in autumn and winter. We believe that the dNDVI-method provides an option for gaining more information on the size and location of landslides, which at the present, are only registered as points in the database. For the Jølster case, this method showed a great improvement with respect to the current practice, both in terms of an increased number of landslides and spatial distribution. This suggests good potential for improving inventories of landslides, necessary in landslide hazard analyses and definition of landslide thresholds.</p>

scholarly journals Shallow landslides stochastic risk modelling based on the precipitation event of August 2005 in Switzerland: results and implications

2013 ◽  
Vol 1 (2) ◽  
pp. 747-791 ◽  
Author(s):  
P. Nicolet ◽  
L. Foresti ◽  
O. Caspar ◽  
M. Jaboyedoff
Keyword(s):  
Risk Model ◽  
Precipitation Amount ◽  
Shallow Landslides ◽  
Precipitation Event ◽  
Damage Cost ◽  
Landslide Occurrence ◽  
Rain Gauges ◽  
Weather Radars ◽  
Large Spread ◽  
Probabilistic Relation

Abstract. Due to their relatively unpredictable characteristics, shallow-landslides represent a risk for human infrastructures. Multiple shallow-landslides can be triggered by large spread precipitation events. The event of August 2005 in Switzerland is used in order to propose a risk model to predict the expected number of landslides based on the precipitation amounts and lithological units. The spatial distribution of rainfall is characterized by blending data coming from operational weather radars and a dense network of rain gauges with an artificial neural network. Lithologies are grouped into four main units, with similar characteristics. Then, from a landslide inventory containing more than 5000 landslides, a probabilistic relation linking the precipitation amount and the lithology to the number of landslides in a 1 km2 cell, is obtained. In a next step, this relation is used to randomly redistribute the landslides using Monte-Carlo simulations. The probability for a landslide to reach a building is assessed using stochastic geometry and the damage cost is assessed from the estimated mean damage cost using an exponential distribution to account for the variability. Although the outputs reproduce well the number of landslides, the number of affected buildings is not reproduced by the model. This seems to results from the human influence on landslide occurrence. Such a model might be useful to characterize the risk resulting from shallow-landslides and its variability.

Sign in / Sign up

Export Citation Format

Share Document